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An inverse, free‐radical emulsion polymerization technique was designed for the preparation of copolymers of acrylamide and sodium acrylate modified with low amounts (<0.5 mol %) of a series of amphiphilic comonomers, the isooctylphenoxy–poly(oxyethylene)(n) methacrylates (1 ≤ n ≤ 12). The products of the reaction were hydrophobically modified water‐soluble polymers (HMWSPs) of high molecular weight encapsulated within water droplets dispersed in an organic medium. Kinetic studies showed that the full‐conversion samples were rather homogeneous in composition because of the specificity of the process. A mechanistic scheme is proposed that accounts for the incorporation level of the amphiphilic comonomer as a function of its hydrophile–lipophile balance and the nature of the redox initiator (hydrophilic or lipophilic). The rheological properties of the HMWSPs in aqueous solutions were investigated as a function of the comonomer content and the nature of the initiator with steady‐flow experiments. The thickening properties were directly correlated to the conditions of synthesis and were optimal when the initiator and the amphiphilic comonomer were located in two distinct phases. A maximum in viscosity was observed for a hydrophobe content of about 0.3 mol %. An examination of the viscosity as a function of the shear rate and time showed that these solutions had all the characteristics of associating polymers. The complex rheological behavior was the result of the balance between interchain and intrachain hydrophobic liaisons and the kinetics of disorganization and reorganization of the network structure. © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 84: 1418–1430, 2002; DOI 10.1002/app.10337 相似文献
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Poly(acrylamide‐diallyldimethyl ammonium chloride‐vinyl trimethoxy silane) [P (AM‐DADMAC‐VTMS)] was prepared by inverse free‐radical emulsion polymerization technique. VTMS segment was hydrolyzed and condensed to form three dimensional networks. The effects of different factors, such as hydrophobic monomer feed ratio, cationic monomer feed ratio, pH value, and NaCl concentration, on decolorization efficiency were studied. Moreover, the decolorization mechanism was also explained by analyzing FTIR spectra and UV‐vis spectra. The introduction of VTMS on flocculant enhanced removal efficiency of dye molecules. With the increasing VTMS, adsorption and net roofing‐sweeping action of hydrophobically modified cationic polyacrylamide played the dominant role in the decoloring process of anion dye. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2011 相似文献
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A series of amphoteric polyacrylamides with different molecular weights and charges were prepared by the copolymerization of acrylamide with sodium acrylate and a subsequent Mannich reaction. The copolymerization was carried out with a redox initiation system via inverse emulsion polymerization. Reaction conditions, factors affecting emulsion stability, and applications as retention aids in papermaking were studied. Experiments showed that an ideal retention aid and a stable latex with wheat‐straw pulp of a shorter fiber length could be obtained under the following conditions: the acrylamide/formaldehyde/dimethylamine ratio was 1/1/1.2, a medium of aldehyde and amine was prepared first and then was dropped into an inverse emulsion of anionic polyacrylamide, the reaction temperature was 45°C, the reaction time was 4 h, and the pH was 5.0. When the anionic degree was 5%, the cationic degree was greater than 20%, the molecular weight was between 2 and 3 million, and the filler retention was higher. © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 84: 343–350, 2002; DOI 10.1002/app.10340 相似文献
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Hydrophobically modified water-soluble polymers have recently become the subject of extensive research because of their use as aqueous viscosity modifiers in oil recovery and latex paint systems. In this study, poly(acrylamide) samples modified with small amounts of a hydrophobic monomer (ethylphenylacrylamide) have been prepared by free radical copolymerization using an aqueous micellar process in which the use of a surfactant ensures the solubilization of the hydrophobe. The copolymers exhibit improved thickening properties with respect to homopoly(acrylamide) analogs due to intennolecular hydrophobic associations. The aqueous solution-copolymer properties strongly depend on the amount of surfactant used in the synthesis. The differences observed between the samples are directly related to the copolymer microstructure, that is to a more or less block distribution of the hydrophobic units. The interactions in aqueous solution of a surfactant (sodium dodecylsulfate (SDS)) with these copolymers have been examined. A strong increase in viscosity is observed upon the addition of SDS below its critical micelle concentration, owing to the formation of mixed micelles of SDS and hydrophobic monomers. The complex rheological behavior observed is explained in terms of the balance between inter and intrachain liaisons. The effects of hydrolysis on the hydrophobic interactions are also discussed. 相似文献
