A new recognition of the binding of cellulose fibrils in papermaking by probing interaction between nanocellulose and cationic hemicellulose

A new recognition of the binding of cellulose fibrils in papermaking by probing interaction between nanocellulose and cationic hemicellulose | Research Square window.SnipcartSettings = { analytics: { enabled: false } }; (function() { var accessVector = localStorage.getItem('access_vector') || ''; window.dataLayer = window.dataLayer || []; if (accessVector) { window.dataLayer.push({ user: { profile: { profileInfo: { snid: accessVector } } } }); } })(); (function(w,d,s,l,i){w[l]=w[l]||[];w[l].push({'gtm.start':new Date().getTime(),event:'gtm.js'});var f=d.getElementsByTagName(s)[0],j=d.createElement(s),dl=l!='dataLayer'?'&l='+l:'';j.async=true;j.src='https://www.googletagmanager.com/gtm.js?id='+i+dl;f.parentNode.insertBefore(j,f);})(window,document,'script','dataLayer','GTM-K279D39R'); Browse Preprints In Review Journals COVID-19 Preprints AJE Video Bytes Research Tools Research Promotion AJE Professional Editing AJE Rubriq About Preprint Platform In Review Editorial Policies Our Team Advisory Board Help Center Sign In Submit a Preprint Cite Share Download PDF Research Article A new recognition of the binding of cellulose fibrils in papermaking by probing interaction between nanocellulose and cationic hemicellulose Xingyu LAN, Shiyu Fu, Yi Kong This is a preprint; it has not been peer reviewed by a journal. https://doi.org/ 10.21203/rs.3.rs-3785502/v1 This work is licensed under a CC BY 4.0 License Status: Published Journal Publication published 08 May, 2024 Read the published version in Cellulose → Version 1 posted 7 You are reading this latest preprint version Abstract The paper industry is constantly seeking innovative ways to improve paper quality, increase process efficiency and reduce environmental impact. The unique properties of cationic modification of hemicellulose provide an opportunity to achieve these goals. Herein, eucalyptus hemicellulose was modified with quaternary ammonium groups to yield cationic hemicellulose (CH), which was used to elaborate structural and functional interactions between CH and cellulose nanofibrils (CNF). These interactions were quantitatively monitored by a quartz crystal microbalance with dissipation (QCM-D). We empirically studied bonding motifs between CNF and hemicellulose by forming films. The degree of substitution (DS) of CH was made between 0.095 and 0.254 by varying the molar ratio of the reaction, leading to a gamut of positive charges in hemicellulose. The adsorption of CH to a CNF surface was related to electrostatic interactions. The high DS of CH had higher adsorption rate and larger adsorption capacity within the CNF-surface, while CH as a reinforcing agent significantly increased the tensile strength of the film by hydrogen bonding, which was 71% higher than that of unmodified hemicellulose. The strong binding between CH and nanocellulose may highlight a platform to develop paper additives and nanocellulose composites for high-value applications. Nanocellulose Cationic hemicellulose (CH) QCM-D Interaction Interfacial adsorption Figures Figure 1 Figure 2 Figure 3 Figure 4 Figure 5 Figure 6 Figure 7 Figure 8 Highlights The interfacial interaction between CH and CNF was investigated by QCM-D Electrostatic forces reinforce the adsorption of CH on the surface of the CNF matrix. Strong interactions between CNF and CH can improve film performance The reinforcing agent CH facilitates the bonding of nanofibrils. 1. Introduction Hemicellulose is an important biomass polysaccharide in nature, accounting for 20.00%~30.00% of plant biomass, with an annual global production of about 60 billion tons, second only to cellulose(Al Manasrah et al., 2012 ; Rao et al., 2023 ). Structurally, hemicellulose is a series of biopolymers composed of various monosaccharides, including xylose, glucose, arabinose, galactose, and mannose, mostly in branched chain structure (Jin et al., 2022 ). Among the various hemicelluloses, xylan is predominant in hardwoods and grass families, while glucomannan mainly occurs in softwoods. Hemicellulose is a very complex component of plant cell walls and is difficult to utilize in a simple way. However, it has many advantages such as cheap and easy to obtain, solubility, degradability and low pollution, which are of great significance in solving the energy and environmental problems faced by all mankind. In the pulp and paper industry, the presence of hemicellulose may affect the properties of paper such as strength, opacity, etc. Natural/modified hemicellulose as a paper additive can improve the mechanical properties of paper, including tensile index, fracture index and tear index (Hu et al., 2016 ). The utilization of hemicellulose as a pulping agent (Sehaqui et al., 2013 ; Silva et al., 2011 ), retention aid (Soliman et al., 1997 ), and wet-end additive (Kong et al., 2018 ) has been the subject of extensive research for a considerable period. In addition, hemicellulose and its derivatives show exciting properties in nanocellulose composites. For example, it can be used as a binding agent for nanocellulose-based biomaterials for 3D printing of packaging, nutraceuticals, tissue engineering or wound dressings (Yang et al., 2020 ). The utilization of biomimetic inks, which are composed of cross-linkable xylan and cellulose nanofibers (CNF), allows for the personalized design of clothing, furniture, and electronics (Markstedt et al., 2017 ). Inspired by cellulose-xyloglucan (XG) interactions in plant cell walls, tough cellulose-XG nanocomposite foams were prepared with superior mechanical properties than other nanocellulose composites previously reported in the literature with comparable densities (Sehaqui et al., 2010 ). Hemicellulose was introduced into CNF by in situ adsorption and pre-adsorption to enhance the structural and mechanical properties of cellulose hydrogels used for wound healing and showed high efficacy in the growth and proliferation of fibroblasts (NIH 3T3) (Shavandi et al., 2020 ). Despite the desirable utilization properties of hemicellulose in paper/cellulose composites, the actual interaction between hemicellulose and cellulose is a key process in the formation of paper/cellulose materials. The surface of cellulose fiber/nanocellulose is slightly negatively charged due to the introduction of carboxyl groups during pulping, bleaching and preparation of nanocellulose (Bohrn et al., 2006 ; Jiang & Hsieh, 2013 ; Zhao et al., 2022 ) and therefore leads to inter-electrostatic repulsions with hemicellulose (Odabas et al., 2016 ), thus weakening the interaction between natural hemicellulose and cellulose. Therefore, chemically modified cationic hemicellulose came into being. It is an important etherified derivative of hemicellulose with a simple preparation process and good water solubility and biodegradability (Chen et al., 2016 ; Postma et al., 2014 ). It is widely used in papermaking additives, strength agents, flocculants and composite membranes (Kong et al., 2018 ; Liu et al., 2011a ; Ren et al., 2007 ; Wang et al., 2021 ). In fact, cationic hemicellulose enhances its adsorption on the surface of the "anionic" nanocellulose through the attractive force of electrostatic interaction (Bai et al., 2012 ; Schwikal et al., 2006 ) . Indeed, there are several key research efforts with respect to the interaction between cationic/natural hemicellulose and the cellulose fiber. Kohnke et al. conducted experiments using three different methods (COD, carbohydrate analysis, and iodine complexation) and observed a significant improvement in the adsorption rate and amount of adsorption (Kohnke et al., 2009 ). Kong et al. added 2.4 wt.% of cationic xylan with a DS of 0.32 to the pulp, resulting in a 63% increase in the tensile index, a 58% increase in the tear index, and a 42% increase in the bursting index (Kong et al., 2018 ). Hu et al. discovered that the maximum absorption of cationic hemicellulose in eucalyptus and pine pulp was 40% and 47% higher, respectively, compared to unmodified hemicellulose (Hu et al., 2015 ). In the latest research progress, the molecular dynamics simulation described in molecular level the interaction of hemicellulose-cellulose (Kong et al., 2022 ; Zhang et al., 2015 ). The mentioned above methods can only detect the end product after interaction but failed to monitor the adsorption process in real time. For cellulose and hemicellulose, the actual mass change during adsorption is minimal and difficult to detect. Furthermore, due to their complex structures, analyzing the reasons for differences in adsorption is also challenging. QCM-D is an efficient mass-sensing technique based on the piezoelectric properties of quartz crystals. In fact, it can provide information about the mass adsorbed on the surface as well as the mechanical behavior of the layer through the measurement of the dissipation factor. QCM-D can also be used in conjunction with surface plasmon resonance (SPR) (Liu et al., 2011b ) or AFM colloid probe microscopy (CPM) (Eronen et al., 2012 ) to cross-validate interaction results. A study utilizing QCM-D investigated the impact of hemicellulose composition and content on the interactions between CNFs. The results revealed that the strength of these interactions varied depending on the composition of hemicellulose (Kumagai & Endo, 2021 ). The influence of various factors such as substitution pattern, molecular weight, and structure of unmodified hemicellulose, as well as adsorption conditions, has been extensively studied using QCM-D (Hatton et al., 2017 ; Jaafar et al., 2019 ; Kumagai & Endo, 2021 ; Lee et al., 2015 ; Lyu et al., 2021 ; Markstedt et al., 2017 ; Yao et al., 2021 ). However, there are fewer studies on the interaction of cationic hemicelluloses from the nanoscale. In this particular study, nanocellulose was employed as a simulation of the microfibrils present on the surface of pulp. The main objective was to investigate the adsorption of cationic hemicellulose, utilized as a wet-end additive in papermaking, onto the nanocellulose matrix. The study aimed to gain a deeper understanding of the underlying mechanism behind the interaction between cationic hemicellulose and nanocellulose. Based on the above considerations, we hypothesized that the interaction between cationic hemicellulose and nanocellulose is mainly influenced by the electrostatic forces, but also driven by structure and hydrogen bonding. To test this hypothesis, hemicellulose was grafted with cationic groups and the real-time adsorption behavior of cationic hemicellulose on nanocellulose matrix was quantitatively monitored by QCM-D. The mechanical properties of composite films made from hemicellulose and nanocellulose were prepared and measured, and the reinforcing mechanism of cationic hemicellulose in nanocellulose composites was investigated. 2. Experiment 2.1 Materials and separation Eucalyptus chips (3cm * 5cm * 2cm) were donated by Juntai Paper Co., Ltd., Hunan Province, China. Eucalyptus chips are pulped by the sulfate method. Hemicellulose was extracted from unbleached eucalyptus pulp with 2M KOH for 24 h, showed in (Fig. 1 ). The solid was retained for CNF preparation after bleaching, and the liquid for hemicellulose was neutralized with 6M acetic acid to pH 5.5 and centrifuged at 5000 rpm. The precipitate was separated as a water-insoluble hemicellulose (Small amount, ignored). The supernatant was precipitated by adding the volume of 95% ethanol, and then centrifuged and freeze-dried to obtain water-soluble hemicellulose (Hr). 0.375 g of water-soluble hemicellulose was dispersed in 45 mL of deionized water containing 0.24 g of sodium hydroxide and stirred for 30 min. Then an amount of 2,3-epoxypropyltrimethylammonium chloride (ETA) was added and the molar ratio of ETA to hemicellulose (xylose unit) varied from 1.0 to 4.0 to obtain cationic hemicellulose with different degrees of substitution. Then 0.36 g of sodium hydroxide was added and stirred at 60°C for 6 h. After reaction, the reactants were neutralized with 2.5 mol/L hydrochloric acid and then precipitated with three times the volume of 95% ethanol, and the precipitate was washed with 75% ethanol and freeze-dried (Hu et al., 2015 ). The eucalyptus pulp was extracted by 2M KOH and bleached, and its main chemical component was cellulose (97%), while the hemicellulose content was 3%. Cellulose nanofibrils (CNF) were prepared by pretreating eucalyptus pulp with 55 wt% sulfuric acid at 45°C for 40 min, followed by high-pressure homogenization. The acid hydrolysis pretreatment made the pulp fibers easier to be stripped of CNFs and had a higher yield when mechanically processed by high-pressure homogenization (Peng et al., 2019 ). The length of CNF varies from 40 to 1200 nm, while the diameter is 10–30 nm and its surface zeta potential is − 36 mV. CNF prepared by the sulfuric acid pretreatment method leads to esterification of fibrils surfaces, which results in negatively charged sulfuric acid groups on these cellulose surfaces. CNF suspensions (1% w/v) can be used after dilution to various concentrations (0.1–0.8 wt%). 2.2 Chemical composition and structural analysis 2.2.1 Chemical composition analysis Hemicellulose was hydrolyzed with 4% H 2 SO 4 at 121°C for 2 h. After the reaction, the hydrolytes were cooled and filtered through a G4 glass filter. The concentration of soluble lignin in the filtrate was determined by UV absorbance at 205 nm, and the solid in the glass filter was dried to a constant weight at 105°C and weighed as insoluble lignin (klason lignin) (Bhagia et al., 2016 ; Luo et al., 2023 ). The filtrate was neutralized with calcium carbonate to pH 6 ~ 7, diluted a certain number of times, filtered through 0.22µm aqueous membrane for carbohydrate analysis by high-performance anion-exchange chromatography (HPAEC) (Dionex ICS-3000, USA) with pulsed amperometric detection, a CarboPac™ PA20 column (3 mm × 150 mm) and a CarboPac™ Guard column (3 mm × 30 mm) (Hu et al., 2015 ; Shi et al., 2013 ). 2.2.2 Elemental analysis The nitrogen and carbon content of cationic hemicellulose was determined using an Element UNICUBE elemental analyzer. The degree of substitution (DS) of cationic hemicellulose was calculated using the following equation, where N% and C% are the nitrogen and carbon content, respectively (Schwikal et al., 2006 ; Schwikal et al., 2011 ). $$\text{D}\text{S}=\frac{60\times N\left(\%\right)}{14\times C\left(\%\right)-72\times N\left(\%\right)}$$ 2.2.3 Molecular weight The molecular weight of hemicellulose was determined using gel permeation chromatography (GPC) (Agilent PL-GPC50 system). The chromatographic column was equipped with a Shodex (Tokyo, Japan) i-101 refractive index detector; the temperature of the chromatographic column was 30 ℃, and the mobile phase was ultrapure water; the molecular weights of PEG as the standard samples were 305000, 242400, 24470, 17800, and 12000 g/mol, respectively. 2.2.4 Zeta potential The zeta potential was measured with a Malvern Zetasizer Nano ZS90. The samples were dissolved in deionized water at a concentration of 1 mg/ml. 2.2.5 Nuclear magnetic resonance analysis 1 H-13C HSQC was performed on a BRUKER AVANCE NEO 500M spectrometer with 36 mg of hemicellulose dissolved in 55 µL of D 2 O. The spectral widths were 11 ppm, 2048 data points for hydrogen dimension F2 ( 1 H) and 190 ppm, 256 data points for carbon dimension F1 ( 13 C); 128 scans (NS) with an inter-scan delay (D1) of 1 second. All data processing was done with MestReNova software (Ding et al., 2019 ). 