Preparation and rheological properties of associative salt tolerant polymer by inverse-phase emulsion polymerization

Preparation and rheological properties of associative salt tolerant polymer by inverse-phase emulsion polymerization | 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 Preparation and rheological properties of associative salt tolerant polymer by inverse-phase emulsion polymerization Xin Wen, Lei Wang, XiaoJuan Lai, Guiru Liu, Wenwen Yang, Yameng Liu This is a preprint; it has not been peer reviewed by a journal. https://doi.org/ 10.21203/rs.3.rs-4081245/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 An associative and salt tolerant p(AM/AMC 12 S/GTE-10) polymer was synthesized through reverse-phase emulsion polymerization of acrylamide (AM), 2-acrylamide-sodium dodecyl sulfonate (AMC 12 S), and the hydrophobic monomer 29-(4-octylphenoxy)-3,6,9,12,15,18,21,24,27-nonaoxanonacosyl methacrylate (GTE-10). The structure and morphology of the polymer obtained were then characterized by FTIR, 1 H-NMR, SEM, TEM, and a laser particle size distribution analyzer. This was followed by an evaluation of its rheological properties, thixotropic properties, and viscoelasticity. The results showed that the hydrophobic monomer GTE-10 was successfully incorporated into the polymer, resulting in a narrow and uniform particle size distribution of the emulsion after polymerization. The addition of salt made the aggregation of p(AM/AMC 12 S/GTE-10) molecules more compact, resulting in a more stable spatial network structure. The p(AM/AMC 12 S/GTE-10) polymer aqueous solution with a mass fraction of 0.7% exhibited excellent temperature resistance at 140 ℃. After being sheared at 120 ℃ and 170 s –1 for 1 h, the polymer solutions with a mass fraction of 0.7%, prepared at a mass concentration of 20000 mg/L NaCl and CaCl 2 aqueous solutions exhibited viscosities of 64.7 and 54.2 mPa·s, respectively, with good shear recovery performance. The energy storage modulus was higher than the loss modulus, and the complex interaction between the metal ion and phenoxyethylene group enhanced the intermolecular forces, resulting in a more stable spatial structure and increased viscoelasticity. Inverse-phase emulsion polymerization salt tolerance rheological property Viscoelasticity Thixotropy Figures Figure 1 Figure 2 Figure 3 Figure 4 Figure 5 Figure 6 Figure 7 Figure 8 Figure 9 Figure 10 Figure 11 Figure 12 Figure 13 1. Introduction Polyacrylamide is a synthetic polymer that can be artificially controlled in terms of relative molecular weight (referred to as molecular weight) and molecular structure by changing the monomer or polymerization method in order to achieve specific thickening and rheological properties [ 1 – 6 ] . With the exploration and development of shale oil and gas resources, hydraulic fracturing has become the main method for unconventional oil and gas reservoir modification, and polymers with storage modulus (G') are essential for efficient friction reduction and proppant carrying [ 7 – 10 ] . By altering the structure of the polymer to change its viscosity, the viscoelasticity can be increased, thereby reducing the amount of polymer used in the fracturing process and enhancing the fluid's carrying capacity for proppants [ 11 – 12 ] .Wu Wei et al. [ 13 ] synthesized a quaternary hydrophobic associative polymer AAMS-1 using acrylamide, 2-acrylamido-2-methylpropane sulfonic acid, methyl acryloyloxyethyltrimethylammonium chloride, and 4-acrylamidobenzenesulfonic acid sodium salt as raw materials through a reverse-phase emulsion polymerization method. The polymer solution with a mass fraction of 0.6% was subjected to continuous shearing for 2 h at 150°C and 170 s − 1 , and the viscosity remained greater than 50 mPa·s, with the storage modulus (G') consistently higher than the loss modulus (G″), indicating excellent viscoelasticity of the system at 150°C. MAO et al. [ 14 ] used acrylamide, acrylic acid, 2-acrylamido-2-methylpropane sulfonic acid, 29-(4-octyloxyphenyl)-3,6,9,12,15,18,21,24,27-nonaoxaoctacosan-1-ol methacrylate (GTE-10) as raw materials to obtain a hydrophobic associative polymer SRHV through aqueous solution polymerization. The SRHV at a mass concentration of 3000 mg/L maintained good viscoelasticity in a 26.5% NaCl aqueous solution at 90 ℃, indicating that the metal ions in the salt solution contributed to the formation of the polymer's internal hydrophobic associative network, which was difficult to disrupt at high temperatures. This article introduces the hydrophobic monomer GTE-10 to prepare a polymer emulsion with a strong hydrophobic association network structure in salt solution and achieve low viscosity and high elasticity rheological behavior using acrylamide (AM), 2-acrylamido dodecane sulfonic acid sodium salt (AMC 12 S), and GTE-10 as raw materials via reverse emulsion polymerization. The structure and morphology of the polymer were characterized by FTIR, 1 HNMR, SEM, TEM, and laser particle size analyzer. The salt resistance and rheological properties of the polymer aqueous solutions were measured to provide new ideas for polymer modification and applications. 2. Experimental Section 2.1 Materials Dichloromethane, Triethylamine, Methylacryloyl Chloride, sodium hydroxide, anhydrous ethanol, sodium chloride (NaCl), anhydrous calcium chloride (CaCl 2 ) (analytical grade, > 99%), and white oil (industrial grade, > 99%) were purchased from Shanghai Aladdin Biochemical Technology Co., Ltd. Acrylamide (AM), potassium persulfate (KPS), and azobisisobutyronitrile (AIBN) (analytical grade reagent, > 99%) were purchased from Shanghai McLan Biochemical Technology Co., Ltd. Ammonium persulfate [(NH 4 ) 2 S 2 O 8 ] and sodium hydrogen sulfite (NaHSO 3 ) (analytical grade reagent, > 99%) were purchased from Jiangshun Chemical Technology Co., Ltd. Sorbitan monostearate (S-80), polysorbate 80 (T-80), and octylphenol ethoxylate (10) (OP-10) (analytical grade reagents, > 99%) were purchased from Hegro Chemical Co., Ltd. (Shanghai). AMC 12 S was purchased from Shanghai Zhixin Chemical Co., Ltd. Deionized water was used in all experiments. The equipment used included a HAKKE Mars 40 rotational viscometer (Thermo Fisher Scientific); an SDT-500C rotating drop tensiometer (Hako Instruments Testing Factory); a BT-9300S laser particle size analyzer (Dandong Bait Instruments Co., Ltd.); a Quanta 450 environmental scanning electron microscope (USA); an LGJ-12 vacuum freeze dryer (Beijing Songyuan Huaxing Technology Development Co., Ltd.); a UU777-1835 non-dilution Ubbelohde viscometer (Beijing Zhongxi Yunda Technology Co., Ltd.); and a Y25/M192941 high-shear homogenizer (Shanghai Yile Electrical Equipment Co., Ltd.). RE-52A rotary evaporator (Shanghai Yarong Biochemical Instrument Factory). 2.2 Synthesis of Hydrophobic Monomer GTE-10 The OP-10 (64.6 g, 0.1 mol) and dichloromethane (250 mL) were weighed and added into a 500 mL reaction flask. The system was cooled in an ice bath until the temperature dropped to 0°C. Then 10.1 g (0.1 mol) of triethylamine was added, followed by a slow drip of 10.5 g (0.1 mol) methacryloyl chloride and dichloromethane using a pressure-equalizing addition funnel. The reaction was allowed to proceed for 8 hours to obtain the crude product. The solvent was then removed using a rotary evaporator to obtain the hydrophobic monomer GTE-10 [ 14 ] . The synthetic route was as follows. Schematic1 Synthesis of monomer GTE-10 AM (240 g, 3.4 mol), AMC12S (32 g, 0.1 mol), hydrophobic monomer GTE-10 (4 g, 0.005 mol), and 2 mL of a 1% mass fraction ammonium persulfate solution were added to 350 g of deionized water to obtain an aqueous phase solution. Then, 100 mL of a 40% mass fraction sodium hydroxide solution was used to adjust the pH of the aqueous phase to 6.5 ~ 7.0. Twenty-two grams of Sorbitan monostearate (S-80) and polysorbate 80 (T-80) were weighed and added to 240 g of white oil to obtain an oil-phase solution. The aqueous phase was mixed evenly with the oil phase, and a high-speed agitator was used for pre-emulsification at 11000 rpm for 15 min to obtain a uniform oil-in-water pre-emulsion. After passing nitrogen gas through the pre-emulsion for 1 h, 3 mL of a 1% mass fraction NaHSO 3 solution was added as an initiator using a micro-injection pump, and the temperature was maintained at 45°C for 2–3 h. After the reaction, the system was cooled to room temperature, and 3.5 g of the phase transfer agent NP-10 was added to obtain a stable polymer emulsion p(AM/AMC 12 S/GTE-10). The synthetic route was as follows. Schematic 2 Synthesis of Reverse Phase Emulsion Polymer P(AM/AMC12S/GTE-10) 2.4 Characterization and Performance Testing of Structure The sample was purified and its structure was characterized by infrared spectroscopy and nuclear magnetic resonance spectrometry. A BT-9300S laser particle size analyzer was used to determine the particle size distribution of the emulsion. The test was performed at 25 ℃, and the obscuration rate was > 2% to evaluate the particle size distribution pattern. The morphologies of the polymer specimens were studied using environmental scanning electron microscopy (SEM). A 0.3% solution of the polymer was prepared using pure water and left for 90 min, dropped onto a conductive adhesive surface, and the surface was freeze-dried with liquid nitrogen. The frozen surfaces of the prepared samples were observed using SEM at an accelerating voltage of 20 kV [ 15 , 16 ] . The samples were dried on a 200-mesh copper grid and characterized by transmission electron microscopy. A HAKKE Mars 40 rotational rheometer was used to test the temperature and shear resistance of the 0.7% polymer. The shear rate, temperature, and heating rate were 170 s − 1 , 90℃,120 ℃, and 0.05 ℃/s, respectively. Continuous shearing was performed for 1 h [ 17 ] . The steady-state and dynamic rheological properties of the polymers were investigated at concentrations of 0.3, 0.5, and 0.7%. Measurements were performed using a cone fabricated from a standard extension–twist coupling (ETC) steel rotor with a diameter of 40 mm, cone angle of 2°, and a gap of 48 mm between the cone center and plate. The scanning stress was set to 0.1–10 Pa to determine the linear viscoelastic region. Subsequently, frequency scans were performed under fixed shear conditions over a frequency range of 0.1–10 Hz to further examine the linear viscoelasticity regions. Before the measurements were acquired, the samples were equilibrated on the plate for 5 min to ensure sufficient accuracy, and the temperature was maintained at 30 ℃ during the experiments [ 18 , 19 ] . 3. Results and Discussion 3.1 Analysis of FT-IR Figure 1 a displays the various absorption peaks: the peak at 3605 cm − 1 corresponds to the stretching vibration of the O–H bond in the carboxyl group; and the peak at 3165 cm − 1 corresponds to the stretching vibration of the N–H bond in the amide group; the peak at 2931 cm − 1 corresponds to the stretching vibration of the N–H bond in the methyl and methylene groups; the peak at 1691 cm − 1 corresponds to the stretching vibration of the C = O bond; the peak at 1552 cm − 1 corresponds to the stretching vibration of the C–N bond and the bending vibration of the N–H bond in the amide group; the peak at 1415 cm − 1 is the characteristic peak of the sulfonic acid group; the peak at 1315 cm − 1 corresponds to the stretching vibration of the C–N bond and the bending vibration of the N–H bond in the secondary amine in the amide group; the peak at 640 cm − 1 is the characteristic peak of –(CH 2 ) 9 –; GTE-10 and p(AM/AMC 12 S/GTE-10) both exhibit corresponding stretching vibration peaks of the C = C bond at 1415, 1450, and 1552 cm − 1 , a bending vibration peak of the C–H bond on the benzene ring at 813 cm − 1 , and a corresponding stretching vibration peak of the C–O–C bond at 1315 cm − 1 . The results indicate that the hydrophobic monomer GTE-10 has been successfully incorporated into the polymer, and the structure of the polymer molecule obtained is consistent with expectations. 