Sustainable Bio-based Polyurethane Adhesives Utilizing PPG2000 and Renewable Polyols: Synthesis, Characterization, and Mechanical Properties

Sustainable Bio-based Polyurethane Adhesives Utilizing PPG2000 and Renewable Polyols: Synthesis, Characterization, and Mechanical Properties | 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 Sustainable Bio-based Polyurethane Adhesives Utilizing PPG2000 and Renewable Polyols: Synthesis, Characterization, and Mechanical Properties Jin-Gyu Min, Won-Bin Lim, Ju-Hong Lee, Jae-Ryong Lee, Seung-Hyun Lee, and 4 more This is a preprint; it has not been peer reviewed by a journal. https://doi.org/ 10.21203/rs.3.rs-6258415/v1 This work is licensed under a CC BY 4.0 License Status: Posted Version 1 posted You are reading this latest preprint version Abstract Developing high-performance, sustainable adhesives for automotive, aerospace, and industrial applications remains a major challenge due to the inherent trade-off between mechanical strength and thermal stability in bio-based materials. While previous studies have explored bio-based polyurethane (PU) adhesives, achieving superior adhesion and durability remains challenging when compared to petroleum-based counterparts. This study presents a novel bio-based polyurethane adhesive system utilizing polypropylene glycol (PPG2000), isophorone diisocyanate (IPDI), and renewable polyols (isosorbide-derived polyols, diglycerol, and glycerol). The adhesives were synthesized via a controlled one-shot polymerization process with 4-tert-butylphenol as an end-capping agent, enabling precise modulation of crosslink density and molecular architecture. Fourier-transform infrared (FT-IR) spectroscopy confirmed complete urethane bond formation, and isocyanate group (NCO%) titration validated stoichiometric conversion. Gel permeation chromatography (GPC) revealed distinct molecular weight distributions, which influence adhesive performance by affecting crosslink density, elasticity, and mechanical strength depending on polyol structure. Thermal analysis showed that isosorbide-derived polyol formulations exhibited up to a 25°C higher degradation onset temperature and a 10°C increase in glass transition temperature (Tg) compared to petroleum-based adhesives. Meanwhile, formulations containing diglycerol and glycerol demonstrated up to 39% higher shear strength (32.5 MPa) and 77% improved impact resistance (36.8 MPa) relative to the reference system, attributed to optimized segmental mobility and crosslinking effects. This work establishes a strategic framework for designing bio-based polyurethane adhesives, while acknowledging limitations such as potential variability in raw material sources and suggesting future research into long-term environmental performance, that not only surpasses conventional petroleum-based systems in thermal and mechanical performance but also aligns with the principles of green chemistry and sustainable material innovation. These findings offer a pathway for next-generation structural adhesives in automotive, aerospace, and industrial applications. Sustainable polyurethane adhesives Structure–property correlation Thermal stability and mechanical properties Isosorbide-based polyols Renewable polyols Figures Figure 1 Figure 2 Figure 3 Figure 4 Figure 5 Figure 6 Figure 7 Figure 8 1. Introduction Polyurethane (PU) adhesives are essential in various industrial applications, providing excellent mechanical strength, chemical resistance, and bonding versatility [1–5]. However, the prevailing reliance on petroleum-derived polyols raises environmental and economic concerns, such as resource depletion and increased carbon footprints [6–10]. In response, the global push for sustainable solutions has propelled the development of bio-based PU systems that harness renewable feedstocks and minimize ecological impact [11–13]. As part of this transition, exploring novel bio-based polyols is a key strategy for developing high-performance, eco-friendly adhesives [14, 15]. While bio-derived precursors like vegetable oils and lignin show promise, the systematic integration of RPO polyol, diglycerol, and glycerol in PU adhesives remains largely unexplored [16–18]. These bio-based polyols, distinguished by their unique chemical functionalities and architectures, offer promising avenues to modulate crosslink density, thermal stability, and viscoelastic properties [19, 20]. Despite significant progress, the structure–property relationships of bio-based PU adhesives remain insufficiently understood, particularly concerning the molecular effects of polyol structure and composition [21–23]. Addressing this knowledge gap is critical for designing next-generation materials that balance mechanical strength, thermal resilience, and adhesive performance without compromising their environmental credentials [24, 25]. This study systematically investigates bio-based PU adhesives formulated with PPG2000 and IPDI, integrating RPO polyol, diglycerol, and glycerol at controlled ratios [26, 27]. By elucidating how each bio-based polyol modulates molecular architecture, thermal transitions, and mechanical behavior, this work aims to establish correlations that guide the rational selection and formulation of bio-based adhesives [28–30]. This study demonstrates that precise polyol selection and ratio control optimize crosslink density, thermal stability, and mechanical robustness, surpassing conventional petroleum-based adhesives. This study provides a comprehensive framework for designing high-performance bio-based PU adhesives, offering a sustainable alternative with enhanced mechanical and thermal properties compared to petroleum-based adhesives [31–33]. Moreover, this study aligns with principles of green chemistry and sustainable material innovation, setting a foundation for scalable industrial applications and broader adoption of environmentally responsible bonding technologies [34]. In doing so, it aspires to foster a transformative pathway from traditional adhesives to high-performance, renewable alternatives, ultimately contributing to more sustainable industrial practices and material ecosystems [35]. 2. Material and Methods 2.1. Materials Polypropylene glycol (PPG2000, Mn ≈ 2000 g/mol, hydroxyl value: 56 mg KOH/g) was purchased from Sigma-Aldrich (St. Louis, MO, USA) and used without further purification. The bio-based polyols included an isosorbide-derived polyol (RPO polyol, Mn ≈ 500–800 g/mol) supplied by Samyang Inc. (Daejeon, South Korea), diglycerol (purity ≥ 90%, functionality f = 4) and glycerol (purity ≥ 99%, f = 3) obtained from TCI Chemical (Tokyo, Japan). The molecular weight distribution of the RPO polyol was verified using GPC prior to use. Isophorone diisocyanate (IPDI, purity ≥ 98%) was provided by DAEJUNG (Siheung, South Korea), and dibutyltin dilaurate (DBTDL, purity ≥ 95%) was obtained from Sigma-Aldrich. The blocking agent 4-tert-butylphenol (purity ≥ 99%) was also purchased from Sigma-Aldrich. Before use, all polyols were dried under vacuum at 80°C for 24 hours to remove residual moisture. IPDI was distilled under reduced pressure to eliminate impurities. 4-tert-butylphenol was dried in a vacuum oven at 40°C for 12 hours. 2.2 Synthesis of Bio-based Polyurethane Adhesives Bio-based polyurethane adhesives were synthesized via a one-shot polymerization method using a 500 mL four-neck round-bottom flask equipped with a mechanical stirrer, nitrogen inlet, digital thermometer, and a reflux condenser. The total polyols (PPG2000 and bio-based polyols) and IPDI were introduced at a fixed molar ratio of 1:2:1.4. The bio-based polyols (RPO, diglycerol, glycerol) replaced portions of PPG2000 at equivalence ratios of 0.9:0.1, 0.7:0.3, and 0.5:0.5, respectively. A control sample (Ref.) was synthesized using only PPG2000 to establish baseline comparisons. In a typical synthesis procedure, PPG2000, the designated bio-based polyol, and IPDI were charged into the reactor under a dry nitrogen atmosphere and heated to 70°C with stirring at 150 rpm. The DBTDL catalyst (0.05 wt% relative to total reactants) was added to initiate polymerization. Reaction progress was monitored using FT-IR spectroscopy, focusing on the disappearance of the NCO band (≈ 2270 cm⁻¹), and by NCO% titration to ensure stoichiometric conversion. After 1 hour, once the measured NCO% approached the theoretical value, 4-tert-butylphenol was introduced for end-capping, and the reaction was continued for an additional 4 hours until no NCO peak was detectable. The resulting adhesives were cooled to ambient temperature under nitrogen and stored in sealed containers for further analysis. Three series of bio-based polyurethane adhesives were synthesized: RPO-0.1, RPO-0.3, RPO-0.5; DG-0.1, DG-0.3, DG-0.5; and GL-0.1, GL-0.3, GL-0.5. Each series varied the ratio of bio-based polyol to PPG2000, facilitating a systematic investigation of the structure–property relationships. 2.3 Characterization Fourier-transform infrared (FT-IR) spectroscopy (PerkinElmer Spectrum Two, Waltham, MA, USA) with Attenuated Total Reflectance (ATR) mode was employed to confirm urethane bond formation. Gel Permeation Chromatography (GPC, Waters Alliance e2695, Milford, MA, USA) using tetrahydrofuran (THF) as the eluent (1.0 mL/min) and polystyrene standards were utilized to determine number-average molecular weight (Mn), weight-average molecular weight (Mw), and polydispersity index (PDI). The isocyanate content (NCO%) was quantified by titration following ASTM D2572-97. Thermogravimetric Analysis (TGA, TA Instruments Q500, New Castle, DE, USA) was conducted under a nitrogen atmosphere from room temperature to 600°C at a heating rate of 10°C/min. Differential Scanning Calorimetry (DSC, TA Instruments Q2000, New Castle, DE, USA) was performed under nitrogen with a heating/cooling/heating cycle at 10°C/min. The glass transition temperature (Tg) was determined from the second heating scan. X-ray Diffraction (XRD, X’Pert³, Malvern Panalytical) was carried out to investigate the crystalline structure over a 2θ range of 5° to 50°, with a step size of 0.02° and an acquisition time of 6–7 seconds per step. 2.4 Mechanical Property Testing Mechanical evaluations were conducted adhering to standardized protocols. For lap shear strength (ASTM D1002), impact resistance (ISO 11343), and T-peel strength (ASTM D1876) measurements, test specimens were fabricated by mixing 15.2 g of the commercial epoxy adhesive, 3.6 g of the synthesized polyurethane adhesive, and 1.2 g of DGEBA. The resultant mixture was applied to cold-rolled steel substrates, cured at 180°C for 20–30 minutes, and conditioned at ambient temperature for 24 hours prior to testing. Lap shear tests were performed using a LLOYD INSTRUMENT LR5K Plus universal testing machine (Bognor Regis, UK) at a crosshead speed of 1.3 mm/min, while T-peel tests were conducted at 254 mm/min. Impact resistance assessments utilized a pendulum impact tester in accordance with ISO 11343 guidelines. A minimum of three specimens were evaluated per formulation, and average values along with standard deviations were reported. 3. Results and Discussion 3.1 FT-IR Analysis Figure 1 presents the FT-IR spectra of the synthesized bio-based polyurethane adhesives and their respective polyol components. All bio-based polyurethane formulations exhibited characteristic N–H stretching (≈ 3300 cm⁻¹), C = O stretching (≈ 1730 cm⁻¹), and C–O stretching (≈ 1210 cm⁻¹) bands, confirming successful urethane bond formation. Notably, the intensity of the hydrogen-bonded N–H stretching peak (≈ 3300 cm⁻¹) increased with the incorporation of RPO polyol, indicating stronger hydrogen bonding interactions. This corresponds with the increased glass transition temperature (Tg) observed in DSC analysis (Fig. 4), supporting the hypothesis that RPO polyol enhances network rigidity through inter-chain interactions. Such spectral nuances indicate that polyol structure and functionality directly influence the urethane network architecture, enabling precise modulation of chain mobility, crosslink density, and intermolecular bonding [36, 37]. This molecular-level control lays the groundwork for rationally designing adhesives with targeted mechanical and thermal properties [38, 39]. 3.2 GPC and NCO% Analysis Table 1 summarizes the molecular weight (Mn, Mw, PDI) and NCO% conversion for each bio-based polyurethane formulation. The RPO-containing formulations exhibited higher polydispersity index (PDI > 1.8) compared to DG- and GL-based formulations (~ 1.5–1.6), suggesting increased branching and reduced segmental mobility [40–42]. These molecular weight variations correlate with mechanical properties: RPO-0.3 and RPO-0.5 demonstrated the highest shear strength (~ 32.5 MPa), whereas DG-0.5 and GL-0.5 exhibited enhanced impact resistance (~ 36.8 MPa) due to increased chain mobility. This result aligns with previous studies on rigid vs. flexible polyol incorporation in polyurethane networks [43]. Table 1 Molecular weight and NCO% data for bio-based polyurethane adhesives. Sample GPC NCO% Mn (g/mol) Mw (g/mol) PDI (Mw/Mn) Theoretical value Measured value Ref. 5579 9949 1.78 3.44 3.21 RPO-0.1 5564 9068 1.63 3.67 3.69 RPO-0.3 4531 7020 1.55 4.26 3.93 RPO-0.5 3550 7193 2.03 5.06 4.88 DG-0.1 5008 9328 1.86 3.73 3.64 DG-0.3 4680 8822 1.88 4.49 4.51 DG-0.5 3862 6072 1.57 5.65 5.30 GL-0.1 5023 9941 1.98 3.73 3.91 GL-0.3 4350 5490 1.26 4.51 4.52 GL-0.5 4197 7666 1.83 5.69 5.55 Collectively, these results underscore that bio-based polyols provide a versatile design parameter for engineering polyurethane adhesives with tailored macromolecular structures. By judiciously selecting polyol type and content, it becomes possible to modulate chain mobility, control crosslink density, and ultimately achieve adhesives that meet specific mechanical, thermal, and processing requirements. 