2.2.6 Thermal stability The cationic hemicellulose was analyzed using a TG209F1 thermogravimetric analyzer from NETZSCH, Germany, with a protective gas of nitrogen, a ramp-up rate of 10°C/min, and a measurement range of 40–600°C. 2.3 Interaction analysis by QCM-D According to a previous study (Liu et al., 2021 ), CNF-coated sensors were prepared by spin-coating method. Prior to spin coating, the QCM-D sensors with silica surface were immersed in sodium dodecyl sulfate solution (2%) for at least 30 min for cleaning, rinsing with milli-Q grade water and drying with nitrogen. The QCM-D sensors were subjected to a 30-minute treatment with an ozone-activated UV cleaner to oxidize impurities and activate the surfaces' silicon hydroxyl groups. The treated QCM-D sensors were then immersed in a 100 mg/L polyethyleneimine (PEI) solution for 30 minutes, rinsed with mill-Q water, and blown dry with mild nitrogen. CNF suspension (0.2 wt%) was then spin-coated onto the sensor with the pre-adsorbed PEI layer at 3000 rpm. Thereafter, the sensors were placed in an oven at 60°C for 2h and stored in a desiccator. Aqueous solutions of different DS cationic hemicelluloses (100 mg/L) were prepared before the experiments. The QCM-D E4 (Biolin Science Ltd., Sweden) was used to monitor the frequency and dissipation changes of the 5 MHz fundamental resonant frequency as well as the 3rd, 5th, 7th, 9th and 11th overtones. The experiments were performed at 25°C. The CNF-coated sensors were installed in the QCM-D chambers and then milli-Q water was passed at a rate of 0.1 mL/min to stabilize the films. After stabilizing the QCM-D system, cationic cellulose solution was introduced into the four chambers. Once adsorption reached equilibrium, a rinse with Milli-Q water was performed to remove loosely bound layers. Each experiment was repeated at least three times (Zhang et al., 2020 ). 2.4 Water contact angle and AFM morphology characterization of sensor surfaces Using an OCA15 20 contact angle meter, 12 µL of ultrapure water is pressed out with a micro syringe at one atmosphere and 50% air humidity, and the carrier table is slowly raised to touch the droplet hanging from the lower end of the syringe so that the droplet remains on the surface of the QCM-D sensor surface. After it equilibrates in air for 1 min, a baseline is selected, the droplet profile is detected, and the contact angle is calculated by the SCA20 software program. AFM (Bruker Dimension Icon) was used to observe the morphological characteristics of the QCM-D sensor surface before and after hemicellulose adsorption. The samples before and after the QCM-D experiment were tested using the tap mode with a scanning frequency of 0.5 Hz. 2.5 Preparation and characterization of hemicellulose-cellulose composite films The composite films were prepared by casting method. 72 mg hemicellulose was added to 50 g CNF suspension (0.8%) and stirred in constant temperature water at 55°C for 1 h, followed by stirring at room temperature for 2 h under magnetic stirring. The mixture was poured into Petri dishes of 10 cm diameter while keeping the total mass of each sample film in each compartment the same, and dried at room temperature until they could be peeled off. The films were stored in standard ambient (T = 23°C, relative humidity = 50%) conditions for 48 h. The thickness of the films was determined by a sheet thickness meter (Lorentzen & Wettre, accuracy to 1 µm) and 5 different areas were measured for each sample and averaged. The mechanical properties were tested on an INSTRON 3300, and the size of the laminated film used for the tensile test was 50 mm x 10 mm. The tensile curve was measured at a tensile speed of 5 mm/min and the tensile force was recorded using a 500 N load cell, with a minimum of 8 strips tested per sample to obtain the average tensile strength. 3. Results and Discussion 3.1 Characterization of hemicellulose and its derivatives The type of hemicellulose used in this paper is mainly xylan, and water-soluble hemicellulose was deliberately prepared, firstly, to facilitate various characterizations, and secondly, because its higher yield facilitates cationic modification. The water-soluble hemicellulose (Hr) was hydrolyzed and analyzed with ion chromatography. It revealed that xylose accounted for 84.9% of carbohydrates in the hydrolyte; thus, it is the main polysaccharide component. There are also some minor components, such as galactose, glucose and glucuronic acid accounting for 1.62%, 1.78% and 4.78%, respectively. In addition, the amount of lignin (6.07%) was detected in the Hr sample, which may contribute to cross-linking of lignin with hemicellulose for a lignin-carbohydrate complex (LCC). During the extraction of hemicellulose from unbleached pulp through alkali treatment, lignin inevitably remained in the prepared hemicellulose, resulting in a darker color (Geng et al., 2019; Liu et al., 2016). In the FTIR spectra of cationic hemicellulose after multiple purifications ( Figure S7 ), the typical aromatic ring vibration-related peaks of lignin were not observed between 1600 and 1500 cm -1 .(Postma et al., 2014) In the present work, hemicellulose was modified with different ratio of ETA as observed in ( Table 1 ). The degree of substitution of cationic hemicellulose increases with molar ratio of ETA to hemicellulose (0.095 to 0.254). If microwave heating is used to assist in the reaction, DS can go to 0.54 (Peng et al., 2012). Cationic hemicellulose is often used as a paper reinforcing agent in the paper industry, and it has been found that the optimal DS range for cationic hemicellulose is 0.1 to 0.3 to improve the tensile and tear strength of paper (Deutschle et al., 2014; Rena et al., 2009; Schwikal et al., 2011). The molecular weight of hemicellulose may affect not only the adsorption behavior of hemicellulose on a cellulose surface, but the adsorption level and the conformation of the adsorbed layer (Yao et al., 2021). The Mw of Hr was 91,000 g/mol, while the molecular weights of CH1 and CH2 after cationization modification were very similar, 110,000 and 109,000 g/mol, respectively. The slight increase in Mw could be attributed to the relatively mild etherification modification reaction, the relatively small amount of ETA, and the fact the main chain of hemicellulose was not degraded and grafted with quaternary ammonium groups. As the molar ratio of ETA to hemicellulose increased, the degree of substitution increased and the Mw decreased to 62,600 g/mol and 59,412 g/mol for CH3 and CH4, respectively. when the concentration of ETA was too high, it leads to degradation of the hemicellulose molecular chain and side reactions, which lead to molecular weight decreases. The molecular weight distribution curves can be found in the GPC chromatographic profiles ( Figure S2 ~ Figure S6 ). The zeta potential of an aqueous solution of hemicellulose was tested, which was -19.7 mV, likely due to the presence of glucuronide groups (Jiang et al., 2014). The zeta potential of the aqueous cationic hemicellulose solution increased significantly with increasing DS due to the grafting of positively charged quaternary ammonium groups by cationic hemicellulose. Table 1. Chemical properties of native/cationic hemicellulose with different DS. Hemicellulose Molar ratio ETA: anhydroxylose N% C% DS Molecular weights (g/mol) Zeta（mV） Mw Mn Mw/Mn Hr - - - 0 9.11⨯10 4 4.12⨯10 4 2.21 -19.7 CH1 1.0 0.70 35.12 0.095 11.0⨯10 4 4.24⨯10 4 2.60 -15 CH2 2.0 1.07 36.88 0.146 10.9⨯10 4 4.00⨯10 4 2.72 -14 CH3 3.0 1.37 36.28 0.201 6.26⨯10 4 3.11⨯10 4 2.02 -7.95 CH4 4.0 1.60 35.10 0.254 5.94⨯10 4 3.07⨯10 4 1.94 -5.86 3.2 Structure of hemicellulose and its derivatives In order to elucidate the effect of hemicellulose structure on adsorption experiments, Hr and CH4 were characterized using 1 H- 13 C HSQC NMR to investigate structural changes before and after modification shown in Table 2 . In the HSQC NMR spectrum of Hr ( Figure 2(a) ), the chemical shifts 101.3/4.41, 101.4/4.59 and 97.1/5.29 are from the (1→4)-linked β-D-glucopyranosyl, 2-O-(4-O-methyl-α-D-glucuronide)-glucopyranosyl xylose, 4-O-methyl-α-D-glucuronide of hemicellulose, respectively, with several carbon atoms and the corresponding hydrogen atoms. The other atomic carbon-hydrogen correlation peaks of (1 → 4)-linked β-D-xylopyranosyl are at 72.7/3.24 (C2-H2),73.6/3.51 (C3-H3), 76.2/3.75 (C4-H4), 63.7/4.03 (C5-Heq) and 63.8/3.30 (C5-Hax) ppm, respectively. The chemical shift intensity of xylose indicates that the sugar group in hemicellulose is mainly xylose, which is the same conclusion as the chemical composition analysis of hemicellulose. The chemical shifts 70.2/3.51, 71.0/3.68,81.4/3.15, 71.9/4.28 are the carbon-hydrogen correlation peaks on C2-H2, C3-H3, C4-H4 and C5-H5 on the unit of glucuronic acid, respectively, and at 59.8/3.41 ppm is the proton peak of the methyl group of 4-O-methyl glucuronide, which indicates the presence of 4-O-methylglucuronide and substitution at the C-2 position, and 76.9/3.39 ppm is the chemical shift of the hydrocarbon-related peak on C2-H2 after attachment of 4-O-methylglucuronide to the xylose unit. These data are consistent with the published reports (Arumugam et al., 2018; Barbieri et al., 2022). According to previous work (Cheng et al., 2018; Peng et al., 2012), after comparing the spectrum of CH4 ( Figure 2(b) ) with that of Hr, most 4-O-methylglucuronide signal peaks disappear and are replaced by the signal peaks of the quaternary ammonium group, with a major intense absorption peak at 54.9/3.17 ppm, caused by the methyl carbon on the quaternary ammonium group. 72.1/3.71, 65.1/4.37and 70.22/3.52 ppm correspond to the carbon-hydrogen related peaks on the quaternary ammonium branched groups C1-H1, C2-H2, and C3-H3, respectively. The presence of these signal peaks confirms that the quaternization of hemicellulose and cationic groups are introduced into the hemicellulose macromolecular backbone. The signal shift of 82.2/3.17 for C2-H2 of (1→4)-β-D-xylopyranose further confirms substitution on C-2 of Hr. The glucose signal in cellulose was detected in 2D NMR in addition to the glycosyl group of hemicellulose. As expected, most lignin was leached out after alkali, leaving behind cellulose and hemicellulose; thus, the hemicellulose extracted from the pulp would contain a small amount of glucose. The combination of glycosyl analysis and 2D NMR results showed that water-soluble hemicellulose (Hr) extracted by alkali contained more glucuronic acid branched chains. However, the glucuronide branched chains detached after modification and the xylan backbone interacted with new quaternary ammonium groups. Table 2 . Chemical shift assignments for hemicellulose in 1H-13C 2D NMR, ax = axial, eq = equatorial. Monosaccharide unit Chemical shift H/C (ppm) 1 2 3 4 5ax 5eq O-CH 3 N-CH 3 → 4)-β-D-Xylp-(1 → 4.41/ 101.3 3.24/ 72.7 3.51/ 73.6 3.75/ 76.2 3.30/ 63.8 4.03/ 63.7 - - → 4,2)-β-D-Xylp-(1 → 4.59/ 101.4 3.39/ 76.9 3.59/ 72.5 3.72/ 76.3 3.37/ 63.2 4.01/ 63.7 - - 4-O-Me-α-D-GlcpA-(1 → 5.29/ 97.1 3.51/ 70.2 3.68/ 71.0 3.15/ 81.4 4.28/ 71.9 - 3.41/ 59.8 - QA 3.71/ 72.1 4.37/ 65.1 3.52/ 70.2 - - - - 3.17/ 54.9 3.3 Thermal stability To further determine the effect of the structure of the cationic hemicellulose on its stability, Thermogravimetry (TG) tests were performed over 40 to 600 °C whose results are shown in Figure 3(a). The thermal decomposition of hemicellulose of different DS is characterized by three distinct stages: (1) 0~150 °C, which is mainly the evaporation of water; (2) 150~350 °C, over which the hemicellulose is rapidly pyrolyzed, and the maximum weight loss of four different DS occurs between 230~290 °C. The starting pyrolysis temperatures of CH1 and CH4 are 180 ℃ and 150 ℃, respectively, above which the mass loss is serious, and the lowering of the starting pyrolysis temperature means the lowering of the thermal stability. In the Derivative Thermogravimetry (DTG) curves ( Figure 3(b) ), the maximum degradation temperatures of CH1 and CH4 were 286 °C and 235 °C, respectively, which indicated thermal robustness of cationic hemicellulose diminished. More specifically, disruption of hydrogen bonds in the molecular chain and degradation of the molecular chain after quaternization are responsible, which represents a complementary conclusion to the molecular weight studies. Therefore, thermal properties further decreased with CH substitution. (3) The third stage from 400 to 600 °C coincides with a decrease in hemicellulose quality due to oxidation of organic matter; when the temperature reaches 600 °C, 35% of the residues are still present, which may be the quaternary ammonium salts from preparation of cationic hemicellulose or specimens that have not undergone degradation. In general, the thermal stability decreased with increasing DS, indicating that the number of CH backbone side chains has an inverse effect on thermal stability, a trend that fits well with past work (Kong et al., 2014; Wang et al., 2021). 3.4 Adsorption behavior of cationic hemicellulose on nanocellulose The role of unmodified hemicellulose in improving the tensile strength of nanocellulose composites has been previously reported (Lucenius et al., 2014). The QCM-D data for unmodified hemicellulose adsorbed on CNF in this study are shown in Figure S8 and can be used as a comparison with the work of others. Our research interest is the adsorption behavior of cationic hemicellulose on CNF. In order to test the hypothesis that the interaction is influenced by electrostatic force and structure, we investigated the interaction between cationic hemicellulose and CNF using QCM-D in pure water to determine the effects of DS, molecular weight and zeta potential on the surface properties of CNF. To facilitate comparison, the results of the adsorption of cationic hemicellulose on CNF-coated sensors are summarized in Table 3 . Figure 4 shows frequency changes monitored using QCM-D indicating the adsorption and desorption behavior occurring on the CNF-coated sensor. A decrease in resonance frequency due to the increase in mass indicates the introduced cationic hemicellulose is adsorbed on the CNF-coated quartz crystal sensor. By comparing the frequency changes, it is possible to assess the relative strength of the interaction between CNF and CH. The adsorption of cationic hemicelluloses on CNF increased with time, with the lower DS cationic hemicelluloses (less than 0.15) showing less variation in CH1 and CH2 frequencies, reaching maximum adsorption within one hour. Surprisingly, CH2 (DS=0.146) showed less adsorption than CH1 (DS=0.095). When molecular weights are similar, the lower the DS of CH (below 0.15), the more cationic hemicellulose molecules are required to compensate for the surface charge of the CNF surface, resulting in a greater adsorption capacity for the low-charge CH, which is consistent with previous work using SPR to study interactions (Wang et al., 2021). When the DS exceeded 0.15, the frequency changed and the adsorption amount started to show a large difference: CH3 and CH4 reached maximum adsorption at 110 min and 210 min, respectively. This may be due to electrostatic attractions, in which CH becomes positively charged and therefore the repulsive force between the negatively charged fibrils decreases resulting in a strong electrostatic attraction interaction. The slope of the F-curve shows that the adsorption rate increases with increasing DS, and the slope of the frequency change (∆F) in the graph shows that the adsorption rate is faster and then slower. The factors affecting the adsorption rate may be related to the zeta potential of the cationic hemicellulose: the larger the zeta potential, the lower the colloidal stability of the solution, and the easier it is to be attracted by the CNF; and secondly, the CNF itself is negatively charged, and has an affinity for the positively charged cationic hemicellulose. After reaching maximum adsorption, the reversible and loosely bound hemicellulose that was adsorbed on the CNF surface was eliminated by flushing the QCM-D chamber with mill-Q water. The partial adsorption between cationic hemicellulose and CNF was reversible, i.e., a weak interaction. Once the rinsing was over, the frequency no longer changed, indicating that the adsorption between the cationic hemicellulose and CNF had become irreversible. This irreversible adsorption is known as strong interaction. The results of QCM-D indicate that CH4 enhances a strong interaction with CNF in the aqueous state. Cationic starch (CS) is widely used as a papermaking chemical to improve paper retention and dry strength (Tammelin et al., 2004). Being also a cationized paper additive, the adsorption amount of cationic hemicellulose (CH3) on nanocellulose fibers was approximately 3.5 times higher than that of cationic starch (with similar degree of substitution and molecular weight). However, the time required to reach adsorption equilibrium was correspondingly longer for cationic hemicellulose (110 minutes), whereas cationic starch reached equilibrium adsorption in a shorter time (10 minutes). Although cationic hemicellulose has a stronger affinity for cellulose, it can be more efficiently used in the paper industry if its adsorption speed is faster. In addition, cationic hemicellulose with DS > 0.15 showed greater adsorption capacity and shorter adsorption equilibrium time compared with acetylation-modified xylan (Jaafar et al., 