3.2 Analysis of 1 H NMR spectroscopy Figure 1 b displays peaks at δ 4.71 corresponding to the solvent peak of deuterated oxide; at δ 0.63 (a) corresponding to the proton peak of the methyl group –CH 3 on the long alkyl chain –(CH 2 ) 7 CH 3 in the monomer GTE-10; at δ 1.16 (b), δ 1.72 (c), and δ 3.11 (d) corresponding to the proton peaks of –CH 2 – within the repeating unit –(CH 2 ) 7 CH 3 ; at δ 6.68 (e) and δ 6.95 (f) corresponding to the two sets of proton peaks on the benzene ring; at δ 4.12 (g), δ 3.88 (h), and δ 3.50 (i) corresponding to the proton peaks of –CH 2 – within the repeating unit –(CH 2 CH 2 O) 10 –; at δ 1.79 (j) corresponding to the proton peak of the –CH 3 on the double bond carbon at the end of GTE-10; and at δ 5.31 (k) and δ 6.09 (l) corresponding to the two sets of proton peaks on the double-bonded carbon. Figure 1 c displays a peak at δ 13.9 (a), which corresponds to the absorption of the methyl group –CH 3 on the long alkyl chain –(CH 2 ) 7 CH 3 in the monomer GTE-10. The peaks at δ 43.2 (b) and δ 46.6 (c) represent the absorption peaks of the repeating unit –(CH 2 ) 7 –. Additionally, the peaks at δ 135.8 (d), δ 129.6 (e), δ 113.7 (f), and δ 156.3 (g) correspond to the absorption peaks of the four carbon groups on the benzene ring. The peak at δ 69.8 (h) corresponds to the absorption peak of the –CH 2 – within the repeating unit –(CH 2 CH 2 O) 10 . Moreover, the peak at δ 167.7 (i) represents the absorption peak of the carbonyl carbon, while the peak at δ 17.8 (k) corresponds to the absorption peak of the –CH 3 group on the double-bonded carbon at the end of GTE-10. Lastly, the peaks at δ 135.2 (j) and δ 126.6 (l) correspond to the absorption peaks of the two double-bonded carbons. Figure 1 d displays the peak at δ 4.71 corresponds to the solvent peak of deuterated oxide. The proton peaks at δ 1.71 (a), δ 1.43 (b), and δ 0.76 (c) are attributed to the main-chain protons of –CH 2 –, –CH–, and –CH 3 , respectively. Additionally, the proton peaks at δ 3.20 (d) and δ 3.28 (g) correspond to the side chain protons of –CH– and –CH 2 – in the monomer AMC 12 S. The peaks at δ 0.91 (e) and δ 1.26 (f) represent the proton peaks of -CH 2 - and -CH 3 in the repeating unit of –(CH 2 ) 9 CH 3 . Furthermore, the peak at δ 3.36 (h) corresponds to the proton peak of –CH 2 – in the repeating unit –(CH 2 CH 2 O) 10 – in the side chain of the functional monomer GTE-10. Lastly, the peak at δ 6.78 (i) represents the proton peak of the benzene ring. These results indicate that the monomers AMC 12 S and GTE-10 both participated in the polymerization reaction, resulting in polymer molecules with the expected structure. 3.3 Particle Size Analysis Figure 2 displays the particle size distribution and microstructure of the emulsion before and after polymerization. As depicted in Fig. 2 a and c, it can be observed that the oil-in-water emulsion formed after pre-emulsification has a larger average particle size and uneven distribution, with a D 50 of 10.45 µm. In contrast, in Fig.s 2b and d, it is evident that the oil-in-water structure becomes more uniform after the completion of the polymerization reaction, with a narrower particle size distribution range and a D 50 of 5.837 µm. This results in a polymer with improved solubility. 3.4 Mechanism of Inverse Emulsion Polymerization The schematic diagram of the reaction mechanism for the synthesis of polymer p(AM/AMC 12 S/GTE-10) via reverse-phase free radical polymerization is shown in Fig. 3 . The polymerization process can be divided into three stages: initiation, propagation, and termination. During the initiation stage, the initiator undergoes redox reactions, and the pre-polymerization radicals are continuously transferred to the growing micelles, driven by the equilibrium swelling of latex particles, to initiate monomer polymerization, leading to an increase in the polymerization rate. As the free monomers in the system are completely encapsulated within the monomer droplets, the polymerization rate becomes relatively constant, and the system enters the propagation stage. In this stage, only latex particles and monomer droplets coexist, representing the golden period for acrylamide polymerization, which is characterized by high exothermicity. The addition of sodium formate as a chain-transfer agent promotes a more regular polymer structure. This stage is characterized by a long duration. Finally, the reaction enters the termination stage, during which the remaining residual monomers continue to react, resulting in a significant decrease in the polymerization rate until all the active monomers are converted into polymer molecules. 3.5 Analysis of Critical Aggregation Concentration by Fluorescent Probes In Fig. 4 a, the hydrophobically associating polymer spontaneously forms micelles and small hydrophobic microdomains capable of dissolving pyrene, serving as a fluorescence probe reflecting the strength of the hydrophobic association effect. In the fluorescence spectrum, the ratio of the absorbance at 373 nm (I 1 ) to the absorbance at 391 nm (I 3 ), denoted as I 1 /I 3 , depends on the polarity of the surrounding environment. When the surrounding microenvironment is more polar, the I 1 /I 3 value is higher; conversely, once the polymer molecules form a distinct dynamic physical cross-linking network, the I 1 /I 3 value significantly decreases. Figure 4 b illustrates the variation in I 1 /I 3 at different concentrations of the p(AM/AMC 12 S/GTE-10). When the concentration is 0.30 wt.%, the value of I 1 /I 3 suddenly decreases. This indicates that when the concentration of the p(AM/AMC 12 S/GTE-10) solution exceeds 0.30 wt.%, the polymer molecules form a large number of hydrophobic regions, weakening the polarity of the surrounding microenvironment of the pyrene probe. Therefore, the apparent viscosity and fluorescence spectrum measurements indicate that the critical association concentration (C*) of p(AM/AMC 12 S/GTE-10) is approximately 0.30–0.35 wt.%. 3.6 Analysis of Salt Tolerance Performance At room temperature, the apparent viscosity changes of the polymers with mass fractions of 0.3%, 0.5%, and 0.7% in different mass concentrations of NaCl and CaCl 2 aqueous solutions are shown in Fig. 5 . The viscosity of the polymer solutions exhibits a trend of first increasing and then decreasing with an increase in the salt solution mass concentration. The initial viscosity of the 0.7% mass fraction polymer solution is 123 mPa·s. In the 80000 mg/L NaCl and CaCl 2 solutions, the apparent viscosities of the 0.7% mass fraction polymer solution were 39 and 24 mPa·s, with viscosity retention rates of 31.71% and 19.51%, respectively. The ability of the phenylethylene group contained in monomer GTE-10 to chelate metal ions reduces the negative effects of electrostatic shielding, increases the hydrodynamic volume, and promotes the formation of spatial network structures, thereby increasing the apparent viscosity of the polymer with increasing polymer mass fraction [ 18 – 19 ] . The introduction of hydrophobic long chains and benzene rings enhances the rigidity of the molecular chains, preventing them from easily coiling and enhancing the salt resistance capabilities of the system. At high salt mass concentrations, the electrostatic shielding of metal ions on the molecular chains exceeds the intermolecular binding effect, compressing the hydrodynamic volume of the polymer molecules and resulting in a decrease in the viscosity of the polymer solution. 3.7 Analysis of SEM SEM images of the polymer p(AM/AMC 12 S/GTE-10) with a mass fraction of 0.3% in pure water and sodium chloride solution with a mass concentration of 10000 mg/L are shown in Fig. 6 . In pure water, the polymer is fully extended, and the functional monomer GTE-10 in the polymer spontaneously aggregates, forming hydrophobic microdomains with certain strength. This leads to the formation of a three-dimensional network structure with intermolecular cohesive interactions, resulting in the viscoelastic behavior of the polymer solution on a macroscopic scale. In saline solution, the phenylethylene group in the functional monomer GTE-10 acts as a chelating agent for salt ions. The filling of the vacant orbital of the metal ions by the lone pair electrons of the ethylene group enhances the intermolecular forces, reduces the impact of electrostatic shielding on the polymer skeleton, and enhances the resistance of the polymer to metal cations. Therefore, the polymer exhibits a stronger spatial network structure in saline solution [ 20 – 21 ] . 3.8 Analysis of temperature resistance performance A mass fraction of 0.7% p(AM/AMC 12 S/GTE-10) solution was prepared in a water solution of NaCl and CaCl 2 with equal mass concentrations of 20000 mg/L at 140 ℃, and its temperature resistance performance is shown in Fig. 7 . The viscosity of the polymer solution continues to decrease with increasing temperature. Hydrophobic modification enhances the cohesive force of the polymer chains, increasing the viscous flow activation energy of the fluid; thus, the polymer exhibits a certain dependency on temperature. As the temperature was increased, the viscosity of the polymer solution decreased. At 140 ℃, the viscosity of the polymer solution in both pure water (Fig. 7 a) and NaCl (Fig. 7 b) solutions was greater than 50 mPa·s (Fig. 7 b). In the CaCl 2 solution (Fig. 7 c), the viscosity of the polymer solution decreased below 50 mPa·s at temperatures higher than 115.3 ℃. Overall, the polymer solution exhibited good temperature resistance. 3.9 Analysis of shear resistance performance A 0.7% (w/w) p(AM/AMC 12 S/GTE-10) solution was prepared in pure water and aqueous solutions of NaCl and CaCl 2 at mass concentrations of 20000 mg/L. The shear-thinning performance of the polymer solution was measured at 90 and 120°C at a constant shear rate of 170 s –1 , as shown in Fig. 8 . With increasing temperature, the viscosity of the polymer solution initially decreased and then plateaued. The intensified thermal motion of the functional groups weakens intermolecular aggregation, leading to a reduction in the viscosity of the polymer solution. Once the temperature stabilized, the temperature dependency of the polymer solution viscosity was eliminated, and a balance was reached between the intermolecular association and molecular thermal motion. Figure 8 a, b, after shearing at 90 and 120°C for 1 h, the viscosity of the polymer solution remained essentially unchanged at 88.7 and 73.2 mPa·s, respectively. Figure 8 c, d the viscosity of the polymer solution after shearing at 90 and 120°C for 1 h in an aqueous NaCl solution with a mass concentration of 20000 mg/L was 79.3 and 64.7 mPa·s, respectively. Meanwhile, in the aqueous CaCl 2 solution with the same mass concentration, the viscosities of the polymer solutions at 90 and 120°C after shearing for 1 h were 63.9 and 54.2 mPa·s, respectively. The presence of hydrophobic long chains and benzene rings in the monomer GTE-10 enhanced the rigidity of the molecular chains and hindered conformational transitions, resulting in a more stable spatial network structure. Additionally, metal ions in the salt solutions form complexes with ethylene oxide groups, reducing the negative impact of the salt ions and enhancing the shear resistance of the polymer solution. 3.10 Analysis of shear resistance performance testing At 30 ℃, the effect of the shear rate at 170, 510, and 1022 s –1 on the viscosity of the polymer solution was alternately investigated, and the results are shown in Fig. 9 a. When the shear rate increased from 170 s –1 to 510 s –1 and then further to 1022 s –1 , the viscosity continued to decrease. When the shear rate was constant, viscosity remained essentially unchanged. After shearing at 1022 s –1 for a certain period of time, the viscosity returned to its initial value upon reverting to 170 s –1 . The results indicate that the polymer viscosity exhibits good shear recovery performance, possibly due to the fact that under high shear rates, the dynamically physical cross-linked network structure formed by molecular aggregation is not completely disrupted. When the shear rate decreases, the aggregation forces lead to the reformation of separated molecular chains into hydrophobic microdomains, which macroscopically manifests as either an increase or return to the initial value of apparent viscosity [ 22 ] . The rheological behavior of polymer solutions can be described by the power law equation as follows: \(\lg \tau =\lg \kappa +{\text{n}}\lg \gamma\) Where τ is the shear stress, κ is the consistency coefficient, γ is the shear rate and n is the power law index. When 0 < n < 1, it represents a pseudoplastic flow, where the apparent viscosity decreases with increasing shear stress or shear rate. When n = 1, it represents an ideal Newtonian fluid. Figure 9 b, A fitting line of the shear rate and shear stress was obtained with lgγ as the abscissa and lgτ as the ordinate, and the fitting equation was y = 0.28839x + 0.90339 (R 2 = 0.99805). Where the power law index is n = 0.28839 < 1, and the consistency coefficient is κ = 8.01. Therefore, the polymer solution is a pseudoplastic fluid and exhibits shear-thinning behavior. 3.11 Analysis of thixotropic performance The thixotropic properties of the polymer aqueous solutions with quality fractions of 0.3, 0.5, and 0.7% were tested, as shown in Fig. 10 a, b, c. As the mass fraction of the polymer solution increased, both the hysteresis loop area and the shear stress increased. This indicates that the increase in intermolecular bonding of the polymer leads to the strengthening of the spatial network structure, resulting in greater resistance to deformation. This, in turn, increases the energy required to break the network structure, demonstrating the excellent shear resistance capabilities of the polymer. 