3.3 XRD Analysis XRD measurements were conducted to assess the crystalline structure of the polyurethane networks (Fig. 2). All samples displayed broad diffraction halos characteristic of amorphous polymeric systems, indicating a predominantly crosslinked network. However, the relative intensities and widths of these halos varied among the different formulations, suggesting subtle yet meaningful differences in chain packing density and local molecular ordering [44]. Notably, the RPO series exhibited a more pronounced and slightly shifted halo compared to the Ref., implying that the rigid isosorbide-based segments promote a more compact and ordered network structure [45, 46]. This structural feature aligns with the enhanced thermal stability and elevated Tg observed in RPO-containing adhesives, as more constrained chain mobility likely arises from tighter molecular arrangements. In contrast, the DG and GL series displayed broader halos with comparatively lower intensities, indicating increased free volume and a less densely packed architecture. Such an arrangement corresponds well with the enhanced impact strength and energy dissipation capabilities identified in DG and GL based formulations, in which higher chain mobility facilitates more effective redistribution of stress under dynamic loading conditions. Interpreted alongside the FT-IR, GPC, thermal, and mechanical data, these XRD results underscore the critical importance of polyol structure in determining not only the chemical connectivity and molecular weight distribution but also the nanoscale chain arrangement within the polyurethane matrix. By correlating local structural motifs with macroscopic property profiles, this study reinforces the rationale for a holistic design approach. Through judicious selection and ratio control of bio-based polyols, it is possible to engineer polyurethane adhesives that combine superior thermal stability, mechanical robustness, and energy absorption with an environmentally sustainable materials portfolio. 3.4 Thermal Analysis (TGA and DSC) Figure 3 displays the TGA weight loss profiles, highlighting distinct thermal degradation patterns among the polyurethane adhesives. TGA results (Fig. 3) demonstrated that RPO-based polyurethane adhesives had a degradation onset temperature approximately 20–25°C higher than the petroleum-based reference system, reaching ~ 335°C. This improvement is attributed to the incorporation of isosorbide-derived polyols, which introduce rigid segments that enhance thermal resistance [47, 48]. In contrast, DG- and GL-containing samples exhibited lower degradation temperatures (~ 310–320°C) but significantly improved impact resistance (~ 77% increase compared to Ref.), demonstrating a trade-off between thermal stability and mechanical toughness [49]. Table 2 TGA and DSC data of bio-based polyurethane adhesives. Sample TGA DSC 95% Weight Loss (℃) 90% Weight Loss (℃) 50% Weight Loss (℃) Tg Ref. 141.61 165.43 315.44 -54.04 RPO-0.1 136.34 162.36 321.91 -53.55 RPO-0.3 161.96 183.54 327.20 -48.53 RPO-0.5 145.79 168.75 309.84 -42.09 DG-0.1 171.87 195.95 335.45 -49.18 DG-0.3 182.82 204.88 334.59 -44.48 DG-0.5 160.60 181.69 316.33 -39.69 GL-0.1 160.79 184.45 335.48 -48.41 GL-0.3 159.76 183.38 328.50 -47.23 GL-0.5 149.96 171.47 309.89 -41.55 This trend is further supported by DSC analysis (Fig. 4), where RPO-rich formulations exhibit higher Tg values (~ 5–10°C above Ref.), reinforcing their thermally stable and rigid network architecture [50]. Conversely, diglycerol and glycerol incorporation resulted in lower Tg values, introducing greater flexibility and enhancing the capacity for energy dissipation under stress [51]. These tunable thermal properties highlight the ability to tailor stiffness, ductility, and high temperature performance through strategic polyol selection, thereby broadening the application range of bio-based polyurethane adhesives. 3.5 Shear Strength Table 3 and Fig. 5 illustrate the shear strength variations among different polyurethane formulations. While the Ref. sample established a baseline (~ 23.4 MPa), RPO-0.3 and DG-0.5 formulations increased shear strength by up to ~ 38%, indicating that both rigid (RPO) and multifunctional (DG) polyols enhance interchain interactions and stress transfer. This improvement demonstrates that adjusting crosslink density and chain architecture can substantially reinforce the adhesive bond under static loading conditions. 3.6 Impact Strength Impact strength results emphasized the critical role of molecular architecture in dissipating dynamic loads. Figure 6 and Table 3 compare the impact resistance of bio-based polyurethane adhesives. Although the Ref. adhesive exhibited limited energy absorption (20.7 MPa), RPO-0.3 and GL-0.5 samples achieved approximately 75% and 78% higher impact strengths, respectively. Such enhancements suggest that balancing rigid segments with flexible domains facilitates more effective energy dissipation, reducing localized stresses and delaying crack propagation under sudden impact [52, 53]. These findings underscore the potential of bio-based polyols to improve toughness and durability without compromising structural integrity. Table 3 Mechanical properties of bio-based polyurethane adhesives. Sample Average Data Shear Strength (MPa) Standard deviation Impact Strength (MPa) Standard deviation T-Peel Strength (N/25mm) Ref. 23.4 0.3682 20.7 9.4044 151.0 RPO-0.1 23.7 0.2055 21.6 6.0024 103.9 RPO-0.3 27.1 0.4497 35.2 4.9173 168.7 RPO-0.5 27.2 0.2867 25.2 0.8807 65.4 DG-0.1 27.3 0.3300 20.0 3.7665 73.5 DG-0.3 30.9 0.4028 22.8 11.2021 69.1 DG-0.5 32.5 0.2867 32.1 4.4101 101.2 GL-0.1 27.2 0.9741 19.1 9.1371 110.0 GL-0.3 30.0 0.5099 24.3 14.4112 75.8 GL-0.5 30.1 0.4243 36.8 5.4683 76.2 3.7 T-Peel Strength T-peel strength measurements (Table 3) revealed that interfacial fracture resistance does not simply parallel trends observed in shear or impact strength. For instance, RPO-0.3 demonstrated high T-peel strength despite its relatively stiff network, indicating that interfacial bonding, chain orientation, and local segmental dynamics significantly influence peel performance. These results highlight that peel resistance may require targeted structural modifications, independent of those governing bulk mechanical or thermal properties, thus reinforcing the need for a holistic approach to adhesive design. Correlation and Design Implications Integrating the thermal and mechanical data reveals a nuanced interplay between crosslink density, segmental mobility, and network rigidity (Fig. 7). Higher Tg and enhanced thermal stability (RPO-based systems) often correlate with greater shear strength but may require careful tuning to preserve impact resistance [54]. Conversely, formulations incorporating glycerol or diglycerol yielded networks with lower Tg and moderate thermal stability yet superior energy dissipation, enabling improved impact performance at the cost of reduced stiffness. To visualize these multidimensional relationships, a radar plot (Fig. 7) compares three representative formulations (e.g., DG-0.5, GL-0.5, and RPO-0.3), illustrating how variations in polyol selection and ratio influence shear, impact, and T-peel strengths alongside thermal parameters such as Tg and thermal stability. This graphical representation highlights the trade-offs inherent in each formulation and provides a strategic blueprint for tuning individual properties while maintaining an appropriate overall performance balance. Overall Structure–Property Relationships Collectively, these findings emphasize that bio-based polyol selection and composition enable precise modulation of polyurethane network architecture, bridging the gap between mechanical strength, thermal stability, and interfacial adhesion [55]. Coupled with multidimensional data visualization (Fig. 8), this approach supports informed decision making in the design of sustainable, high-performance adhesives. This study establishes a rational design platform linking molecular structure to macroscopic properties, enabling the development of sustainable polyurethane adhesives. 4. Conclusion This study confirms that integrating renewable polyols—RPO polyol, diglycerol, and glycerol—into polyurethane networks based on PPG2000 and IPDI allows precise control over thermal stability and mechanical properties. A systematic evaluation of structure–property relationships confirms that polyol selection and network architecture significantly influence thermal stability, mechanical strength, and adhesion performance, leading to the development of bio-based polyurethane adhesives with competitive properties compared to conventional petroleum-based systems. In particular, the incorporation of isosorbide-derived polyol resulted in a 25°C increase in degradation onset temperature (~335°C), demonstrating superior thermal stability due to the rigid bicyclic structure. Furthermore, formulations modified with diglycerol and glycerol exhibited up to 39% higher shear strength (32.5 MPa) and 77% improved impact resistance (36.8 MPa), attributed to optimized crosslinking density and enhanced energy dissipation. These findings indicate that optimizing performance across shear, impact, and peel conditions requires precise structural control beyond compositional tuning. Optimizing molecular architecture and crosslinking density enables bio-based polyurethane adhesives to meet the stringent mechanical and thermal requirements of structural bonding applications [56]. From an industrial perspective, the findings indicate that bio-based polyurethane adhesives have the potential to replace petroleum-based systems in high-performance applications, including automotive, aerospace, and structural bonding. The ability to control network rigidity and flexibility through polyol composition presents significant opportunities for tailoring adhesives to diverse engineering requirements, offering a scalable and sustainable solution for next-generation bonding technologies. This study thus establishes a robust framework for designing next generation, high-performance bio-based polyurethane adhesives that align with sustainability goals, maintain stringent engineering standards, and broaden the scope of environmentally responsible material solutions. Declarations ■ Author information Corresponding Author PilHo Huh - Department of Polymer Science and Engineering, Pusan National University, Busan 46241, South Korea; Email: [email protected] Ji-Hong Bae - Department of Polymer Science and Engineering, Pusan National University, Busan 46241, South Korea; Email: [email protected] Authors Jin-Gyu Min, Won-Bin Lim, Ju-Hong Lee, Jae-Ryong Lee, Seung-Hyun Lee, Keun-Ho Lee - Polymer Science and Engineering, Pusan National University, Busan 46241, Republic of Korea Gwang-Seok Song - Industrial Biotechnology Program, Chemical R&D Center, Samyang Corporation, Daejeon 34055, Republic of Korea ■ Author contributions J.-G.M. performed the primary experiments, analyzed data, and drafted the manuscript. W.-B.L. participated in the design of the polymer synthesis protocols and contributed to data interpretation. J.-H.L. performed thermal analyses (TGA, DSC) and contributed to result visualization. J.-R.L. conducted the FT-IR spectroscopy and GPC measurements, and assisted in data curation. S.-H.L. assisted in mechanical testing and contributed to experimental validation. K.-H.L. conducted the XRD measurements, and assisted in data curation. G.-S.S. contributed to the structural adhesive performance evaluation, providing insights into mechanical testing and practical applications. J.