2019), arabinoxylan (Kohnke et al., 2011) and water-soluble xylan (Lyu et al., 2021) without chemically modification, which indicated that the appropriate modification method and DS could significantly improve the affinity of hemicellulose for cellulose microfibrils, and the modified hemicellulose had a better industrial utilization as chemicals. Comparing these three hemicelluloses with different side chain groups, the strength of their interaction with cellulose microfibrils also varies depending on their own structure. Although the conditions of this study are different from other studies, the factors affecting the affinity are the same, i.e., the structure is the main factor affecting the hemicellulose-cellulose interaction. However, the results in Table 3 show that the charged cationic hemicellulose significantly affects the strength of the interaction when DS > 0.15, so we believe that the charge is one of the important factors affecting the interaction, perhaps even more than the structure. As the electrostatic interaction is driven, it will have a very significant effect on the adsorption rate and adsorption amount of hemicellulose on the nanocellulose matrix as well as the adsorption equilibrium time, which verifies our hypothesis that the interaction between hemicellulose and cellulose is mainly influenced by the electrostatic and structural effects. Figure 5(a) shows dissipation variation, which can be further explained by monitoring the viscoelasticity of the adsorbed layer on the CNF-coated sensor (Voinova et al., 1999). The dissipation factor is defined as the ratio of dissipated energy to stored energy when an oscillatory stress is applied to the surface layer of the sensor, and the change in dissipation represents the structural change that occurs under stress, which is related to the stiffness of the adsorbed film. As shown in the graph, the dissipation factor increases with time due to the accumulation of a large amount of cationic hemicellulose on the surface of CNF, which increases the thickness of the adsorption layer. The change in dissipation corresponds to the change in frequency, and their trends are similar. To evaluate the viscoelasticity of the adsorbed layer on the CNF-coated sensor, the change in dissipation (ΔD) is plotted as a function of the change in frequency (ΔF) in Figure 5(b) . The viscoelastic properties are related to the slope of the resulting curve (∆D-∆F), which qualitatively shows a change in polymer conformation. The lower the slope, the stiffer the adsorbed layer is, while a steeper slope indicates that the adsorbed layer is softer and more mobile (Kohnke et al., 2011; Tammelin et al., 2006). This indicates that the cationic hemicellulose layer adsorbed on cellulose has a similar conformation regardless of the variation of DS. In addition, the degree of denseness and rigidity of the adsorbed layer changes accordingly as the adsorption of the adsorbed layer changes with rinse water. A lower slope indicates that the adsorbed layer is rigid. CH3 has a poor affinity for CNF, and compared to other cationic hemicelluloses, CH3 forms a softer (less dissipative) adsorption layer, which may be due to its greater water absorption. In addition, other researchers found by QCM-D that according to the molecular entanglement theory, the higher the molecular weight, the more entangled the molecular chains are, and the more water is adsorbed between the molecules, leading to greater adsorption (Tammelin et al., 2004; Yao et al., 2021). However, combining the experimental results of QCM-D and Molecular weight, the charge of hemicellulose was found to be more important than its molecular weight, similar to conclusions reached in previous studies (Kabel et al., 2007; Saarinen et al., 2009), which also indicates that the hemicellulose-cellulose adsorption behavior in QCM-D was mainly driven by electrostatic effects. Table 3 . Results of hemicellulose samples adsorbed on CNF surfaces in real-time quantitative QCM-D experiments and comparison with previous reports Hemicellulose Sample -∆F Max (Hz) ∆D MAX -∆F Irreversible (Hz) ∆D Irreversible Time Max （min） Hr 8 2.5 5 1.6 105 CH1(DS=0.095) 14 2.5 11 2 65 CH2(DS=0.146) 15 2.4 10 1.6 65 CH3(DS=0.201) 31 6.5 22 4 110 CH4(DS=0.254) 65 10 55 8 210 Cationic starch (DS=0.2) (Kontturi et al., 2008) - - 6.3 0.2 10 Acetylated xylan(Jaafar et al., 2019) 18 0.8 17 0.7 50 arabinoxylan(Kohnke et al., 2011) 16 3.5 15.5 3.4 200 water-soluble xylan(Lyu et al., 2021) 18 - 15 - 150 ∆Fmax and ∆Dmax represent the frequency and dissipation values when CH adsorption on the CNF surface reaches equilibrium, respectively, and ∆F Irreversible and ∆D Irreversible are the frequency and dissipation values for irreversible adsorption 3.5 Water contact angle test of QCM-D sensor surface before and after adsorption In order to characterize the morphology and hydrophilicity of the QCM-D sensors' surfaces before and after adsorption, we tested the static contact angles of the Silica-coated, CNF-coated, and CH4-treated sensors' surfaces, respectively, at room temperature. As shown in the Figure 6(d) , the untreated quartz crystal sensor surface has the strongest hydrophobicity at a static contact angle of about 95° due to the silica-coated surface ( Figure S9 ). After spin-coating the CNF, the sensor surface was almost completely and uniformly covered by the randomly oriented CNF as can be seen from Figure 6(a) , and the Ra was measured to be 4.88 nm ( Figure S10 ). The surface water contact angle was reduced to 36°, which is similar to the previous report (Mohan et al., 2014; Zhang et al., 2018), indicating that the CNF made the sensor surface much more hydrophilic. After the CNF-coated sensor adsorbed cationic hemicellulose, when a water droplet was placed on the surface of the sensor, the water droplet was quickly absorbed by the coating, which indicated that the coating had better hydrophilicity, as evidenced by the decrease in the surface contact angle. This may be because the adsorption of cationic hemicellulose on CNF affects the structure of the adsorption layer, and the amorphous CH4 changes the roughness of the sensor surface ( Figure 6(c) and Figure S11 ), which has an effect on the accessibility of the surface functional groups, so there is better hydrophilicity. Interestingly, this behavior is similar to the coating of hemicellulose on paper (Nechita et al., 2021). This suggests that the interaction between cationic hemicellulose and nanocellulose has an effect on the surface properties of nanocellulose, and this revelation may perhaps allow CH to be used as a coating agent for surface of paper or cellulosic membrane, which is the idea of high-value application of cationic hemicellulose. 3.6 Hemicellulose-cellulose composite film In order to speculate the role of hydrogen bonding in the interaction process, three different hemicelluloses, Hr, CH1, and CH4, were each mixed with CNF to make films with an average thickness of 50 μm, where the average maximum tensile stress strengths of the composite films ( Figure. 7(a )) were 27 MPa, 36 MPa, and 46 MPa, respectively, and the tensile strain curves are shown in Figure. 7(b) . The high mechanical properties of the hemicellulose-nanocellulose composite films are a result of the cationic hemicellulose which enhances the adhesion and mechanical properties of the fibrils by reducing the electrostatic repulsive force between the microfibrils. At the same time, the presence of CH interferes with the hydrogen bonding interactions between cellulose macromolecules. Amorphous cationic hemicellulose adsorbed on the cellulose surface promotes the penetration of water into the crystalline regions of the cellulose nanofibrils, leading to swelling and increasing the size of the nanofibrils, which alters the degree of interlacing between the fibrils and thus enhances the film-binding strength. In addition, cationic hemicellulose acted as a plasticizer to enhance the toughness of the composite film, and it can be speculated that it enhanced the dispersion of CNF during the film formation process, which is essential to avoid fibrils aggregation and defects in the composite film (Hu et al., 2022; Lucenius et al., 2014). As shown in the SEM image of the composite film ( Figure 7(a) ), hemicellulose acts as a binder to fill the voids between the cellulose fibrils to form a dense hemicellulose-nanocellulose composite film. Compared with Hr, the charged CH4 on the surface greatly increases the strength of the composite film. The combined action of the hydroxyl group (OH -) and the charged group in the cationic hemicellulose molecule results in more hydrogen bonds between the cellulose and hemicellulose, thus promoting the bonding between the fibrils and significantly improving the mechanical properties (Bai et al., 2012). In conclusion, the cationic hemicellulose significantly increased the tensile strength of the cellulose composite film or paper, similar to previous work (Hu et al., 2022; Kohnke et al., 2009; Wang et al., 2021) and corresponds to the experimental results of QCM-D. Figure 8 shows the process of cellulose chain strengthening by cationic hemicellulose, including microfibril swelling, electrostatic interaction and hydrogen bonding. Conclusions Cationic hemicelluloses with DS from 0.09 to 0.254 were synthesized by grafting 2,3-epoxypropyltrimethylammonium chloride (ETA) onto hemicelluloses isolated from eucalyptus wood. Cationic hemicellulose was adsorbed onto CNF-coated sensors using QCM-D. The positively charged group grafted hemicellulose improves the adsorption rate and adsorption volume while forming a stiffer and thicker adsorption layer than unmodified hemicellulose. The interaction between CH and CNF in the pure water state was mainly driven by electrostatics. Compared to natural hemicellulose, the addition of 15 wt% cationic hemicellulose (DS = 0.254) increased the maximum tensile stress strength of the hemicellulose-cellulose composite film by up to 71%. Cationic hemicellulose can increase the hydrogen bonding within the microfibrils thereby improving the strength of the composite films. In conclusion, these results validate the hypothesis in the introduction that the interaction between cationic hemicellulose and nanocellulose is influenced by the hemicellulose structure, electrostatic force and hydrogen bonding. This study may provide an idea for the high value utilization of nanocellulose and hemicellulose. Declarations Acknowledgements We thank the MCPF (Materials Characterization and Preparation Facility) of the Hong Kong University of Science and Technology (Guangzhou) for their contribution to the characterization of this work. Funding This work was supported by the National Natural Science Foundation of China (22078114), the National Key Research and Development Program (2021YFE0104500), Key Research and Development Program of Guangzhou Science and Technology Program (202103000011), and the Natural Science Foundation of Guangdong Province (2021A1515010360). Author Contributions Statement X.L.: performed the experiment, contributed significantly to data analyses and wrote the manuscript. S.F.: contributed to the conception of the study and manuscript revision. Y.K.: helped perform the preparation of samples. Competing interests The authors declare no competing interests. Confict of interest The authors declare no competing interests Availability of data and materials All data generated or analyzed during this study are included in this submitted article. Ethics approval and consent to participate All authors have consented to participate on the manuscript. 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Supplementary Files SupplementaryMaterial.docx Cite Share Download PDF Status: Published Journal Publication published 08 May, 2024 Read the published version in Cellulose → Version 1 posted Editorial decision: Revision requested 26 Jan, 2024 Reviews received at journal 11 Jan, 2024 Reviewers agreed at journal 28 Dec, 2023 Reviewers invited by journal 27 Dec, 2023 Editor assigned by journal 23 Dec, 2023 Submission checks completed at journal 23 Dec, 2023 First submitted to journal 21 Dec, 2023 You are reading this latest preprint version Research Square lets you share your work early, gain feedback from the community, and start making changes to your manuscript prior to peer review in a journal. As a division of Research Square Company, we’re committed to making research communication faster, fairer, and more useful. We do this by developing innovative software and high quality services for the global research community. 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Also discoverable on Platform About Our Team In Review Editorial Policies Advisory Board Help Center Resources Author Services Accessibility API Access RSS feed Manage Cookie Preferences © Research Square 2026 | ISSN 2693-5015 (online) Privacy Policy Terms of Service Do Not Sell My Personal Information {"props":{"pageProps":{"initialData":{"identity":"rs-3785502","acceptedTermsAndConditions":true,"allowDirectSubmit":false,"archivedVersions":[],"articleType":"Research Article","associatedPublications":[],"authors":[{"id":263772779,"identity":"93ad9f62-f6e4-4886-a8f4-5469bc7f597e","order_by":0,"name":"Xingyu LAN","email":"","orcid":"","institution":"South China University of Technology","correspondingAuthor":false,"submittingAuthor":false,"prefix":"","firstName":"Xingyu","middleName":"","lastName":"LAN","suffix":""},{"id":263772780,"identity":"31b25098-c475-4574-b387-a43b00dd75e3","order_by":1,"name":"Shiyu Fu","email":"data:image/png;base64,iVBORw0KGgoAAAANSUhEUgAAAZAAAAAyAQMAAABI0h/eAAAABlBMVEX///8AAABVwtN+AAAACXBIWXMAAA7EAAAOxAGVKw4bAAAAxklEQVRIiWNgGAWjYDACCQaGDwwVUA4PkVoYZzCcATLYSNLC2EaKFvnZPYbNvPPq5A3uNzA+eNvGIG9OSIvBnTNALdsOG244xsBsOLeNwXBnAyEtEjnmj3m3HUgwOMbAJs3bxpBgcICQw2bkAG2ZUwfSwv6bKC0MN0BaGpjBtjATpcXgRlph45xjhw1nHktslpxzTsJwA2GHJW9seFNTJ893+PDBD2/KbOQJO4yBwwDKYGxgACcGwoD9ATGqRsEoGAWjYCQDAGinPjgRehNVAAAAAElFTkSuQmCC","orcid":"","institution":"South China University of Technology","correspondingAuthor":true,"submittingAuthor":false,"prefix":"","firstName":"Shiyu","middleName":"","lastName":"Fu","suffix":""},{"id":263772781,"identity":"1204749b-0d8b-4918-9e92-5ca325b1c1e1","order_by":2,"name":"Yi Kong","email":"","orcid":"","institution":"South China University of Technology","correspondingAuthor":false,"submittingAuthor":false,"prefix":"","firstName":"Yi","middleName":"","lastName":"Kong","suffix":""}],"badges":[],"createdAt":"2023-12-21 07:44:25","currentVersionCode":1,"declarations":"","doi":"10.21203/rs.3.rs-3785502/v1","doiUrl":"https://doi.org/10.21203/rs.3.rs-3785502/v1","draftVersion":[],"editorialEvents":[{"content":"https://doi.org/10.1007/s10570-024-05926-5","type":"published","date":"2024-05-09T01:03:51+00:00"}],"editorialNote":"","failedWorkflow":false,"files":[{"id":48886960,"identity":"d70efc67-e16f-4957-af46-a14328671afc","added_by":"auto","created_at":"2023-12-28 06:01:08","extension":"png","order_by":1,"title":"Figure 1","display":"","copyAsset":false,"role":"figure","size":48159,"visible":true,"origin":"","legend":"\u003cp\u003eThe preparation of CNF and cationic hemicellulose from eucalyptus wood.\u003c/p\u003e","description":"","filename":"1.png","url":"https://assets-eu.researchsquare.com/files/rs-3785502/v1/647c089a2edbf373ba3eed84.png"},{"id":48887152,"identity":"ba453344-0b52-476e-8042-b77d38eb4cfb","added_by":"auto","created_at":"2023-12-28 06:09:08","extension":"jpg","order_by":2,"title":"Figure 2","display":"","copyAsset":false,"role":"figure","size":440573,"visible":true,"origin":"","legend":"\u003cp\u003e1H and 13C 2D HSQC spectra of water-soluble hemicellulose (a) and cationic hemicellulose (CH4) (b)\u003c/p\u003e\n\u003cp\u003eNumbering scheme for hemicellulose and side chain quaternary ammonium groups;\u003c/p\u003e\n\u003cp\u003enamed as follows: X, xylose unit; U, 4- O-methyl-α-D -glucuronide unit; Glc, glucose unit; QA, quaternary ammonium group.\u003c/p\u003e","description":"","filename":"Figure2.jpg","url":"https://assets-eu.researchsquare.com/files/rs-3785502/v1/c62d9af84cb98e7f100e6cf5.jpg"},{"id":48886963,"identity":"88ed4a94-865b-4306-bc7f-b8baeb5e529b","added_by":"auto","created_at":"2023-12-28 06:01:08","extension":"jpg","order_by":3,"title":"Figure 3","display":"","copyAsset":false,"role":"figure","size":45388,"visible":true,"origin":"","legend":"\u003cp\u003eTG (a) and DTG (b)curves for Cationic hemicellulose.