3.12 Analysis of viscoelastic performance Polymer solutions are viscoelastic fluids that exhibit non-Newtonian viscosity and normal stress differences under steady shear flow. The presence of normal stress differences leads to various special flow phenomena such as the Weissenberg effect, suspended siphons, and jet expansion [ 23 ] . Therefore, to analyze the variation rules of viscoelasticity in polymer solutions, parameters such as G″, G′, complex modulus (G*), and the first normal stress difference (N 1 ) were determined. 3.12.1 Trends in changes of G' and G'' The curves of G' and G" versus the stress and frequency for polymer solutions with different mass fractions in NaCl at a mass concentration of 20,000 mg/L, CaCl 2 at a mass concentration of 10,000 mg/L, and deionized water are presented in Figs. 11 and 12 . As shown in Fig. 11 a, for polymer solutions with mass fractions of 0.3% and 0.5%, G′ and G″ remain stable in the low-stress range, showing a linear viscoelastic region that reflects the structural strength of the polymer solution. As the stress continues to increase, G′ and G″ show a decreasing trend, with G′ < G″, transitioning to a non-linear viscoelastic region, indicating the disruption of the spatial network structure of the solution under shear stress, displaying shear thinning behavior. For the polymer solution with a mass fraction of 0.7%, there is a clear linear viscoelastic region in the stress scan range of 0 ~ 10 Pa, with G′ > G″, exhibiting elastic fluid behavior. As the mass fraction of the polymer increases, the intermolecular binding becomes stronger, resulting in a more stable and difficult-to-break spatial structure. Additionally, the Fig. 11 b, c appropriately concentrated salt solutions can enhance the binding effect, contributing to an increase in the viscoelasticity of polymer molecules. As shown in Fig. 12 , as the shear frequency increases, the G′ and G″ values of the polymer solution increase. As shown in Fig. 12 a, the 0.3% mass fraction polymer solution in pure water exhibits predominantly intramolecular association at lower frequencies, where the viscoelasticity is mainly contributed by the higher molecular weight, leading to G′ < G″, showing viscous flow. As the frequency increases from low to high, the intermolecular association strengthens, and the complex network structure provides better elasticity, with G′ dominating, indicating elastic flow. As shown in Fig. 12 b and c, the viscoelasticity of the polymer in a salt solution is greater than that in pure water because of the chelation reaction between metal ions and styrene groups, which enhances intermolecular forces and results in a dense network structure, accompanied by an increase in structural viscosity. Therefore, increasing the structural viscosity of the polymer can increase the viscoelasticity of the solution. 3.12.2 Trends in Changes of G* G* studies the linear viscoelastic behavior of polymer solutions, reflecting both the viscosity and elastic characteristics of the fluid. It can be obtained based on G′ and G″ [ 24 , 25 ] , and the equation is as follows: $${G^{\text{*}}}=G^{\prime}+{\text{i}}G^{\prime\prime}=\sqrt {{{G^{\prime}}^2}+{{G^{\prime\prime}}^2}}$$ Figure 13 a depicts the increase in G* as the shear frequency increases, approaching a linear trend. This phenomenon is attributed to the formation of a stable spatial network structure between polymer molecules. This results in increased resistance to deformation in polymer solutions as shear frequency rises, as evidenced by the increase in G*. Under the same mass fraction, the value of G* in salt solutions is greater than that in pure water. The dynamically physical crosslinked network formed by hydrophobically modified polymers is less affected by inorganic salts. This results in enhanced resistance to salt-induced viscosity enhancement and an increase in viscoelasticity. To compare the viscoelastic properties of polymer solutions with varying mass fractions, the complex modulus values at a frequency of 1 Hz were chosen for comparison. With the increasing mass fractions of the polymer, the values of G* in both pure water and saline solutions showed an increased trend. Among them, the trend of Fig. 13 b increase in a 20000 mg/L NaCl solution is the steepest, and the Fig. 13 c followed by the 10000 mg/L CaCl 2 solution. This indicates that appropriately concentrated salt solutions are conducive to enhancing the viscoelasticity of polymer molecules. When the mass fraction of the polymer is in the range of 0.3–0.5%, the increase in G* is slow. However, when the mass fraction is in the range of 0.5–0.7%, the slope of the curve is steeper, leading to a faster increase in G*. At lower mass fractions, viscoelasticity is primarily determined by the intramolecular binding of polymer molecules. With the increase in mass fractions, intermolecular binding strengthens, leading to the formation of a complex network structure, resulting in a significant increase in G*. 4. Conclusions (1) The functional monomer GTE-10, which contains a benzene ring and phenylethylene group, was introduced into reverse emulsion polymerization to prepare a polymer emulsion with a robust hydrophobic associative network structure in a saline environment. The polymer was characterized using FTIR and 1 H-NMR spectroscopy. The SEM results indicated that the polymer exhibited a dense spatial network structure under saltwater conditions. (2) The results of the temperature and shear resistance tests showed that at 90 and 120 ℃ under a shear rate of 170 s –1 , the viscosity of a 0.7% mass fraction polymer aqueous solution remained at 88.7 and 73.2 mPa·s, respectively, while the viscosity of a 0.7% mass fraction polymer salt solution was greater than 50 mPa·s. Thixotropic performance tests revealed that the polymer solutions exhibited good shear recovery properties of their viscosity. (3) The viscoelasticity test results indicated that when the mass fraction of the polymer solution increased from 0.3–0.7%, a significant linear viscoelastic region appeared, with G' > G″, indicating an elastic fluid behavior. In saltwater, metal ions undergo chelation with the phenylethylene group, enhancing the associative effect and leading to a more stable spatial structure that is difficult to disrupt, resulting in higher viscoelasticity. Declarations Conflicts of interest There are no conflicts of interest to declare. Ethical Approval not applicable Funding This research was supported by the Service Program for Foreign Experts of Shaanxi Province of China ( 2023WGZJ-ZD-03), Key R&D Program of Shaanxi Province (2023-YBGY-307), Industrialization Project of Shaanxi Provincial Education Department( 21JC005), and Science and Technology Program of Xi’an, China (22GXFW0014). Availability of data and materials All of the material is owned by the authors and no permissions are required. Author contributions Xin Wen: Conceptualization; Data curation. Roles/Writing - original draft,Writing - review & editing. Lei Wang : Funding acquisition; Methodology. Xiao-juan Lai : Investigation; Project administration. Gui-ru Liu : Software. Wen-wen Yang : Supervision. Ya-meng Liu : Formal analysis. All of the material is owned by the authors and no permissions are required. References Zhu S, Xue X, Zhang J, Zhang S, Liu Z (2022) Application and Optimization of the Rheological Model for a Hydrophobically Associating Dendrimer Polymer.Polymers14, 1747. Zhang L Q (2017) Study on settlement law of proppant in slippery water. Contemporary Chemical Industry 46(4): 711-714. Shao Y, Mao J C, Yang B, Zhao J Z, Yang X J (2020) High performance hydrophobic associated polymer for fracturing fluids with low-dosage. Petroleum Chemistry 60(2): 219-225. Pan Y, Feng J N, Yang S C, Zain U, Zhang H Y (2018) Synthesis of thermo-salt-resistant hydrophobic associated polyacrylamide and its prospect. Applied Chemical Industry 47(8): 1772-1777. Jiao Y B, Chen Y J, Yang H, Wang C Q (2024) Experimental characterization on fracture behavior of UHPMC under small-scale sample tensile testing: Acoustic emission monitoring and digital image correlation 130,104342 Kang W L, Hou X Y, Chen C,Shao S,Zhang X F,Zhu T Y,Wang T Y,Yang H B (2019) Study on rheological behavior and salt-thickening mechanism of a synthesized twin-tailed hydrophobically modified polyacrylamide. Journal of Molecular Liquids 294(C): 111619-111626. Pu W F, Du D J, Liu R (2018) Preparation and evaluation of supramolecular fracturing fluid of hydrophobically associative polymer and viscoelastic surfactant. Journal of Petroleum Science and Engineering 167: 568-576. Ma X P, Mu H L, Hu Y Y, Yang S W (2021) Synthesis and properties of hydrophobically associating polymer fracturing fluid. Colloids and Surfaces A: Physicochemical and Engineering Aspects 626: 127013-127013. Bai Z F, Li M Z (2023) Prediction of Proppant Settling Velocity in Fiber-Containing Fracturing Fluids. ACS Omega, 8(35): 31857–31869. Shi J M, Wu Z L, Deng Q C,Liu L, Zhang X F,Wu X Y,Wang Y G (2021) Synthesis of hydrophobically associating polymer: Temperature resistance and salt tolerance properties. Polymer Bulletin 79: 4581-4591. Yin S F, Ma H F, Cheng Z H, Zou Q L, Li Y M, Jia H S, Zhang K X (2019) Permeability enhancement mechanism of sand‐carrying hydraulic fracturing in deep mining: A case study of uncovering coal in cross‐cut. Energy Science & Engineering, 7(5):1867-1881. He J, Li T T, Wang M X, Fagn X, Nan B B (2014) Study on the influencing factors of the relationship between the viscosity of clean fracturing fluid and its suspended sand. Journal of Yangtze University, 11(14): 73-76. Wu W, Liu P P, Sun H, Zhang X Y (2016) Synthesis and application of AAMS-1 hydrophobic association polymer thickener for fracturing fluid. Drilling Fluid and Completion Fluid, 33(5): 114-118. Mao J C, Cao H M, Zhang H,Du A Q, Xue J X, Lin C, Yang X J,Wang Q H, Mao J H, Chen A (2022) Design of salt-responsive low-viscosity and high-elasticity hydrophobic association polymers and study of association structure changes under high-salt conditions. Colloids and Surfaces A: Physicochemical and Engineering Aspects 650: 129512-129524. Che E Q (2020) Study and application of water in oil polyacrylamide prepared by inverse emulsion polymerization. Xi 'an: Shaanxi University of Science & Technology. Li Y W (2019) Synthesis and properties of hydrophobically associating polyacrylamide in inverse microemulsion.Tianjin: Hebei University of Technology. Cao T Y, Liu Q P , Hu J S (2007) Synthesis principle, performance and application of polymer emulsion. Beijing: Chemical Industry Press 19-28. Pu W F, Jiang F, He Y Y, Wei B, Tang Y L (2016) Synthesis of a novel comb micro-block hydrophobically associating copolymer for Ca2+/Mg2+ resistance. RSC Advances 6(49): 43634-43637. Pu W F, Jiang F, Wei B, Tang Y L, He Y Y (2017) Influences of structure and multi-intermolecular forces on rheological and oil displacement properties of polymer solutions in the presence of Ca2+/Mg2+. RSC Advances 7(8): 4430-4436. Fan M L, Wang L, Li J, He P, Lai X Y,Gao J H, Liu G R, Wen X (2022) Preparation of supramolecular viscoelastic polymers with shear, temperature, and salt resistance/ sensitivity by amphiphilic functional monomer modification[J]. Polymer Testing 116: 107799-107810. Liu Y, Wang L, Liu L F, Yasir M F, Wen X, Lu L J (2022) Rheological properties of hydrophobic associating polymer solutions in response to salt stimulation[J]. Fine Chemicals 39(7): 1486-1494. Mao J C, Zhang H, Xue J X (2022) Correction to: Investigation of a hydrophobically associating polymer’s temperature and salt resistance for fracturing fluid thickener[J]. Colloid and Polymer Science 300(9): 569-582. Shi X D (2015) Viscoelastic properties and stability of high temperature resistant polymers.Daqing: Northeast Petroleum University. Xue X S (2005) Effect of molecular structure on viscoelasticity of associated polymers and their seepage characteristics in porous media. Chengdu: Southwest Petroleum Institute. Xia H F, Zhang J R, Liu S Y (2011) Viscoelasticity of polyacrylamide solution and its influencing factors. Journal of Daqing Petroleum Institute 35(1): 37-41,115-116. Additional Declarations No competing interests reported. 