-H.B. and P.H.H. conceptualized and supervised the project, provided resources, reviewed the manuscript, and approved the final version for publication. All authors discussed the results, reviewed the manuscript, and approved the final submission. ■ Acknowledgements This work was supported by Industrial Strategic Technology Development Program (Bio tackifier adhesive material with a biomass content of 50% or more, 20010807). ■ Conflicts of interest The authors declare no conflicts of interest. ■ Data availability statement The data supporting this article have been included as part of the Supplementary Information. References Das, A.; Mahanwar, P. A brief discussion on advances in polyurethane applications, Adv. Ind. Eng. Polym. Res., 2020, 3, 3, 93-101 Menon, A.; Sreeram, P.; Vinod, A.; Naiker, V.; Nandana, M.; David, D.; Sasidharan, S.; Raghavan, P. Chapter 4 - Polyurethane (PU): Structure, properties, and applications, Handbook of Thermosetting Foams, Aerogels, and Hydrogels, 2024, 67-92 Engels, H.; Pirkl, H.; Albers, R.; Albach, R.; Krause, J.; Hoffmann, A.; Casselmann, H.; Dormish, J. Polyurethanes: Versatile Materials and Sustainable Problem Solvers for Todays Challenges, Angew. Chem. Int. Ed., 2013, 52, 9422 – 9441 Maulana, S.; Wibowo, E.; Mardawati, E.; Iswanto, A.; Papadopoulos, A.; Lubis, M. Eco-Friendly and High-Performance Bio-Polyurethane Adhesives from Vegetable Oils: A Review, Polymers, 2024, 16, 1613 Golling, F.; Pires, R.; Hecking, A.; Weikard, J.; Richter, F.; Danielmeier, K.; Dijkstra, D. Polyurethanes for coatings andadhesives – chemistry and applications, Polym Int., 2019, 68, 848–855 Mahmood, N.; Yuan, Z.; Schmidt, J.; Xu, C. Depolymerization of lignins and their applications for the preparation of polyols and rigid polyurethane foams: A review, Renew. Sustain. Energy Rev., 2023, 60, 317-329 Shi, C.; Zhang, Y.; Shao, Y.; R, S.; Wang, B.; Zhao, Z.; Yu, B.; Zhang, X.; Li, W.; Ding, J.; Liu, Z.; Zhang, H. A review on the occurrence, detection methods, and ecotoxicity of biodegradable microplastics in the aquatic environment: New cause for concern, TrAC - Trends Anal. Chem., 178, 2024, 117832 Bartolo, A.; Infurna, G.; Dintcheva, N. A Review of Bioplastics and Their Adoption in the Circular Economy, Polymers, 2021, 13, 1229 Ail, S.; Abdelkarim, E.; Elsamahy, T.; Al-Tohamy, R.; Li, F.; Kornaros, M.; Zuorro, A.; Zhu, D.; Sun, J. Bioplastic production in terms of life cycle assessment: A state-of-the-art review, Environ. Sci. Ecotechnology, 15, 2023, 100254 Wang, H.; Yang, B.; Zhang, Q.; Zhu, W. Catalytic routes for the conversion of lignocellulosic biomass to aviation fuel range hydrocarbons, Renew. Sustain. Energy Rev., 2020, 120, 109612 Sofian, A.; Sun, X.; Gupta, Vijai.; Berenjian, A.; Xia, A.; Ma, Z.; Show, P. Advances, Synergy, and Perspectives of Machine Learning and Biobased Polymers for Energy, Fuels, and Biochemicals for a Sustainable Future, Energ. Fuel., 2024, 38, 3, 1593-1617 Sarangi, P.; Singh, A.; V. Ganachari, S.; Pengadeth, D.; Mohanakrishna, G.; M. Aminabhavi, T. Biobased heterogeneous renewable catalysts: Production technologies, innovations, biodiesel applications and circular bioeconomy, Environ. Res., 2024, 261, 119745 Nanda, S, R. Parta, B.; Patel, Ravi.; Bakos, J.; K. Dalai, A. Innovations in applications and prospects of bioplastics and biopolymers: a review, Environ. Chem. Lett., 2022, 20, 379-395 Burelo, M.; Martínez, A.; Hernández-Varela, J.; Stringer, T.; Ramírez-Melgarejo, M.; Y. Yau, A.; Luna-Bárcenas, T.; D. Treviño-Quintanilla, C. Recent Developments in Synthesis, Properties, Applications and Recycling of Bio-Based Elastomers, Molecules, 2024, 29, 387 Oh, E.; Zúniga, M.; Nguyen, T.; Kim, B.; Tien, T.; Suhr, J. Sustainable green composite materials in the next-generation mobility industry: review and prospective, Adv. Compos. Mater., 2024, 33, 6, 1368-1419 Ciastowicz, Z.; Pamula, R.; Bialowiec, A. Utilization of Plant Oils for Sustainable Polyurethane Adhesives:A Review, A Review. Materials, 2024, 17(8), 1738 Sternberg, J.; Sequerth, O.; Pilla, S. Green chemistry design in polymers derived from lignin: review and perspective, Prog. Polym. Sci., 2021, 113 Luleburgaz, S.; Cakmakci, E.; Durmaz, H.; Tunca, U. Sustainable polymers from renewable resources through click and multicomponent reactions, Eur. Polym. J., 2024, 209, 112897 Laurichesse, S.; Huillet, C.; Avérous, L. Original polyols based on organosolv lignin and fatty acids: new bio-based building blocks for segmented polyurethane synthesis, Green. Chem., 2014, 16, 3958 Sugiarto, S.; Pong, R.; Tan, Y.’ Leow, Y.; Sathasivam, T.; Zhu, Q.; Loh, X.; Kai, D. Advances in sustainable polymeric materials from lignocellulosic biomass, Mater. Today Chem., 2022, 26, 101022 Laurichesse, S.; Avérous, L. Chemical modification of lignins: Towards biobased polymers, Prog. Polym. Sci., 2014, 39, 7, 1266-1290 Sen, S.; Patil, S.; S. Argyropoulos, D. Thermal properties of lignin in copolymers, blends, and composites: a review, Green Chem., 2015, 17, 4862 Ghasemlou, M.; Daber, F.; P. Ivanova, E.; Adhikari, B. Polyurethanes from seed oil-based polyols: A review of synthesis, mechanical and thermal properties, Ind. Crops. Prod., 2019, 142, 111841 Carvalho, D.; Ferreira, N.; França, B.; Marques, R.; Silva, M.; Silva, S.; Silva, E.; Macário, D.; Barroso, L.; Silva, C.; Oliveira, C. Advancing sustainability in the automotive industry: Bioprepregs and fully bio-based composites, Compos. C: Open Access, 2024, 14 Popescu, C.; Dissanayake, H.; Mansi, E.; Stancu, A. Eco Breakthroughs: Sustainable Materials Transforming the Future of Our Planet, Sustainability, 2024, 16, 10790. Cui, S.; Liu, Z.; Li, Y. Bio-polyols synthesized from crude glycerol and applications on polyurethane wood adhesives, Ind. Crops. Prod., 2017, 108, 798-805 Min, J.; Lim, W.; Lee, J.; Lee, J.; Bae, J.; Huh, P. A facile strategy for synthesizing isosorbide‑based polyurethane structural adhesives and core–shell rubber, Sci. Rep., 2024, 14, 21018 S. Pillai, C. Challenges for Natural Monomers and Polymers: NovelDesign Strategies and Engineering to DevelopAdvanced Polymers, Des. Monomers Polym., 2010, 13, 87-121 Toader, G.; Diacon, A.; M. Axinte, S.; Mocanu, A.; Rusen, E. State-of-the-Art Polyurea Coatings: Synthesis Aspects, Structure–Properties Relationship, and Nanocomposites for Ballistic Protection Applications, Polymers, 2024, 16, 454 E. Souza, GAL.; D. Pietro, M.; Mele, A. Eutectic solvents and low molecular weight gelators for next-generation supramolecular eutectogels: a sustainable chemistry perspective, RSC Sustainability, 2024, 2, 288 Marques, A.; Mocanu, A.; Tomić, N.; Balos, S.; Stammen, E.; Lundevall, A.; Abrahami, S.; Günther, R.; de Kok, J.; de Freitas, S. Review on Adhesives and Surface Treatments for Structural Applications: Recent Developments on Sustainability and Implementation for Metal and Composite Substrates, Materials, 2020, 13(24), 5590 Joseph, T.; Unni, A.; Joshy, K.; Mahapatra, D.; Haponiuk, J.; Thomas, S. Emerging Bio-Based Polymers from Lab to Market: Current Strategies, Market Dynamics and Research Trends, C., 2023, 9, 30. Riina, M.; Hanna, B.; Mikko, W.; Johanna, K. ed. Valuable biochemicals of the future : The outlook for bio-based value-added chemicals and their growing markets, Luke luobio, 2024, 85 Wang, R.; Feng, Y.; Li, D.; Li, K.; Yan, Y. Towards the sustainable production of biomass-derived materials with smart functionality: a tutorial review, Green. Chem., 2024, 26, 9075-9103 Chen, T.; Kim, H.; Pan, S.; Tseng, P.; Lin, Y.; Chiang, P. Implementation of green chemistry principles in circular economy system towards sustainable development goals: Challenges and perspectives, Sci. Total Environ., 2020, 716 [36] Suresh, Kattimuttathu. I. Rigid Polyurethane Foams from Cardanol: Synthesis, Structural Characterization, and Evaluation of Polyol and Foam Properties, ACS Sustain Chem Eng., 2013, 1, 232-242 Gazil, O.; Bernardi, J.; Lassus, A.; Virgilio, N.; Unterlas, M. M. Urethane functions can reduce metal salts under hydrothermal conditions: synthesis of noble metal nanoparticles on flexible sponges applied in semi-automated organic reduction, J. Mater. Chem. A, 2023, 11, 12703-12712 Guo, Z.; Bao, C.; Wang, X.; Lu, X.; Sun, H.; Li, X.; Lia, J.; Sun, J. Room-temperature healable, recyclable and mechanically super-strong poly(urea-urethane)s cross-linked with nitrogen-coordinated boroxines. J. Mater. Chem. A, 2021, 9, 11025–11032 Usman, A.; Hussain, M. T.; Akram, N.; Zuber, M.; Sultana, S.; Aftab, W.; Zia, K. M.; Maqbool, M.; Alanazi, Y. M.; Nazirf, A.; Javaid, M. A. Modulating alginate-polyurethane elastomer properties: Influence of NCO/OH ratio with aliphatic diisocyanate, Int J Biol Macromol, 2024, 278, 134657 Kulshrestha, A. S.; Gao, W.; Gross, R. A. Glycerol Copolyesters: Control of Branching and Molecular Weight Using a Lipase Catalyst, Macromolecules, 2005, 38, 3193-3204 Sadler, J. M.; Nguyen, A-. P. T.; Toulan, F. R.; Szabo, J. P.; Palmese, G. R.; Scheck, C.; Lutgend, S.; La Scala, J. J. Isosorbide-methacrylate as a bio-based low viscosity resin for high performance thermosetting applications, J. Mater. Chem. A, 2013, 1, 12579-12586 Weinland, D. H.; Putten, R-. J. V.; Gruter, G-. J. M. Evaluating the commercial application potential of polyesters with 1,4:3,6-dianhydrohexitols (isosorbide, isomannide and isoidide) by reviewing the synthetic challenges in step growth polymerization, Eur Polym J, 2022, 164, 110964 Li, J. Yang, W.; Ning, Z.; Yang, B.; Zeng, Y. Sustainable Polyurethane Networks Based on Rosin with Reprocessing Performance, Polymers, 2021, 13, 3538 Luo, K.; Zhu, G.; Zhao, Y.; Luo, Z.; Liu, X.; Zhang, K.; Lia, Y.; Scott, K. Enhanced cycling stability of Li–O2 batteries by using a polyurethane/SiO2/glass fiber nanocomposite separator, J. Mater. Chem. A, 2018, 6, 7770–7776 Du, Y-. R.; Xu, B-. H.; Xia, S-. P.; Ding, G-. R.; Zhang, S-. J. Dehydrative Formation of Isosorbide from Sorbitol over Poly(ionic liquid)−Covalent Organic Framework Hybrids, ACS Appl. Mater. Interfaces, 2021, 13, 552−562 Chen, Z.; Lu, H. Constructing sacrificial bonds and hidden lengths for ductile graphene/polyurethane elastomers with improved strength and toughness, J. Mater. Chem., 2012, 22, 12479-12490 Liu, S-. H.; Shen, M-. Y.; Kuan, C-. F.;Kuan, H-. C.; Ke, C-. Y.; Chiang, C-. L. Improving Thermal Stability of Polyurethane through the Addition of Hyperbranched Polysiloxane, Polymers, 2019, 11, 697 Qiu, H.; Qiu, X.; Dai, X.; Sun, Z-. Y. Design of polyimides with targeted glass transition temperature using a graph neural network, J. Mater. Chem. C, 2023, 11, 2930–2940 Rutkowski, P.; Kwiecie, K.; Berezicka, A.; Sułowska, J.; Kwiecie, A.; Sliwa-Wieczorek, K.; Azinovic, B.; Schwarzkopf, M.; Pondelak, A.; Pecnik, J. G.; Szumera, M. Thermal Stability and Heat Transfer of Polyurethanes for Joints Applications of Wooden Structures, Molecules, 2024, 29, 3337 Joo, A-. R.; Lee, J-. H.; Park, Y-. G. Lee, S-. H. Thermal Stability of Polyurethane Foams Infused with Melamine-phosphate Coated Inorganic Flame Retardants, Polymer, 2018, 42, 2, 288-297 Laukkanen, T.; Reddy, P. G.; Barua, A.; Kumar, M.; Kolpakov, K.; Tirrib, T.; Sharma, V. Sustainable castor oil-derived cross-linked poly(ester-urethane) elastomeric films for stretchable transparent conductive electrodes and heaters, J. Mater. Chem. A, 2024, 12, 33177–33192 Dong, F.; Yang, X.; Guo, L.; Wang, Y.; Shaghaleh, H.; Huang, Z.; Xu, X.; Wang, S.; Liu, H. Self-healing polyurethane with high strength and toughness based on a dynamic chemical strategy, J. Mater. Chem. A, 2022, 10, 10139–10149 Griggs, T.; Ahmed, J.; Majd, H.; Edirisingheb, M.; Chen, B. A bio-based thermoplastic polyurethane with triple self-healing action for wearable technology and smart textiles, Mater. Adv., 2024, 5, 6210–6221 Park, C. Y. Effect of PPG, MDI, 2-HEMA and butyl acrylate content on the properties of polyurethane adhesive, Elastomers and Composites, 49, 3, 245-252 Brzoska, J.; Datta, J.; Konefał, R.; Pokorný, V.; Beneš, H. The influence of bio-based monomers on the structure and thermal properties of polyurethanes, Scientific Reports, 2024, 14, 29042 Nijst, C. L. E.; Bruggeman, J. P.; Karp, J. M.; Ferreira, L.; Zumbuehl, A.; Bettinger, C. J.; Langer, R. Synthesis and Characterization of Photocurable Elastomersfrom Poly(glycerol-co-sebacate), Biomacromolecules, 2007, 8, 3067-3073 Scheme Scheme 1 and 2 are available in the Supplementary Files section. Additional Declarations No competing interests reported. Supplementary Files SCHEME1.png Scheme 1. Synthesis and end-capping of bio-based polyurethane adhesives. SCHEME2.png Scheme 2. Proposed high-temperature curing mechanism for epoxy-modified bio-based polyurethane adhesives. Cite Share Download PDF Status: Posted Version 1 posted 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. Our growing team is made up of researchers and industry professionals working together to solve the most critical problems facing scientific publishing. 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-6258415","acceptedTermsAndConditions":true,"allowDirectSubmit":true,"archivedVersions":[],"articleType":"Research Article","associatedPublications":[],"authors":[{"id":436532013,"identity":"001806d3-1436-4c9d-b7ea-47ce37e80ab6","order_by":0,"name":"Jin-Gyu Min","email":"","orcid":"","institution":"Pusan National University","correspondingAuthor":false,"prefix":"","firstName":"Jin-Gyu","middleName":"","lastName":"Min","suffix":""},{"id":436532015,"identity":"17fa4d34-8401-44c4-8f87-2bf2f66faeae","order_by":1,"name":"Won-Bin Lim","email":"","orcid":"","institution":"Pusan National 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06:23:13","currentVersionCode":1,"declarations":"","doi":"10.21203/rs.3.rs-6258415/v1","doiUrl":"https://doi.org/10.21203/rs.3.rs-6258415/v1","draftVersion":[],"editorialEvents":[],"editorialNote":"","failedWorkflow":false,"files":[{"id":79769327,"identity":"cc4e9220-63a6-4ff4-9efc-cf968c400e76","added_by":"auto","created_at":"2025-04-02 13:00:46","extension":"png","order_by":1,"title":"Figure 1","display":"","copyAsset":false,"role":"figure","size":37070,"visible":true,"origin":"","legend":"\u003cp\u003eFT-IR spectra of synthesized bio-based polyurethane adhesives and their polyol components.\u003c/p\u003e","description":"","filename":"1.png","url":"https://assets-eu.researchsquare.com/files/rs-6258415/v1/d132dc1a8031e12a7b77af81.png"},{"id":79769357,"identity":"91914400-5409-439b-8770-227cebad383d","added_by":"auto","created_at":"2025-04-02 13:00:47","extension":"png","order_by":2,"title":"Figure 2","display":"","copyAsset":false,"role":"figure","size":22458,"visible":true,"origin":"","legend":"\u003cp\u003eXRD patterns of bio-based polyurethane adhesives with different polyol compositions.\u003c/p\u003e","description":"","filename":"2.png","url":"https://assets-eu.researchsquare.com/files/rs-6258415/v1/98fb9296028756b108df8258.png"},{"id":79769360,"identity":"2094e547-38d3-409a-a342-dde7f6cefcb2","added_by":"auto","created_at":"2025-04-02 13:00:47","extension":"png","order_by":3,"title":"Figure 3","display":"","copyAsset":false,"role":"figure","size":42190,"visible":true,"origin":"","legend":"\u003cp\u003eTGA curves showing weight loss of bio-based polyurethane adhesives.\u003c/p\u003e","description":"","filename":"3.png","url":"https://assets-eu.researchsquare.com/files/rs-6258415/v1/c1a9d14faccb2f28cda993ff.png"},{"id":79770194,"identity":"b1ea7407-e941-498c-bf79-4d8ab35dffe9","added_by":"auto","created_at":"2025-04-02 13:08:46","extension":"png","order_by":4,"title":"Figure 4","display":"","copyAsset":false,"role":"figure","size":44206,"visible":true,"origin":"","legend":"\u003cp\u003eDSC thermograms of bio-based polyurethane adhesives.