\u003c/p\u003e","description":"","filename":"Figure3.jpg","url":"https://assets-eu.researchsquare.com/files/rs-3785502/v1/b77efbd9e494c0249ae296d0.jpg"},{"id":48886967,"identity":"7055fcd6-0404-43e7-bcb4-d83b8d115e39","added_by":"auto","created_at":"2023-12-28 06:01:08","extension":"jpg","order_by":4,"title":"Figure 4","display":"","copyAsset":false,"role":"figure","size":87989,"visible":true,"origin":"","legend":"\u003cp\u003eChange in frequency (3\u003csup\u003erd\u003c/sup\u003e overtone) as a function of time when CH is adsorbed on the CNF-coated sensor surface.\u003c/p\u003e","description":"","filename":"Figure4.jpg","url":"https://assets-eu.researchsquare.com/files/rs-3785502/v1/ac77f2101b20b4ad5506ef9f.jpg"},{"id":48886961,"identity":"96def786-e83b-4d17-83f8-7e9217e57cd0","added_by":"auto","created_at":"2023-12-28 06:01:08","extension":"jpg","order_by":5,"title":"Figure 5","display":"","copyAsset":false,"role":"figure","size":40691,"visible":true,"origin":"","legend":"\u003cp\u003e\u003cstrong\u003e(a)\u003c/strong\u003e change of dissipation (3\u003csup\u003erd\u003c/sup\u003e overtone) with time when CH is adsorbed on the surface of the CNF-coated sensor surface,\u003cstrong\u003e (b)\u003c/strong\u003e change of dissipation value as a function of frequency change.\u003c/p\u003e","description":"","filename":"Figure5.jpg","url":"https://assets-eu.researchsquare.com/files/rs-3785502/v1/92c74b6a9bbeff9fa3ea59d7.jpg"},{"id":48886966,"identity":"e173b092-f5c0-48f5-af1f-87da66197945","added_by":"auto","created_at":"2023-12-28 06:01:08","extension":"jpg","order_by":6,"title":"Figure 6","display":"","copyAsset":false,"role":"figure","size":2396567,"visible":true,"origin":"","legend":"\u003cp\u003eMorphology of the sensor chip before and after adsorption (a) CNF-coated sensor surface; (b) CH1-treated sensor surface; (c) CH4-treated sensor surface. (d) Contact angles of water droplets on silica-coated, CNF-coated and CH4-treatd QCM-D sensor surfaces at 25 °C, respectively.\u003c/p\u003e","description":"","filename":"Figure6.jpg","url":"https://assets-eu.researchsquare.com/files/rs-3785502/v1/97cfd2e7eb7aa991e215f06d.jpg"},{"id":48887779,"identity":"6e21955d-1d1e-416f-a9dc-dffd26a69c7d","added_by":"auto","created_at":"2023-12-28 06:17:08","extension":"jpg","order_by":7,"title":"Figure 7","display":"","copyAsset":false,"role":"figure","size":1134390,"visible":true,"origin":"","legend":"\u003cp\u003e\u003cstrong\u003e(a) \u003c/strong\u003eTensile properties of hemicellulose - nanocellulose composite films; \u003cstrong\u003e(b) \u003c/strong\u003eTensile-strain curves of hemicellulose-nanocellulose composite films; \u003cstrong\u003e(c)\u003c/strong\u003e SEM images of the surfaces of CNF+Hr (i), CNF+CH1(ii) and CNF+CH4 (iii) composite films, respectively.\u003c/p\u003e","description":"","filename":"Figure7.jpg","url":"https://assets-eu.researchsquare.com/files/rs-3785502/v1/83c0db852f8fd097e3542b9e.jpg"},{"id":48887154,"identity":"9cac33a8-62b3-44de-98d8-cd91197840ed","added_by":"auto","created_at":"2023-12-28 06:09:09","extension":"jpg","order_by":8,"title":"Figure 8","display":"","copyAsset":false,"role":"figure","size":139721,"visible":true,"origin":"","legend":"\u003cp\u003eSchematic process of adsorption of cationic hemicellulose on cellulose during composite film formation.\u003c/p\u003e","description":"","filename":"Figure8.jpg","url":"https://assets-eu.researchsquare.com/files/rs-3785502/v1/8fb6d75a65b43ab04f1825cb.jpg"},{"id":56210155,"identity":"4bacb2c2-4b51-40d0-843c-5266d020f246","added_by":"auto","created_at":"2024-05-10 01:04:00","extension":"pdf","order_by":0,"title":"","display":"","copyAsset":false,"role":"manuscript-pdf","size":1802909,"visible":true,"origin":"","legend":"","description":"","filename":"manuscript.pdf","url":"https://assets-eu.researchsquare.com/files/rs-3785502/v1/5834303d-9ff4-4033-8a8f-f9b1d6a0628f.pdf"},{"id":48886968,"identity":"bd99267c-e31f-4047-96ef-eee070455c67","added_by":"auto","created_at":"2023-12-28 06:01:08","extension":"docx","order_by":1,"title":"","display":"","copyAsset":false,"role":"supplement","size":3330217,"visible":true,"origin":"","legend":"","description":"","filename":"SupplementaryMaterial.docx","url":"https://assets-eu.researchsquare.com/files/rs-3785502/v1/f392a3a20e345affb8658630.docx"}],"financialInterests":"No competing interests reported.","formattedTitle":"A new recognition of the binding of cellulose fibrils in papermaking by probing interaction between nanocellulose and cationic hemicellulose","fulltext":[{"header":"Highlights","content":"\u003cul\u003e\n \u003cli\u003eThe interfacial interaction between CH and CNF was investigated by QCM-D\u003c/li\u003e\n \u003cli\u003eElectrostatic forces reinforce the adsorption of CH on the surface of the CNF matrix.\u003c/li\u003e\n \u003cli\u003eStrong interactions between CNF and CH can improve film performance\u003c/li\u003e\n \u003cli\u003eThe reinforcing agent CH facilitates the bonding of nanofibrils. \u0026nbsp;\u003c/li\u003e\n\u003c/ul\u003e"},{"header":"1. Introduction","content":"\u003cp\u003eHemicellulose is an important biomass polysaccharide in nature, accounting for 20.00%~30.00% of plant biomass, with an annual global production of about 60\u0026nbsp;billion tons, second only to cellulose(Al Manasrah et al., \u003cspan citationid=\"CR1\" class=\"CitationRef\"\u003e2012\u003c/span\u003e; Rao et al., \u003cspan citationid=\"CR44\" class=\"CitationRef\"\u003e2023\u003c/span\u003e). Structurally, hemicellulose is a series of biopolymers composed of various monosaccharides, including xylose, glucose, arabinose, galactose, and mannose, mostly in branched chain structure (Jin et al., \u003cspan citationid=\"CR20\" class=\"CitationRef\"\u003e2022\u003c/span\u003e). Among the various hemicelluloses, xylan is predominant in hardwoods and grass families, while glucomannan mainly occurs in softwoods. Hemicellulose is a very complex component of plant cell walls and is difficult to utilize in a simple way. However, it has many advantages such as cheap and easy to obtain, solubility, degradability and low pollution, which are of great significance in solving the energy and environmental problems faced by all mankind.\u003c/p\u003e \u003cp\u003eIn the pulp and paper industry, the presence of hemicellulose may affect the properties of paper such as strength, opacity, etc. Natural/modified hemicellulose as a paper additive can improve the mechanical properties of paper, including tensile index, fracture index and tear index (Hu et al., \u003cspan citationid=\"CR15\" class=\"CitationRef\"\u003e2016\u003c/span\u003e). The utilization of hemicellulose as a pulping agent (Sehaqui et al., \u003cspan citationid=\"CR51\" class=\"CitationRef\"\u003e2013\u003c/span\u003e; Silva et al., \u003cspan citationid=\"CR54\" class=\"CitationRef\"\u003e2011\u003c/span\u003e), retention aid (Soliman et al., \u003cspan citationid=\"CR55\" class=\"CitationRef\"\u003e1997\u003c/span\u003e), and wet-end additive (Kong et al., \u003cspan citationid=\"CR24\" class=\"CitationRef\"\u003e2018\u003c/span\u003e) has been the subject of extensive research for a considerable period. In addition, hemicellulose and its derivatives show exciting properties in nanocellulose composites. For example, it can be used as a binding agent for nanocellulose-based biomaterials for 3D printing of packaging, nutraceuticals, tissue engineering or wound dressings (Yang et al., \u003cspan citationid=\"CR60\" class=\"CitationRef\"\u003e2020\u003c/span\u003e). The utilization of biomimetic inks, which are composed of cross-linkable xylan and cellulose nanofibers (CNF), allows for the personalized design of clothing, furniture, and electronics (Markstedt et al., \u003cspan citationid=\"CR37\" class=\"CitationRef\"\u003e2017\u003c/span\u003e). Inspired by cellulose-xyloglucan (XG) interactions in plant cell walls, tough cellulose-XG nanocomposite foams were prepared with superior mechanical properties than other nanocellulose composites previously reported in the literature with comparable densities (Sehaqui et al., \u003cspan citationid=\"CR50\" class=\"CitationRef\"\u003e2010\u003c/span\u003e). Hemicellulose was introduced into CNF by in situ adsorption and pre-adsorption to enhance the structural and mechanical properties of cellulose hydrogels used for wound healing and showed high efficacy in the growth and proliferation of fibroblasts (NIH 3T3) (Shavandi et al., \u003cspan citationid=\"CR52\" class=\"CitationRef\"\u003e2020\u003c/span\u003e).\u003c/p\u003e \u003cp\u003eDespite the desirable utilization properties of hemicellulose in paper/cellulose composites, the actual interaction between hemicellulose and cellulose is a key process in the formation of paper/cellulose materials. The surface of cellulose fiber/nanocellulose is slightly negatively charged due to the introduction of carboxyl groups during pulping, bleaching and preparation of nanocellulose (Bohrn et al., \u003cspan citationid=\"CR6\" class=\"CitationRef\"\u003e2006\u003c/span\u003e; Jiang \u0026amp; Hsieh, \u003cspan citationid=\"CR18\" class=\"CitationRef\"\u003e2013\u003c/span\u003e; Zhao et al., \u003cspan citationid=\"CR65\" class=\"CitationRef\"\u003e2022\u003c/span\u003e) and therefore leads to inter-electrostatic repulsions with hemicellulose (Odabas et al., \u003cspan citationid=\"CR40\" class=\"CitationRef\"\u003e2016\u003c/span\u003e), thus weakening the interaction between natural hemicellulose and cellulose. Therefore, chemically modified cationic hemicellulose came into being. It is an important etherified derivative of hemicellulose with a simple preparation process and good water solubility and biodegradability (Chen et al., \u003cspan citationid=\"CR7\" class=\"CitationRef\"\u003e2016\u003c/span\u003e; Postma et al., \u003cspan citationid=\"CR43\" class=\"CitationRef\"\u003e2014\u003c/span\u003e). It is widely used in papermaking additives, strength agents, flocculants and composite membranes (Kong et al., \u003cspan citationid=\"CR24\" class=\"CitationRef\"\u003e2018\u003c/span\u003e; Liu et al., \u003cspan citationid=\"CR32\" class=\"CitationRef\"\u003e2011a\u003c/span\u003e; Ren et al., \u003cspan citationid=\"CR45\" class=\"CitationRef\"\u003e2007\u003c/span\u003e; Wang et al., \u003cspan citationid=\"CR59\" class=\"CitationRef\"\u003e2021\u003c/span\u003e). In fact, cationic hemicellulose enhances its adsorption on the surface of the \"anionic\" nanocellulose through the attractive force of electrostatic interaction (Bai et al., \u003cspan citationid=\"CR3\" class=\"CitationRef\"\u003e2012\u003c/span\u003e; Schwikal et al., \u003cspan citationid=\"CR48\" class=\"CitationRef\"\u003e2006\u003c/span\u003e) .\u003c/p\u003e \u003cp\u003eIndeed, there are several key research efforts with respect to the interaction between cationic/natural hemicellulose and the cellulose fiber. Kohnke et al. conducted experiments using three different methods (COD, carbohydrate analysis, and iodine complexation) and observed a significant improvement in the adsorption rate and amount of adsorption (Kohnke et al., \u003cspan citationid=\"CR22\" class=\"CitationRef\"\u003e2009\u003c/span\u003e). Kong et al. added 2.4 wt.% of cationic xylan with a DS of 0.32 to the pulp, resulting in a 63% increase in the tensile index, a 58% increase in the tear index, and a 42% increase in the bursting index (Kong et al., \u003cspan citationid=\"CR24\" class=\"CitationRef\"\u003e2018\u003c/span\u003e). Hu et al. discovered that the maximum absorption of cationic hemicellulose in eucalyptus and pine pulp was 40% and 47% higher, respectively, compared to unmodified hemicellulose (Hu et al., \u003cspan citationid=\"CR14\" class=\"CitationRef\"\u003e2015\u003c/span\u003e).\u003c/p\u003e \u003cp\u003eIn the latest research progress, the molecular dynamics simulation described in molecular level the interaction of hemicellulose-cellulose (Kong et al., \u003cspan citationid=\"CR26\" class=\"CitationRef\"\u003e2022\u003c/span\u003e; Zhang et al., \u003cspan citationid=\"CR62\" class=\"CitationRef\"\u003e2015\u003c/span\u003e). The mentioned above methods can only detect the end product after interaction but failed to monitor the adsorption process in real time. For cellulose and hemicellulose, the actual mass change during adsorption is minimal and difficult to detect. Furthermore, due to their complex structures, analyzing the reasons for differences in adsorption is also challenging. QCM-D is an efficient mass-sensing technique based on the piezoelectric properties of quartz crystals. In fact, it can provide information about the mass adsorbed on the surface as well as the mechanical behavior of the layer through the measurement of the dissipation factor. QCM-D can also be used in conjunction with surface plasmon resonance (SPR) (Liu et al., \u003cspan citationid=\"CR33\" class=\"CitationRef\"\u003e2011b\u003c/span\u003e) or AFM colloid probe microscopy (CPM) (Eronen et al., \u003cspan citationid=\"CR11\" class=\"CitationRef\"\u003e2012\u003c/span\u003e) to cross-validate interaction results. A study utilizing QCM-D investigated the impact of hemicellulose composition and content on the interactions between CNFs. The results revealed that the strength of these interactions varied depending on the composition of hemicellulose (Kumagai \u0026amp; Endo, \u003cspan citationid=\"CR28\" class=\"CitationRef\"\u003e2021\u003c/span\u003e). The influence of various factors such as substitution pattern, molecular weight, and structure of unmodified hemicellulose, as well as adsorption conditions, has been extensively studied using QCM-D (Hatton et al., \u003cspan citationid=\"CR13\" class=\"CitationRef\"\u003e2017\u003c/span\u003e; Jaafar et al., \u003cspan citationid=\"CR17\" class=\"CitationRef\"\u003e2019\u003c/span\u003e; Kumagai \u0026amp; Endo, \u003cspan citationid=\"CR28\" class=\"CitationRef\"\u003e2021\u003c/span\u003e; Lee et al., \u003cspan citationid=\"CR29\" class=\"CitationRef\"\u003e2015\u003c/span\u003e; Lyu et al., \u003cspan citationid=\"CR36\" class=\"CitationRef\"\u003e2021\u003c/span\u003e; Markstedt et al., \u003cspan citationid=\"CR37\" class=\"CitationRef\"\u003e2017\u003c/span\u003e; Yao et al., \u003cspan citationid=\"CR61\" class=\"CitationRef\"\u003e2021\u003c/span\u003e). However, there are fewer studies on the interaction of cationic hemicelluloses from the nanoscale. In this particular study, nanocellulose was employed as a simulation of the microfibrils present on the surface of pulp. The main objective was to investigate the adsorption of cationic hemicellulose, utilized as a wet-end additive in papermaking, onto the nanocellulose matrix. The study aimed to gain a deeper understanding of the underlying mechanism behind the interaction between cationic hemicellulose and nanocellulose.\u003c/p\u003e \u003cp\u003eBased on the above considerations, we hypothesized that the interaction between cationic hemicellulose and nanocellulose is mainly influenced by the electrostatic forces, but also driven by structure and hydrogen bonding. To test this hypothesis, hemicellulose was grafted with cationic groups and the real-time adsorption behavior of cationic hemicellulose on nanocellulose matrix was quantitatively monitored by QCM-D. The mechanical properties of composite films made from hemicellulose and nanocellulose were prepared and measured, and the reinforcing mechanism of cationic hemicellulose in nanocellulose composites was investigated.\u003c/p\u003e"},{"header":"2. Experiment","content":"\u003cdiv id=\"Sec3\" class=\"Section2\"\u003e\n \u003ch2\u003e2.1 Materials and separation\u003c/h2\u003e\n \u003cp\u003eEucalyptus chips (3cm * 5cm * 2cm) were donated by Juntai Paper Co., Ltd., Hunan Province, China. Eucalyptus chips are pulped by the sulfate method. Hemicellulose was extracted from unbleached eucalyptus pulp with 2M KOH for 24 h, showed in (Fig.\u0026nbsp;\u003cspan class=\"InternalRef\"\u003e1\u003c/span\u003e). The solid was retained for CNF preparation after bleaching, and the liquid for hemicellulose was neutralized with 6M acetic acid to pH 5.5 and centrifuged at 5000 rpm. The precipitate was separated as a water-insoluble hemicellulose (Small amount, ignored). The supernatant was precipitated by adding the volume of 95% ethanol, and then centrifuged and freeze-dried to obtain water-soluble hemicellulose (Hr).