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-4081245","acceptedTermsAndConditions":true,"allowDirectSubmit":true,"archivedVersions":[],"articleType":"Research Article","associatedPublications":[],"authors":[{"id":279938489,"identity":"e919f9f5-c0c1-491c-a514-c8c974977f22","order_by":0,"name":"Xin Wen","email":"","orcid":"","institution":"Shaanxi University of Science and Technology","correspondingAuthor":false,"prefix":"","firstName":"Xin","middleName":"","lastName":"Wen","suffix":""},{"id":279938490,"identity":"262e6b6b-9a05-44c7-b1fd-8a039e43956d","order_by":1,"name":"Lei Wang","email":"data:image/png;base64,iVBORw0KGgoAAAANSUhEUgAAAZAAAAAyAQMAAABI0h/eAAAABlBMVEX///8AAABVwtN+AAAACXBIWXMAAA7EAAAOxAGVKw4bAAAA90lEQVRIiWNgGAWjYBACNvkDIMqCgY29ASp0gIAWfgkwJcHAxgNSmkCEFskZUC0MEglEajG43WP4ueCXhByf5PNnkj9/MMjx3Uhg/FyAT8udM8bSM/skjNmkc8ykeRIYjCVvJDBLz8Cn5UDuBmneHonENukcNmmgwxI33EhgY+bBr2Xzb6CW+jbJ488kfyQw1BPUIjkjd5s0zw+JBDYJBjMJoMMSDAhp4ec5/82at0HCsI0nx9iaJ03CcOaZh83S+LSwsbcl3+b5YyMv33784c0fNjbyfMeTD37GpwUMGNvgTFDMMjYQ0gAEf4hQMwpGwSgYBSMXAADLHEX6fIvYNwAAAABJRU5ErkJggg==","orcid":"","institution":"Shaanxi University of Science and Technology","correspondingAuthor":true,"prefix":"","firstName":"Lei","middleName":"","lastName":"Wang","suffix":""},{"id":279938494,"identity":"6b77f8b8-cbcc-444c-8606-e4d230bd4750","order_by":2,"name":"XiaoJuan Lai","email":"","orcid":"","institution":"Shaanxi University of Science and Technology","correspondingAuthor":false,"prefix":"","firstName":"XiaoJuan","middleName":"","lastName":"Lai","suffix":""},{"id":279938498,"identity":"115c3f44-e8ca-46c5-a844-7e39b414b904","order_by":3,"name":"Guiru Liu","email":"","orcid":"","institution":"Shaanxi University of Science and Technology","correspondingAuthor":false,"prefix":"","firstName":"Guiru","middleName":"","lastName":"Liu","suffix":""},{"id":279938501,"identity":"92caab7b-72ed-43a5-b877-ff8772218414","order_by":4,"name":"Wenwen Yang","email":"","orcid":"","institution":"Shaanxi University of Science and Technology","correspondingAuthor":false,"prefix":"","firstName":"Wenwen","middleName":"","lastName":"Yang","suffix":""},{"id":279938503,"identity":"ef341f37-20d6-44a5-b1af-b9d920b13058","order_by":5,"name":"Yameng Liu","email":"","orcid":"","institution":"Shaanxi University of Science and Technology","correspondingAuthor":false,"prefix":"","firstName":"Yameng","middleName":"","lastName":"Liu","suffix":""}],"badges":[],"createdAt":"2024-03-12 08:03:55","currentVersionCode":1,"declarations":"","doi":"10.21203/rs.3.rs-4081245/v1","doiUrl":"https://doi.org/10.21203/rs.3.rs-4081245/v1","draftVersion":[],"editorialEvents":[],"editorialNote":"","failedWorkflow":false,"files":[{"id":52967900,"identity":"52da1e21-36c7-403e-9d30-fc446de05c19","added_by":"auto","created_at":"2024-03-19 07:37:02","extension":"png","order_by":1,"title":"Figure 1","display":"","copyAsset":false,"role":"figure","size":271501,"visible":true,"origin":"","legend":"\u003cp\u003e(a) FT-IR spectra of GTE-10 and p(AM/AMC\u003csub\u003e12\u003c/sub\u003eS/GTE-10), (b)\u003csup\u003e1\u003c/sup\u003eHNMR spectra of GTE-10, (c)\u003csup\u003e 13\u003c/sup\u003eCNMR spectra of GTE-10, (d)\u003csup\u003e 1\u003c/sup\u003eHNMR spectrum of p(AM/AMC\u003csub\u003e12\u003c/sub\u003eS/GTE-10).\u003c/p\u003e\n\u003cp\u003e3.3 Particle Size Analysis\u003c/p\u003e","description":"","filename":"floatimage3.png","url":"https://assets-eu.researchsquare.com/files/rs-4081245/v1/4f7a0cd3ddc31313a74791b3.png"},{"id":52966547,"identity":"4355e8f9-ef8b-4766-9344-0ebac2934c57","added_by":"auto","created_at":"2024-03-19 07:21:02","extension":"png","order_by":2,"title":"Figure 2","display":"","copyAsset":false,"role":"figure","size":398887,"visible":true,"origin":"","legend":"\u003cp\u003eParticle size distribution and corresponding TEM imagesof emulsion before (a, c) and after (b, d) polymerization.\u003c/p\u003e","description":"","filename":"floatimage4.png","url":"https://assets-eu.researchsquare.com/files/rs-4081245/v1/c3d4551e5a0ee06b2b762fca.png"},{"id":52967236,"identity":"27c42671-8847-4a18-9208-6f2c6f0518a6","added_by":"auto","created_at":"2024-03-19 07:29:02","extension":"png","order_by":3,"title":"Figure 3","display":"","copyAsset":false,"role":"figure","size":182711,"visible":true,"origin":"","legend":"\u003cp\u003ePolymerization mechanism of inverse emulsion p(AM/AMC\u003csub\u003e12\u003c/sub\u003eS/GTE-10)\u003c/p\u003e","description":"","filename":"5.png","url":"https://assets-eu.researchsquare.com/files/rs-4081245/v1/94b2fdbd67f4f0ece37be7b1.png"},{"id":52966553,"identity":"e58de0bf-ee99-40c3-9cd8-9218a48ea01b","added_by":"auto","created_at":"2024-03-19 07:21:02","extension":"png","order_by":4,"title":"Figure 4","display":"","copyAsset":false,"role":"figure","size":133511,"visible":true,"origin":"","legend":"\u003cp\u003eFluorescence probe of polymer p (AM/AMC12S/ GTE-10) with different concentration (a), the ratio of I1/I3 at different concentrations of polymer p(AM/AMC12S/GTE-10) (b).\u003c/p\u003e","description":"","filename":"floatimage6.png","url":"https://assets-eu.researchsquare.com/files/rs-4081245/v1/a9133c9510ff10baca76b8df.png"},{"id":52966558,"identity":"d6abd953-7986-4b19-b7be-042bd38f2e37","added_by":"auto","created_at":"2024-03-19 07:21:03","extension":"png","order_by":5,"title":"Figure 5","display":"","copyAsset":false,"role":"figure","size":146143,"visible":true,"origin":"","legend":"\u003cp\u003eEffect of salt solution with different mass concentrations on polymer apparent viscosity.\u003c/p\u003e","description":"","filename":"floatimage7.png","url":"https://assets-eu.researchsquare.com/files/rs-4081245/v1/ec9db942b397a4c00f307588.png"},{"id":52966555,"identity":"b7f718aa-e11e-4d68-986e-2cf7d824d8a6","added_by":"auto","created_at":"2024-03-19 07:21:02","extension":"png","order_by":6,"title":"Figure 6","display":"","copyAsset":false,"role":"figure","size":680662,"visible":true,"origin":"","legend":"\u003cp\u003eSEM images of p(AM/AMC\u003csub\u003e12\u003c/sub\u003eS/GTE-10) in clear water(a) and (b), salt water(c) and (d).\u003c/p\u003e","description":"","filename":"floatimage8.png","url":"https://assets-eu.researchsquare.com/files/rs-4081245/v1/9c8e0a5b32f782980b6ae9cc.png"},{"id":52966557,"identity":"69f8e162-8926-4b29-8b4f-ae090f23051e","added_by":"auto","created_at":"2024-03-19 07:21:03","extension":"png","order_by":7,"title":"Figure 7","display":"","copyAsset":false,"role":"figure","size":176143,"visible":true,"origin":"","legend":"\u003cp\u003eTemperature resistance of p(AM/AMC\u003csub\u003e12\u003c/sub\u003eS/GTE-10) solutions with a mass fraction of 0.7%:(a) deionized water, (b)NaCl, (c) CaCl\u003csub\u003e2\u003c/sub\u003e.\u003c/p\u003e","description":"","filename":"floatimage9.png","url":"https://assets-eu.researchsquare.com/files/rs-4081245/v1/22a86be9de62d1db2362c331.png"},{"id":52966551,"identity":"45bbd73e-4f19-4e16-87f2-ff2a0c839f4c","added_by":"auto","created_at":"2024-03-19 07:21:02","extension":"png","order_by":8,"title":"Figure 8","display":"","copyAsset":false,"role":"figure","size":295756,"visible":true,"origin":"","legend":"\u003cp\u003eShear resistance of p(AM/AMC\u003csub\u003e12\u003c/sub\u003eS/GTE-10) aqueous solution with a mass fraction of 0.7%, 90℃(a), 120℃(b), Shear resistance curves of polymer with a mass fraction of 0.7% in salt solutions，90℃(c), 120℃(d).\u003c/p\u003e","description":"","filename":"floatimage10.png","url":"https://assets-eu.researchsquare.com/files/rs-4081245/v1/cd8330c9afdd37537112d99d.png"},{"id":52966556,"identity":"6d35b0e9-465b-4a05-a5a4-a7f4f57a67a6","added_by":"auto","created_at":"2024-03-19 07:21:03","extension":"png","order_by":9,"title":"Figure 9","display":"","copyAsset":false,"role":"figure","size":125173,"visible":true,"origin":"","legend":"\u003cp\u003eViscosity curves of polymer aqueous solution with a mass fraction of 0.7% at different shear rates(a), fitted Curve of Shear Rate and Shear Stress (b).\u003c/p\u003e","description":"","filename":"floatimage11.png","url":"https://assets-eu.researchsquare.com/files/rs-4081245/v1/eddc26eb0058126525a1f02e.png"},{"id":52966548,"identity":"31840b1b-7d36-447d-a4fb-9487cb5ae911","added_by":"auto","created_at":"2024-03-19 07:21:02","extension":"png","order_by":10,"title":"Figure 10","display":"","copyAsset":false,"role":"figure","size":158926,"visible":true,"origin":"","legend":"\u003cp\u003eThixotropic properties of polymer solutions with different mass fractions\u003c/p\u003e","description":"","filename":"floatimage12.png","url":"https://assets-eu.researchsquare.com/files/rs-4081245/v1/ef8888b0edbd54e601cd9a0c.png"},{"id":52967239,"identity":"addc285e-5dc8-4375-a333-5835a439e8de","added_by":"auto","created_at":"2024-03-19 07:29:03","extension":"png","order_by":11,"title":"Figure 11","display":"","copyAsset":false,"role":"figure","size":260819,"visible":true,"origin":"","legend":"\u003cp\u003eChange curves of \u003cem\u003eG' \u003c/em\u003eand \u003cem\u003eG\"\u003c/em\u003e of polymer solution with stress: (a) deionized water, (b) NaCl solution with a mass concentration of 20000 mg/L, (c) CaCl\u003csub\u003e2\u003c/sub\u003e solution with a mass concentration of 10000 mg/L.\u003c/p\u003e","description":"","filename":"floatimage13.png","url":"https://assets-eu.researchsquare.com/files/rs-4081245/v1/e7598f3f32c4411fd6a98895.png"},{"id":52966554,"identity":"b02e72ed-a266-445d-99b4-cd616eab80ff","added_by":"auto","created_at":"2024-03-19 07:21:02","extension":"png","order_by":12,"title":"Figure 12","display":"","copyAsset":false,"role":"figure","size":243217,"visible":true,"origin":"","legend":"\u003cp\u003eChange curves of \u003cem\u003eG' \u003c/em\u003eand \u003cem\u003eG\"\u003c/em\u003e of polymer solution with frequency: (a) deionized water, (b) solution with a mass concentration of 20000 mg/L, (c) CaCl\u003csub\u003e2\u003c/sub\u003e solution with a mass concentration of 10000 mg/L.\u003c/p\u003e","description":"","filename":"floatimage14.png","url":"https://assets-eu.researchsquare.com/files/rs-4081245/v1/45fc812ca9e86e092acd3f1c.png"},{"id":52967237,"identity":"7ac992fc-88e7-422c-8e5c-38f670c36524","added_by":"auto","created_at":"2024-03-19 07:29:02","extension":"png","order_by":13,"title":"Figure 13","display":"","copyAsset":false,"role":"figure","size":207817,"visible":true,"origin":"","legend":"\u003cp\u003eChange curves of \u003cem\u003eG\u003c/em\u003e\u003csup\u003e*\u003c/sup\u003e with frequency: (a) deionized water, (b) NaCl solution with a mass concentration of 20000 mg/L, (c) CaCl\u003csub\u003e2\u003c/sub\u003e solution with a mass concentration of 10000 mg/L.\u003c/p\u003e","description":"","filename":"floatimage15.png","url":"https://assets-eu.researchsquare.com/files/rs-4081245/v1/279dda81549f7ac4220d0d56.png"},{"id":53036937,"identity":"7fe50598-ec18-462e-b584-2eb97cb38566","added_by":"auto","created_at":"2024-03-19 22:07:37","extension":"pdf","order_by":0,"title":"","display":"","copyAsset":false,"role":"manuscript-pdf","size":1759389,"visible":true,"origin":"","legend":"","description":"","filename":"manuscript.pdf","url":"https://assets-eu.researchsquare.com/files/rs-4081245/v1/705370d2-ebbe-4a2a-b9aa-ddb53eb13848.pdf"}],"financialInterests":"No competing interests reported.","formattedTitle":"Preparation and rheological properties of associative salt tolerant polymer by inverse-phase emulsion polymerization","fulltext":[{"header":"1. Introduction","content":"\u003cp\u003ePolyacrylamide is a synthetic polymer that can be artificially controlled in terms of relative molecular weight (referred to as molecular weight) and molecular structure by changing the monomer or polymerization method in order to achieve specific thickening and rheological properties \u003csup\u003e[\u003cspan additionalcitationids=\"CR2 CR3 CR4 CR5\" citationid=\"CR1\" class=\"CitationRef\"\u003e1\u003c/span\u003e\u0026ndash;\u003cspan citationid=\"CR6\" class=\"CitationRef\"\u003e6\u003c/span\u003e]\u003c/sup\u003e. With the exploration and development of shale oil and gas resources, hydraulic fracturing has become the main method for unconventional oil and gas reservoir modification, and polymers with storage modulus (G') are essential for efficient friction reduction and proppant carrying \u003csup\u003e[\u003cspan additionalcitationids=\"CR8 CR9\" citationid=\"CR7\" class=\"CitationRef\"\u003e7\u003c/span\u003e\u0026ndash;\u003cspan citationid=\"CR10\" class=\"CitationRef\"\u003e10\u003c/span\u003e]\u003c/sup\u003e. By altering the structure of the polymer to change its viscosity, the viscoelasticity can be increased, thereby reducing the amount of polymer used in the fracturing process and enhancing the fluid's carrying capacity for proppants \u003csup\u003e[\u003cspan citationid=\"CR11\" class=\"CitationRef\"\u003e11\u003c/span\u003e\u0026ndash;\u003cspan citationid=\"CR12\" class=\"CitationRef\"\u003e12\u003c/span\u003e]\u003c/sup\u003e.Wu Wei et al. \u003csup\u003e[\u003cspan citationid=\"CR13\" class=\"CitationRef\"\u003e13\u003c/span\u003e]\u003c/sup\u003e synthesized a quaternary hydrophobic associative polymer AAMS-1 using acrylamide, 2-acrylamido-2-methylpropane sulfonic acid, methyl acryloyloxyethyltrimethylammonium chloride, and 4-acrylamidobenzenesulfonic acid sodium salt as raw materials through a reverse-phase emulsion polymerization method. The polymer solution with a mass fraction of 0.6% was subjected to continuous shearing for 2 h at 150\u0026deg;C and 170 s\u003csup\u003e\u0026minus;\u0026thinsp;1\u003c/sup\u003e, and the viscosity remained greater than 50 mPa\u0026middot;s, with the storage modulus (G') consistently higher than the loss modulus (G\u0026Prime;), indicating excellent viscoelasticity of the system at 150\u0026deg;C. MAO et al.