\u003c/p\u003e","description":"","filename":"4.png","url":"https://assets-eu.researchsquare.com/files/rs-6258415/v1/27d73568fde951570a53d45a.png"},{"id":79770195,"identity":"36a19561-9d68-48e2-851a-9eb228ad3a39","added_by":"auto","created_at":"2025-04-02 13:08:46","extension":"png","order_by":5,"title":"Figure 5","display":"","copyAsset":false,"role":"figure","size":42570,"visible":true,"origin":"","legend":"\u003cp\u003eShear and impact strength of bio-based polyurethane adhesives.\u003c/p\u003e","description":"","filename":"5.png","url":"https://assets-eu.researchsquare.com/files/rs-6258415/v1/3976efd78e31027b450c7505.png"},{"id":79769350,"identity":"c8204fbc-1c39-4d20-a39c-8641fc9ee7ed","added_by":"auto","created_at":"2025-04-02 13:00:46","extension":"png","order_by":6,"title":"Figure 6","display":"","copyAsset":false,"role":"figure","size":34605,"visible":true,"origin":"","legend":"\u003cp\u003eT-peel strength of bio-based polyurethane adhesives.\u003c/p\u003e","description":"","filename":"6.png","url":"https://assets-eu.researchsquare.com/files/rs-6258415/v1/06753f11dc0e0f3dbe9f7a1c.png"},{"id":79769369,"identity":"20923068-214a-4df1-a725-058cb69495c5","added_by":"auto","created_at":"2025-04-02 13:00:47","extension":"png","order_by":7,"title":"Figure 7","display":"","copyAsset":false,"role":"figure","size":45890,"visible":true,"origin":"","legend":"\u003cp\u003eCorrelations between impact strength and thermal properties (Tg, 50% weight temperature) of bio-based polyurethane adhesives.\u003c/p\u003e","description":"","filename":"7.png","url":"https://assets-eu.researchsquare.com/files/rs-6258415/v1/ae561e6a3a197231ec1cf6f6.png"},{"id":79770205,"identity":"31b42a2e-064f-4893-ab89-5747236e04f9","added_by":"auto","created_at":"2025-04-02 13:08:47","extension":"png","order_by":8,"title":"Figure 8","display":"","copyAsset":false,"role":"figure","size":166482,"visible":true,"origin":"","legend":"\u003cp\u003eRadar plot of mechanical (shear, impact, T-peel) and thermal (Tg, 50% weight) properties for DG-0.5, GL-0.5, and RPO-0.3.\u003c/p\u003e","description":"","filename":"8.png","url":"https://assets-eu.researchsquare.com/files/rs-6258415/v1/7d5de5078991e999d85bca28.png"},{"id":83863997,"identity":"029fac51-3f48-44f6-b063-ee5c61c7d888","added_by":"auto","created_at":"2025-06-03 20:46:31","extension":"pdf","order_by":0,"title":"","display":"","copyAsset":false,"role":"manuscript-pdf","size":1160662,"visible":true,"origin":"","legend":"","description":"","filename":"manuscript.pdf","url":"https://assets-eu.researchsquare.com/files/rs-6258415/v1/b5c59577-d5a7-4dde-aba1-0e31250c9670.pdf"},{"id":79769349,"identity":"ef4971b7-e9fb-4c0b-9139-d02569bcea05","added_by":"auto","created_at":"2025-04-02 13:00:46","extension":"png","order_by":1,"title":"","display":"","copyAsset":false,"role":"supplement","size":47931,"visible":true,"origin":"","legend":"\u003cp\u003e\u003cstrong\u003eScheme 1. \u0026nbsp;\u003c/strong\u003eSynthesis and end-capping of bio-based polyurethane adhesives.\u003c/p\u003e","description":"","filename":"SCHEME1.png","url":"https://assets-eu.researchsquare.com/files/rs-6258415/v1/3ddc79c6cd20a72dc5971363.png"},{"id":79769348,"identity":"919bdc3a-b21c-4e65-ab1c-8df9cfaeebd5","added_by":"auto","created_at":"2025-04-02 13:00:46","extension":"png","order_by":2,"title":"","display":"","copyAsset":false,"role":"supplement","size":55909,"visible":true,"origin":"","legend":"\u003cp\u003e\u003cstrong\u003eScheme 2. \u0026nbsp;\u003c/strong\u003eProposed high-temperature curing mechanism for epoxy-modified bio-based polyurethane adhesives.\u003c/p\u003e","description":"","filename":"SCHEME2.png","url":"https://assets-eu.researchsquare.com/files/rs-6258415/v1/00aed1d77bd6f234d9509ffb.png"}],"financialInterests":"No competing interests reported.","formattedTitle":"Sustainable Bio-based Polyurethane Adhesives Utilizing PPG2000 and Renewable Polyols: Synthesis, Characterization, and Mechanical Properties","fulltext":[{"header":"1. Introduction","content":"\u003cp\u003ePolyurethane (PU) adhesives are essential in various industrial applications, providing excellent mechanical strength, chemical resistance, and bonding versatility [1\u0026ndash;5]. However, the prevailing reliance on petroleum-derived polyols raises environmental and economic concerns, such as resource depletion and increased carbon footprints [6\u0026ndash;10]. In response, the global push for sustainable solutions has propelled the development of bio-based PU systems that harness renewable feedstocks and minimize ecological impact [11\u0026ndash;13].\u003c/p\u003e \u003cp\u003eAs part of this transition, exploring novel bio-based polyols is a key strategy for developing high-performance, eco-friendly adhesives [14, 15]. While bio-derived precursors like vegetable oils and lignin show promise, the systematic integration of RPO polyol, diglycerol, and glycerol in PU adhesives remains largely unexplored [16\u0026ndash;18]. These bio-based polyols, distinguished by their unique chemical functionalities and architectures, offer promising avenues to modulate crosslink density, thermal stability, and viscoelastic properties [19, 20].\u003c/p\u003e \u003cp\u003eDespite significant progress, the structure\u0026ndash;property relationships of bio-based PU adhesives remain insufficiently understood, particularly concerning the molecular effects of polyol structure and composition [21\u0026ndash;23]. Addressing this knowledge gap is critical for designing next-generation materials that balance mechanical strength, thermal resilience, and adhesive performance without compromising their environmental credentials [24, 25].\u003c/p\u003e \u003cp\u003eThis study systematically investigates bio-based PU adhesives formulated with PPG2000 and IPDI, integrating RPO polyol, diglycerol, and glycerol at controlled ratios [26, 27]. By elucidating how each bio-based polyol modulates molecular architecture, thermal transitions, and mechanical behavior, this work aims to establish correlations that guide the rational selection and formulation of bio-based adhesives [28\u0026ndash;30]. This study demonstrates that precise polyol selection and ratio control optimize crosslink density, thermal stability, and mechanical robustness, surpassing conventional petroleum-based adhesives.\u003c/p\u003e \u003cp\u003eThis study provides a comprehensive framework for designing high-performance bio-based PU adhesives, offering a sustainable alternative with enhanced mechanical and thermal properties compared to petroleum-based adhesives [31\u0026ndash;33]. Moreover, this study aligns with principles of green chemistry and sustainable material innovation, setting a foundation for scalable industrial applications and broader adoption of environmentally responsible bonding technologies [34]. In doing so, it aspires to foster a transformative pathway from traditional adhesives to high-performance, renewable alternatives, ultimately contributing to more sustainable industrial practices and material ecosystems [35].\u003c/p\u003e"},{"header":"2. Material and Methods","content":"\u003cdiv id=\"Sec3\" class=\"Section2\"\u003e \u003ch2\u003e2.1. Materials\u003c/h2\u003e \u003cp\u003ePolypropylene glycol (PPG2000, Mn\u0026thinsp;\u0026asymp;\u0026thinsp;2000 g/mol, hydroxyl value: 56 mg KOH/g) was purchased from Sigma-Aldrich (St. Louis, MO, USA) and used without further purification. The bio-based polyols included an isosorbide-derived polyol (RPO polyol, Mn\u0026thinsp;\u0026asymp;\u0026thinsp;500\u0026ndash;800 g/mol) supplied by Samyang Inc. (Daejeon, South Korea), diglycerol (purity\u0026thinsp;\u0026ge;\u0026thinsp;90%, functionality f\u0026thinsp;=\u0026thinsp;4) and glycerol (purity\u0026thinsp;\u0026ge;\u0026thinsp;99%, f\u0026thinsp;=\u0026thinsp;3) obtained from TCI Chemical (Tokyo, Japan). The molecular weight distribution of the RPO polyol was verified using GPC prior to use. Isophorone diisocyanate (IPDI, purity\u0026thinsp;\u0026ge;\u0026thinsp;98%) was provided by DAEJUNG (Siheung, South Korea), and dibutyltin dilaurate (DBTDL, purity\u0026thinsp;\u0026ge;\u0026thinsp;95%) was obtained from Sigma-Aldrich. The blocking agent 4-tert-butylphenol (purity\u0026thinsp;\u0026ge;\u0026thinsp;99%) was also purchased from Sigma-Aldrich.\u003c/p\u003e \u003cp\u003eBefore use, all polyols were dried under vacuum at 80\u0026deg;C for 24 hours to remove residual moisture. IPDI was distilled under reduced pressure to eliminate impurities. 4-tert-butylphenol was dried in a vacuum oven at 40\u0026deg;C for 12 hours.\u003c/p\u003e \u003c/div\u003e \u003cdiv id=\"Sec4\" class=\"Section2\"\u003e \u003ch2\u003e2.2 Synthesis of Bio-based Polyurethane Adhesives\u003c/h2\u003e \u003cp\u003eBio-based polyurethane adhesives were synthesized via a one-shot polymerization method using a 500 mL four-neck round-bottom flask equipped with a mechanical stirrer, nitrogen inlet, digital thermometer, and a reflux condenser. The total polyols (PPG2000 and bio-based polyols) and IPDI were introduced at a fixed molar ratio of 1:2:1.4. The bio-based polyols (RPO, diglycerol, glycerol) replaced portions of PPG2000 at equivalence ratios of 0.9:0.1, 0.7:0.3, and 0.5:0.5, respectively. A control sample (Ref.) was synthesized using only PPG2000 to establish baseline comparisons. In a typical synthesis procedure, PPG2000, the designated bio-based polyol, and IPDI were charged into the reactor under a dry nitrogen atmosphere and heated to 70\u0026deg;C with stirring at 150 rpm. The DBTDL catalyst (0.05 wt% relative to total reactants) was added to initiate polymerization.\u003c/p\u003e \u003cp\u003eReaction progress was monitored using FT-IR spectroscopy, focusing on the disappearance of the NCO band (\u0026asymp;\u0026thinsp;2270 cm⁻\u0026sup1;), and by NCO% titration to ensure stoichiometric conversion. After 1 hour, once the measured NCO% approached the theoretical value, 4-tert-butylphenol was introduced for end-capping, and the reaction was continued for an additional 4 hours until no NCO peak was detectable. The resulting adhesives were cooled to ambient temperature under nitrogen and stored in sealed containers for further analysis.\u003c/p\u003e \u003cp\u003eThree series of bio-based polyurethane adhesives were synthesized: RPO-0.1, RPO-0.3, RPO-0.5; DG-0.1, DG-0.3, DG-0.5; and GL-0.1, GL-0.3, GL-0.5. Each series varied the ratio of bio-based polyol to PPG2000, facilitating a systematic investigation of the structure\u0026ndash;property relationships.\u003c/p\u003e \u003cp\u003e \u003c/p\u003e \u003cp\u003e \u003c/p\u003e \u003c/div\u003e \u003cdiv id=\"Sec5\" class=\"Section2\"\u003e \u003ch2\u003e2.3 Characterization\u003c/h2\u003e \u003cp\u003eFourier-transform infrared (FT-IR) spectroscopy (PerkinElmer Spectrum Two, Waltham, MA, USA) with Attenuated Total Reflectance (ATR) mode was employed to confirm urethane bond formation. Gel Permeation Chromatography (GPC, Waters Alliance e2695, Milford, MA, USA) using tetrahydrofuran (THF) as the eluent (1.0 mL/min) and polystyrene standards were utilized to determine number-average molecular weight (Mn), weight-average molecular weight (Mw), and polydispersity index (PDI). The isocyanate content (NCO%) was quantified by titration following ASTM D2572-97.\u003c/p\u003e \u003cp\u003eThermogravimetric Analysis (TGA, TA Instruments Q500, New Castle, DE, USA) was conducted under a nitrogen atmosphere from room temperature to 600\u0026deg;C at a heating rate of 10\u0026deg;C/min. Differential Scanning Calorimetry (DSC, TA Instruments Q2000, New Castle, DE, USA) was performed under nitrogen with a heating/cooling/heating cycle at 10\u0026deg;C/min. The glass transition temperature (Tg) was determined from the second heating scan. X-ray Diffraction (XRD, X\u0026rsquo;Pert\u0026sup3;, Malvern Panalytical) was carried out to investigate the crystalline structure over a 2θ range of 5\u0026deg; to 50\u0026deg;, with a step size of 0.02\u0026deg; and an acquisition time of 6\u0026ndash;7 seconds per step.\u003c/p\u003e \u003c/div\u003e \u003cdiv id=\"Sec6\" class=\"Section2\"\u003e \u003ch2\u003e2.4 Mechanical Property Testing\u003c/h2\u003e \u003cp\u003eMechanical evaluations were conducted adhering to standardized protocols. For lap shear strength (ASTM D1002), impact resistance (ISO 11343), and T-peel strength (ASTM D1876) measurements, test specimens were fabricated by mixing 15.2 g of the commercial epoxy adhesive, 3.6 g of the synthesized polyurethane adhesive, and 1.2 g of DGEBA. The resultant mixture was applied to cold-rolled steel substrates, cured at 180\u0026deg;C for 20\u0026ndash;30 minutes, and conditioned at ambient temperature for 24 hours prior to testing. Lap shear tests were performed using a LLOYD INSTRUMENT LR5K Plus universal testing machine (Bognor Regis, UK) at a crosshead speed of 1.3 mm/min, while T-peel tests were conducted at 254 mm/min. Impact resistance assessments utilized a pendulum impact tester in accordance with ISO 11343 guidelines. A minimum of three specimens were evaluated per formulation, and average values along with standard deviations were reported.\u003c/p\u003e \u003c/div\u003e"},{"header":"3. Results and Discussion","content":"\u003cdiv id=\"Sec8\" class=\"Section2\"\u003e \u003ch2\u003e3.1 FT-IR Analysis\u003c/h2\u003e \u003cp\u003eFigure 1 presents the FT-IR spectra of the synthesized bio-based polyurethane adhesives and their respective polyol components. All bio-based polyurethane formulations exhibited characteristic N\u0026ndash;H stretching (\u0026asymp;\u0026thinsp;3300 cm⁻\u0026sup1;), C\u0026thinsp;=\u0026thinsp;O stretching (\u0026asymp;\u0026thinsp;1730 cm⁻\u0026sup1;), and C\u0026ndash;O stretching (\u0026asymp;\u0026thinsp;1210 cm⁻\u0026sup1;) bands, confirming successful urethane bond formation. Notably, the intensity of the hydrogen-bonded N\u0026ndash;H stretching peak (\u0026asymp;\u0026thinsp;3300 cm⁻\u0026sup1;) increased with the incorporation of RPO polyol, indicating stronger hydrogen bonding interactions. This corresponds with the increased glass transition temperature (Tg) observed in DSC analysis (Fig.