\u003c/p\u003e\n \u003cp\u003e0.375 g of water-soluble hemicellulose was dispersed in 45 mL of deionized water containing 0.24 g of sodium hydroxide and stirred for 30 min. Then an amount of 2,3-epoxypropyltrimethylammonium chloride (ETA) was added and the molar ratio of ETA to hemicellulose (xylose unit) varied from 1.0 to 4.0 to obtain cationic hemicellulose with different degrees of substitution. Then 0.36 g of sodium hydroxide was added and stirred at 60\u0026deg;C for 6 h. After reaction, the reactants were neutralized with 2.5 mol/L hydrochloric acid and then precipitated with three times the volume of 95% ethanol, and the precipitate was washed with 75% ethanol and freeze-dried (Hu et al., \u003cspan class=\"CitationRef\"\u003e2015\u003c/span\u003e).\u003c/p\u003e\n \u003cp\u003eThe eucalyptus pulp was extracted by 2M KOH and bleached, and its main chemical component was cellulose (97%), while the hemicellulose content was 3%. Cellulose nanofibrils (CNF) were prepared by pretreating eucalyptus pulp with 55 wt% sulfuric acid at 45\u0026deg;C for 40 min, followed by high-pressure homogenization. The acid hydrolysis pretreatment made the pulp fibers easier to be stripped of CNFs and had a higher yield when mechanically processed by high-pressure homogenization (Peng et al., \u003cspan class=\"CitationRef\"\u003e2019\u003c/span\u003e). The length of CNF varies from 40 to 1200 nm, while the diameter is 10\u0026ndash;30 nm and its surface zeta potential is \u0026minus;\u0026thinsp;36 mV. CNF prepared by the sulfuric acid pretreatment method leads to esterification of fibrils surfaces, which results in negatively charged sulfuric acid groups on these cellulose surfaces. CNF suspensions (1% w/v) can be used after dilution to various concentrations (0.1\u0026ndash;0.8 wt%).\u003c/p\u003e\n\u003c/div\u003e\n\u003cdiv id=\"Sec4\" class=\"Section2\"\u003e\n \u003ch2\u003e2.2 Chemical composition and structural analysis\u003c/h2\u003e\n \u003cdiv id=\"Sec5\" class=\"Section3\"\u003e\n \u003ch2\u003e2.2.1 Chemical composition analysis\u003c/h2\u003e\n \u003cp\u003eHemicellulose was hydrolyzed with 4% H\u003csub\u003e2\u003c/sub\u003eSO\u003csub\u003e4\u003c/sub\u003e at 121\u0026deg;C for 2 h. After the reaction, the hydrolytes were cooled and filtered through a G4 glass filter. The concentration of soluble lignin in the filtrate was determined by UV absorbance at 205 nm, and the solid in the glass filter was dried to a constant weight at 105\u0026deg;C and weighed as insoluble lignin (klason lignin) (Bhagia et al., \u003cspan class=\"CitationRef\"\u003e2016\u003c/span\u003e; Luo et al., \u003cspan class=\"CitationRef\"\u003e2023\u003c/span\u003e). The filtrate was neutralized with calcium carbonate to pH 6\u0026thinsp;~\u0026thinsp;7, diluted a certain number of times, filtered through 0.22\u0026micro;m aqueous membrane for carbohydrate analysis by high-performance anion-exchange chromatography (HPAEC) (Dionex ICS-3000, USA) with pulsed amperometric detection, a CarboPac\u0026trade; PA20 column (3 mm \u0026times; 150 mm) and a CarboPac\u0026trade; Guard column (3 mm \u0026times; 30 mm) (Hu et al., \u003cspan class=\"CitationRef\"\u003e2015\u003c/span\u003e; Shi et al., \u003cspan class=\"CitationRef\"\u003e2013\u003c/span\u003e).\u003c/p\u003e\n \u003c/div\u003e\n\u003c/div\u003e\n\u003cdiv id=\"Sec6\" class=\"Section2\"\u003e\n \u003ch2\u003e2.2.2 Elemental analysis\u003c/h2\u003e\n \u003cp\u003eThe nitrogen and carbon content of cationic hemicellulose was determined using an Element UNICUBE elemental analyzer. The degree of substitution (DS) of cationic hemicellulose was calculated using the following equation, where N% and C% are the nitrogen and carbon content, respectively (Schwikal et al., \u003cspan class=\"CitationRef\"\u003e2006\u003c/span\u003e; Schwikal et al., \u003cspan class=\"CitationRef\"\u003e2011\u003c/span\u003e).\u003c/p\u003e\n \u003cdiv id=\"Equa\" class=\"Equation\"\u003e\n \u003cdiv class=\"mathdisplay\" id=\"FileID_Equa\" name=\"EquationSource\"\u003e$$\\text{D}\\text{S}=\\frac{60\\times N\\left(\\%\\right)}{14\\times C\\left(\\%\\right)-72\\times N\\left(\\%\\right)}$$\u003c/div\u003e\n \u003c/div\u003e\n\u003c/div\u003e\n\u003cdiv id=\"Sec7\" class=\"Section2\"\u003e\n \u003ch2\u003e2.2.3 Molecular weight\u003c/h2\u003e\n \u003cp\u003eThe molecular weight of hemicellulose was determined using gel permeation chromatography (GPC) (Agilent PL-GPC50 system). The chromatographic column was equipped with a Shodex (Tokyo, Japan) i-101 refractive index detector; the temperature of the chromatographic column was 30 ℃, and the mobile phase was ultrapure water; the molecular weights of PEG as the standard samples were 305000, 242400, 24470, 17800, and 12000 g/mol, respectively.\u003c/p\u003e\n\u003c/div\u003e\n\u003cdiv id=\"Sec8\" class=\"Section2\"\u003e\n \u003ch2\u003e2.2.4 Zeta potential\u003c/h2\u003e\n \u003cp\u003eThe zeta potential was measured with a Malvern Zetasizer Nano ZS90. The samples were dissolved in deionized water at a concentration of 1 mg/ml.\u003c/p\u003e\n\u003c/div\u003e\n\u003cdiv id=\"Sec9\" class=\"Section2\"\u003e\n \u003ch2\u003e2.2.5 Nuclear magnetic resonance analysis\u003c/h2\u003e\n \u003cp\u003e\u003csup\u003e1\u003c/sup\u003eH-13C HSQC was performed on a BRUKER AVANCE NEO 500M spectrometer with 36 mg of hemicellulose dissolved in 55 \u0026micro;L of D\u003csub\u003e2\u003c/sub\u003eO. The spectral widths were 11 ppm, 2048 data points for hydrogen dimension F2 (\u003csup\u003e1\u003c/sup\u003eH) and 190 ppm, 256 data points for carbon dimension F1 (\u003csup\u003e13\u003c/sup\u003eC); 128 scans (NS) with an inter-scan delay (D1) of 1 second. All data processing was done with MestReNova software (Ding et al., \u003cspan class=\"CitationRef\"\u003e2019\u003c/span\u003e).\u003c/p\u003e\n\u003c/div\u003e\n\u003cdiv id=\"Sec10\" class=\"Section2\"\u003e\n \u003ch2\u003e2.2.6 Thermal stability\u003c/h2\u003e\n \u003cp\u003eThe cationic hemicellulose was analyzed using a TG209F1 thermogravimetric analyzer from NETZSCH, Germany, with a protective gas of nitrogen, a ramp-up rate of 10\u0026deg;C/min, and a measurement range of 40\u0026ndash;600\u0026deg;C.\u003c/p\u003e\n\u003c/div\u003e\n\u003cdiv id=\"Sec11\" class=\"Section2\"\u003e\n \u003ch2\u003e2.3 Interaction analysis by QCM-D\u003c/h2\u003e\n \u003cp\u003eAccording to a previous study (Liu et al., \u003cspan class=\"CitationRef\"\u003e2021\u003c/span\u003e), CNF-coated sensors were prepared by spin-coating method. Prior to spin coating, the QCM-D sensors with silica surface were immersed in sodium dodecyl sulfate solution (2%) for at least 30 min for cleaning, rinsing with milli-Q grade water and drying with nitrogen. The QCM-D sensors were subjected to a 30-minute treatment with an ozone-activated UV cleaner to oxidize impurities and activate the surfaces\u0026apos; silicon hydroxyl groups. The treated QCM-D sensors were then immersed in a 100 mg/L polyethyleneimine (PEI) solution for 30 minutes, rinsed with mill-Q water, and blown dry with mild nitrogen. CNF suspension (0.2 wt%) was then spin-coated onto the sensor with the pre-adsorbed PEI layer at 3000 rpm. Thereafter, the sensors were placed in an oven at 60\u0026deg;C for 2h and stored in a desiccator.\u003c/p\u003e\n \u003cp\u003eAqueous solutions of different DS cationic hemicelluloses (100 mg/L) were prepared before the experiments. The QCM-D E4 (Biolin Science Ltd., Sweden) was used to monitor the frequency and dissipation changes of the 5 MHz fundamental resonant frequency as well as the 3rd, 5th, 7th, 9th and 11th overtones. The experiments were performed at 25\u0026deg;C. The CNF-coated sensors were installed in the QCM-D chambers and then milli-Q water was passed at a rate of 0.1 mL/min to stabilize the films. After stabilizing the QCM-D system, cationic cellulose solution was introduced into the four chambers. Once adsorption reached equilibrium, a rinse with Milli-Q water was performed to remove loosely bound layers. Each experiment was repeated at least three times (Zhang et al., \u003cspan class=\"CitationRef\"\u003e2020\u003c/span\u003e).\u003c/p\u003e\n\u003c/div\u003e\n\u003cdiv id=\"Sec12\" class=\"Section2\"\u003e\n \u003ch2\u003e2.4 Water contact angle and AFM morphology characterization of sensor surfaces\u003c/h2\u003e\n \u003cp\u003eUsing an OCA15 20 contact angle meter, 12 \u0026micro;L of ultrapure water is pressed out with a micro syringe at one atmosphere and 50% air humidity, and the carrier table is slowly raised to touch the droplet hanging from the lower end of the syringe so that the droplet remains on the surface of the QCM-D sensor surface. After it equilibrates in air for 1 min, a baseline is selected, the droplet profile is detected, and the contact angle is calculated by the SCA20 software program.\u003c/p\u003e\n \u003cp\u003eAFM (Bruker Dimension Icon) was used to observe the morphological characteristics of the QCM-D sensor surface before and after hemicellulose adsorption. The samples before and after the QCM-D experiment were tested using the tap mode with a scanning frequency of 0.5 Hz.\u003c/p\u003e\n\u003c/div\u003e\n\u003cdiv id=\"Sec13\" class=\"Section2\"\u003e\n \u003ch2\u003e2.5 Preparation and characterization of hemicellulose-cellulose composite films\u003c/h2\u003e\n \u003cp\u003eThe composite films were prepared by casting method. 72 mg hemicellulose was added to 50 g CNF suspension (0.8%) and stirred in constant temperature water at 55\u0026deg;C for 1 h, followed by stirring at room temperature for 2 h under magnetic stirring. The mixture was poured into Petri dishes of 10 cm diameter while keeping the total mass of each sample film in each compartment the same, and dried at room temperature until they could be peeled off. The films were stored in standard ambient (T\u0026thinsp;=\u0026thinsp;23\u0026deg;C, relative humidity\u0026thinsp;=\u0026thinsp;50%) conditions for 48 h. The thickness of the films was determined by a sheet thickness meter (Lorentzen \u0026amp; Wettre, accuracy to 1 \u0026micro;m) and 5 different areas were measured for each sample and averaged. The mechanical properties were tested on an INSTRON 3300, and the size of the laminated film used for the tensile test was 50 mm x 10 mm. The tensile curve was measured at a tensile speed of 5 mm/min and the tensile force was recorded using a 500 N load cell, with a minimum of 8 strips tested per sample to obtain the average tensile strength.\u003c/p\u003e\n\u003c/div\u003e"},{"header":"3. Results and Discussion","content":"\u003cp\u003e\u003cstrong\u003e3.1 Characterization of hemicellulose and its derivatives\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eThe type of hemicellulose used in this paper is mainly xylan, and water-soluble hemicellulose was deliberately prepared, firstly, to facilitate various characterizations, and secondly, because its higher yield facilitates cationic modification. The water-soluble hemicellulose (Hr) was hydrolyzed and analyzed with ion chromatography. It revealed that xylose accounted for 84.9% of carbohydrates in the hydrolyte; thus, it is the main polysaccharide component. There are also some minor components, such as galactose, glucose and glucuronic acid accounting for 1.62%, 1.78% and 4.78%, respectively. In addition, the amount of lignin (6.07%) was detected in the Hr sample, which may contribute to cross-linking of lignin with hemicellulose for a lignin-carbohydrate complex (LCC). During the extraction of hemicellulose from unbleached pulp through alkali treatment, lignin inevitably remained in the prepared hemicellulose, resulting in a darker color (Geng et al., 2019; Liu et al., 2016). \u0026nbsp;In the FTIR spectra of cationic hemicellulose after multiple purifications (\u003cstrong\u003eFigure S7\u003c/strong\u003e), the typical aromatic ring vibration-related peaks of lignin were not observed between 1600 and 1500 cm\u003csup\u003e-1\u003c/sup\u003e.(Postma et al., 2014) \u0026nbsp;\u003c/p\u003e\n\u003cp\u003eIn the present work, hemicellulose was modified with different ratio of ETA as observed in (\u003cstrong\u003eTable 1\u003c/strong\u003e). The degree of substitution of cationic hemicellulose increases with molar ratio of ETA to hemicellulose (0.095 to 0.254). If microwave heating is used to assist in the reaction, DS can go to 0.54 (Peng et al., 2012). Cationic hemicellulose is often used as a paper reinforcing agent in the paper industry, and it has been found that the optimal DS range for cationic hemicellulose is 0.1 to 0.3 to improve the tensile and tear strength of paper (Deutschle et al., 2014; Rena et al., 2009; Schwikal et al., 2011).\u0026nbsp;\u003c/p\u003e\n\u003cp\u003eThe molecular weight of hemicellulose may affect not only the adsorption behavior of hemicellulose on a cellulose surface, but the adsorption level and the conformation of the adsorbed layer\u0026nbsp;(Yao et al., 2021). The Mw of Hr was 91,000 g/mol, while the molecular weights of CH1 and CH2 after cationization modification were very similar, 110,000 and 109,000 g/mol, respectively. The slight increase in Mw could be attributed to the relatively mild etherification modification reaction, the relatively small amount of ETA, and the fact the main chain of hemicellulose was not degraded and grafted with quaternary ammonium groups. As the molar ratio of ETA to hemicellulose increased, the degree of substitution increased and the Mw decreased to 62,600 g/mol and 59,412 g/mol for CH3 and CH4, respectively. when the concentration of ETA was too high, it leads to degradation of the hemicellulose molecular chain and side reactions, which lead to molecular weight decreases. The molecular weight distribution curves can be found in the GPC chromatographic profiles (\u003cstrong\u003eFigure S2 ~ Figure S6\u003c/strong\u003e).\u0026nbsp;\u003c/p\u003e\n\u003cp\u003eThe zeta potential of an aqueous solution of hemicellulose was tested, which was -19.7 mV, likely due to the presence of glucuronide groups (Jiang et al., 2014). The zeta potential of the aqueous cationic hemicellulose solution increased significantly with increasing DS due to the grafting of positively charged quaternary ammonium groups by cationic hemicellulose.\u0026nbsp;\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eTable 1.\u0026nbsp;\u003c/strong\u003eChemical properties of native/cationic hemicellulose with different DS.