\u003csup\u003e[\u003cspan citationid=\"CR14\" class=\"CitationRef\"\u003e14\u003c/span\u003e]\u003c/sup\u003e used acrylamide, acrylic acid, 2-acrylamido-2-methylpropane sulfonic acid, 29-(4-octyloxyphenyl)-3,6,9,12,15,18,21,24,27-nonaoxaoctacosan-1-ol methacrylate (GTE-10) as raw materials to obtain a hydrophobic associative polymer SRHV through aqueous solution polymerization. The SRHV at a mass concentration of 3000 mg/L maintained good viscoelasticity in a 26.5% NaCl aqueous solution at 90 ℃, indicating that the metal ions in the salt solution contributed to the formation of the polymer's internal hydrophobic associative network, which was difficult to disrupt at high temperatures.\u003c/p\u003e \u003cp\u003eThis article introduces the hydrophobic monomer GTE-10 to prepare a polymer emulsion with a strong hydrophobic association network structure in salt solution and achieve low viscosity and high elasticity rheological behavior using acrylamide (AM), 2-acrylamido dodecane sulfonic acid sodium salt (AMC\u003csub\u003e12\u003c/sub\u003eS), and GTE-10 as raw materials via reverse emulsion polymerization. The structure and morphology of the polymer were characterized by FTIR, \u003csup\u003e1\u003c/sup\u003eHNMR, SEM, TEM, and laser particle size analyzer. The salt resistance and rheological properties of the polymer aqueous solutions were measured to provide new ideas for polymer modification and applications.\u003c/p\u003e"},{"header":"2. Experimental Section","content":"\u003cdiv id=\"Sec3\" class=\"Section2\"\u003e \u003ch2\u003e2.1 Materials\u003c/h2\u003e \u003cp\u003eDichloromethane, Triethylamine, Methylacryloyl Chloride, sodium hydroxide, anhydrous ethanol, sodium chloride (NaCl), anhydrous calcium chloride (CaCl\u003csub\u003e2\u003c/sub\u003e) (analytical grade, \u0026gt;\u0026thinsp;99%), and white oil (industrial grade, \u0026gt;\u0026thinsp;99%) were purchased from Shanghai Aladdin Biochemical Technology Co., Ltd. Acrylamide (AM), potassium persulfate (KPS), and azobisisobutyronitrile (AIBN) (analytical grade reagent, \u0026gt;\u0026thinsp;99%) were purchased from Shanghai McLan Biochemical Technology Co., Ltd. Ammonium persulfate [(NH\u003csub\u003e4\u003c/sub\u003e)\u003csub\u003e2\u003c/sub\u003eS\u003csub\u003e2\u003c/sub\u003eO\u003csub\u003e8\u003c/sub\u003e] and sodium hydrogen sulfite (NaHSO\u003csub\u003e3\u003c/sub\u003e) (analytical grade reagent, \u0026gt;\u0026thinsp;99%) were purchased from Jiangshun Chemical Technology Co., Ltd. Sorbitan monostearate (S-80), polysorbate 80 (T-80), and octylphenol ethoxylate (10) (OP-10) (analytical grade reagents, \u0026gt;\u0026thinsp;99%) were purchased from Hegro Chemical Co., Ltd. (Shanghai). AMC\u003csub\u003e12\u003c/sub\u003eS was purchased from Shanghai Zhixin Chemical Co., Ltd. Deionized water was used in all experiments.\u003c/p\u003e \u003cp\u003eThe equipment used included a HAKKE Mars 40 rotational viscometer (Thermo Fisher Scientific); an SDT-500C rotating drop tensiometer (Hako Instruments Testing Factory); a BT-9300S laser particle size analyzer (Dandong Bait Instruments Co., Ltd.); a Quanta 450 environmental scanning electron microscope (USA); an LGJ-12 vacuum freeze dryer (Beijing Songyuan Huaxing Technology Development Co., Ltd.); a UU777-1835 non-dilution Ubbelohde viscometer (Beijing Zhongxi Yunda Technology Co., Ltd.); and a Y25/M192941 high-shear homogenizer (Shanghai Yile Electrical Equipment Co., Ltd.). RE-52A rotary evaporator (Shanghai Yarong Biochemical Instrument Factory).\u003c/p\u003e \u003c/div\u003e \u003cdiv id=\"Sec4\" class=\"Section2\"\u003e \u003ch2\u003e2.2 Synthesis of Hydrophobic Monomer GTE-10\u003c/h2\u003e \u003cp\u003eThe OP-10 (64.6 g, 0.1 mol) and dichloromethane (250 mL) were weighed and added into a 500 mL reaction flask. The system was cooled in an ice bath until the temperature dropped to 0\u0026deg;C. Then 10.1 g (0.1 mol) of triethylamine was added, followed by a slow drip of 10.5 g (0.1 mol) methacryloyl chloride and dichloromethane using a pressure-equalizing addition funnel. The reaction was allowed to proceed for 8 hours to obtain the crude product. The solvent was then removed using a rotary evaporator to obtain the hydrophobic monomer GTE-10\u003csup\u003e[\u003cspan citationid=\"CR14\" class=\"CitationRef\"\u003e14\u003c/span\u003e]\u003c/sup\u003e. The synthetic route was as follows.\u003c/p\u003e \u003cp\u003e \u003c/p\u003e \u003cp\u003eSchematic1 Synthesis of monomer GTE-10\u003c/p\u003e \u003cp\u003eAM (240 g, 3.4 mol), AMC12S (32 g, 0.1 mol), hydrophobic monomer GTE-10 (4 g, 0.005 mol), and 2 mL of a 1% mass fraction ammonium persulfate solution were added to 350 g of deionized water to obtain an aqueous phase solution. Then, 100 mL of a 40% mass fraction sodium hydroxide solution was used to adjust the pH of the aqueous phase to 6.5\u0026thinsp;~\u0026thinsp;7.0. Twenty-two grams of Sorbitan monostearate (S-80) and polysorbate 80 (T-80) were weighed and added to 240 g of white oil to obtain an oil-phase solution. The aqueous phase was mixed evenly with the oil phase, and a high-speed agitator was used for pre-emulsification at 11000 rpm for 15 min to obtain a uniform oil-in-water pre-emulsion. After passing nitrogen gas through the pre-emulsion for 1 h, 3 mL of a 1% mass fraction NaHSO\u003csub\u003e3\u003c/sub\u003e solution was added as an initiator using a micro-injection pump, and the temperature was maintained at 45\u0026deg;C for 2\u0026ndash;3 h. After the reaction, the system was cooled to room temperature, and 3.5 g of the phase transfer agent NP-10 was added to obtain a stable polymer emulsion p(AM/AMC\u003csub\u003e12\u003c/sub\u003eS/GTE-10). The synthetic route was as follows.\u003c/p\u003e \u003cp\u003e \u003c/p\u003e \u003cp\u003eSchematic 2 Synthesis of Reverse Phase Emulsion Polymer P(AM/AMC12S/GTE-10)\u003c/p\u003e \u003c/div\u003e \u003cdiv id=\"Sec5\" class=\"Section2\"\u003e \u003ch2\u003e2.4 Characterization and Performance Testing of Structure\u003c/h2\u003e \u003cp\u003eThe sample was purified and its structure was characterized by infrared spectroscopy and nuclear magnetic resonance spectrometry. A BT-9300S laser particle size analyzer was used to determine the particle size distribution of the emulsion. The test was performed at 25 ℃, and the obscuration rate was \u0026gt;\u0026thinsp;2% to evaluate the particle size distribution pattern. The morphologies of the polymer specimens were studied using environmental scanning electron microscopy (SEM). A 0.3% solution of the polymer was prepared using pure water and left for 90 min, dropped onto a conductive adhesive surface, and the surface was freeze-dried with liquid nitrogen. The frozen surfaces of the prepared samples were observed using SEM at an accelerating voltage of 20 kV \u003csup\u003e[\u003cspan citationid=\"CR15\" class=\"CitationRef\"\u003e15\u003c/span\u003e, \u003cspan citationid=\"CR16\" class=\"CitationRef\"\u003e16\u003c/span\u003e]\u003c/sup\u003e. The samples were dried on a 200-mesh copper grid and characterized by transmission electron microscopy. A HAKKE Mars 40 rotational rheometer was used to test the temperature and shear resistance of the 0.7% polymer. The shear rate, temperature, and heating rate were 170 s\u003csup\u003e\u0026minus;\u0026thinsp;1\u003c/sup\u003e, 90℃,120 ℃, and 0.05 ℃/s, respectively. Continuous shearing was performed for 1 h \u003csup\u003e[\u003cspan citationid=\"CR17\" class=\"CitationRef\"\u003e17\u003c/span\u003e]\u003c/sup\u003e. The steady-state and dynamic rheological properties of the polymers were investigated at concentrations of 0.3, 0.5, and 0.7%. Measurements were performed using a cone fabricated from a standard extension\u0026ndash;twist coupling (ETC) steel rotor with a diameter of 40 mm, cone angle of 2\u0026deg;, and a gap of 48 mm between the cone center and plate. The scanning stress was set to 0.1\u0026ndash;10 Pa to determine the linear viscoelastic region. Subsequently, frequency scans were performed under fixed shear conditions over a frequency range of 0.1\u0026ndash;10 Hz to further examine the linear viscoelasticity regions. Before the measurements were acquired, the samples were equilibrated on the plate for 5 min to ensure sufficient accuracy, and the temperature was maintained at 30 ℃ during the experiments \u003csup\u003e[\u003cspan citationid=\"CR18\" class=\"CitationRef\"\u003e18\u003c/span\u003e, \u003cspan citationid=\"CR19\" class=\"CitationRef\"\u003e19\u003c/span\u003e]\u003c/sup\u003e.\u003c/p\u003e \u003c/div\u003e"},{"header":"3. Results and Discussion","content":"\u003cdiv id=\"Sec7\" class=\"Section2\"\u003e \u003ch2\u003e3.1 Analysis of FT-IR\u003c/h2\u003e \u003cp\u003eFigure\u0026nbsp;\u003cspan refid=\"Fig1\" class=\"InternalRef\"\u003e1\u003c/span\u003ea displays the various absorption peaks: the peak at 3605 cm\u003csup\u003e\u0026minus;\u0026thinsp;1\u003c/sup\u003e corresponds to the stretching vibration of the O\u0026ndash;H bond in the carboxyl group; and the peak at 3165 cm\u003csup\u003e\u0026minus;\u0026thinsp;1\u003c/sup\u003e corresponds to the stretching vibration of the N\u0026ndash;H bond in the amide group; the peak at 2931 cm\u003csup\u003e\u0026minus;\u0026thinsp;1\u003c/sup\u003e corresponds to the stretching vibration of the N\u0026ndash;H bond in the methyl and methylene groups; the peak at 1691 cm\u003csup\u003e\u0026minus;\u0026thinsp;1\u003c/sup\u003e corresponds to the stretching vibration of the C\u0026thinsp;=\u0026thinsp;O bond; the peak at 1552 cm\u003csup\u003e\u0026minus;\u0026thinsp;1\u003c/sup\u003e corresponds to the stretching vibration of the C\u0026ndash;N bond and the bending vibration of the N\u0026ndash;H bond in the amide group; the peak at 1415 cm\u003csup\u003e\u0026minus;\u0026thinsp;1\u003c/sup\u003e is the characteristic peak of the sulfonic acid group; the peak at 1315 cm\u003csup\u003e\u0026minus;\u0026thinsp;1\u003c/sup\u003e corresponds to the stretching vibration of the C\u0026ndash;N bond and the bending vibration of the N\u0026ndash;H bond in the secondary amine in the amide group; the peak at 640 cm\u003csup\u003e\u0026minus;\u0026thinsp;1\u003c/sup\u003e is the characteristic peak of \u0026ndash;(CH\u003csub\u003e2\u003c/sub\u003e)\u003csub\u003e9\u003c/sub\u003e\u0026ndash;; GTE-10 and p(AM/AMC\u003csub\u003e12\u003c/sub\u003eS/GTE-10) both exhibit corresponding stretching vibration peaks of the C\u0026thinsp;=\u0026thinsp;C bond at 1415, 1450, and 1552 cm\u003csup\u003e\u0026minus;\u0026thinsp;1\u003c/sup\u003e, a bending vibration peak of the C\u0026ndash;H bond on the benzene ring at 813 cm\u003csup\u003e\u0026minus;\u0026thinsp;1\u003c/sup\u003e, and a corresponding stretching vibration peak of the C\u0026ndash;O\u0026ndash;C bond at 1315 cm\u003csup\u003e\u0026minus;\u0026thinsp;1\u003c/sup\u003e. The results indicate that the hydrophobic monomer GTE-10 has been successfully incorporated into the polymer, and the structure of the polymer molecule obtained is consistent with expectations.\u003c/p\u003e \u003c/div\u003e \u003cdiv id=\"Sec8\" class=\"Section2\"\u003e \u003ch2\u003e3.2 Analysis of \u003csup\u003e1\u003c/sup\u003eH NMR spectroscopy\u003c/h2\u003e \u003cp\u003eFigure\u0026nbsp;\u003cspan refid=\"Fig1\" class=\"InternalRef\"\u003e1\u003c/span\u003eb displays peaks at δ 4.71 corresponding to the solvent peak of deuterated oxide; at δ 0.63 (a) corresponding to the proton peak of the methyl group \u0026ndash;CH\u003csub\u003e3\u003c/sub\u003e on the long alkyl chain \u0026ndash;(CH\u003csub\u003e2\u003c/sub\u003e)\u003csub\u003e7\u003c/sub\u003eCH\u003csub\u003e3\u003c/sub\u003e in the monomer GTE-10; at δ 1.16 (b), δ 1.72 (c), and δ 3.11 (d) corresponding to the proton peaks of \u0026ndash;CH\u003csub\u003e2\u003c/sub\u003e\u0026ndash; within the repeating unit \u0026ndash;(CH\u003csub\u003e2\u003c/sub\u003e)\u003csub\u003e7\u003c/sub\u003eCH\u003csub\u003e3\u003c/sub\u003e; at δ 6.68 (e) and δ 6.95 (f) corresponding to the two sets of proton peaks on the benzene ring; at δ 4.12 (g), δ 3.88 (h), and δ 3.50 (i) corresponding to the proton peaks of \u0026ndash;CH\u003csub\u003e2\u003c/sub\u003e\u0026ndash; within the repeating unit \u0026ndash;(CH\u003csub\u003e2\u003c/sub\u003eCH\u003csub\u003e2\u003c/sub\u003eO)\u003csub\u003e10\u003c/sub\u003e\u0026ndash;; at δ 1.79 (j) corresponding to the proton peak of the \u0026ndash;CH\u003csub\u003e3\u003c/sub\u003e on the double bond carbon at the end of GTE-10; and at δ 5.31 (k) and δ 6.09 (l) corresponding to the two sets of proton peaks on the double-bonded carbon.