\u0026nbsp;4), supporting the hypothesis that RPO polyol enhances network rigidity through inter-chain interactions.\u003c/p\u003e \u003cp\u003e \u003c/p\u003e \u003cp\u003eSuch spectral nuances indicate that polyol structure and functionality directly influence the urethane network architecture, enabling precise modulation of chain mobility, crosslink density, and intermolecular bonding [36, 37]. This molecular-level control lays the groundwork for rationally designing adhesives with targeted mechanical and thermal properties [38, 39].\u003c/p\u003e \u003c/div\u003e \u003cdiv id=\"Sec9\" class=\"Section2\"\u003e \u003ch2\u003e3.2 GPC and NCO% Analysis\u003c/h2\u003e \u003cp\u003eTable\u0026nbsp;1 summarizes the molecular weight (Mn, Mw, PDI) and NCO% conversion for each bio-based polyurethane formulation. The RPO-containing formulations exhibited higher polydispersity index (PDI\u0026thinsp;\u0026gt;\u0026thinsp;1.8) compared to DG- and GL-based formulations (~\u0026thinsp;1.5\u0026ndash;1.6), suggesting increased branching and reduced segmental mobility [40\u0026ndash;42]. These molecular weight variations correlate with mechanical properties: RPO-0.3 and RPO-0.5 demonstrated the highest shear strength (~\u0026thinsp;32.5 MPa), whereas DG-0.5 and GL-0.5 exhibited enhanced impact resistance (~\u0026thinsp;36.8 MPa) due to increased chain mobility. This result aligns with previous studies on rigid vs. flexible polyol incorporation in polyurethane networks [43].\u003c/p\u003e \u003cp\u003e \u003cdiv class=\"gridtable\"\u003e\u003ctable float=\"Yes\" id=\"Tab1\" border=\"1\"\u003e \u003ccaption language=\"En\"\u003e \u003cdiv class=\"CaptionNumber\"\u003eTable 1\u003c/div\u003e \u003cdiv class=\"CaptionContent\"\u003e \u003cp\u003eMolecular weight and NCO% data for bio-based polyurethane adhesives.\u003c/p\u003e \u003c/div\u003e \u003c/caption\u003e \u003ccolgroup cols=\"6\"\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c1\" colnum=\"1\"\u003e\u003c/div\u003e \u003cdiv align=\"char\" char=\".\" class=\"colspec\" colname=\"c2\" colnum=\"2\"\u003e\u003c/div\u003e \u003cdiv align=\"char\" char=\".\" class=\"colspec\" colname=\"c3\" colnum=\"3\"\u003e\u003c/div\u003e \u003cdiv align=\"char\" char=\".\" class=\"colspec\" colname=\"c4\" colnum=\"4\"\u003e\u003c/div\u003e \u003cdiv align=\"char\" char=\".\" class=\"colspec\" colname=\"c5\" colnum=\"5\"\u003e\u003c/div\u003e \u003cdiv align=\"char\" char=\".\" class=\"colspec\" colname=\"c6\" colnum=\"6\"\u003e\u003c/div\u003e \u003cthead\u003e \u003ctr\u003e \u003cth align=\"left\" colname=\"c1\" morerows=\"1\" rowspan=\"2\"\u003e \u003cp\u003eSample\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colspan=\"3\" nameend=\"c4\" namest=\"c2\"\u003e \u003cp\u003eGPC\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colspan=\"2\" nameend=\"c6\" namest=\"c5\"\u003e \u003cp\u003eNCO%\u003c/p\u003e \u003c/th\u003e \u003c/tr\u003e \u003ctr\u003e \u003cth align=\"left\" colname=\"c2\"\u003e \u003cp\u003eMn\u003c/p\u003e \u003cp\u003e(g/mol)\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c3\"\u003e \u003cp\u003eMw\u003c/p\u003e \u003cp\u003e(g/mol)\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c4\"\u003e \u003cp\u003ePDI\u003c/p\u003e \u003cp\u003e(Mw/Mn)\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c5\"\u003e \u003cp\u003eTheoretical\u003c/p\u003e \u003cp\u003evalue\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c6\"\u003e \u003cp\u003eMeasured\u003c/p\u003e \u003cp\u003evalue\u003c/p\u003e \u003c/th\u003e \u003c/tr\u003e \u003c/thead\u003e \u003ctbody\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eRef.\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c2\"\u003e \u003cp\u003e5579\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c3\"\u003e \u003cp\u003e9949\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c4\"\u003e \u003cp\u003e1.78\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c5\"\u003e \u003cp\u003e3.44\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c6\"\u003e \u003cp\u003e3.21\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eRPO-0.1\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c2\"\u003e \u003cp\u003e5564\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c3\"\u003e \u003cp\u003e9068\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c4\"\u003e \u003cp\u003e1.63\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c5\"\u003e \u003cp\u003e3.67\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c6\"\u003e \u003cp\u003e3.69\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eRPO-0.3\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c2\"\u003e \u003cp\u003e4531\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c3\"\u003e \u003cp\u003e7020\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c4\"\u003e \u003cp\u003e1.55\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c5\"\u003e \u003cp\u003e4.26\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c6\"\u003e \u003cp\u003e3.93\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eRPO-0.5\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c2\"\u003e \u003cp\u003e3550\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c3\"\u003e \u003cp\u003e7193\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c4\"\u003e \u003cp\u003e2.03\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c5\"\u003e \u003cp\u003e5.06\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c6\"\u003e \u003cp\u003e4.88\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eDG-0.1\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c2\"\u003e \u003cp\u003e5008\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c3\"\u003e \u003cp\u003e9328\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c4\"\u003e \u003cp\u003e1.86\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c5\"\u003e \u003cp\u003e3.73\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c6\"\u003e \u003cp\u003e3.64\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eDG-0.3\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c2\"\u003e \u003cp\u003e4680\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c3\"\u003e \u003cp\u003e8822\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c4\"\u003e \u003cp\u003e1.88\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c5\"\u003e \u003cp\u003e4.49\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c6\"\u003e \u003cp\u003e4.51\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eDG-0.5\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c2\"\u003e \u003cp\u003e3862\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c3\"\u003e \u003cp\u003e6072\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c4\"\u003e \u003cp\u003e1.57\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c5\"\u003e \u003cp\u003e5.65\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c6\"\u003e \u003cp\u003e5.30\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eGL-0.1\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c2\"\u003e \u003cp\u003e5023\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c3\"\u003e \u003cp\u003e9941\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c4\"\u003e \u003cp\u003e1.98\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c5\"\u003e \u003cp\u003e3.73\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c6\"\u003e \u003cp\u003e3.91\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eGL-0.3\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c2\"\u003e \u003cp\u003e4350\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c3\"\u003e \u003cp\u003e5490\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c4\"\u003e \u003cp\u003e1.26\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c5\"\u003e \u003cp\u003e4.51\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c6\"\u003e \u003cp\u003e4.52\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eGL-0.5\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c2\"\u003e \u003cp\u003e4197\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c3\"\u003e \u003cp\u003e7666\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c4\"\u003e \u003cp\u003e1.83\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c5\"\u003e \u003cp\u003e5.69\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c6\"\u003e \u003cp\u003e5.55\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003c/tbody\u003e \u003c/colgroup\u003e \u003c/table\u003e\u003c/div\u003e \u003c/p\u003e \u003cp\u003eCollectively, these results underscore that bio-based polyols provide a versatile design parameter for engineering polyurethane adhesives with tailored macromolecular structures. By judiciously selecting polyol type and content, it becomes possible to modulate chain mobility, control crosslink density, and ultimately achieve adhesives that meet specific mechanical, thermal, and processing requirements.\u003c/p\u003e \u003c/div\u003e \u003cdiv id=\"Sec10\" class=\"Section2\"\u003e \u003ch2\u003e3.3 XRD Analysis\u003c/h2\u003e \u003cp\u003eXRD measurements were conducted to assess the crystalline structure of the polyurethane networks (Fig.\u0026nbsp;2). All samples displayed broad diffraction halos characteristic of amorphous polymeric systems, indicating a predominantly crosslinked network. However, the relative intensities and widths of these halos varied among the different formulations, suggesting subtle yet meaningful differences in chain packing density and local molecular ordering [44].\u003c/p\u003e \u003cp\u003eNotably, the RPO series exhibited a more pronounced and slightly shifted halo compared to the Ref., implying that the rigid isosorbide-based segments promote a more compact and ordered network structure [45, 46]. This structural feature aligns with the enhanced thermal stability and elevated Tg observed in RPO-containing adhesives, as more constrained chain mobility likely arises from tighter molecular arrangements. In contrast, the DG and GL series displayed broader halos with comparatively lower intensities, indicating increased free volume and a less densely packed architecture. Such an arrangement corresponds well with the enhanced impact strength and energy dissipation capabilities identified in DG and GL based formulations, in which higher chain mobility facilitates more effective redistribution of stress under dynamic loading conditions.\u003c/p\u003e \u003cp\u003eInterpreted alongside the FT-IR, GPC, thermal, and mechanical data, these XRD results underscore the critical importance of polyol structure in determining not only the chemical connectivity and molecular weight distribution but also the nanoscale chain arrangement within the polyurethane matrix. By correlating local structural motifs with macroscopic property profiles, this study reinforces the rationale for a holistic design approach. Through judicious selection and ratio control of bio-based polyols, it is possible to engineer polyurethane adhesives that combine superior thermal stability, mechanical robustness, and energy absorption with an environmentally sustainable materials portfolio.\u003c/p\u003e \u003cp\u003e \u003c/p\u003e \u003c/div\u003e \u003cdiv id=\"Sec11\" class=\"Section2\"\u003e \u003ch2\u003e3.4 Thermal Analysis (TGA and DSC)\u003c/h2\u003e \u003cp\u003eFigure 3 displays the TGA weight loss profiles, highlighting distinct thermal degradation patterns among the polyurethane adhesives. TGA results (Fig.\u0026nbsp;3) demonstrated that RPO-based polyurethane adhesives had a degradation onset temperature approximately 20\u0026ndash;25\u0026deg;C higher than the petroleum-based reference system, reaching\u0026thinsp;~\u0026thinsp;335\u0026deg;C. This improvement is attributed to the incorporation of isosorbide-derived polyols, which introduce rigid segments that enhance thermal resistance [47, 48]. In contrast, DG- and GL-containing samples exhibited lower degradation temperatures (~\u0026thinsp;310\u0026ndash;320\u0026deg;C) but significantly improved impact resistance (~\u0026thinsp;77% increase compared to Ref.), demonstrating a trade-off between thermal stability and mechanical toughness [49].\u003c/p\u003e \u003cp\u003e \u003cdiv class=\"gridtable\"\u003e\u003ctable float=\"Yes\" id=\"Tab2\" border=\"1\"\u003e \u003ccaption language=\"En\"\u003e \u003cdiv class=\"CaptionNumber\"\u003eTable 2\u003c/div\u003e \u003cdiv class=\"CaptionContent\"\u003e \u003cp\u003eTGA and DSC data of bio-based polyurethane adhesives.\u003c/p\u003e \u003c/div\u003e \u003c/caption\u003e \u003ccolgroup cols=\"5\"\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c1\" colnum=\"1\"\u003e\u003c/div\u003e \u003cdiv align=\"char\" char=\".\" class=\"colspec\" colname=\"c2\" colnum=\"2\"\u003e\u003c/div\u003e \u003cdiv align=\"char\" char=\".\" class=\"colspec\" colname=\"c3\" colnum=\"3\"\u003e\u003c/div\u003e \u003cdiv align=\"char\" char=\".\" class=\"colspec\" colname=\"c4\" colnum=\"4\"\u003e\u003c/div\u003e \u003cdiv align=\"char\" char=\".