\u003c/p\u003e\n\u003ctable border=\"0\" cellspacing=\"0\" cellpadding=\"0\" align=\"\" width=\"666\"\u003e\n \u003ctbody\u003e\n \u003ctr\u003e\n \u003ctd width=\"14.414414414414415%\" rowspan=\"2\" valign=\"top\"\u003e\n \u003cp\u003eHemicellulose\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"14.114114114114114%\" rowspan=\"2\" valign=\"top\"\u003e\n \u003cp\u003eMolar ratio\u003c/p\u003e\n \u003cp\u003eETA: anhydroxylose\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"8.85885885885886%\" rowspan=\"2\" valign=\"top\"\u003e\n \u003cp\u003eN%\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"8.85885885885886%\" rowspan=\"2\" valign=\"top\"\u003e\n \u003cp\u003eC%\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"9.15915915915916%\" rowspan=\"2\" valign=\"top\"\u003e\n \u003cp\u003eDS\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"34.83483483483484%\" colspan=\"3\" valign=\"top\"\u003e\n \u003cp\u003eMolecular weights (g/mol)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"9.75975975975976%\" rowspan=\"2\" valign=\"top\"\u003e\n \u003cp\u003eZeta（mV）\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd width=\"35.3448275862069%\" valign=\"top\"\u003e\n \u003cp\u003eMw\u003c/p\u003e\n \u003cp\u003e\u0026nbsp;\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"34.91379310344828%\" valign=\"top\"\u003e\n \u003cp\u003eMn\u003c/p\u003e\n \u003cp\u003e\u0026nbsp;\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"29.74137931034483%\" valign=\"top\"\u003e\n \u003cp\u003eMw/Mn\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd width=\"14.414414414414415%\" valign=\"top\"\u003e\n \u003cp\u003eHr\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"14.114114114114114%\" valign=\"top\"\u003e\n \u003cp\u003e-\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"8.85885885885886%\" valign=\"top\"\u003e\n \u003cp\u003e-\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"8.85885885885886%\" valign=\"top\"\u003e\n \u003cp\u003e-\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"9.15915915915916%\" valign=\"top\"\u003e\n \u003cp\u003e0\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"12.312312312312311%\" valign=\"top\"\u003e\n \u003cp\u003e9.11⨯10\u003csup\u003e4\u003c/sup\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"12.162162162162161%\" valign=\"top\"\u003e\n \u003cp\u003e4.12⨯10\u003csup\u003e4\u003c/sup\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"10.36036036036036%\" valign=\"top\"\u003e\n \u003cp\u003e2.21\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"9.75975975975976%\" valign=\"top\"\u003e\n \u003cp\u003e-19.7\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd width=\"14.414414414414415%\" valign=\"top\"\u003e\n \u003cp\u003eCH1\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"14.114114114114114%\" valign=\"top\"\u003e\n \u003cp\u003e1.0\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"8.85885885885886%\" valign=\"top\"\u003e\n \u003cp\u003e0.70\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"8.85885885885886%\" valign=\"top\"\u003e\n \u003cp\u003e35.12\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"9.15915915915916%\" valign=\"top\"\u003e\n \u003cp\u003e0.095\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"12.312312312312311%\" valign=\"top\"\u003e\n \u003cp\u003e11.0⨯10\u003csup\u003e4\u003c/sup\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"12.162162162162161%\" valign=\"top\"\u003e\n \u003cp\u003e4.24⨯10\u003csup\u003e4\u003c/sup\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"10.36036036036036%\" valign=\"top\"\u003e\n \u003cp\u003e2.60\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"9.75975975975976%\" valign=\"top\"\u003e\n \u003cp\u003e-15\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd width=\"14.414414414414415%\" valign=\"top\"\u003e\n \u003cp\u003eCH2\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"14.114114114114114%\" valign=\"top\"\u003e\n \u003cp\u003e2.0\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"8.85885885885886%\" valign=\"top\"\u003e\n \u003cp\u003e1.07\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"8.85885885885886%\" valign=\"top\"\u003e\n \u003cp\u003e36.88\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"9.15915915915916%\" valign=\"top\"\u003e\n \u003cp\u003e0.146\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"12.312312312312311%\" valign=\"top\"\u003e\n \u003cp\u003e10.9⨯10\u003csup\u003e4\u003c/sup\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"12.162162162162161%\" valign=\"top\"\u003e\n \u003cp\u003e4.00⨯10\u003csup\u003e4\u003c/sup\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"10.36036036036036%\" valign=\"top\"\u003e\n \u003cp\u003e2.72\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"9.75975975975976%\" valign=\"top\"\u003e\n \u003cp\u003e-14\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd width=\"14.414414414414415%\" valign=\"top\"\u003e\n \u003cp\u003eCH3\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"14.114114114114114%\" valign=\"top\"\u003e\n \u003cp\u003e3.0\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"8.85885885885886%\" valign=\"top\"\u003e\n \u003cp\u003e1.37\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"8.85885885885886%\" valign=\"top\"\u003e\n \u003cp\u003e36.28\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"9.15915915915916%\" valign=\"top\"\u003e\n \u003cp\u003e0.201\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"12.312312312312311%\" valign=\"top\"\u003e\n \u003cp\u003e6.26⨯10\u003csup\u003e4\u003c/sup\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"12.162162162162161%\" valign=\"top\"\u003e\n \u003cp\u003e3.11⨯10\u003csup\u003e4\u003c/sup\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"10.36036036036036%\" valign=\"top\"\u003e\n \u003cp\u003e2.02\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"9.75975975975976%\" valign=\"top\"\u003e\n \u003cp\u003e-7.95\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd width=\"14.414414414414415%\" valign=\"top\"\u003e\n \u003cp\u003eCH4\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"14.114114114114114%\" valign=\"top\"\u003e\n \u003cp\u003e4.0\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"8.85885885885886%\" valign=\"top\"\u003e\n \u003cp\u003e1.60\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"8.85885885885886%\" valign=\"top\"\u003e\n \u003cp\u003e35.10\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"9.15915915915916%\" valign=\"top\"\u003e\n \u003cp\u003e0.254\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"12.312312312312311%\" valign=\"top\"\u003e\n \u003cp\u003e5.94⨯10\u003csup\u003e4\u003c/sup\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"12.162162162162161%\" valign=\"top\"\u003e\n \u003cp\u003e3.07⨯10\u003csup\u003e4\u003c/sup\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"10.36036036036036%\" valign=\"top\"\u003e\n \u003cp\u003e1.94\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"9.75975975975976%\" valign=\"top\"\u003e\n \u003cp\u003e-5.86\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003c/tbody\u003e\n\u003c/table\u003e\n\u003cp\u003e\u003cstrong\u003e3.2 Structure of hemicellulose and its derivatives\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eIn order to elucidate the effect of hemicellulose structure on adsorption experiments, Hr and CH4 were characterized using \u003csup\u003e1\u003c/sup\u003eH-\u003csup\u003e13\u003c/sup\u003eC HSQC NMR to investigate structural changes before and after modification shown in\u003cstrong\u003e\u0026nbsp;Table 2\u003c/strong\u003e.\u003c/p\u003e\n\u003cp\u003eIn the HSQC NMR spectrum of Hr (\u003cstrong\u003eFigure 2(a)\u003c/strong\u003e), the chemical shifts 101.3/4.41, 101.4/4.59 and 97.1/5.29 are from the (1\u0026rarr;4)-linked \u0026beta;-D-glucopyranosyl, 2-O-(4-O-methyl-\u0026alpha;-D-glucuronide)-glucopyranosyl xylose, 4-O-methyl-\u0026alpha;-D-glucuronide of hemicellulose, respectively, with several carbon atoms and the corresponding hydrogen atoms. The other atomic carbon-hydrogen correlation peaks of (1 \u0026rarr; 4)-linked \u0026beta;-D-xylopyranosyl are at 72.7/3.24 (C2-H2),73.6/3.51 (C3-H3), 76.2/3.75 (C4-H4), 63.7/4.03 (C5-Heq) and 63.8/3.30 (C5-Hax) ppm, respectively. The chemical shift intensity of xylose indicates that the sugar group in hemicellulose is mainly xylose, which is the same conclusion as the chemical composition analysis of hemicellulose. The chemical shifts 70.2/3.51, 71.0/3.68,81.4/3.15, 71.9/4.28 are the carbon-hydrogen correlation peaks on C2-H2, C3-H3, C4-H4 and C5-H5 on the unit of glucuronic acid, respectively, and at 59.8/3.41 ppm is the proton peak of the methyl group of 4-O-methyl glucuronide, which indicates the presence of 4-O-methylglucuronide and substitution at the C-2 position, and 76.9/3.39 ppm is the chemical shift of the hydrocarbon-related peak on C2-H2 after attachment of 4-O-methylglucuronide to the xylose unit. These data are consistent with the published reports (Arumugam et al., 2018; Barbieri et al., 2022). \u0026nbsp;\u003c/p\u003e\n\u003cp\u003eAccording to previous work\u0026nbsp;(Cheng et al., 2018; Peng et al., 2012), after comparing the spectrum of CH4 (\u003cstrong\u003eFigure 2(b)\u003c/strong\u003e) with that of Hr, most 4-O-methylglucuronide signal peaks disappear and are replaced by the signal peaks of the quaternary ammonium group, with a major intense absorption peak at 54.9/3.17 ppm, caused by the methyl carbon on the quaternary ammonium group. 72.1/3.71, 65.1/4.37and 70.22/3.52 ppm correspond to the carbon-hydrogen related peaks on the quaternary ammonium branched groups C1-H1, C2-H2, and C3-H3, respectively. The presence of these signal peaks confirms that the quaternization of hemicellulose and cationic groups are introduced into the hemicellulose macromolecular backbone. The signal shift of 82.2/3.17 for C2-H2 of (1\u0026rarr;4)-\u0026beta;-D-xylopyranose further confirms substitution on C-2 of Hr.\u0026nbsp;\u003c/p\u003e\n\u003cp\u003eThe glucose signal in cellulose was detected in 2D NMR in addition to the glycosyl group of hemicellulose. As expected, most lignin was leached out after alkali, leaving behind cellulose and hemicellulose; thus, the hemicellulose extracted from the pulp would contain a small amount of glucose. The combination of glycosyl analysis and 2D NMR results showed that water-soluble hemicellulose (Hr) extracted by alkali contained more glucuronic acid branched chains. However, the glucuronide branched chains detached after modification and the xylan backbone interacted with new quaternary ammonium groups.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eTable 2\u003c/strong\u003e. Chemical shift assignments for hemicellulose in 1H-13C 2D NMR, ax = axial, eq = equatorial.\u0026nbsp;\u003c/p\u003e\n\u003ctable border=\"0\" cellspacing=\"0\" cellpadding=\"0\" align=\"\" width=\"623\"\u003e\n \u003ctbody\u003e\n \u003ctr\u003e\n \u003ctd width=\"23.434991974317818%\" rowspan=\"2\" valign=\"top\"\u003e\n \u003cp\u003eMonosaccharide unit\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"76.56500802568219%\" colspan=\"8\" valign=\"top\"\u003e\n \u003cp\u003eChemical shift H/C (ppm)\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd width=\"13.263157894736842%\" valign=\"top\"\u003e\n \u003cp\u003e1\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"12.631578947368421%\" valign=\"top\"\u003e\n \u003cp\u003e2\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"12.631578947368421%\" valign=\"top\"\u003e\n \u003cp\u003e3\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"12.631578947368421%\" valign=\"top\"\u003e\n \u003cp\u003e4\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"12.631578947368421%\" valign=\"top\"\u003e\n \u003cp\u003e5ax\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"12.631578947368421%\" valign=\"top\"\u003e\n \u003cp\u003e5eq\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"12.631578947368421%\" valign=\"top\"\u003e\n \u003cp\u003eO-CH\u003csub\u003e3\u003c/sub\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"10.947368421052632%\" valign=\"top\"\u003e\n \u003cp\u003eN-CH\u003csub\u003e3\u003c/sub\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd width=\"23.51046698872786%\" valign=\"top\"\u003e\n \u003cp\u003e\u0026rarr; 4)-\u0026beta;-D-Xylp-(1 \u0026rarr;\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"10.144927536231885%\" valign=\"top\"\u003e\n \u003cp\u003e4.41/\u003c/p\u003e\n \u003cp\u003e101.3\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"9.66183574879227%\" valign=\"top\"\u003e\n \u003cp\u003e3.24/\u003c/p\u003e\n \u003cp\u003e72.7\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"9.66183574879227%\" valign=\"top\"\u003e\n \u003cp\u003e3.51/\u003c/p\u003e\n \u003cp\u003e73.6\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"9.66183574879227%\" valign=\"top\"\u003e\n \u003cp\u003e3.75/\u003c/p\u003e\n \u003cp\u003e76.2\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"9.66183574879227%\" valign=\"top\"\u003e\n \u003cp\u003e3.30/\u003c/p\u003e\n \u003cp\u003e63.8\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"9.66183574879227%\" valign=\"top\"\u003e\n \u003cp\u003e4.03/\u003c/p\u003e\n \u003cp\u003e63.7\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"9.66183574879227%\" valign=\"top\"\u003e\n \u003cp\u003e-\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"8.373590982286634%\" valign=\"top\"\u003e\n \u003cp\u003e-\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd width=\"23.51046698872786%\" valign=\"top\"\u003e\n \u003cp\u003e\u0026rarr; 4,2)-\u0026beta;-D-Xylp-(1 \u0026rarr;\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"10.144927536231885%\" valign=\"top\"\u003e\n \u003cp\u003e4.59/\u003c/p\u003e\n \u003cp\u003e101.4\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"9.66183574879227%\" valign=\"top\"\u003e\n \u003cp\u003e3.39/\u003c/p\u003e\n \u003cp\u003e76.9\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"9.66183574879227%\" valign=\"top\"\u003e\n \u003cp\u003e3.59/\u003c/p\u003e\n \u003cp\u003e72.5\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"9.66183574879227%\" valign=\"top\"\u003e\n \u003cp\u003e3.72/\u003c/p\u003e\n \u003cp\u003e76.3\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"9.66183574879227%\" valign=\"top\"\u003e\n \u003cp\u003e3.37/\u003c/p\u003e\n \u003cp\u003e63.2\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"9.66183574879227%\" valign=\"top\"\u003e\n \u003cp\u003e4.01/\u003c/p\u003e\n \u003cp\u003e63.7\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"9.66183574879227%\" valign=\"top\"\u003e\n \u003cp\u003e-\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"8.373590982286634%\" valign=\"top\"\u003e\n \u003cp\u003e-\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd width=\"23.51046698872786%\" valign=\"top\"\u003e\n \u003cp\u003e4-O-Me-\u0026alpha;-D-GlcpA-(1 \u0026rarr;\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"10.144927536231885%\" valign=\"top\"\u003e\n \u003cp\u003e5.29/\u003c/p\u003e\n \u003cp\u003e97.1\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"9.66183574879227%\" valign=\"top\"\u003e\n \u003cp\u003e3.51/\u003c/p\u003e\n \u003cp\u003e70.2\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"9.66183574879227%\" valign=\"top\"\u003e\n \u003cp\u003e3.68/\u003c/p\u003e\n \u003cp\u003e71.0\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"9.66183574879227%\" valign=\"top\"\u003e\n \u003cp\u003e3.15/\u003c/p\u003e\n \u003cp\u003e81.4\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"9.66183574879227%\" valign=\"top\"\u003e\n \u003cp\u003e4.28/\u003c/p\u003e\n \u003cp\u003e71.9\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"9.66183574879227%\" valign=\"top\"\u003e\n \u003cp\u003e-\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"9.66183574879227%\" valign=\"top\"\u003e\n \u003cp\u003e3.41/\u003c/p\u003e\n \u003cp\u003e59.8\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"8.373590982286634%\" valign=\"top\"\u003e\n \u003cp\u003e-\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd width=\"23.51046698872786%\" valign=\"top\"\u003e\n \u003cp\u003eQA\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"10.144927536231885%\" valign=\"top\"\u003e\n \u003cp\u003e3.71/\u003c/p\u003e\n \u003cp\u003e72.1\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"9.66183574879227%\" valign=\"top\"\u003e\n \u003cp\u003e4.37/\u003c/p\u003e\n \u003cp\u003e65.1\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"9.66183574879227%\" valign=\"top\"\u003e\n \u003cp\u003e3.52/\u003c/p\u003e\n \u003cp\u003e70.2\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"9.66183574879227%\" valign=\"top\"\u003e\n \u003cp\u003e-\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"9.66183574879227%\" valign=\"top\"\u003e\n \u003cp\u003e-\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"9.66183574879227%\" valign=\"top\"\u003e\n \u003cp\u003e-\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"9.66183574879227%\" valign=\"top\"\u003e\n \u003cp\u003e-\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"8.373590982286634%\" valign=\"top\"\u003e\n \u003cp\u003e3.17/\u003c/p\u003e\n \u003cp\u003e54.9\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003c/tbody\u003e\n\u003c/table\u003e\n\u003cp\u003e\u003cstrong\u003e\u0026nbsp;\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003e3.3 Thermal stability\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eTo further determine the effect of the structure of the cationic hemicellulose on its stability, Thermogravimetry (TG) tests were performed over 40 to 600 \u0026deg;C whose results are shown in \u003cstrong\u003eFigure 3(a).\u003c/strong\u003e\u0026nbsp;\u003c/p\u003e\n\u003cp\u003eThe thermal decomposition of hemicellulose of different DS is characterized by three distinct stages: (1) 0~150 \u0026deg;C, which is mainly the evaporation of water; (2) 150~350 \u0026deg;C, over which the hemicellulose is rapidly pyrolyzed, and the maximum weight loss of four different DS occurs between 230~290 \u0026deg;C. The starting pyrolysis temperatures of CH1 and CH4 are 180 ℃ and 150 ℃, respectively, above which the mass loss is serious, and the lowering of the starting pyrolysis temperature means the lowering of the thermal stability. In the Derivative Thermogravimetry (DTG) curves (\u003cstrong\u003eFigure 3(b)\u003c/strong\u003e), the maximum degradation temperatures of CH1 and CH4 were 286 \u0026deg;C and 235 \u0026deg;C, respectively, which indicated thermal robustness of cationic hemicellulose diminished. More specifically, disruption of hydrogen bonds in the molecular chain and degradation of the molecular chain after quaternization are responsible, which represents a complementary conclusion to the molecular weight studies. Therefore, thermal properties further decreased with CH substitution. (3) The third stage from 400 to 600 \u0026deg;C coincides with a decrease in hemicellulose quality due to oxidation of organic matter; when the temperature reaches 600 \u0026deg;C, 35% of the residues are still present, which may be the quaternary ammonium salts from preparation of cationic hemicellulose or specimens that have not undergone degradation. In general, the thermal stability decreased with increasing DS, indicating that the number of CH backbone side chains has an inverse effect on thermal stability, a trend that fits well with past work (Kong et al., 2014; Wang et al., 2021).