\u003c/p\u003e \u003cp\u003eFigure\u0026nbsp;\u003cspan refid=\"Fig1\" class=\"InternalRef\"\u003e1\u003c/span\u003ec displays a peak at δ 13.9 (a), which corresponds to the absorption of the methyl group \u0026ndash;CH\u003csub\u003e3\u003c/sub\u003e on the long alkyl chain \u0026ndash;(CH\u003csub\u003e2\u003c/sub\u003e)\u003csub\u003e7\u003c/sub\u003eCH\u003csub\u003e3\u003c/sub\u003e in the monomer GTE-10. The peaks at δ 43.2 (b) and δ 46.6 (c) represent the absorption peaks of the repeating unit \u0026ndash;(CH\u003csub\u003e2\u003c/sub\u003e)\u003csub\u003e7\u003c/sub\u003e\u0026ndash;. Additionally, the peaks at δ 135.8 (d), δ 129.6 (e), δ 113.7 (f), and δ 156.3 (g) correspond to the absorption peaks of the four carbon groups on the benzene ring. The peak at δ 69.8 (h) corresponds to the absorption peak of the \u0026ndash;CH\u003csub\u003e2\u003c/sub\u003e\u0026ndash; within the repeating unit \u0026ndash;(CH\u003csub\u003e2\u003c/sub\u003eCH\u003csub\u003e2\u003c/sub\u003eO)\u003csub\u003e10\u003c/sub\u003e. Moreover, the peak at δ 167.7 (i) represents the absorption peak of the carbonyl carbon, while the peak at δ 17.8 (k) corresponds to the absorption peak of the \u0026ndash;CH\u003csub\u003e3\u003c/sub\u003e group on the double-bonded carbon at the end of GTE-10. Lastly, the peaks at δ 135.2 (j) and δ 126.6 (l) correspond to the absorption peaks of the two double-bonded carbons.\u003c/p\u003e \u003cp\u003eFigure\u0026nbsp;\u003cspan refid=\"Fig1\" class=\"InternalRef\"\u003e1\u003c/span\u003ed displays the peak at δ 4.71 corresponds to the solvent peak of deuterated oxide. The proton peaks at δ 1.71 (a), δ 1.43 (b), and δ 0.76 (c) are attributed to the main-chain protons of \u0026ndash;CH\u003csub\u003e2\u003c/sub\u003e\u0026ndash;, \u0026ndash;CH\u0026ndash;, and \u0026ndash;CH\u003csub\u003e3\u003c/sub\u003e, respectively. Additionally, the proton peaks at δ 3.20 (d) and δ 3.28 (g) correspond to the side chain protons of \u0026ndash;CH\u0026ndash; and \u0026ndash;CH\u003csub\u003e2\u003c/sub\u003e\u0026ndash; in the monomer AMC\u003csub\u003e12\u003c/sub\u003eS. The peaks at δ 0.91 (e) and δ 1.26 (f) represent the proton peaks of -CH\u003csub\u003e2\u003c/sub\u003e- and -CH\u003csub\u003e3\u003c/sub\u003e in the repeating unit of \u0026ndash;(CH\u003csub\u003e2\u003c/sub\u003e)\u003csub\u003e9\u003c/sub\u003eCH\u003csub\u003e3\u003c/sub\u003e. Furthermore, the peak at δ 3.36 (h) corresponds to the proton peak of \u0026ndash;CH\u003csub\u003e2\u003c/sub\u003e\u0026ndash; in the repeating unit \u0026ndash;(CH\u003csub\u003e2\u003c/sub\u003eCH\u003csub\u003e2\u003c/sub\u003eO)\u003csub\u003e10\u003c/sub\u003e\u0026ndash; in the side chain of the functional monomer GTE-10. Lastly, the peak at δ 6.78 (i) represents the proton peak of the benzene ring. These results indicate that the monomers AMC\u003csub\u003e12\u003c/sub\u003eS and GTE-10 both participated in the polymerization reaction, resulting in polymer molecules with the expected structure.\u003c/p\u003e \u003cp\u003e \u003c/p\u003e \u003c/div\u003e \u003cdiv id=\"Sec9\" class=\"Section2\"\u003e \u003ch2\u003e3.3 Particle Size Analysis\u003c/h2\u003e \u003cp\u003e \u003c/p\u003e \u003cp\u003eFigure\u0026nbsp;\u003cspan refid=\"Fig2\" class=\"InternalRef\"\u003e2\u003c/span\u003e displays the particle size distribution and microstructure of the emulsion before and after polymerization. As depicted in Fig.\u0026nbsp;\u003cspan refid=\"Fig2\" class=\"InternalRef\"\u003e2\u003c/span\u003ea and c, it can be observed that the oil-in-water emulsion formed after pre-emulsification has a larger average particle size and uneven distribution, with a D\u003csub\u003e50\u003c/sub\u003e of 10.45 \u0026micro;m. In contrast, in Fig.s 2b and d, it is evident that the oil-in-water structure becomes more uniform after the completion of the polymerization reaction, with a narrower particle size distribution range and a D\u003csub\u003e50\u003c/sub\u003e of 5.837 \u0026micro;m. This results in a polymer with improved solubility.\u003c/p\u003e \u003c/div\u003e \u003cdiv id=\"Sec10\" class=\"Section2\"\u003e \u003ch2\u003e3.4 Mechanism of Inverse Emulsion Polymerization\u003c/h2\u003e \u003cp\u003e \u003c/p\u003e \u003cp\u003eThe schematic diagram of the reaction mechanism for the synthesis of polymer p(AM/AMC\u003csub\u003e12\u003c/sub\u003eS/GTE-10) via reverse-phase free radical polymerization is shown in Fig.\u0026nbsp;\u003cspan refid=\"Fig3\" class=\"InternalRef\"\u003e3\u003c/span\u003e. The polymerization process can be divided into three stages: initiation, propagation, and termination. During the initiation stage, the initiator undergoes redox reactions, and the pre-polymerization radicals are continuously transferred to the growing micelles, driven by the equilibrium swelling of latex particles, to initiate monomer polymerization, leading to an increase in the polymerization rate. As the free monomers in the system are completely encapsulated within the monomer droplets, the polymerization rate becomes relatively constant, and the system enters the propagation stage. In this stage, only latex particles and monomer droplets coexist, representing the golden period for acrylamide polymerization, which is characterized by high exothermicity. The addition of sodium formate as a chain-transfer agent promotes a more regular polymer structure. This stage is characterized by a long duration. Finally, the reaction enters the termination stage, during which the remaining residual monomers continue to react, resulting in a significant decrease in the polymerization rate until all the active monomers are converted into polymer molecules.\u003c/p\u003e \u003c/div\u003e \u003cdiv id=\"Sec11\" class=\"Section2\"\u003e \u003ch2\u003e3.5 Analysis of Critical Aggregation Concentration by Fluorescent Probes\u003c/h2\u003e \u003cp\u003eIn Fig.\u0026nbsp;\u003cspan refid=\"Fig4\" class=\"InternalRef\"\u003e4\u003c/span\u003ea, the hydrophobically associating polymer spontaneously forms micelles and small hydrophobic microdomains capable of dissolving pyrene, serving as a fluorescence probe reflecting the strength of the hydrophobic association effect. In the fluorescence spectrum, the ratio of the absorbance at 373 nm (I\u003csub\u003e1\u003c/sub\u003e) to the absorbance at 391 nm (I\u003csub\u003e3\u003c/sub\u003e), denoted as I\u003csub\u003e1\u003c/sub\u003e/I\u003csub\u003e3\u003c/sub\u003e, depends on the polarity of the surrounding environment. When the surrounding microenvironment is more polar, the I\u003csub\u003e1\u003c/sub\u003e/I\u003csub\u003e3\u003c/sub\u003e value is higher; conversely, once the polymer molecules form a distinct dynamic physical cross-linking network, the I\u003csub\u003e1\u003c/sub\u003e/I\u003csub\u003e3\u003c/sub\u003e value significantly decreases. Figure\u0026nbsp;\u003cspan refid=\"Fig4\" class=\"InternalRef\"\u003e4\u003c/span\u003eb illustrates the variation in I\u003csub\u003e1\u003c/sub\u003e/I\u003csub\u003e3\u003c/sub\u003e at different concentrations of the p(AM/AMC\u003csub\u003e12\u003c/sub\u003eS/GTE-10). When the concentration is 0.30 wt.%, the value of I\u003csub\u003e1\u003c/sub\u003e/I\u003csub\u003e3\u003c/sub\u003e suddenly decreases. This indicates that when the concentration of the p(AM/AMC\u003csub\u003e12\u003c/sub\u003eS/GTE-10) solution exceeds 0.30 wt.%, the polymer molecules form a large number of hydrophobic regions, weakening the polarity of the surrounding microenvironment of the pyrene probe. Therefore, the apparent viscosity and fluorescence spectrum measurements indicate that the critical association concentration (C*) of p(AM/AMC\u003csub\u003e12\u003c/sub\u003eS/GTE-10) is approximately 0.30\u0026ndash;0.35 wt.%.\u003c/p\u003e \u003cp\u003e \u003c/p\u003e \u003c/div\u003e \u003cdiv id=\"Sec12\" class=\"Section2\"\u003e \u003ch2\u003e3.6 Analysis of Salt Tolerance Performance\u003c/h2\u003e \u003cp\u003eAt room temperature, the apparent viscosity changes of the polymers with mass fractions of 0.3%, 0.5%, and 0.7% in different mass concentrations of NaCl and CaCl\u003csub\u003e2\u003c/sub\u003e aqueous solutions are shown in Fig.\u0026nbsp;\u003cspan refid=\"Fig5\" class=\"InternalRef\"\u003e5\u003c/span\u003e. The viscosity of the polymer solutions exhibits a trend of first increasing and then decreasing with an increase in the salt solution mass concentration. The initial viscosity of the 0.7% mass fraction polymer solution is 123 mPa\u0026middot;s. In the 80000 mg/L NaCl and CaCl\u003csub\u003e2\u003c/sub\u003e solutions, the apparent viscosities of the 0.7% mass fraction polymer solution were 39 and 24 mPa\u0026middot;s, with viscosity retention rates of 31.71% and 19.51%, respectively. The ability of the phenylethylene group contained in monomer GTE-10 to chelate metal ions reduces the negative effects of electrostatic shielding, increases the hydrodynamic volume, and promotes the formation of spatial network structures, thereby increasing the apparent viscosity of the polymer with increasing polymer mass fraction \u003csup\u003e[\u003cspan citationid=\"CR18\" class=\"CitationRef\"\u003e18\u003c/span\u003e\u0026ndash;\u003cspan citationid=\"CR19\" class=\"CitationRef\"\u003e19\u003c/span\u003e]\u003c/sup\u003e. The introduction of hydrophobic long chains and benzene rings enhances the rigidity of the molecular chains, preventing them from easily coiling and enhancing the salt resistance capabilities of the system. At high salt mass concentrations, the electrostatic shielding of metal ions on the molecular chains exceeds the intermolecular binding effect, compressing the hydrodynamic volume of the polymer molecules and resulting in a decrease in the viscosity of the polymer solution.\u003c/p\u003e \u003cp\u003e \u003c/p\u003e \u003c/div\u003e \u003cdiv id=\"Sec13\" class=\"Section2\"\u003e \u003ch2\u003e3.7 Analysis of SEM\u003c/h2\u003e \u003cp\u003e \u003c/p\u003e \u003cp\u003eSEM images of the polymer p(AM/AMC\u003csub\u003e12\u003c/sub\u003eS/GTE-10) with a mass fraction of 0.3% in pure water and sodium chloride solution with a mass concentration of 10000 mg/L are shown in Fig.\u0026nbsp;\u003cspan refid=\"Fig6\" class=\"InternalRef\"\u003e6\u003c/span\u003e. In pure water, the polymer is fully extended, and the functional monomer GTE-10 in the polymer spontaneously aggregates, forming hydrophobic microdomains with certain strength. This leads to the formation of a three-dimensional network structure with intermolecular cohesive interactions, resulting in the viscoelastic behavior of the polymer solution on a macroscopic scale. In saline solution, the phenylethylene group in the functional monomer GTE-10 acts as a chelating agent for salt ions. The filling of the vacant orbital of the metal ions by the lone pair electrons of the ethylene group enhances the intermolecular forces, reduces the impact of electrostatic shielding on the polymer skeleton, and enhances the resistance of the polymer to metal cations. Therefore, the polymer exhibits a stronger spatial network structure in saline solution \u003csup\u003e[\u003cspan citationid=\"CR20\" class=\"CitationRef\"\u003e20\u003c/span\u003e\u0026ndash;\u003cspan citationid=\"CR21\" class=\"CitationRef\"\u003e21\u003c/span\u003e]\u003c/sup\u003e.\u003c/p\u003e \u003c/div\u003e \u003cdiv id=\"Sec14\" class=\"Section2\"\u003e \u003ch2\u003e3.8 Analysis of temperature resistance performance\u003c/h2\u003e \u003cp\u003eA mass fraction of 0.7% p(AM/AMC\u003csub\u003e12\u003c/sub\u003eS/GTE-10) solution was prepared in a water solution of NaCl and CaCl\u003csub\u003e2\u003c/sub\u003e with equal mass concentrations of 20000 mg/L at 140 ℃, and its temperature resistance performance is shown in Fig.\u0026nbsp;\u003cspan refid=\"Fig7\" class=\"InternalRef\"\u003e7\u003c/span\u003e. The viscosity of the polymer solution continues to decrease with increasing temperature. Hydrophobic modification enhances the cohesive force of the polymer chains, increasing the viscous flow activation energy of the fluid; thus, the polymer exhibits a certain dependency on temperature. As the temperature was increased, the viscosity of the polymer solution decreased. At 140 ℃, the viscosity of the polymer solution in both pure water (Fig.\u0026nbsp;\u003cspan refid=\"Fig7\" class=\"InternalRef\"\u003e7\u003c/span\u003ea) and NaCl (Fig.\u0026nbsp;\u003cspan refid=\"Fig7\" class=\"InternalRef\"\u003e7\u003c/span\u003eb) solutions was greater than 50 mPa\u0026middot;s (Fig.\u0026nbsp;\u003cspan refid=\"Fig7\" class=\"InternalRef\"\u003e7\u003c/span\u003eb). In the CaCl\u003csub\u003e2\u003c/sub\u003e solution (Fig.\u0026nbsp;\u003cspan refid=\"Fig7\" class=\"InternalRef\"\u003e7\u003c/span\u003ec), the viscosity of the polymer solution decreased below 50 mPa\u0026middot;s at temperatures higher than 115.3 ℃. Overall, the polymer solution exhibited good temperature resistance.