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Hydrophobically modified hydroxyethyl cellulose (BD‐HAHEC) was synthesized by the macromolecular reaction of hydroxyethyl cellulose (HEC) with bromododecane (BD). Study of the effects of polymer concentration, shear rate, temperature, and electrolytes on the rheological behavior of BD‐HAHEC indicated that the polymers had high viscosity, excellent viscosity retention in brine water, good thermal stability, and surface activity. Furthermore, investigation of the micromorphology of BD‐HAHEC solutions revealed the close relationship of rheological behavior and a hydrophobically associating effect. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 100: 3346–3352, 2006 相似文献
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Copolymers of acrylamide, 2‐acrylamide‐2‐methylpropanesulfate (AMPS), and hydrophobic monomer N‐arylalkylacrylamide (BAAM) were synthesized by free‐radical micellar copolymerization. The effects of the copolymer, BAAM, AMPS, and NaCl concentrations and the pH value on the apparent viscosity of the copolymers were studied. The solution viscosities increased sharply when the copolymer concentration was higher than the critical associating concentration. The apparent viscosities of aqueous solutions of poly(N‐arylalkylacrylamide‐co‐acrylamide‐co‐2‐acrylamide‐2‐methylpropanesulfate) (PBAMS) increased with increasing BAAM and AMPS concentrations. PBAMS exhibited good salt resistance. With increasing pH, the apparent viscosities first increased and then decreased. Dilute PBAMS solutions exhibited Newtonian behavior, whereas semidilute aqueous and salt solutions exhibited shear‐thickening behavior at a lower shear rate and pseudoplastic behavior at a higher rate. Upon the removal of shear, the aqueous solution viscosities recovered and became even greater than the original viscosity, but the salt solution viscosities could not recover instantaneously. The elastic properties of PBAMS solutions were more dominant than the viscous properties, and this suggested a significant buildup of a network structure. © 2005 Wiley Periodicals, Inc. J Appl Polym Sci 97: 316–321, 2005 相似文献
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In this study, the viscoelastic behavior of hydrophobically modified polyelectrolytes obtained from the hydrolysis of cationic acid salts (CAS's) as a function of their zwitterion fraction (x) and anion fraction (z) was studied. The dynamic viscosity (η′) dependence on frequency of polymer solutions of polybetaine/anionic polyelectrolyte (APE) with various compositions of x and z in 0.1N NaCl showed typical shear thinning behavior. η′ of a solution of CAS 4 (M2‐4 (4 mol % hydrophobe)) attained a maximum value in the presence of 1.67 equiv of NaOH (corresponding to an x : z ratio of 33 : 67) and decreased with any further addition of NaOH. We suggest this maximum to be a result of a combined effect of coil expansion and hydrophobic association. The influence of the temperature and concentration on η′ of CAS 4 (M2‐4) treated with 1.67 equiv of NaOH was also investigated. The rheology of CAS 4 (M2‐4) samples treated with 1.67, 1.81, and 2.0 equiv of NaOH suggested a reversible network. However, for APE 7 (M2‐5 (5 mol % hydrophobe)), elastic behavior was dominant, and the formation of highly interconnected three‐dimensional networks was suggested. At lower x : z ratios, the effect of coil expansion due to a higher APE fraction was more than counterbalanced by the lower degree of intermolecular hydrophobic associations, whereas at higher x : z ratios, coil contraction became the predominant effect. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2009 相似文献
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反相乳液聚合合成聚丙烯酰胺 总被引:1,自引:0,他引:1
以甲苯为介质,Span80/Span20为乳化剂,叔丁基过氧化氢/亚硫酸氢钠氧化还原体系为引发剂,采用反相乳液聚合制备了分子量高达9.4×106的聚丙烯酰胺乳液。研究了乳化剂种类及用量、引发剂种类及用量、油水比、单体浓度,反应温度对共聚物相对分子量、聚合转化率以及聚合反应速率的影响。其最佳聚合配方及工艺条件为:油水体积比为1.4,单体浓度30%,引发剂用量0.003%,乳化剂用量12%,聚合温度30℃。 相似文献
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The acrylamide‐based hydrophobically associating zwitterionic polymer was prepared, which was composed of dimethyl‐dodecyl‐allyl ammonium chloride as hydrophobic group and carboxyl betaine 2‐(4‐acrylamido‐propyl‐dimethyl ammonic)‐sodium acetate as functional group. Hydrophobically associating polyacrylamide (HAPAM) was also prepared for comparative study. The behaviors of polymers in pure water and salt solutions were investigated by the means of apparent viscosity test, laser light scattering, atomic force microscope, and fluorescence experiments. The viscosities of polymer solution increased with the increasing of salt concentration, which indicated that the addition of salt resulted in significant antipolyelectrolyte effect in the zwitterionic polymer solution. The results of dynamic laser light scattering experiment also showed that the average hydrodynamic diameters of the zwitterionic polymer molecules increased with the increasing of salt concentration. The network structures had been observed by atomic force microscope and the addition of salt strengthened the formation of network structures. The results of fluorescence experiment showed that the addition of salt could enhance the association of hyrophobically zwitterionic polymer. © 2013 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2014 , 131, 39707. 相似文献