\u0026nbsp;\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003e3.4 Adsorption behavior of cationic hemicellulose on nanocellulose\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eThe role of unmodified hemicellulose in improving the tensile strength of nanocellulose composites has been previously reported (Lucenius et al., 2014). The QCM-D data for unmodified hemicellulose adsorbed on CNF in this study are shown in \u003cstrong\u003eFigure S8\u003c/strong\u003e and can be used as a comparison with the work of others. Our research interest is the adsorption behavior of cationic hemicellulose on CNF. In order to test the hypothesis that the interaction is influenced by electrostatic force and structure, we investigated the interaction between cationic hemicellulose and CNF using QCM-D in pure water to determine the effects of DS, molecular weight and zeta potential on the surface properties of CNF. To facilitate comparison, the results of the adsorption of cationic hemicellulose on CNF-coated sensors are summarized in \u003cstrong\u003eTable 3\u003c/strong\u003e.\u0026nbsp;\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eFigure 4\u003c/strong\u003e shows frequency changes monitored using QCM-D indicating the adsorption and desorption behavior occurring on the CNF-coated sensor. A decrease in resonance frequency due to the increase in mass indicates the introduced cationic hemicellulose is adsorbed on the CNF-coated quartz crystal sensor. By comparing the frequency changes, it is possible to assess the relative strength of the interaction between CNF and CH. The adsorption of cationic hemicelluloses on CNF increased with time, with the lower DS cationic hemicelluloses (less than 0.15) showing less variation in CH1 and CH2 frequencies, reaching maximum adsorption within one hour. Surprisingly, CH2 (DS=0.146) showed less adsorption than CH1 (DS=0.095). When molecular weights are similar, the lower the DS of CH (below 0.15), the more cationic hemicellulose molecules are required to compensate for the surface charge of the CNF surface, resulting in a greater adsorption capacity for the low-charge CH, which is consistent with previous work using SPR to study interactions (Wang et al., 2021).\u0026nbsp;\u003c/p\u003e\n\u003cp\u003eWhen the DS exceeded 0.15, the frequency changed and the adsorption amount started to show a large difference: CH3 and CH4 reached maximum adsorption at 110 min and 210 min, respectively. This may be due to electrostatic attractions, in which CH becomes positively charged and therefore the repulsive force between the negatively charged fibrils decreases resulting in a strong electrostatic attraction interaction. The slope of the F-curve shows that the adsorption rate increases with increasing DS, and the slope of the frequency change (∆F) in the graph shows that the adsorption rate is faster and then slower. The factors affecting the adsorption rate may be related to the zeta potential of the cationic hemicellulose: the larger the zeta potential, the lower the colloidal stability of the solution, and the easier it is to be attracted by the CNF; and secondly, the CNF itself is negatively charged, and has an affinity for the positively charged cationic hemicellulose. After reaching maximum adsorption, the reversible and loosely bound hemicellulose that was adsorbed on the CNF surface was eliminated by flushing the QCM-D chamber with mill-Q water. The partial adsorption between cationic hemicellulose and CNF was reversible, i.e., a weak interaction. Once the rinsing was over, the frequency no longer changed, indicating that the adsorption between the cationic hemicellulose and CNF had become irreversible. This irreversible adsorption is known as strong interaction. The results of QCM-D indicate that CH4 enhances a strong interaction with CNF in the aqueous state. Cationic starch (CS) is widely used as a papermaking chemical to improve paper retention and dry strength (Tammelin et al., 2004). Being also a cationized paper additive, the adsorption amount of cationic hemicellulose (CH3) on nanocellulose fibers was approximately 3.5 times higher than that of cationic starch (with similar degree of substitution and molecular weight). However, the time required to reach adsorption equilibrium was correspondingly longer for cationic hemicellulose (110 minutes), whereas cationic starch reached equilibrium adsorption in a shorter time (10 minutes). Although cationic hemicellulose has a stronger affinity for cellulose, it can be more efficiently used in the paper industry if its adsorption speed is faster.\u0026nbsp;\u003c/p\u003e\n\u003cp\u003eIn addition, cationic hemicellulose with DS \u0026gt; 0.15 showed greater adsorption capacity and shorter adsorption equilibrium time compared with acetylation-modified xylan (Jaafar et al., 2019), arabinoxylan (Kohnke et al., 2011) and water-soluble xylan (Lyu et al., 2021) without chemically modification, which indicated that the appropriate modification method and DS could significantly improve the affinity of hemicellulose for cellulose microfibrils, and the modified hemicellulose had a better industrial utilization as chemicals. Comparing these three hemicelluloses with different side chain groups, the strength of their interaction with cellulose microfibrils also varies depending on their own structure. Although the conditions of this study are different from other studies, the factors affecting the affinity are the same, i.e., the structure is the main factor affecting the hemicellulose-cellulose interaction. However, the results in \u003cstrong\u003eTable 3\u003c/strong\u003e show that the charged cationic hemicellulose significantly affects the strength of the interaction when DS \u0026gt; 0.15, so we believe that the charge is one of the important factors affecting the interaction, perhaps even more than the structure. As the electrostatic interaction is driven, it will have a very significant effect on the adsorption rate and adsorption amount of hemicellulose on the nanocellulose matrix as well as the adsorption equilibrium time, which verifies our hypothesis that the interaction between hemicellulose and cellulose is mainly influenced by the electrostatic and structural effects.\u0026nbsp;\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eFigure 5(a)\u003c/strong\u003e shows dissipation variation, which can be further explained by monitoring the viscoelasticity of the adsorbed layer on the CNF-coated sensor (Voinova et al., 1999). The dissipation factor is defined as the ratio of dissipated energy to stored energy when an oscillatory stress is applied to the surface layer of the sensor, and the change in dissipation represents the structural change that occurs under stress, which is related to the stiffness of the adsorbed film. As shown in the graph, the dissipation factor increases with time due to the accumulation of a large amount of cationic hemicellulose on the surface of CNF, which increases the thickness of the adsorption layer. The change in dissipation corresponds to the change in frequency, and their trends are similar.\u003c/p\u003e\n\u003cp\u003eTo evaluate the viscoelasticity of the adsorbed layer on the CNF-coated sensor, the change in dissipation (\u0026Delta;D) is plotted as a function of the change in frequency (\u0026Delta;F) in \u003cstrong\u003eFigure 5(b)\u003c/strong\u003e. The viscoelastic properties are related to the slope of the resulting curve (∆D-∆F), which qualitatively shows a change in polymer conformation. The lower the slope, the stiffer the adsorbed layer is, while a steeper slope indicates that the adsorbed layer is softer and more mobile\u0026nbsp;(Kohnke et al., 2011; Tammelin et al., 2006). This indicates that the cationic hemicellulose layer adsorbed on cellulose has a similar conformation regardless of the variation of DS. In addition, the degree of denseness and rigidity of the adsorbed layer changes accordingly as the adsorption of the adsorbed layer changes with rinse water. A lower slope indicates that the adsorbed layer is rigid. CH3 has a poor affinity for CNF, and compared to other cationic hemicelluloses, CH3 forms a softer (less dissipative) adsorption layer, which may be due to its greater water absorption.\u003c/p\u003e\n\u003cp\u003eIn addition, other researchers found by QCM-D that according to the molecular entanglement theory, the higher the molecular weight, the more entangled the molecular chains are, and the more water is adsorbed between the molecules, leading to greater adsorption\u0026nbsp;(Tammelin et al., 2004; Yao et al., 2021). However, combining the experimental results of QCM-D and Molecular weight, the charge of hemicellulose was found to be more important than its molecular weight, similar to conclusions reached in previous studies\u0026nbsp;(Kabel et al., 2007; Saarinen et al., 2009), which also indicates that the hemicellulose-cellulose adsorption behavior in QCM-D was mainly driven by electrostatic effects.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eTable 3\u003c/strong\u003e. Results of hemicellulose samples adsorbed on CNF surfaces in real-time quantitative QCM-D experiments and comparison with previous reports\u0026nbsp;\u003c/p\u003e\n\u003ctable border=\"0\" cellspacing=\"0\" cellpadding=\"0\" width=\"645\"\u003e\n \u003ctbody\u003e\n \u003ctr\u003e\n \u003ctd width=\"28.173374613003094%\" valign=\"top\"\u003e\n \u003cp\u003eHemicellulose Sample\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"14.086687306501547%\" valign=\"top\"\u003e\n \u003cp\u003e-∆F\u003csub\u003eMax\u003c/sub\u003e\u003c/p\u003e\n \u003cp\u003e(Hz)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"14.086687306501547%\" valign=\"top\"\u003e\n \u003cp\u003e∆D\u003csub\u003eMAX\u003c/sub\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"19.659442724458206%\" valign=\"top\"\u003e\n \u003cp\u003e-∆F\u003csub\u003eIrreversible\u003c/sub\u003e\u003c/p\u003e\n \u003cp\u003e(Hz)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"11.30030959752322%\" valign=\"top\"\u003e\n \u003cp\u003e∆D\u003csub\u003eIrreversible\u003c/sub\u003e\u003c/p\u003e\n \u003cp\u003e\u003cstrong\u003e\u0026nbsp;\u003c/strong\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"12.693498452012383%\" valign=\"top\"\u003e\n \u003cp\u003eTime\u003csub\u003eMax\u003c/sub\u003e\u003c/p\u003e\n \u003cp\u003e（min）\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd width=\"28.173374613003094%\" valign=\"top\"\u003e\n \u003cp\u003eHr\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"14.086687306501547%\" valign=\"top\"\u003e\n \u003cp\u003e8\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"14.086687306501547%\" valign=\"top\"\u003e\n \u003cp\u003e2.5\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"19.659442724458206%\" valign=\"top\"\u003e\n \u003cp\u003e5\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"11.30030959752322%\" valign=\"top\"\u003e\n \u003cp\u003e1.6\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"12.693498452012383%\" valign=\"top\"\u003e\n \u003cp\u003e105\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd width=\"28.173374613003094%\" valign=\"top\"\u003e\n \u003cp\u003eCH1(DS=0.095)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"14.086687306501547%\" valign=\"top\"\u003e\n \u003cp\u003e14\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"14.086687306501547%\" valign=\"top\"\u003e\n \u003cp\u003e2.5\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"19.659442724458206%\" valign=\"top\"\u003e\n \u003cp\u003e11\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"11.30030959752322%\" valign=\"top\"\u003e\n \u003cp\u003e2\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"12.693498452012383%\" valign=\"top\"\u003e\n \u003cp\u003e65\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd width=\"28.173374613003094%\" valign=\"top\"\u003e\n \u003cp\u003eCH2(DS=0.146)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"14.086687306501547%\" valign=\"top\"\u003e\n \u003cp\u003e15\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"14.086687306501547%\" valign=\"top\"\u003e\n \u003cp\u003e2.4\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"19.659442724458206%\" valign=\"top\"\u003e\n \u003cp\u003e10\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"11.30030959752322%\" valign=\"top\"\u003e\n \u003cp\u003e1.6\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"12.693498452012383%\" valign=\"top\"\u003e\n \u003cp\u003e65\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd width=\"28.173374613003094%\" valign=\"top\"\u003e\n \u003cp\u003eCH3(DS=0.201)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"14.086687306501547%\" valign=\"top\"\u003e\n \u003cp\u003e31\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"14.086687306501547%\" valign=\"top\"\u003e\n \u003cp\u003e6.5\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"19.659442724458206%\" valign=\"top\"\u003e\n \u003cp\u003e22\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"11.30030959752322%\" valign=\"top\"\u003e\n \u003cp\u003e4\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"12.693498452012383%\" valign=\"top\"\u003e\n \u003cp\u003e110\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd width=\"28.173374613003094%\" valign=\"top\"\u003e\n \u003cp\u003eCH4(DS=0.254)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"14.086687306501547%\" valign=\"top\"\u003e\n \u003cp\u003e65\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"14.086687306501547%\" valign=\"top\"\u003e\n \u003cp\u003e10\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"19.659442724458206%\" valign=\"top\"\u003e\n \u003cp\u003e55\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"11.30030959752322%\" valign=\"top\"\u003e\n \u003cp\u003e8\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"12.693498452012383%\" valign=\"top\"\u003e\n \u003cp\u003e210\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd width=\"28.173374613003094%\" valign=\"top\"\u003e\n \u003cp\u003eCationic starch (DS=0.2)\u0026nbsp;(Kontturi et al., 2008)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"14.086687306501547%\" valign=\"top\"\u003e\n \u003cp\u003e-\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"14.086687306501547%\" valign=\"top\"\u003e\n \u003cp\u003e-\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"19.659442724458206%\" valign=\"top\"\u003e\n \u003cp\u003e6.3\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"11.30030959752322%\" valign=\"top\"\u003e\n \u003cp\u003e0.2\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"12.693498452012383%\" valign=\"top\"\u003e\n \u003cp\u003e10\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd width=\"28.173374613003094%\" valign=\"top\"\u003e\n \u003cp\u003eAcetylated xylan(Jaafar et al., 2019)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"14.086687306501547%\" valign=\"top\"\u003e\n \u003cp\u003e18\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"14.086687306501547%\" valign=\"top\"\u003e\n \u003cp\u003e0.8\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"19.659442724458206%\" valign=\"top\"\u003e\n \u003cp\u003e17\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"11.30030959752322%\" valign=\"top\"\u003e\n \u003cp\u003e0.7\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"12.693498452012383%\" valign=\"top\"\u003e\n \u003cp\u003e50\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd width=\"28.173374613003094%\" valign=\"top\"\u003e\n \u003cp\u003earabinoxylan(Kohnke et al., 2011)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"14.086687306501547%\" valign=\"top\"\u003e\n \u003cp\u003e16\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"14.086687306501547%\" valign=\"top\"\u003e\n \u003cp\u003e3.5\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"19.659442724458206%\" valign=\"top\"\u003e\n \u003cp\u003e15.5\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"11.30030959752322%\" valign=\"top\"\u003e\n \u003cp\u003e3.4\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"12.693498452012383%\" valign=\"top\"\u003e\n \u003cp\u003e200\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd width=\"28.173374613003094%\" valign=\"top\"\u003e\n \u003cp\u003ewater-soluble xylan(Lyu et al., 2021)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"14.086687306501547%\" valign=\"top\"\u003e\n \u003cp\u003e18\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"14.086687306501547%\" valign=\"top\"\u003e\n \u003cp\u003e-\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"19.659442724458206%\" valign=\"top\"\u003e\n \u003cp\u003e15\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"11.30030959752322%\" valign=\"top\"\u003e\n \u003cp\u003e-\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"12.693498452012383%\" valign=\"top\"\u003e\n \u003cp\u003e150\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003c/tbody\u003e\n\u003c/table\u003e\n\u003cp\u003e∆Fmax and ∆Dmax represent the frequency and dissipation values when CH adsorption on the CNF surface reaches equilibrium, respectively, and ∆F\u003csub\u003eIrreversible\u003c/sub\u003e and ∆D\u003csub\u003eIrreversible\u003c/sub\u003e are the frequency and dissipation values for irreversible adsorption\u003cstrong\u003e\u0026nbsp;\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003e3.5 Water contact angle test of QCM-D sensor surface before and after adsorption\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eIn order to characterize the morphology and hydrophilicity of the QCM-D sensors\u0026apos; surfaces before and after adsorption, we tested the static contact angles of the Silica-coated, CNF-coated, and CH4-treated sensors\u0026apos; surfaces, respectively, at room temperature. As shown in the \u003cstrong\u003eFigure 6(d)\u003c/strong\u003e, the untreated quartz crystal sensor surface has the strongest hydrophobicity at a static contact angle of about 95\u0026deg; due to the silica-coated surface (\u003cstrong\u003eFigure S9\u003c/strong\u003e). After spin-coating the CNF, the sensor surface was almost completely and uniformly covered by the randomly oriented CNF as can be seen from \u003cstrong\u003eFigure 6(a)\u003c/strong\u003e, and the Ra was measured to be 4.88 nm (\u003cstrong\u003eFigure S10\u003c/strong\u003e). The surface water contact angle was reduced to 36\u0026deg;, which is similar to the previous report\u0026nbsp;(Mohan et al., 2014; Zhang et al., 2018), indicating that the CNF made the sensor surface much more hydrophilic. After the CNF-coated sensor adsorbed cationic hemicellulose, when a water droplet was placed on the surface of the sensor, the water droplet was quickly absorbed by the coating, which indicated that the coating had better hydrophilicity, as evidenced by the decrease in the surface contact angle. This may be because the adsorption of cationic hemicellulose on CNF affects the structure of the adsorption layer, and the amorphous CH4 changes the roughness of the sensor surface (\u003cstrong\u003eFigure 6(c)\u0026nbsp;\u003c/strong\u003eand\u003cstrong\u003e\u0026nbsp;Figure S11\u003c/strong\u003e), which has an effect on the accessibility of the surface functional groups, so there is better hydrophilicity. Interestingly, this behavior is similar to the coating of hemicellulose on paper\u0026nbsp;(Nechita et al., 2021). This suggests that the interaction between cationic hemicellulose and nanocellulose has an effect on the surface properties of nanocellulose, and this revelation may perhaps allow CH to be used as a coating agent for surface of paper or cellulosic membrane, which is the idea of high-value application of cationic hemicellulose.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003e3.6 Hemicellulose-cellulose composite film\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eIn order to speculate the role of hydrogen bonding in the interaction process, three different hemicelluloses, Hr, CH1, and CH4, were each mixed with CNF to make films with an average thickness of 50 \u0026mu;m, where the average maximum tensile stress strengths of the composite films (\u003cstrong\u003eFigure. 7(a\u003c/strong\u003e)) were 27 MPa, 36 MPa, and 46 MPa, respectively, and the tensile strain curves are shown in \u003cstrong\u003eFigure. 7(b)\u003c/strong\u003e. The high mechanical properties of the hemicellulose-nanocellulose composite films are a result of the cationic hemicellulose which enhances the adhesion and mechanical properties of the fibrils by reducing the electrostatic repulsive force between the microfibrils. At the same time, the presence of CH interferes with the hydrogen bonding interactions between cellulose macromolecules. Amorphous cationic hemicellulose adsorbed on the cellulose surface promotes the penetration of water into the crystalline regions of the cellulose nanofibrils, leading to swelling and increasing the size of the nanofibrils, which alters the degree of interlacing between the fibrils and thus enhances the film-binding strength. In addition, cationic hemicellulose acted as a plasticizer to enhance the toughness of the composite film, and it can be speculated that it enhanced the dispersion of CNF during the film formation process, which is essential to avoid fibrils aggregation and defects in the composite film\u0026nbsp;(Hu et al., 2022; Lucenius et al., 2014). As shown in the SEM image of the composite film (\u003cstrong\u003eFigure 7(a)\u003c/strong\u003e), hemicellulose acts as a binder to fill the voids between the cellulose fibrils to form a dense hemicellulose-nanocellulose composite film.\u003c/p\u003e\n\u003cp\u003eCompared with Hr, the charged CH4 on the surface greatly increases the strength of the composite film. The combined action of the hydroxyl group (OH -) and the charged group in the cationic hemicellulose molecule results in more hydrogen bonds between the cellulose and hemicellulose, thus promoting the bonding between the fibrils and significantly improving the mechanical properties (Bai et al., 2012). In conclusion, the cationic hemicellulose significantly increased the tensile strength of the cellulose composite film or paper, similar to previous work (Hu et al., 2022; Kohnke et al., 2009; Wang et al., 2021) and corresponds to the experimental results of QCM-D. \u003cstrong\u003eFigure 8\u003c/strong\u003e shows the process of cellulose chain strengthening by cationic hemicellulose, including microfibril swelling, electrostatic interaction and hydrogen bonding.\u003c/p\u003e"},{"header":"Conclusions","content":"\u003cp\u003eCationic hemicelluloses with DS from 0.09 to 0.254 were synthesized by grafting 2,3-epoxypropyltrimethylammonium chloride (ETA) onto hemicelluloses isolated from eucalyptus wood. Cationic hemicellulose was adsorbed onto CNF-coated sensors using QCM-D. The positively charged group grafted hemicellulose improves the adsorption rate and adsorption volume while forming a stiffer and thicker adsorption layer than unmodified hemicellulose. The interaction between CH and CNF in the pure water state was mainly driven by electrostatics. Compared to natural hemicellulose, the addition of 15 wt% cationic hemicellulose (DS\u0026thinsp;=\u0026thinsp;0.254) increased the maximum tensile stress strength of the hemicellulose-cellulose composite film by up to 71%. Cationic hemicellulose can increase the hydrogen bonding within the microfibrils thereby improving the strength of the composite films. In conclusion, these results validate the hypothesis in the introduction that the interaction between cationic hemicellulose and nanocellulose is influenced by the hemicellulose structure, electrostatic force and hydrogen bonding. This study may provide an idea for the high value utilization of nanocellulose and hemicellulose.\u003c/p\u003e"},{"header":"Declarations","content":"\u003cp\u003e\u003cstrong\u003eAcknowledgements\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eWe thank the MCPF (Materials Characterization and Preparation Facility) of the Hong Kong University of Science and Technology (Guangzhou) for their contribution to the characterization of this work.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eFunding\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eThis work was supported by the National Natural Science Foundation of China (22078114), the National Key Research and Development Program (2021YFE0104500), Key Research and Development Program of Guangzhou Science and Technology Program (202103000011), and the Natural Science Foundation of Guangdong Province (2021A1515010360).\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eAuthor Contributions Statement\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eX.L.: performed the experiment, contributed significantly to data analyses and wrote the manuscript.\u0026nbsp;\u003c/p\u003e\n\u003cp\u003eS.F.: contributed to the conception of the study and manuscript revision.\u0026nbsp;\u003c/p\u003e\n\u003cp\u003eY.K.: helped perform the preparation of samples.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eCompeting interests\u0026nbsp;\u003c/strong\u003eThe authors declare no competing interests.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eConfict of interest\u003c/strong\u003e The authors declare no competing interests\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eAvailability of data and materials\u003c/strong\u003e All data generated or analyzed during this study are included in this submitted article.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eEthics approval and consent to participate\u003c/strong\u003e All authors have consented to participate on the manuscript.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eConsent for publication\u003c/strong\u003e All authors have approved the final version of the manuscript.\u003c/p\u003e"},{"header":"References","content":"\u003col\u003e\n \u003cli\u003eAl Manasrah, M., Kallioinen, M., Ilvesniemi, H., Manttari, M. 2012. Recovery of galactoglucomannan from wood hydrolysate using regenerated cellulose ultrafiltration membranes. \u003cem\u003eBioresource Technology\u003c/em\u003e, \u003cstrong\u003e114\u003c/strong\u003e, 375-381.\u003c/li\u003e\n \u003cli\u003eArumugam, N., Biely, P., Puchart, V., Singh, S., Pillai, S. 2018. Structure of peanut shell xylan and its conversion to oligosaccharides. \u003cem\u003eProcess Biochemistry\u003c/em\u003e, \u003cstrong\u003e72\u003c/strong\u003e, 124-129.\u003c/li\u003e\n \u003cli\u003eBai, L.K., Hu, H.R., Xu, J.F. 2012. Influences of configuration and molecular weight of hemicelluloses on their paper-strengthening effects. \u003cem\u003eCarbohydrate Polymers\u003c/em\u003e, \u003cstrong\u003e88\u003c/strong\u003e(4), 1258-1263.\u003c/li\u003e\n \u003cli\u003eBarbieri, S.F., Amaral, S.D., Mazepa, E., Santana, A.P., Sassaki, G.L., Silveira, J.L.M. 2022. 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Adsorption of paper strength additives to hardwood fibres with different surface charges and their effect on paper strength. \u003cem\u003eCellulose\u003c/em\u003e, \u003cstrong\u003e29\u003c/strong\u003e(4), 2617-2632.\u003c/li\u003e\n\u003c/ol\u003e"}],"fulltextSource":"","fullText":"","funders":[],"hasAdminPriorityOnWorkflow":false,"hasManuscriptDocX":true,"hasOptedInToPreprint":true,"hasPassedJournalQc":"","hasAnyPriority":false,"hideJournal":false,"highlight":"","institution":"","isAcceptedByJournal":true,"isAuthorSuppliedPdf":false,"isDeskRejected":"","isHiddenFromSearch":false,"isInQc":false,"isInWorkflow":false,"isPdf":false,"isPdfUpToDate":true,"isWithdrawnOrRetracted":false,"journal":{"display":true,"email":"[email protected]","identity":"cellulose","isNatureJournal":false,"hasQc":true,"allowDirectSubmit":false,"externalIdentity":"cels","sideBox":"Learn more about [Cellulose](https://www.springer.com/journal/10570)","snPcode":"10570","submissionUrl":"https://submission.nature.com/new-submission/10570/3","title":"Cellulose","twitterHandle":"","acdcEnabled":true,"dfaEnabled":true,"editorialSystem":"em","reportingPortfolio":"Springer Hybrid","inReviewEnabled":true,"inReviewRevisionsEnabled":false},"keywords":"Nanocellulose, Cationic hemicellulose (CH), QCM-D, Interaction, Interfacial adsorption","lastPublishedDoi":"10.21203/rs.3.rs-3785502/v1","lastPublishedDoiUrl":"https://doi.org/10.21203/rs.3.rs-3785502/v1","license":{"name":"CC BY 4.0","url":"https://creativecommons.org/licenses/by/4.0/"},"manuscriptAbstract":"The paper industry is constantly seeking innovative ways to improve paper quality, increase process efficiency and reduce environmental impact. The unique properties of cationic modification of hemicellulose provide an opportunity to achieve these goals. Herein, eucalyptus hemicellulose was modified with quaternary ammonium groups to yield cationic hemicellulose (CH), which was used to elaborate structural and functional interactions between CH and cellulose nanofibrils (CNF). These interactions were quantitatively monitored by a quartz crystal microbalance with dissipation (QCM-D). We empirically studied bonding motifs between CNF and hemicellulose by forming films. The degree of substitution (DS) of CH was made between 0.095 and 0.254 by varying the molar ratio of the reaction, leading to a gamut of positive charges in hemicellulose. The adsorption of CH to a CNF surface was related to electrostatic interactions. The high DS of CH had higher adsorption rate and larger adsorption capacity within the CNF-surface, while CH as a reinforcing agent significantly increased the tensile strength of the film by hydrogen bonding, which was 71% higher than that of unmodified hemicellulose. The strong binding between CH and nanocellulose may highlight a platform to develop paper additives and nanocellulose composites for high-value applications.","manuscriptTitle":"A new recognition of the binding of cellulose fibrils in papermaking by probing interaction between nanocellulose and cationic hemicellulose","msid":"","msnumber":"","nonDraftVersions":[{"code":1,"date":"2023-12-28 06:01:03","doi":"10.21203/rs.3.rs-3785502/v1","editorialEvents":[{"type":"communityComments","content":0},{"type":"decision","content":"Revision requested","date":"2024-01-26T17:07:35+00:00","index":"","fulltext":""},{"type":"editorInvitedReview","content":"","date":"2024-01-11T10:38:18+00:00","index":"hide","fulltext":""},{"type":"reviewerAgreed","content":"44fdfb52-f771-4572-85e6-328a20787b50","date":"2023-12-28T07:22:13+00:00","index":"hide","fulltext":""},{"type":"reviewersInvited","content":"","date":"2023-12-27T17:33:47+00:00","index":"","fulltext":""},{"type":"editorAssigned","content":"","date":"2023-12-23T05:28:37+00:00","index":"","fulltext":""},{"type":"checksComplete","content":"","date":"2023-12-23T05:28:37+00:00","index":"","fulltext":""},{"type":"submitted","content":"Cellulose","date":"2023-12-21T07:39:20+00:00","index":"","fulltext":""}],"status":"published","journal":{"display":true,"email":"[email protected]","identity":"cellulose","isNatureJournal":false,"hasQc":true,"allowDirectSubmit":false,"externalIdentity":"cels","sideBox":"Learn more about [Cellulose](https://www.springer.com/journal/10570)","snPcode":"10570","submissionUrl":"https://submission.nature.com/new-submission/10570/3","title":"Cellulose","twitterHandle":"","acdcEnabled":true,"dfaEnabled":true,"editorialSystem":"em","reportingPortfolio":"Springer Hybrid","inReviewEnabled":true,"inReviewRevisionsEnabled":false}}],"origin":"","ownerIdentity":"15bd385d-8080-45e4-9f43-d55c757468aa","owner":[],"postedDate":"December 28th, 2023","published":true,"recentEditorialEvents":[],"rejectedJournal":[],"revision":"","amendment":"","status":"published-in-journal","subjectAreas":[],"tags":[],"updatedAt":"2024-05-10T01:03:51+00:00","versionOfRecord":{"articleIdentity":"rs-3785502","link":"https://doi.org/10.1007/s10570-024-05926-5","journal":{"identity":"cellulose","isVorOnly":false,"title":"Cellulose"},"publishedOn":"2024-05-09 01:03:51","publishedOnDateReadable":"May 9th, 2024"},"versionCreatedAt":"2023-12-28 06:01:03","video":"","vorDoi":"10.1007/s10570-024-05926-5","vorDoiUrl":"https://doi.org/10.1007/s10570-024-05926-5","workflowStages":[]},"version":"v1","identity":"rs-3785502","journalConfig":"researchsquare"},"__N_SSP":true},"page":"/article/[identity]/[[...version]]","query":{"redirect":"/article/rs-3785502","identity":"rs-3785502","version":["v1"]},"buildId":"7rjqhiLT3MXkJMwkYKINL","isFallback":false,"isExperimentalCompile":false,"dynamicIds":[84888],"gssp":true,"scriptLoader":[]}