\u003c/p\u003e \u003cp\u003e \u003c/p\u003e \u003c/div\u003e \u003cdiv id=\"Sec15\" class=\"Section2\"\u003e \u003ch2\u003e3.9 Analysis of shear resistance performance\u003c/h2\u003e \u003cp\u003eA 0.7% (w/w) p(AM/AMC\u003csub\u003e12\u003c/sub\u003eS/GTE-10) solution was prepared in pure water and aqueous solutions of NaCl and CaCl\u003csub\u003e2\u003c/sub\u003e at mass concentrations of 20000 mg/L. The shear-thinning performance of the polymer solution was measured at 90 and 120\u0026deg;C at a constant shear rate of 170 s\u003csup\u003e\u0026ndash;1\u003c/sup\u003e, as shown in Fig.\u0026nbsp;\u003cspan refid=\"Fig8\" class=\"InternalRef\"\u003e8\u003c/span\u003e. With increasing temperature, the viscosity of the polymer solution initially decreased and then plateaued. The intensified thermal motion of the functional groups weakens intermolecular aggregation, leading to a reduction in the viscosity of the polymer solution. Once the temperature stabilized, the temperature dependency of the polymer solution viscosity was eliminated, and a balance was reached between the intermolecular association and molecular thermal motion. Figure\u0026nbsp;\u003cspan refid=\"Fig8\" class=\"InternalRef\"\u003e8\u003c/span\u003ea, b, after shearing at 90 and 120\u0026deg;C for 1 h, the viscosity of the polymer solution remained essentially unchanged at 88.7 and 73.2 mPa\u0026middot;s, respectively. Figure\u0026nbsp;\u003cspan refid=\"Fig8\" class=\"InternalRef\"\u003e8\u003c/span\u003ec, d the viscosity of the polymer solution after shearing at 90 and 120\u0026deg;C for 1 h in an aqueous NaCl solution with a mass concentration of 20000 mg/L was 79.3 and 64.7 mPa\u0026middot;s, respectively. Meanwhile, in the aqueous CaCl\u003csub\u003e2\u003c/sub\u003e solution with the same mass concentration, the viscosities of the polymer solutions at 90 and 120\u0026deg;C after shearing for 1 h were 63.9 and 54.2 mPa\u0026middot;s, respectively. The presence of hydrophobic long chains and benzene rings in the monomer GTE-10 enhanced the rigidity of the molecular chains and hindered conformational transitions, resulting in a more stable spatial network structure. Additionally, metal ions in the salt solutions form complexes with ethylene oxide groups, reducing the negative impact of the salt ions and enhancing the shear resistance of the polymer solution.\u003c/p\u003e \u003cp\u003e \u003c/p\u003e \u003c/div\u003e \u003cdiv id=\"Sec16\" class=\"Section2\"\u003e \u003ch2\u003e3.10 Analysis of shear resistance performance testing\u003c/h2\u003e \u003cp\u003eAt 30 ℃, the effect of the shear rate at 170, 510, and 1022 s\u003csup\u003e\u0026ndash;1\u003c/sup\u003e on the viscosity of the polymer solution was alternately investigated, and the results are shown in Fig.\u0026nbsp;\u003cspan refid=\"Fig9\" class=\"InternalRef\"\u003e9\u003c/span\u003ea. When the shear rate increased from 170 s\u003csup\u003e\u0026ndash;1\u003c/sup\u003e to 510 s\u003csup\u003e\u0026ndash;1\u003c/sup\u003e and then further to 1022 s\u003csup\u003e\u0026ndash;1\u003c/sup\u003e, the viscosity continued to decrease. When the shear rate was constant, viscosity remained essentially unchanged. After shearing at 1022 s\u003csup\u003e\u0026ndash;1\u003c/sup\u003e for a certain period of time, the viscosity returned to its initial value upon reverting to 170 s\u003csup\u003e\u0026ndash;1\u003c/sup\u003e. The results indicate that the polymer viscosity exhibits good shear recovery performance, possibly due to the fact that under high shear rates, the dynamically physical cross-linked network structure formed by molecular aggregation is not completely disrupted. When the shear rate decreases, the aggregation forces lead to the reformation of separated molecular chains into hydrophobic microdomains, which macroscopically manifests as either an increase or return to the initial value of apparent viscosity \u003csup\u003e[\u003cspan citationid=\"CR22\" class=\"CitationRef\"\u003e22\u003c/span\u003e]\u003c/sup\u003e.\u003c/p\u003e \u003cp\u003eThe rheological behavior of polymer solutions can be described by the power law equation as follows:\u003c/p\u003e \u003cp\u003e \u003cspan class=\"InlineEquation\"\u003e \u003cspan class=\"mathinline\"\u003e\\(\\lg \\tau =\\lg \\kappa +{\\text{n}}\\lg \\gamma\\)\u003c/span\u003e \u003c/span\u003e \u003c/p\u003e \u003cp\u003eWhere τ is the shear stress, κ is the consistency coefficient, γ is the shear rate and n is the power law index. When 0\u0026thinsp;\u0026lt;\u0026thinsp;n\u0026thinsp;\u0026lt;\u0026thinsp;1, it represents a pseudoplastic flow, where the apparent viscosity decreases with increasing shear stress or shear rate. When n\u0026thinsp;=\u0026thinsp;1, it represents an ideal Newtonian fluid.\u003c/p\u003e \u003cp\u003eFigure\u0026nbsp;\u003cspan refid=\"Fig9\" class=\"InternalRef\"\u003e9\u003c/span\u003eb, A fitting line of the shear rate and shear stress was obtained with lgγ as the abscissa and lgτ as the ordinate, and the fitting equation was y\u0026thinsp;=\u0026thinsp;0.28839x\u0026thinsp;+\u0026thinsp;0.90339 (R\u003csup\u003e2\u003c/sup\u003e\u0026thinsp;=\u0026thinsp;0.99805). Where the power law index is n\u0026thinsp;=\u0026thinsp;0.28839\u0026thinsp;\u0026lt;\u0026thinsp;1, and the consistency coefficient is κ\u0026thinsp;=\u0026thinsp;8.01. Therefore, the polymer solution is a pseudoplastic fluid and exhibits shear-thinning behavior.\u003c/p\u003e \u003cp\u003e \u003c/p\u003e \u003c/div\u003e \u003cdiv id=\"Sec17\" class=\"Section2\"\u003e \u003ch2\u003e3.11 Analysis of thixotropic performance\u003c/h2\u003e \u003cp\u003e \u003c/p\u003e \u003cp\u003eThe thixotropic properties of the polymer aqueous solutions with quality fractions of 0.3, 0.5, and 0.7% were tested, as shown in Fig.\u0026nbsp;\u003cspan refid=\"Fig10\" class=\"InternalRef\"\u003e10\u003c/span\u003ea, b, c. As the mass fraction of the polymer solution increased, both the hysteresis loop area and the shear stress increased. This indicates that the increase in intermolecular bonding of the polymer leads to the strengthening of the spatial network structure, resulting in greater resistance to deformation. This, in turn, increases the energy required to break the network structure, demonstrating the excellent shear resistance capabilities of the polymer.\u003c/p\u003e \u003c/div\u003e \u003cdiv id=\"Sec18\" class=\"Section2\"\u003e \u003ch2\u003e3.12 Analysis of viscoelastic performance\u003c/h2\u003e \u003cp\u003ePolymer solutions are viscoelastic fluids that exhibit non-Newtonian viscosity and normal stress differences under steady shear flow. The presence of normal stress differences leads to various special flow phenomena such as the Weissenberg effect, suspended siphons, and jet expansion \u003csup\u003e[\u003cspan citationid=\"CR23\" class=\"CitationRef\"\u003e23\u003c/span\u003e]\u003c/sup\u003e. Therefore, to analyze the variation rules of viscoelasticity in polymer solutions, parameters such as G\u0026Prime;, G\u0026prime;, complex modulus (G*), and the first normal stress difference (N\u003csub\u003e1\u003c/sub\u003e) were determined.\u003c/p\u003e \u003c/div\u003e \u003cdiv id=\"Sec19\" class=\"Section2\"\u003e \u003ch2\u003e3.12.1 Trends in changes of G' and G''\u003c/h2\u003e \u003cp\u003eThe curves of G' and G\" versus the stress and frequency for polymer solutions with different mass fractions in NaCl at a mass concentration of 20,000 mg/L, CaCl\u003csub\u003e2\u003c/sub\u003e at a mass concentration of 10,000 mg/L, and deionized water are presented in Figs.\u0026nbsp;\u003cspan refid=\"Fig11\" class=\"InternalRef\"\u003e11\u003c/span\u003e and \u003cspan refid=\"Fig12\" class=\"InternalRef\"\u003e12\u003c/span\u003e.\u003c/p\u003e \u003cp\u003e \u003c/p\u003e \u003cp\u003eAs shown in Fig.\u0026nbsp;\u003cspan refid=\"Fig11\" class=\"InternalRef\"\u003e11\u003c/span\u003ea, for polymer solutions with mass fractions of 0.3% and 0.5%, G\u0026prime; and G\u0026Prime; remain stable in the low-stress range, showing a linear viscoelastic region that reflects the structural strength of the polymer solution. As the stress continues to increase, G\u0026prime; and G\u0026Prime; show a decreasing trend, with G\u0026prime; \u0026lt; G\u0026Prime;, transitioning to a non-linear viscoelastic region, indicating the disruption of the spatial network structure of the solution under shear stress, displaying shear thinning behavior. For the polymer solution with a mass fraction of 0.7%, there is a clear linear viscoelastic region in the stress scan range of 0\u0026thinsp;~\u0026thinsp;10 Pa, with G\u0026prime; \u0026gt; G\u0026Prime;, exhibiting elastic fluid behavior. As the mass fraction of the polymer increases, the intermolecular binding becomes stronger, resulting in a more stable and difficult-to-break spatial structure. Additionally, the Fig.\u0026nbsp;\u003cspan refid=\"Fig11\" class=\"InternalRef\"\u003e11\u003c/span\u003eb, c appropriately concentrated salt solutions can enhance the binding effect, contributing to an increase in the viscoelasticity of polymer molecules.\u003c/p\u003e \u003cp\u003e \u003c/p\u003e \u003cp\u003eAs shown in Fig.\u0026nbsp;\u003cspan refid=\"Fig12\" class=\"InternalRef\"\u003e12\u003c/span\u003e, as the shear frequency increases, the G\u0026prime; and G\u0026Prime; values of the polymer solution increase. As shown in Fig.\u0026nbsp;\u003cspan refid=\"Fig12\" class=\"InternalRef\"\u003e12\u003c/span\u003ea, the 0.3% mass fraction polymer solution in pure water exhibits predominantly intramolecular association at lower frequencies, where the viscoelasticity is mainly contributed by the higher molecular weight, leading to G\u0026prime; \u0026lt; G\u0026Prime;, showing viscous flow. As the frequency increases from low to high, the intermolecular association strengthens, and the complex network structure provides better elasticity, with G\u0026prime; dominating, indicating elastic flow. As shown in Fig.\u0026nbsp;\u003cspan refid=\"Fig12\" class=\"InternalRef\"\u003e12\u003c/span\u003eb and c, the viscoelasticity of the polymer in a salt solution is greater than that in pure water because of the chelation reaction between metal ions and styrene groups, which enhances intermolecular forces and results in a dense network structure, accompanied by an increase in structural viscosity. Therefore, increasing the structural viscosity of the polymer can increase the viscoelasticity of the solution.\u003c/p\u003e \u003c/div\u003e \u003cdiv id=\"Sec20\" class=\"Section2\"\u003e \u003ch2\u003e3.12.2 Trends in Changes of G*\u003c/h2\u003e \u003cp\u003eG* studies the linear viscoelastic behavior of polymer solutions, reflecting both the viscosity and elastic characteristics of the fluid. It can be obtained based on G\u0026prime; and G\u0026Prime; \u003csup\u003e[\u003cspan citationid=\"CR24\" class=\"CitationRef\"\u003e24\u003c/span\u003e, \u003cspan citationid=\"CR25\" class=\"CitationRef\"\u003e25\u003c/span\u003e]\u003c/sup\u003e, and the equation is as follows:\u003c/p\u003e \u003cp\u003e \u003cdiv id=\"Equa\" class=\"Equation\"\u003e \u003cdiv format=\"TEX\" class=\"mathdisplay\" id=\"FileID_Equa\" name=\"EquationSource\"\u003e\n$${G^{\\text{*}}}=G^{\\prime}+{\\text{i}}G^{\\prime\\prime}=\\sqrt {{{G^{\\prime}}^2}+{{G^{\\prime\\prime}}^2}}$$\u003c/div\u003e \u003c/div\u003e \u003c/p\u003e \u003cp\u003e \u003c/p\u003e \u003cp\u003eFigure\u0026nbsp;\u003cspan refid=\"Fig14\" class=\"InternalRef\"\u003e13\u003c/span\u003ea depicts the increase in G* as the shear frequency increases, approaching a linear trend. This phenomenon is attributed to the formation of a stable spatial network structure between polymer molecules. This results in increased resistance to deformation in polymer solutions as shear frequency rises, as evidenced by the increase in G*. Under the same mass fraction, the value of G* in salt solutions is greater than that in pure water. The dynamically physical crosslinked network formed by hydrophobically modified polymers is less affected by inorganic salts. This results in enhanced resistance to salt-induced viscosity enhancement and an increase in viscoelasticity. To compare the viscoelastic properties of polymer solutions with varying mass fractions, the complex modulus values at a frequency of 1 Hz were chosen for comparison. With the increasing mass fractions of the polymer, the values of G* in both pure water and saline solutions showed an increased trend. Among them, the trend of Fig.\u0026nbsp;\u003cspan refid=\"Fig14\" class=\"InternalRef\"\u003e13\u003c/span\u003eb increase in a 20000 mg/L NaCl solution is the steepest, and the Fig.