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Yin-tao Li Shi-feng Zhang Shan-qiang Wang Zhi-yu He Yuan-lin Zhou Hui Ren 《应用聚合物科学杂志》2020,137(41):49234
Hydrophobically associating copolymers using acrylamide (AM), acrylic acid (AA), and Styrene (St) as comonomers were successfully prepared by self-emulsified microemulsion polymerization, in which low-molecular-weight AM/AA/St copolymers as surfactant and AM as cosurfactant. The structure and chemical composition of AM/AA/St copolymers were characterized by Fourier transform infrared, nuclear magnetic (NMR), and differential scanning calorimeter. The content of PSt in the copolymers is determined by 1H nuclear magnetic resonance spectra, suggesting that the self-made polymer surfactant can disperse uniformly the St monomers to improve the copolymerization efficiency. Furthermore, the polymerization mechanism of the self-emulsified microemulsion method is explored preliminarily. During the synthesis of the copolymers, the purified copolymer solution is obtained in one step without using a small molecular emulsifier such as sodium dodecyl sulfate, in order to avoid the complicated post-treatment process of the small molecular emulsifier. The copolymers revealed good hydrophobic association properties and low surface tension. 相似文献
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Hydrophobically modified polymers were synthesized via esterification reactions between a commercial triblock copolymer composed of ethylene oxide (EO) and propylene oxide (PO) segments (EO20PO70EO20) and lauric and oleic acids. Rheological studies of aqueous systems containing the original copolymer and the synthesized products were performed to evaluate the effects of chemical modification, the presence of salt, and temperature on the rheology of the systems due to changes in the micellar structures. It was verified that the systems containing the synthesized products presented shear‐thinning behavior even in the absence of salt. In addition, increasing the temperature and salt concentration enhanced the hydrophobic character of the poly(propylene oxide) segment and reduced the hydration of the poly(ethylene oxide) segment; this favored the adequate packing needed to form long, wormlike micelles and resulted in pronounced shear thinning. The formation of a complex micelle structure probably occurred in the systems above the critical micellar temperature of the original copolymer because under this condition the molecules presented three alternate hydrophobic segments that had to dive into the micelle structure. The formation of long, wormlike micelles was also evidenced by the Maxwellian behavior observed in rheological oscillatory measurements. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2010 相似文献
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氧化还原引发下的淀粉、丙烯酸反相乳液聚合 总被引:3,自引:0,他引:3
以环己烷为连续相,Span20为乳化剂,采用氧化还原引发体系,通过反相乳液聚合技术,合成淀粉、丙烯酸接枝共聚物。并用红外光谱对共聚物进行了表征。研究结果表明:采用氧化还原引发剂可使聚合反应低温快速进行,在过硫酸钾为3.1mmol/L,亚硫酸氢钠为3.1mmol/L,单体丙烯酸浓度为2.6mol/L,反应温度为30℃,反应时间为3h,乳化剂浓度为5%时,单体转化率为92.6%、淀粉接枝率为43.2%、淀粉接枝效率56.4%。 相似文献
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采用反相乳液聚合,以淀粉、丙烯酰胺为原料,过硫酸铵为引发剂制备了淀粉丙烯酰胺聚合物。实验表明,最佳反应条件为:引发剂加量为单体总量的0.1%,油水体积比为1∶1,反应温度为60℃,反应时间为4 h。淀粉丙烯酰胺聚合物的除浊率可达89%,吸水率达350%。 相似文献
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引发剂在乳液聚合反应中起着十分重要的作用,本文主要论述了引发剂对聚合反应速率,聚合物粒子形态,单体转化率的影响。 相似文献
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Beatriz S. Chagas Dilon L. P. Machado Roberto B. Haag Celso R. De Souza Elizabete F. Lucas 《应用聚合物科学杂志》2004,91(6):3686-3692
Acrylamide and tridecyl acrylate copolymers were synthesized by micellar copolymerization to obtain water‐soluble, hydrophobically modified polymers. Rheological properties of the obtained polymer solutions were evaluated and compared to those of solutions of a commercial polyacrylamide currently used in the petroleum industry. The behavior of the copolymer solutions was studied as a function of the variation of hydrophobic monomer content incorporated in the copolymer as well as the salt content of the aqueous medium, for diluted and semi‐diluted regimens. Comparative studies of such effects on the intrinsic viscosity and the critical concentration of those polymers were conducted. The increase in hydrophobic monomer content produced a sudden increase in the bulk and absolute viscosity of the polymeric solutions, a trend that was more intense from a certain concentration typical for each polymer. Salt addition led to lower bulk viscosity caused by a stronger interaction among hydrophobic groups, resulting from minimized exposure of such groups and water. The same effect was observed for the critical concentration. A comparison of the synthesized polymers with industrial polyacrylamide showed that the synthesized polymers were characterized by advantageously high shear strength and high salt resistance. However, in the absence of salts, higher copolymer amounts were needed to prepare solutions whose viscosity was the same as that of commercial polyacrylamide. © 2004 Wiley Periodicals, Inc. J Appl Polym Sci 91: 3686–3692, 2004 相似文献