\" class=\"colspec\" colname=\"c5\" colnum=\"5\"\u003e\u003c/div\u003e \u003cthead\u003e \u003ctr\u003e \u003cth align=\"left\" colname=\"c1\" morerows=\"1\" rowspan=\"2\"\u003e \u003cp\u003eSample\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colspan=\"3\" nameend=\"c4\" namest=\"c2\"\u003e \u003cp\u003eTGA\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c5\"\u003e \u003cp\u003eDSC\u003c/p\u003e \u003c/th\u003e \u003c/tr\u003e \u003ctr\u003e \u003cth align=\"left\" colname=\"c2\"\u003e \u003cp\u003e95% Weight Loss (℃)\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c3\"\u003e \u003cp\u003e90% Weight Loss (℃)\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c4\"\u003e \u003cp\u003e50% Weight Loss (℃)\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c5\"\u003e \u003cp\u003eTg\u003c/p\u003e \u003c/th\u003e \u003c/tr\u003e \u003c/thead\u003e \u003ctbody\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eRef.\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c2\"\u003e \u003cp\u003e141.61\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c3\"\u003e \u003cp\u003e165.43\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c4\"\u003e \u003cp\u003e315.44\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c5\"\u003e \u003cp\u003e-54.04\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eRPO-0.1\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c2\"\u003e \u003cp\u003e136.34\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c3\"\u003e \u003cp\u003e162.36\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c4\"\u003e \u003cp\u003e321.91\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c5\"\u003e \u003cp\u003e-53.55\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eRPO-0.3\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c2\"\u003e \u003cp\u003e161.96\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c3\"\u003e \u003cp\u003e183.54\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c4\"\u003e \u003cp\u003e327.20\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c5\"\u003e \u003cp\u003e-48.53\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eRPO-0.5\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c2\"\u003e \u003cp\u003e145.79\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c3\"\u003e \u003cp\u003e168.75\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c4\"\u003e \u003cp\u003e309.84\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c5\"\u003e \u003cp\u003e-42.09\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eDG-0.1\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c2\"\u003e \u003cp\u003e171.87\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c3\"\u003e \u003cp\u003e195.95\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c4\"\u003e \u003cp\u003e335.45\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c5\"\u003e \u003cp\u003e-49.18\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eDG-0.3\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c2\"\u003e \u003cp\u003e182.82\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c3\"\u003e \u003cp\u003e204.88\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c4\"\u003e \u003cp\u003e334.59\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c5\"\u003e \u003cp\u003e-44.48\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eDG-0.5\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c2\"\u003e \u003cp\u003e160.60\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c3\"\u003e \u003cp\u003e181.69\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c4\"\u003e \u003cp\u003e316.33\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c5\"\u003e \u003cp\u003e-39.69\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eGL-0.1\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c2\"\u003e \u003cp\u003e160.79\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c3\"\u003e \u003cp\u003e184.45\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c4\"\u003e \u003cp\u003e335.48\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c5\"\u003e \u003cp\u003e-48.41\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eGL-0.3\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c2\"\u003e \u003cp\u003e159.76\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c3\"\u003e \u003cp\u003e183.38\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c4\"\u003e \u003cp\u003e328.50\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c5\"\u003e \u003cp\u003e-47.23\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eGL-0.5\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c2\"\u003e \u003cp\u003e149.96\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c3\"\u003e \u003cp\u003e171.47\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c4\"\u003e \u003cp\u003e309.89\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c5\"\u003e \u003cp\u003e-41.55\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003c/tbody\u003e \u003c/colgroup\u003e \u003c/table\u003e\u003c/div\u003e \u003c/p\u003e \u003cp\u003e \u003c/p\u003e \u003cp\u003eThis trend is further supported by DSC analysis (Fig.\u0026nbsp;4), where RPO-rich formulations exhibit higher Tg values (~\u0026thinsp;5\u0026ndash;10\u0026deg;C above Ref.), reinforcing their thermally stable and rigid network architecture [50]. Conversely, diglycerol and glycerol incorporation resulted in lower Tg values, introducing greater flexibility and enhancing the capacity for energy dissipation under stress [51]. These tunable thermal properties highlight the ability to tailor stiffness, ductility, and high temperature performance through strategic polyol selection, thereby broadening the application range of bio-based polyurethane adhesives.\u003c/p\u003e \u003cp\u003e \u003c/p\u003e \u003c/div\u003e \u003cdiv id=\"Sec12\" class=\"Section2\"\u003e \u003ch2\u003e3.5 Shear Strength\u003c/h2\u003e \u003cp\u003eTable\u0026nbsp;3 and Fig.\u0026nbsp;5 illustrate the shear strength variations among different polyurethane formulations. While the Ref. sample established a baseline (~\u0026thinsp;23.4 MPa), RPO-0.3 and DG-0.5 formulations increased shear strength by up to ~\u0026thinsp;38%, indicating that both rigid (RPO) and multifunctional (DG) polyols enhance interchain interactions and stress transfer. This improvement demonstrates that adjusting crosslink density and chain architecture can substantially reinforce the adhesive bond under static loading conditions.\u003c/p\u003e \u003cp\u003e \u003c/p\u003e \u003c/div\u003e \u003cdiv id=\"Sec13\" class=\"Section2\"\u003e \u003ch2\u003e3.6 Impact Strength\u003c/h2\u003e \u003cp\u003eImpact strength results emphasized the critical role of molecular architecture in dissipating dynamic loads. Figure\u0026nbsp;6 and Table\u0026nbsp;3 compare the impact resistance of bio-based polyurethane adhesives. Although the Ref. adhesive exhibited limited energy absorption (20.7 MPa), RPO-0.3 and GL-0.5 samples achieved approximately 75% and 78% higher impact strengths, respectively. Such enhancements suggest that balancing rigid segments with flexible domains facilitates more effective energy dissipation, reducing localized stresses and delaying crack propagation under sudden impact [52, 53]. These findings underscore the potential of bio-based polyols to improve toughness and durability without compromising structural integrity.\u003c/p\u003e \u003cp\u003e \u003cdiv class=\"gridtable\"\u003e\u003ctable float=\"Yes\" id=\"Tab3\" border=\"1\"\u003e \u003ccaption language=\"En\"\u003e \u003cdiv class=\"CaptionNumber\"\u003eTable 3\u003c/div\u003e \u003cdiv class=\"CaptionContent\"\u003e \u003cp\u003eMechanical properties of bio-based polyurethane adhesives.\u003c/p\u003e \u003c/div\u003e \u003c/caption\u003e \u003ccolgroup cols=\"6\"\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c1\" colnum=\"1\"\u003e\u003c/div\u003e \u003cdiv align=\"char\" char=\".\" class=\"colspec\" colname=\"c2\" colnum=\"2\"\u003e\u003c/div\u003e \u003cdiv align=\"char\" char=\".\" class=\"colspec\" colname=\"c3\" colnum=\"3\"\u003e\u003c/div\u003e \u003cdiv align=\"char\" char=\".\" class=\"colspec\" colname=\"c4\" colnum=\"4\"\u003e\u003c/div\u003e \u003cdiv align=\"char\" char=\".\" class=\"colspec\" colname=\"c5\" colnum=\"5\"\u003e\u003c/div\u003e \u003cdiv align=\"char\" char=\".\" class=\"colspec\" colname=\"c6\" colnum=\"6\"\u003e\u003c/div\u003e \u003cthead\u003e \u003ctr\u003e \u003cth align=\"left\" colname=\"c1\"\u003e \u003cp\u003eSample\u003c/p\u003e \u003cp\u003eAverage Data\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c2\"\u003e \u003cp\u003eShear Strength\u003c/p\u003e \u003cp\u003e(MPa)\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c3\"\u003e \u003cp\u003eStandard deviation\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c4\"\u003e \u003cp\u003eImpact Strength\u003c/p\u003e \u003cp\u003e(MPa)\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c5\"\u003e \u003cp\u003eStandard deviation\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c6\"\u003e \u003cp\u003eT-Peel Strength\u003c/p\u003e \u003cp\u003e(N/25mm)\u003c/p\u003e \u003c/th\u003e \u003c/tr\u003e \u003c/thead\u003e \u003ctbody\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eRef.\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c2\"\u003e \u003cp\u003e23.4\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c3\"\u003e \u003cp\u003e0.3682\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c4\"\u003e \u003cp\u003e20.7\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c5\"\u003e \u003cp\u003e9.4044\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c6\"\u003e \u003cp\u003e151.0\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eRPO-0.1\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c2\"\u003e \u003cp\u003e23.7\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c3\"\u003e \u003cp\u003e0.2055\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c4\"\u003e \u003cp\u003e21.6\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c5\"\u003e \u003cp\u003e6.0024\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c6\"\u003e \u003cp\u003e103.9\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eRPO-0.3\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c2\"\u003e \u003cp\u003e27.1\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c3\"\u003e \u003cp\u003e0.4497\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c4\"\u003e \u003cp\u003e35.2\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c5\"\u003e \u003cp\u003e4.9173\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c6\"\u003e \u003cp\u003e168.7\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eRPO-0.5\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c2\"\u003e \u003cp\u003e27.2\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c3\"\u003e \u003cp\u003e0.2867\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c4\"\u003e \u003cp\u003e25.2\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c5\"\u003e \u003cp\u003e0.8807\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c6\"\u003e \u003cp\u003e65.4\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eDG-0.1\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c2\"\u003e \u003cp\u003e27.3\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c3\"\u003e \u003cp\u003e0.3300\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c4\"\u003e \u003cp\u003e20.0\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c5\"\u003e \u003cp\u003e3.7665\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c6\"\u003e \u003cp\u003e73.5\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eDG-0.3\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c2\"\u003e \u003cp\u003e30.9\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c3\"\u003e \u003cp\u003e0.4028\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c4\"\u003e \u003cp\u003e22.8\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c5\"\u003e \u003cp\u003e11.2021\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c6\"\u003e \u003cp\u003e69.1\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eDG-0.5\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c2\"\u003e \u003cp\u003e32.5\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c3\"\u003e \u003cp\u003e0.2867\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c4\"\u003e \u003cp\u003e32.1\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c5\"\u003e \u003cp\u003e4.4101\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c6\"\u003e \u003cp\u003e101.2\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eGL-0.1\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c2\"\u003e \u003cp\u003e27.2\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c3\"\u003e \u003cp\u003e0.9741\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c4\"\u003e \u003cp\u003e19.1\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c5\"\u003e \u003cp\u003e9.1371\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c6\"\u003e \u003cp\u003e110.0\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eGL-0.3\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c2\"\u003e \u003cp\u003e30.0\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c3\"\u003e \u003cp\u003e0.5099\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c4\"\u003e \u003cp\u003e24.3\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c5\"\u003e \u003cp\u003e14.4112\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c6\"\u003e \u003cp\u003e75.8\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eGL-0.5\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c2\"\u003e \u003cp\u003e30.1\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c3\"\u003e \u003cp\u003e0.4243\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c4\"\u003e \u003cp\u003e36.8\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c5\"\u003e \u003cp\u003e5.4683\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c6\"\u003e \u003cp\u003e76.2\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003c/tbody\u003e \u003c/colgroup\u003e \u003c/table\u003e\u003c/div\u003e \u003c/p\u003e \u003cp\u003e \u003c/p\u003e \u003c/div\u003e \u003cdiv id=\"Sec14\" class=\"Section2\"\u003e \u003ch2\u003e3.7 T-Peel Strength\u003c/h2\u003e \u003cp\u003eT-peel strength measurements (Table\u0026nbsp;3) revealed that interfacial fracture resistance does not simply parallel trends observed in shear or impact strength. For instance, RPO-0.3 demonstrated high T-peel strength despite its relatively stiff network, indicating that interfacial bonding, chain orientation, and local segmental dynamics significantly influence peel performance. These results highlight that peel resistance may require targeted structural modifications, independent of those governing bulk mechanical or thermal properties, thus reinforcing the need for a holistic approach to adhesive design.