\u0026nbsp;\u003cspan refid=\"Fig14\" class=\"InternalRef\"\u003e13\u003c/span\u003ec followed by the 10000 mg/L CaCl\u003csub\u003e2\u003c/sub\u003e solution. This indicates that appropriately concentrated salt solutions are conducive to enhancing the viscoelasticity of polymer molecules. When the mass fraction of the polymer is in the range of 0.3\u0026ndash;0.5%, the increase in G* is slow. However, when the mass fraction is in the range of 0.5\u0026ndash;0.7%, the slope of the curve is steeper, leading to a faster increase in G*. At lower mass fractions, viscoelasticity is primarily determined by the intramolecular binding of polymer molecules. With the increase in mass fractions, intermolecular binding strengthens, leading to the formation of a complex network structure, resulting in a significant increase in G*.\u003c/p\u003e \u003c/div\u003e"},{"header":"4. Conclusions","content":"\u003cp\u003e(1) The functional monomer GTE-10, which contains a benzene ring and phenylethylene group, was introduced into reverse emulsion polymerization to prepare a polymer emulsion with a robust hydrophobic associative network structure in a saline environment. The polymer was characterized using FTIR and \u003csup\u003e1\u003c/sup\u003eH-NMR spectroscopy. The SEM results indicated that the polymer exhibited a dense spatial network structure under saltwater conditions.\u003c/p\u003e \u003cp\u003e(2) The results of the temperature and shear resistance tests showed that at 90 and 120 ℃ under a shear rate of 170 s\u003csup\u003e\u0026ndash;1\u003c/sup\u003e, the viscosity of a 0.7% mass fraction polymer aqueous solution remained at 88.7 and 73.2 mPa\u0026middot;s, respectively, while the viscosity of a 0.7% mass fraction polymer salt solution was greater than 50 mPa\u0026middot;s. Thixotropic performance tests revealed that the polymer solutions exhibited good shear recovery properties of their viscosity.\u003c/p\u003e \u003cp\u003e(3) The viscoelasticity test results indicated that when the mass fraction of the polymer solution increased from 0.3\u0026ndash;0.7%, a significant linear viscoelastic region appeared, with G' \u0026gt; G\u0026Prime;, indicating an elastic fluid behavior. In saltwater, metal ions undergo chelation with the phenylethylene group, enhancing the associative effect and leading to a more stable spatial structure that is difficult to disrupt, resulting in higher viscoelasticity.\u003c/p\u003e"},{"header":"Declarations","content":"\u003cp\u003e\u003cstrong\u003eConflicts of interest\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eThere are no conflicts of interest to declare.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eEthical Approval\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003enot applicable\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eFunding\u003c/strong\u003e\u003cstrong\u003e\u0026nbsp;\u003c/strong\u003eThis research was supported by the Service Program for Foreign Experts of Shaanxi Province of China ( 2023WGZJ-ZD-03), Key R\u0026amp;D Program of Shaanxi Province\u0026nbsp;(2023-YBGY-307), Industrialization Project of Shaanxi Provincial Education Department( 21JC005), and Science and Technology Program of Xi\u0026rsquo;an, China\u0026nbsp;(22GXFW0014).\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eAvailability of data and materials\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eAll of the material is owned by the authors and no permissions are required.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eAuthor contributions\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eXin Wen:\u003c/strong\u003e Conceptualization; Data curation. Roles/Writing - original draft,Writing - review \u0026amp; editing. \u003cstrong\u003eLei Wang\u003c/strong\u003e: Funding acquisition; Methodology. \u003cstrong\u003eXiao-juan Lai\u003c/strong\u003e: Investigation; Project administration. \u003cstrong\u003eGui-ru Liu\u003c/strong\u003e: Software. \u003cstrong\u003eWen-wen Yang\u003c/strong\u003e: Supervision. \u003cstrong\u003eYa-meng Liu\u003c/strong\u003e: Formal analysis. All of the material is owned by the authors and no permissions are required.\u003c/p\u003e"},{"header":"References","content":"\u003col\u003e\n\u003cli\u003eZhu S, Xue X, Zhang J, Zhang S, Liu Z (2022) Application and Optimization of the Rheological Model for a Hydrophobically Associating Dendrimer Polymer.Polymers14, 1747.\u003c/li\u003e\n\u003cli\u003eZhang L Q (2017) Study on settlement law of proppant in slippery water. Contemporary Chemical Industry 46(4): 711-714.\u003c/li\u003e\n\u003cli\u003eShao Y, Mao J C, Yang B, Zhao J Z, Yang X J (2020) High performance hydrophobic associated polymer for fracturing fluids with low-dosage. Petroleum Chemistry 60(2): 219-225.\u003c/li\u003e\n\u003cli\u003ePan Y, Feng J N, Yang S C, Zain U, Zhang H Y (2018) Synthesis of thermo-salt-resistant hydrophobic associated polyacrylamide and its prospect. Applied Chemical Industry 47(8): 1772-1777.\u003c/li\u003e\n\u003cli\u003eJiao Y B, Chen Y J, Yang H, Wang C Q (2024) Experimental characterization on fracture behavior of UHPMC under small-scale sample tensile testing: Acoustic emission monitoring and digital image correlation 130,104342\u003c/li\u003e\n\u003cli\u003eKang W L, Hou X Y, Chen C,Shao S,Zhang X F,Zhu T Y,Wang T Y,Yang H B (2019) Study on rheological behavior and salt-thickening mechanism of a synthesized twin-tailed hydrophobically modified polyacrylamide. Journal of Molecular Liquids 294(C): 111619-111626.\u003c/li\u003e\n\u003cli\u003ePu W F, Du D J, Liu R (2018) Preparation and evaluation of supramolecular fracturing fluid of hydrophobically associative polymer and viscoelastic surfactant. Journal of Petroleum Science and Engineering 167: 568-576.\u003c/li\u003e\n\u003cli\u003eMa X P, Mu H L, Hu Y Y, Yang S W (2021) Synthesis and properties of hydrophobically associating polymer fracturing fluid. Colloids and Surfaces A: Physicochemical and Engineering Aspects 626: 127013-127013.\u003c/li\u003e\n\u003cli\u003eBai Z F, Li M Z (2023) Prediction of Proppant Settling Velocity in Fiber-Containing Fracturing Fluids. ACS Omega, 8(35): 31857\u0026ndash;31869.\u003c/li\u003e\n\u003cli\u003eShi J M, Wu Z L, Deng Q C,Liu L, Zhang X F,Wu X Y,Wang Y G (2021) Synthesis of hydrophobically associating polymer: Temperature resistance and salt tolerance properties. Polymer Bulletin 79: 4581-4591.\u003c/li\u003e\n\u003cli\u003eYin S F, Ma H F, Cheng Z H, Zou Q L, Li Y M, Jia H S, Zhang K X (2019) Permeability enhancement mechanism of sand‐carrying hydraulic fracturing in deep mining: A case study of uncovering coal in cross‐cut. Energy Science \u0026amp; Engineering, 7(5):1867-1881.\u003c/li\u003e\n\u003cli\u003eHe J, Li T T, Wang M X, Fagn X, Nan B B (2014) Study on the influencing factors of the relationship between the viscosity of clean fracturing fluid and its suspended sand. Journal of Yangtze University, 11(14): 73-76.\u003c/li\u003e\n\u003cli\u003eWu W, Liu P P, Sun H, Zhang X Y (2016) Synthesis and application of AAMS-1 hydrophobic association polymer thickener for fracturing fluid. Drilling Fluid and Completion Fluid, 33(5): 114-118.\u003c/li\u003e\n\u003cli\u003eMao J C, Cao H M, Zhang H,Du A Q, Xue J X, Lin C, Yang X J,Wang Q H, Mao J H, Chen A (2022) Design of salt-responsive low-viscosity and high-elasticity hydrophobic association polymers and study of association structure changes under high-salt conditions. Colloids and Surfaces A: Physicochemical and Engineering Aspects 650: 129512-129524.\u003c/li\u003e\n\u003cli\u003eChe E Q (2020) Study and application of water in oil polyacrylamide prepared by inverse emulsion polymerization. Xi \u0026apos;an: Shaanxi University of Science \u0026amp; Technology.\u003c/li\u003e\n\u003cli\u003eLi Y W (2019) Synthesis and properties of hydrophobically associating polyacrylamide in inverse microemulsion.Tianjin: Hebei University of Technology.\u003c/li\u003e\n\u003cli\u003eCao T Y, Liu Q P , Hu J S (2007) Synthesis principle, performance and application of polymer emulsion. Beijing: Chemical Industry Press 19-28.\u003c/li\u003e\n\u003cli\u003ePu W F, Jiang F, He Y Y, Wei B, Tang Y L (2016) Synthesis of a novel comb micro-block hydrophobically associating copolymer for Ca2+/Mg2+ resistance. RSC Advances 6(49): 43634-43637.\u003c/li\u003e\n\u003cli\u003ePu W F, Jiang F, Wei B, Tang Y L, He Y Y (2017) Influences of structure and multi-intermolecular forces on rheological and oil displacement properties of polymer solutions in the presence of Ca2+/Mg2+. RSC Advances 7(8): 4430-4436.\u003c/li\u003e\n\u003cli\u003eFan M L, Wang L, Li J, He P, Lai X Y,Gao J H, Liu G R, Wen X (2022) Preparation of supramolecular viscoelastic polymers with shear, temperature, and salt resistance/ sensitivity by amphiphilic functional monomer modification[J]. Polymer Testing 116: 107799-107810.\u003c/li\u003e\n\u003cli\u003eLiu Y, Wang L, Liu L F, Yasir M F, Wen X, Lu L J (2022) Rheological properties of hydrophobic associating polymer solutions in response to salt stimulation[J]. Fine Chemicals 39(7): 1486-1494.\u003c/li\u003e\n\u003cli\u003eMao J C, Zhang H, Xue J X (2022) Correction to: Investigation of a hydrophobically associating polymer\u0026rsquo;s temperature and salt resistance for fracturing fluid thickener[J]. Colloid and Polymer Science 300(9): 569-582.\u003c/li\u003e\n\u003cli\u003eShi X D (2015) Viscoelastic properties and stability of high temperature resistant polymers.Daqing: Northeast Petroleum University.\u003c/li\u003e\n\u003cli\u003eXue X S (2005) Effect of molecular structure on viscoelasticity of associated polymers and their seepage characteristics in porous media. Chengdu: Southwest Petroleum Institute.\u003c/li\u003e\n\u003cli\u003eXia H F, Zhang J R, Liu S Y (2011) Viscoelasticity of polyacrylamide solution and its influencing factors. Journal of Daqing Petroleum Institute 35(1): 37-41,115-116.\u003c/li\u003e\n\u003c/ol\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":"Inverse-phase emulsion polymerization, salt tolerance, rheological property, Viscoelasticity, Thixotropy","lastPublishedDoi":"10.21203/rs.3.rs-4081245/v1","lastPublishedDoiUrl":"https://doi.org/10.21203/rs.3.rs-4081245/v1","license":{"name":"CC BY 4.0","url":"https://creativecommons.org/licenses/by/4.0/"},"manuscriptAbstract":"\u003cp\u003eAn associative and salt tolerant p(AM/AMC\u003csub\u003e12\u003c/sub\u003eS/GTE-10) polymer was synthesized through reverse-phase emulsion polymerization of acrylamide (AM), 2-acrylamide-sodium dodecyl sulfonate (AMC\u003csub\u003e12\u003c/sub\u003eS), and the hydrophobic monomer 29-(4-octylphenoxy)-3,6,9,12,15,18,21,24,27-nonaoxanonacosyl methacrylate (GTE-10). The structure and morphology of the polymer obtained were then characterized by FTIR, \u003csup\u003e1\u003c/sup\u003eH-NMR, SEM, TEM, and a laser particle size distribution analyzer. This was followed by an evaluation of its rheological properties, thixotropic properties, and viscoelasticity. The results showed that the hydrophobic monomer GTE-10 was successfully incorporated into the polymer, resulting in a narrow and uniform particle size distribution of the emulsion after polymerization. The addition of salt made the aggregation of p(AM/AMC\u003csub\u003e12\u003c/sub\u003eS/GTE-10) molecules more compact, resulting in a more stable spatial network structure. The p(AM/AMC\u003csub\u003e12\u003c/sub\u003eS/GTE-10) polymer aqueous solution with a mass fraction of 0.7% exhibited excellent temperature resistance at 140 ℃. After being sheared at 120 ℃ and 170 s\u003csup\u003e\u0026ndash;1\u003c/sup\u003e for 1 h, the polymer solutions with a mass fraction of 0.7%, prepared at a mass concentration of 20000 mg/L NaCl and CaCl\u003csub\u003e2\u003c/sub\u003e aqueous solutions exhibited viscosities of 64.7 and 54.2 mPa\u0026middot;s, respectively, with good shear recovery performance. The energy storage modulus was higher than the loss modulus, and the complex interaction between the metal ion and phenoxyethylene group enhanced the intermolecular forces, resulting in a more stable spatial structure and increased viscoelasticity.\u003c/p\u003e","manuscriptTitle":"Preparation and rheological properties of associative salt tolerant polymer by inverse-phase emulsion polymerization","msid":"","msnumber":"","nonDraftVersions":[{"code":1,"date":"2024-03-19 07:20:57","doi":"10.21203/rs.3.rs-4081245/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":"ee1aa8bc-c462-4232-bc6c-f9faefbf1398","owner":[],"postedDate":"March 19th, 2024","published":true,"recentEditorialEvents":[],"rejectedJournal":[],"revision":"","amendment":"","status":"posted","subjectAreas":[],"tags":[],"updatedAt":"2024-03-19T21:59:29+00:00","versionOfRecord":[],"versionCreatedAt":"2024-03-19 07:20:57","video":"","vorDoi":"","vorDoiUrl":"","workflowStages":[]},"version":"v1","identity":"rs-4081245","journalConfig":"researchsquare"},"__N_SSP":true},"page":"/article/[identity]/[[...version]]","query":{"redirect":"/article/rs-4081245","identity":"rs-4081245","version":["v1"]},"buildId":"qtupq5eGEP_6zYnWcrvyt","isFallback":false,"isExperimentalCompile":false,"dynamicIds":[84888],"gssp":true,"scriptLoader":[]}