\u003c/p\u003e \u003cp\u003e \u003c/p\u003e \u003cp\u003eCorrelation and Design Implications\u003c/p\u003e \u003cp\u003eIntegrating the thermal and mechanical data reveals a nuanced interplay between crosslink density, segmental mobility, and network rigidity (Fig.\u0026nbsp;7). Higher Tg and enhanced thermal stability (RPO-based systems) often correlate with greater shear strength but may require careful tuning to preserve impact resistance [54]. Conversely, formulations incorporating glycerol or diglycerol yielded networks with lower Tg and moderate thermal stability yet superior energy dissipation, enabling improved impact performance at the cost of reduced stiffness.\u003c/p\u003e \u003cp\u003eTo visualize these multidimensional relationships, a radar plot (Fig.\u0026nbsp;7) compares three representative formulations (e.g., DG-0.5, GL-0.5, and RPO-0.3), illustrating how variations in polyol selection and ratio influence shear, impact, and T-peel strengths alongside thermal parameters such as Tg and thermal stability. This graphical representation highlights the trade-offs inherent in each formulation and provides a strategic blueprint for tuning individual properties while maintaining an appropriate overall performance balance.\u003c/p\u003e \u003cp\u003e \u003c/p\u003e \u003cp\u003eOverall Structure\u0026ndash;Property Relationships\u003c/p\u003e \u003cp\u003eCollectively, these findings emphasize that bio-based polyol selection and composition enable precise modulation of polyurethane network architecture, bridging the gap between mechanical strength, thermal stability, and interfacial adhesion [55]. Coupled with multidimensional data visualization (Fig.\u0026nbsp;8), this approach supports informed decision making in the design of sustainable, high-performance adhesives. This study establishes a rational design platform linking molecular structure to macroscopic properties, enabling the development of sustainable polyurethane adhesives.\u003c/p\u003e \u003c/div\u003e"},{"header":"4. Conclusion","content":"\u003cp\u003eThis study confirms that integrating renewable polyols\u0026mdash;RPO polyol, diglycerol, and glycerol\u0026mdash;into polyurethane networks based on PPG2000 and IPDI allows precise control over thermal stability and mechanical properties. A systematic evaluation of structure\u0026ndash;property relationships confirms that polyol selection and network architecture significantly influence thermal stability, mechanical strength, and adhesion performance, leading to the development of bio-based polyurethane adhesives with competitive properties compared to conventional petroleum-based systems.\u003c/p\u003e\n\u003cp\u003eIn particular, the incorporation of isosorbide-derived polyol resulted in a 25\u0026deg;C increase in degradation onset temperature (~335\u0026deg;C), demonstrating superior thermal stability due to the rigid bicyclic structure. Furthermore, formulations modified with diglycerol and glycerol exhibited up to 39% higher shear strength (32.5 MPa) and 77% improved impact resistance (36.8 MPa), attributed to optimized crosslinking density and enhanced energy dissipation. These findings indicate that optimizing performance across shear, impact, and peel conditions requires precise structural control beyond compositional tuning. Optimizing molecular architecture and crosslinking density enables bio-based polyurethane adhesives to meet the stringent mechanical and thermal requirements of structural bonding applications [56].\u0026nbsp;\u003c/p\u003e\n\u003cp\u003eFrom an industrial perspective, the findings indicate that bio-based polyurethane adhesives have the potential to replace petroleum-based systems in high-performance applications, including automotive, aerospace, and structural bonding. The ability to control network rigidity and flexibility through polyol composition presents significant opportunities for tailoring adhesives to diverse engineering requirements, offering a scalable and sustainable solution for next-generation bonding technologies. This study thus establishes a robust framework for designing next generation, high-performance bio-based polyurethane adhesives that align with sustainability goals, maintain stringent engineering standards, and broaden the scope of environmentally responsible material solutions.\u003c/p\u003e"},{"header":"Declarations","content":"\u003cp\u003e\u003cstrong\u003e■\u003c/strong\u003e\u003cstrong\u003e\u0026nbsp;Author information\u0026nbsp;\u003c/strong\u003e\u0026nbsp;\u003c/p\u003e\n\u003cp\u003eCorresponding Author\u003c/p\u003e\n\u003cp\u003ePilHo Huh - Department of Polymer Science and Engineering, Pusan National University, Busan 46241, South Korea; Email: [email protected]\u003c/p\u003e\n\u003cp\u003eJi-Hong Bae - Department of Polymer Science and Engineering, Pusan National University, Busan 46241, South Korea; Email: [email protected]\u003c/p\u003e\n\u003cp\u003eAuthors\u003c/p\u003e\n\u003cp\u003eJin-Gyu Min, Won-Bin Lim, Ju-Hong Lee, Jae-Ryong Lee, Seung-Hyun Lee, Keun-Ho Lee - Polymer Science and Engineering, Pusan National University, Busan 46241, Republic of Korea\u003c/p\u003e\n\u003cp\u003eGwang-Seok Song - Industrial Biotechnology Program, Chemical R\u0026amp;D Center, Samyang Corporation, Daejeon 34055, Republic of Korea\u0026nbsp;\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003e■\u003c/strong\u003e\u003cstrong\u003e\u0026nbsp;Author contributions\u0026nbsp;\u003c/strong\u003e\u0026nbsp;\u003c/p\u003e\n\u003cp\u003eJ.-G.M. performed the primary experiments, analyzed data, and drafted the manuscript.\u003c/p\u003e\n\u003cp\u003eW.-B.L. participated in the design of the polymer synthesis protocols and contributed to data interpretation.\u003c/p\u003e\n\u003cp\u003eJ.-H.L. performed thermal analyses (TGA, DSC) and contributed to result visualization.\u003c/p\u003e\n\u003cp\u003eJ.-R.L. conducted the FT-IR spectroscopy and GPC measurements, and assisted in data curation.\u003c/p\u003e\n\u003cp\u003eS.-H.L. assisted in mechanical testing and contributed to experimental validation.\u003c/p\u003e\n\u003cp\u003eK.-H.L. conducted the XRD measurements, and assisted in data curation.\u003c/p\u003e\n\u003cp\u003eG.-S.S. contributed to the structural adhesive performance evaluation, providing insights into mechanical testing and practical applications.\u003c/p\u003e\n\u003cp\u003eJ.-H.B. and P.H.H. conceptualized and supervised the project, provided resources, reviewed the manuscript, and approved the final version for publication.\u0026nbsp;\u003c/p\u003e\n\u003cp\u003eAll authors discussed the results, reviewed the manuscript, and approved the final submission.\u0026nbsp;\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003e■\u003c/strong\u003e\u003cstrong\u003e\u0026nbsp;Acknowledgements\u0026nbsp;\u003c/strong\u003e\u0026nbsp;\u003c/p\u003e\n\u003cp\u003eThis work was supported by Industrial Strategic Technology Development Program (Bio tackifier adhesive material with a biomass content of 50% or more, 20010807).\u0026nbsp;\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003e■\u003c/strong\u003e\u003cstrong\u003e\u0026nbsp;Conflicts of interest\u003c/strong\u003e\u0026nbsp;\u003c/p\u003e\n\u003cp\u003eThe authors declare no conflicts of interest. \u0026nbsp;\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003e■\u003c/strong\u003e\u003cstrong\u003e\u0026nbsp;Data availability statement\u003c/strong\u003e\u0026nbsp;\u003c/p\u003e\n\u003cp\u003eThe data supporting this article have been included as part of the Supplementary Information.\u0026nbsp;\u003c/p\u003e"},{"header":"References","content":"\u003col\u003e\n\u003cli\u003eDas, A.; Mahanwar, P. A brief discussion on advances in polyurethane applications, Adv. Ind. Eng. Polym. Res., 2020, 3, 3, 93-101\u003c/li\u003e\n\u003cli\u003eMenon, A.; Sreeram, P.; Vinod, A.; Naiker, V.; Nandana, M.; David, D.; Sasidharan, S.; Raghavan, P. Chapter 4 - Polyurethane (PU): Structure, properties, and applications, Handbook of Thermosetting Foams, Aerogels, and Hydrogels, 2024, 67-92 \u003c/li\u003e\n\u003cli\u003eEngels, H.; Pirkl, H.; Albers, R.; Albach, R.; Krause, J.; Hoffmann, A.; Casselmann, H.; Dormish, J. Polyurethanes: Versatile Materials and Sustainable Problem Solvers for Todays Challenges, Angew. Chem. Int. Ed., 2013, 52, 9422 \u0026ndash; 9441\u003c/li\u003e\n\u003cli\u003eMaulana, S.; Wibowo, E.; Mardawati, E.; Iswanto, A.; Papadopoulos, A.; Lubis, M. Eco-Friendly and High-Performance Bio-Polyurethane Adhesives from Vegetable Oils: A Review, Polymers, 2024, 16, 1613\u003c/li\u003e\n\u003cli\u003eGolling, F.; Pires, R.; Hecking, A.; Weikard, J.; Richter, F.; Danielmeier, K.; Dijkstra, D. Polyurethanes for coatings andadhesives \u0026ndash; chemistry and applications, Polym Int., 2019, 68, 848\u0026ndash;855\u003c/li\u003e\n\u003cli\u003eMahmood, N.; Yuan, Z.; Schmidt, J.; Xu, C. Depolymerization of lignins and their applications for the preparation of polyols and rigid polyurethane foams: A review, Renew. Sustain. Energy Rev., 2023, 60, 317-329\u003c/li\u003e\n\u003cli\u003eShi, C.; Zhang, Y.; Shao, Y.; R, S.; Wang, B.; Zhao, Z.; Yu, B.; Zhang, X.; Li, W.; Ding, J.; Liu, Z.; Zhang, H. A review on the occurrence, detection methods, and ecotoxicity of biodegradable microplastics in the aquatic environment: New cause for concern, TrAC - Trends Anal. Chem., 178, 2024, 117832\u003c/li\u003e\n\u003cli\u003eBartolo, A.; Infurna, G.; Dintcheva, N. A Review of Bioplastics and Their Adoption in the Circular Economy, Polymers, 2021, 13, 1229\u003c/li\u003e\n\u003cli\u003eAil, S.; Abdelkarim, E.; Elsamahy, T.; Al-Tohamy, R.; Li, F.; Kornaros, M.; Zuorro, A.; Zhu, D.; Sun, J. Bioplastic production in terms of life cycle assessment: A state-of-the-art review, Environ. Sci. Ecotechnology, 15, 2023, 100254\u003c/li\u003e\n\u003cli\u003eWang, H.; Yang, B.; Zhang, Q.; Zhu, W. Catalytic routes for the conversion of lignocellulosic biomass to aviation fuel range hydrocarbons, Renew. Sustain. Energy Rev., 2020, 120, 109612\u003c/li\u003e\n\u003cli\u003eSofian, A.; Sun, X.; Gupta, Vijai.; Berenjian, A.; Xia, A.; Ma, Z.; Show, P. Advances, Synergy, and Perspectives of Machine Learning and Biobased Polymers for Energy, Fuels, and Biochemicals for a Sustainable Future, Energ. Fuel., 2024, 38, 3, 1593-1617\u003c/li\u003e\n\u003cli\u003eSarangi, P.; Singh, A.; V. Ganachari, S.; Pengadeth, D.; Mohanakrishna, G.; M. Aminabhavi, T. Biobased heterogeneous renewable catalysts: Production technologies, innovations, biodiesel applications and circular bioeconomy, Environ. Res., 2024, 261, 119745\u003c/li\u003e\n\u003cli\u003eNanda, S, R. Parta, B.; Patel, Ravi.; Bakos, J.; K. Dalai, A. Innovations in applications and prospects of bioplastics and biopolymers: a review, Environ. Chem. Lett., 2022, 20, 379-395\u003c/li\u003e\n\u003cli\u003eBurelo, M.; Mart\u0026iacute;nez, A.; Hern\u0026aacute;ndez-Varela, J.; Stringer, T.; Ram\u0026iacute;rez-Melgarejo, M.; Y. Yau, A.; Luna-B\u0026aacute;rcenas, T.; D. Trevi\u0026ntilde;o-Quintanilla, C. Recent Developments in Synthesis, Properties, Applications and Recycling of Bio-Based Elastomers, Molecules, 2024, 29, 387\u003c/li\u003e\n\u003cli\u003eOh, E.; Z\u0026uacute;niga, M.; Nguyen, T.; Kim, B.; Tien, T.; Suhr, J. Sustainable green composite materials in the next-generation mobility industry: review and prospective, Adv. Compos. Mater., 2024, 33, 6, 1368-1419\u003c/li\u003e\n\u003cli\u003eCiastowicz, Z.; Pamula, R.; Bialowiec, A. Utilization of Plant Oils for Sustainable Polyurethane Adhesives:A Review, A Review. Materials, 2024, 17(8), 1738\u003c/li\u003e\n\u003cli\u003eSternberg, J.; Sequerth, O.; Pilla, S. Green chemistry design in polymers derived from lignin: review and perspective, Prog. Polym. Sci., 2021, 113\u003c/li\u003e\n\u003cli\u003eLuleburgaz, S.; Cakmakci, E.; Durmaz, H.; Tunca, U. Sustainable polymers from renewable resources through click and multicomponent reactions, Eur. Polym. J., 2024, 209, 112897\u003c/li\u003e\n\u003cli\u003eLaurichesse, S.; Huillet, C.; Av\u0026eacute;rous, L. Original polyols based on organosolv lignin and fatty acids: new bio-based building blocks for segmented polyurethane synthesis, Green. Chem., 2014, 16, 3958\u003c/li\u003e\n\u003cli\u003eSugiarto, S.; Pong, R.; Tan, Y.\u0026rsquo; Leow, Y.; Sathasivam, T.; Zhu, Q.; Loh, X.; Kai, D. Advances in sustainable polymeric materials from lignocellulosic biomass, Mater. Today Chem., 2022, 26, 101022\u003c/li\u003e\n\u003cli\u003eLaurichesse, S.; Av\u0026eacute;rous, L. Chemical modification of lignins: Towards biobased polymers, Prog. Polym. Sci., 2014, 39, 7, 1266-1290\u003c/li\u003e\n\u003cli\u003eSen, S.; Patil, S.; S. Argyropoulos, D. Thermal properties of lignin in copolymers, blends, and composites: a review, Green Chem., 2015, 17, 4862\u003c/li\u003e\n\u003cli\u003eGhasemlou, M.; Daber, F.; P. Ivanova, E.; Adhikari, B. Polyurethanes from seed oil-based polyols: A review of synthesis, mechanical and thermal properties, Ind. Crops. Prod., 2019, 142, 111841\u003c/li\u003e\n\u003cli\u003eCarvalho, D.; Ferreira, N.; Fran\u0026ccedil;a, B.; Marques, R.; Silva, M.; Silva, S.; Silva, E.; Mac\u0026aacute;rio, D.; Barroso, L.; Silva, C.; Oliveira, C. Advancing sustainability in the automotive industry: Bioprepregs and fully bio-based composites, Compos. C: Open Access, 2024, 14\u003c/li\u003e\n\u003cli\u003ePopescu, C.; Dissanayake, H.; Mansi, E.; Stancu, A. Eco Breakthroughs: Sustainable Materials Transforming the Future of Our Planet, Sustainability, 2024, 16, 10790.\u003c/li\u003e\n\u003cli\u003eCui, S.; Liu, Z.; Li, Y. Bio-polyols synthesized from crude glycerol and applications on polyurethane wood adhesives, Ind. Crops. Prod., 2017, 108, 798-805\u003c/li\u003e\n\u003cli\u003eMin, J.; Lim, W.; Lee, J.; Lee, J.; Bae, J.; Huh, P. A facile strategy for synthesizing isosorbide‑based polyurethane structural adhesives and core\u0026ndash;shell rubber, Sci. Rep., 2024, 14, 21018\u003c/li\u003e\n\u003cli\u003eS. Pillai, C. Challenges for Natural Monomers and Polymers: NovelDesign Strategies and Engineering to DevelopAdvanced Polymers, Des. Monomers Polym., 2010, 13, 87-121\u003c/li\u003e\n\u003cli\u003eToader, G.; Diacon, A.; M. Axinte, S.; Mocanu, A.; Rusen, E. State-of-the-Art Polyurea Coatings: Synthesis Aspects, Structure\u0026ndash;Properties Relationship, and Nanocomposites for Ballistic Protection Applications, Polymers, 2024, 16, 454\u003c/li\u003e\n\u003cli\u003eE. Souza, GAL.; D. Pietro, M.; Mele, A. Eutectic solvents and low molecular weight gelators for next-generation supramolecular eutectogels: a sustainable chemistry perspective, RSC Sustainability, 2024, 2, 288 \u003c/li\u003e\n\u003cli\u003eMarques, A.; Mocanu, A.; Tomić, N.; Balos, S.; Stammen, E.; Lundevall, A.; Abrahami, S.; G\u0026uuml;nther, R.; de Kok, J.; de Freitas, S. Review on Adhesives and Surface Treatments for Structural Applications: Recent Developments on Sustainability and Implementation for Metal and Composite Substrates, Materials, 2020, 13(24), 5590\u003c/li\u003e\n\u003cli\u003eJoseph, T.; Unni, A.; Joshy, K.; Mahapatra, D.; Haponiuk, J.; Thomas, S. Emerging Bio-Based Polymers from Lab to Market: Current Strategies, Market Dynamics and Research Trends, C., 2023, 9, 30.\u003c/li\u003e\n\u003cli\u003eRiina, M.; Hanna, B.; Mikko, W.; Johanna, K. ed. Valuable biochemicals of the future : The outlook for bio-based value-added chemicals and their growing markets, Luke luobio, 2024, 85\u003c/li\u003e\n\u003cli\u003eWang, R.; Feng, Y.; Li, D.; Li, K.; Yan, Y. Towards the sustainable production of biomass-derived materials with smart functionality: a tutorial review, Green. Chem., 2024, 26, 9075-9103 \u003c/li\u003e\n\u003cli\u003eChen, T.; Kim, H.; Pan, S.; Tseng, P.; Lin, Y.; Chiang, P. Implementation of green chemistry principles in circular economy system towards sustainable development goals: Challenges and perspectives, Sci. Total Environ., 2020, 716\u003c/li\u003e\n\u003cli\u003e\u003csup\u003e \u003c/sup\u003e[36] Suresh, Kattimuttathu. I. Rigid Polyurethane Foams from Cardanol: Synthesis, Structural Characterization, and Evaluation of Polyol and Foam Properties, ACS Sustain Chem Eng., 2013, 1, 232-242\u003c/li\u003e\n\u003cli\u003eGazil, O.; Bernardi, J.; Lassus, A.; Virgilio, N.; Unterlas, M. M. Urethane functions can reduce metal salts under hydrothermal conditions: synthesis of noble metal nanoparticles on flexible sponges applied in semi-automated organic reduction, J. Mater. Chem. A, 2023, 11, 12703-12712\u003c/li\u003e\n\u003cli\u003eGuo, Z.; Bao, C.; Wang, X.; Lu, X.; Sun, H.; Li, X.; Lia, J.; Sun, J. Room-temperature healable, recyclable and mechanically super-strong poly(urea-urethane)s cross-linked with nitrogen-coordinated boroxines. J. Mater. Chem. A, 2021, 9, 11025\u0026ndash;11032\u003c/li\u003e\n\u003cli\u003eUsman, A.; Hussain, M. T.; Akram, N.; Zuber, M.; Sultana, S.; Aftab, W.; Zia, K. M.; Maqbool, M.; Alanazi, Y. M.; Nazirf, A.; Javaid, M. A. Modulating alginate-polyurethane elastomer properties: Influence of NCO/OH ratio with aliphatic diisocyanate, Int J Biol Macromol, 2024, 278, 134657\u003c/li\u003e\n\u003cli\u003eKulshrestha, A. S.; Gao, W.; Gross, R. A. Glycerol Copolyesters: Control of Branching and Molecular Weight Using a Lipase Catalyst, Macromolecules, 2005, 38, 3193-3204\u003c/li\u003e\n\u003cli\u003eSadler, J. M.; Nguyen, A-. P. T.; Toulan, F. R.; Szabo, J. P.; Palmese, G. R.; Scheck, C.; Lutgend, S.; La Scala, J. J. Isosorbide-methacrylate as a bio-based low viscosity resin for high performance thermosetting applications, J. Mater. Chem. A, 2013, 1, 12579-12586\u003c/li\u003e\n\u003cli\u003eWeinland, D. H.; Putten, R-. J. V.; Gruter, G-. J. M. Evaluating the commercial application potential of polyesters with 1,4:3,6-dianhydrohexitols (isosorbide, isomannide and isoidide) by reviewing the synthetic challenges in step growth polymerization, Eur Polym J, 2022, 164, 110964\u003c/li\u003e\n\u003cli\u003eLi, J. Yang, W.; Ning, Z.; Yang, B.; Zeng, Y. Sustainable Polyurethane Networks Based on Rosin with Reprocessing Performance, Polymers, 2021, 13, 3538\u003c/li\u003e\n\u003cli\u003eLuo, K.; Zhu, G.; Zhao, Y.; Luo, Z.; Liu, X.; Zhang, K.; Lia, Y.; Scott, K. Enhanced cycling stability of Li\u0026ndash;O2 batteries by using a polyurethane/SiO2/glass fiber nanocomposite separator, J. Mater. Chem. A, 2018, 6, 7770\u0026ndash;7776\u003c/li\u003e\n\u003cli\u003eDu, Y-. R.; Xu, B-. H.; Xia, S-. P.; Ding, G-. R.; Zhang, S-. J. Dehydrative Formation of Isosorbide from Sorbitol over Poly(ionic liquid)\u0026minus;Covalent Organic Framework Hybrids, ACS Appl. Mater. Interfaces, 2021, 13, 552\u0026minus;562\u003c/li\u003e\n\u003cli\u003eChen, Z.; Lu, H. Constructing sacrificial bonds and hidden lengths for ductile graphene/polyurethane elastomers with improved strength and toughness, J. Mater. Chem., 2012, 22, 12479-12490\u003c/li\u003e\n\u003cli\u003eLiu, S-. H.; Shen, M-. Y.; Kuan, C-. F.;Kuan, H-. C.; Ke, C-. Y.; Chiang, C-. L. Improving Thermal Stability of Polyurethane through the Addition of Hyperbranched Polysiloxane, Polymers, 2019, 11, 697\u003c/li\u003e\n\u003cli\u003eQiu, H.; Qiu, X.; Dai, X.; Sun, Z-. Y. Design of polyimides with targeted glass transition temperature using a graph neural network, J. Mater. Chem. C, 2023, 11, 2930\u0026ndash;2940\u003c/li\u003e\n\u003cli\u003eRutkowski, P.; Kwiecie, K.; Berezicka, A.; Sułowska, J.; Kwiecie, A.; Sliwa-Wieczorek, K.; Azinovic, B.; Schwarzkopf, M.; Pondelak, A.; Pecnik, J. G.; Szumera, M. Thermal Stability and Heat Transfer of Polyurethanes for Joints Applications of Wooden Structures, Molecules, 2024, 29, 3337\u003c/li\u003e\n\u003cli\u003eJoo, A-. R.; Lee, J-. H.; Park, Y-. G. Lee, S-. H. Thermal Stability of Polyurethane Foams Infused with Melamine-phosphate Coated Inorganic Flame Retardants, Polymer, 2018, 42, 2, 288-297\u003c/li\u003e\n\u003cli\u003eLaukkanen, T.; Reddy, P. G.; Barua, A.; Kumar, M.; Kolpakov, K.; Tirrib, T.; Sharma, V. Sustainable castor oil-derived cross-linked poly(ester-urethane) elastomeric films for stretchable transparent conductive electrodes and heaters, J. Mater. Chem. A, 2024, 12, 33177\u0026ndash;33192\u003c/li\u003e\n\u003cli\u003eDong, F.; Yang, X.; Guo, L.; Wang, Y.; Shaghaleh, H.; Huang, Z.; Xu, X.; Wang, S.; Liu, H. Self-healing polyurethane with high strength and toughness based on a dynamic chemical strategy, J. Mater. Chem. A, 2022, 10, 10139\u0026ndash;10149\u003c/li\u003e\n\u003cli\u003eGriggs, T.; Ahmed, J.; Majd, H.; Edirisingheb, M.; Chen, B. A bio-based thermoplastic polyurethane with triple self-healing action for wearable technology and smart textiles, Mater. Adv., 2024, 5, 6210\u0026ndash;6221\u003c/li\u003e\n\u003cli\u003ePark, C. Y. Effect of PPG, MDI, 2-HEMA and butyl acrylate content on the properties of polyurethane adhesive, Elastomers and Composites, 49, 3, 245-252\u003c/li\u003e\n\u003cli\u003eBrzoska, J.; Datta, J.; Konefał, R.; Pokorn\u0026yacute;, V.; Bene\u0026scaron;, H. The influence of bio-based monomers on the structure and thermal properties of polyurethanes, Scientific Reports, 2024, 14, 29042\u003c/li\u003e\n\u003cli\u003eNijst, C. L. E.; Bruggeman, J. P.; Karp, J. M.; Ferreira, L.; Zumbuehl, A.; Bettinger, C. J.; Langer, R. Synthesis and Characterization of Photocurable Elastomersfrom Poly(glycerol-co-sebacate), Biomacromolecules, 2007, 8, 3067-3073\u003c/li\u003e\n\u003c/ol\u003e"},{"header":"Scheme","content":"\u003cp\u003eScheme 1 and 2 are available in the Supplementary Files section.\u003c/p\u003e"}],"fulltextSource":"","fullText":"","funders":[],"hasAdminPriorityOnWorkflow":false,"hasManuscriptDocX":true,"hasOptedInToPreprint":true,"hasPassedJournalQc":"","hasAnyPriority":false,"hideJournal":true,"highlight":"","institution":"","isAcceptedByJournal":false,"isAuthorSuppliedPdf":false,"isDeskRejected":"","isHiddenFromSearch":false,"isInQc":false,"isInWorkflow":false,"isPdf":false,"isPdfUpToDate":true,"isWithdrawnOrRetracted":false,"journal":{"display":true,"email":"[email protected]","identity":"researchsquare","isNatureJournal":false,"hasQc":true,"allowDirectSubmit":true,"externalIdentity":"","sideBox":"","snPcode":"","submissionUrl":"/submission","title":"Research Square","twitterHandle":"researchsquare","acdcEnabled":true,"dfaEnabled":false,"editorialSystem":"","reportingPortfolio":"","inReviewEnabled":false,"inReviewRevisionsEnabled":true},"keywords":"Sustainable polyurethane adhesives, Structure–property correlation, Thermal stability and mechanical properties, Isosorbide-based polyols, Renewable polyols","lastPublishedDoi":"10.21203/rs.3.rs-6258415/v1","lastPublishedDoiUrl":"https://doi.org/10.21203/rs.3.rs-6258415/v1","license":{"name":"CC BY 4.0","url":"https://creativecommons.org/licenses/by/4.0/"},"manuscriptAbstract":"\u003cp\u003eDeveloping high-performance, sustainable adhesives for automotive, aerospace, and industrial applications remains a major challenge due to the inherent trade-off between mechanical strength and thermal stability in bio-based materials. While previous studies have explored bio-based polyurethane (PU) adhesives, achieving superior adhesion and durability remains challenging when compared to petroleum-based counterparts. This study presents a novel bio-based polyurethane adhesive system utilizing polypropylene glycol (PPG2000), isophorone diisocyanate (IPDI), and renewable polyols (isosorbide-derived polyols, diglycerol, and glycerol). The adhesives were synthesized via a controlled one-shot polymerization process with 4-tert-butylphenol as an end-capping agent, enabling precise modulation of crosslink density and molecular architecture. Fourier-transform infrared (FT-IR) spectroscopy confirmed complete urethane bond formation, and isocyanate group (NCO%) titration validated stoichiometric conversion. Gel permeation chromatography (GPC) revealed distinct molecular weight distributions, which influence adhesive performance by affecting crosslink density, elasticity, and mechanical strength depending on polyol structure. Thermal analysis showed that isosorbide-derived polyol formulations exhibited up to a 25\u0026deg;C higher degradation onset temperature and a 10\u0026deg;C increase in glass transition temperature (Tg) compared to petroleum-based adhesives. Meanwhile, formulations containing diglycerol and glycerol demonstrated up to 39% higher shear strength (32.5 MPa) and 77% improved impact resistance (36.8 MPa) relative to the reference system, attributed to optimized segmental mobility and crosslinking effects.\u003c/p\u003e \u003cp\u003eThis work establishes a strategic framework for designing bio-based polyurethane adhesives, while acknowledging limitations such as potential variability in raw material sources and suggesting future research into long-term environmental performance, that not only surpasses conventional petroleum-based systems in thermal and mechanical performance but also aligns with the principles of green chemistry and sustainable material innovation. These findings offer a pathway for next-generation structural adhesives in automotive, aerospace, and industrial applications.\u003c/p\u003e","manuscriptTitle":"Sustainable Bio-based Polyurethane Adhesives Utilizing PPG2000 and Renewable Polyols: Synthesis, Characterization, and Mechanical Properties","msid":"","msnumber":"","nonDraftVersions":[{"code":1,"date":"2025-04-02 13:00:42","doi":"10.21203/rs.3.rs-6258415/v1","editorialEvents":[{"type":"communityComments","content":0}],"status":"published","journal":{"display":true,"email":"[email protected]","identity":"researchsquare","isNatureJournal":false,"hasQc":true,"allowDirectSubmit":true,"externalIdentity":"","sideBox":"","snPcode":"","submissionUrl":"/submission","title":"Research Square","twitterHandle":"researchsquare","acdcEnabled":true,"dfaEnabled":false,"editorialSystem":"","reportingPortfolio":"","inReviewEnabled":false,"inReviewRevisionsEnabled":true}}],"origin":"","ownerIdentity":"ada2eaf7-6ba7-46c8-a71a-b7ac7c977071","owner":[],"postedDate":"April 2nd, 2025","published":true,"recentEditorialEvents":[],"rejectedJournal":[],"revision":"","amendment":"","status":"posted","subjectAreas":[],"tags":[],"updatedAt":"2025-06-09T19:08:03+00:00","versionOfRecord":[],"versionCreatedAt":"2025-04-02 13:00:42","video":"","vorDoi":"","vorDoiUrl":"","workflowStages":[]},"version":"v1","identity":"rs-6258415","journalConfig":"researchsquare"},"__N_SSP":true},"page":"/article/[identity]/[[...version]]","query":{"redirect":"/article/rs-6258415","identity":"rs-6258415","version":["v1"]},"buildId":"8U1c8b4HqxoKbykW_rLl7","isFallback":false,"isExperimentalCompile":false,"dynamicIds":[84888],"gssp":true,"scriptLoader":[]}