温敏缔合共聚物P(NaAMPS-VCL-DVB)的合成及溶液特性

采用自由基胶束聚合法合成了新型的2-甲基-2-丙烯酰胺基丙磺酸钠(NaAMPS)/N-乙烯基己内酰胺(VCL)/二乙烯苯(DVB)温敏缔合共聚物(PAVD)。用红外光谱(FT-IR)、核磁共振(1H-NMR)、元素分析和凝胶渗透色谱(GPC)确定了PAVD的分子结构和重均分子量;研究了共聚物溶液的温敏增稠特性,并进一步考察了共聚物质量浓度、盐浓度等因素对其温敏增稠性能的影响。结果表明,当共聚物溶液达到一定浓度时,其具有优良的温敏增稠性,且增稠效果随共聚物质量浓度及外加盐浓度的增加而增强。抗老化实验结果表明,PAVD在80℃时具有优良的耐温抗老化性能。     

热缔合型阳离子纤维素的制备及性能

以羟乙基纤维素(HEC)、正丁基缩水甘油醚(BGE)和2,3-环氧丙基三甲基氯化铵(GTA)为原料,通过改变纤维素衍生物亲水基和疏水基的比例调控亲水-亲油平衡的方法制备了热缔合型阳离子纤维素(TACC)。首先,HEC与BGE反应制备了疏水化纤维素(HBPEC);然后,HBPEC与不同质量的GTA反应制备了4种不同GTA取代度的热缔合型阳离子纤维素(TACC)。采用FTIR、~1HNMR、元素分析对TACC进行了表征,证实TACC上已成功接枝了BGE和GTA。考察了GTA取代度、TACC质量浓度、NaCl浓度及剪切速率对TACC温敏增稠性能的影响。结果表明:40℃下,当GTA的取代度从0.12增加到0.32时,15 g/L的TACC水溶液的最大黏度(η_(max))从13 mPa·s增大到54 mPa·s,最大与最小黏度比(η_(max)/η_(min))从1.5增加到7.0,与最大黏度对应的温度(T_(max))从25℃升高到40℃;TACC浓度的增大使水溶液黏度及温敏增稠性能提高;相反地,NaCl浓度的增加会使TACC水溶液的黏度和温敏增稠性能降低,且会使T_(max)减小。     

HPAM-g-P(NIPA-co-DMAM)的合成与温敏行为

利用端基转换法合成了不同组成及相对分子质量的端丙烯酰胺基聚（N-异丙基丙烯酰胺-co-N,N-二甲基丙烯酰胺）［poly(NIPA-co-DMAM), PID］大分子单体;与丙烯酰胺聚合后再水解，得到以PID为侧链，浊点在37～63℃的接枝共聚物［HPAM-g-P(NIPA-co-DMAM), HGPID］。利用¹H NMR及端基分析等对大分子单体和接枝物的组成及结构进行了表征;考察了接枝共聚物侧链的组成和链长、共聚物质量浓度和外加盐浓度等因素对其水溶液的热敏特性及温敏增稠性的影响。     

热缔合接枝物HPAM-g-PNIPAm的温敏增稠性能

采用流变仪与毛细管粘度计研究了热缔合接枝聚合物———水解聚丙烯酰胺-g-聚(N-异丙基丙烯酰胺)(HPAM-g-PNIPAm)盐水溶液流变特性,测定了外加盐浓度、聚合物浓度、剪切速率及接枝率和接枝链长对HPAM-g-PNIPAm温敏增稠效果的影响。结果表明,此接枝聚合物在接枝率大于4%,接枝侧链相对分子质量大于8000且聚合物质量浓度大于2g/L时具有较强的温敏增稠性,即在30～50℃水溶液中,粘度随温度的升高而增大,且增稠效果随外加盐浓度的升高而加大。     

Thermoresponsive behaviour in aqueous solution of poly(maleic acid‐alt‐vinyl acetate) grafted with poly(N‐isopropylacrylamide)

The synthesis of a thermoresponsive graft copolymer consisting of a maleic acid/vinyl acetate alternating copolymer backbone (MAc‐alt‐VA) and poly(N‐isopropylacrylamide) (PNIPAM) side chains is reported. Turbidimetric measurements in dilute aqueous solutions showed that no macroscopic phase separation takes place when the temperature is raised above the lower critical solution temperature (LCST) of PNIPAM, even at pH = 2. Moreover, in semi‐dilute aqueous solutions, a pronounced thermally induced viscosity increase (thermothickening) was observed. This thermoresponsive behaviour has been attributed to the interconnection of the hydrophilic MAc‐alt‐VA graft copolymer backbones by means of the hydrophobic PNIPAM side chain aggregates formed as the temperature increases above the LCST of this polymer. Copyright © 2004 Society of Chemical Industry     

Thermoresponsive sodium alginate‐g‐poly(N‐isopropylacrylamide) copolymers III. Solution properties

Stimuli‐responsive biocompatible and biodegradable materials can be obtained by combining polysaccharides with polymers exhibiting lower critical solution temperature (LCST) phase behavior, such as poly(N‐isopropylacrylamide) (PNIPAAm). The behavior of aqueous solutions of sodium alginate (NaAl) grafted with PNIPAAm (NaAl‐g‐PNIPAAm) copolymers as a function of composition and temperature is presented. The products obtained exhibit a remarkable thermothickening behavior in aqueous solutions if the degree of grafting, the concentration, and the temperature are higher than some critical values. The sol–gel‐phase transition temperatures have been determined. It was found that at temperatures below LCST the systems behave like a solution, whereas at temperatures above LCST, the solutions behave like a stiff gel, because of PNIPAAm segregation. This behavior is reversible and could find applications in tissue engineering and drug delivery systems. © 2012 Wiley Periodicals, Inc. J. Appl. Polym. Sci., 2013     

热增稠型智能凝胶的研究进展、应用及展望

着重介绍热增稠型水凝胶的设计、制备方法及热缔合机理,并对其应用前景作了简单的评述;同时展望了热增稠凝胶在油田开发中的应用。     

Synthesis and Thermothickening Behavior of Graft Copolymers Based on poly(N,N-Diethylacrylamide-co-N,N-Dismethylacrylamide) Side Chains

A new type of thermothickening graft copolymer was synthesized through free radical copolymerization and grafting onto technique in aqueous solution. Their molecular structure combines a hydrophilic backbone based on poly(acrylicacid-co-2-acrylamido-2-methylpropane sulfonic acid and thermosensitive side chains based on N,N-diethylacrylamide and N,N-dimethylacrylamide (DMAA). The lower critical solution temperature of poly(N,N-diethylacrylamide) was increased easily by copolymerizing with hydrophilic monomers DMAA. The results demonstrate that the polymers in aqueous solution exhibit a significant increase in viscosity with the temperature rising and their thermothickening behavior is related to various physicochemical parameters such as the concentration of the polymer, shear rate, chemical composition of side chains, salt concentration, and pH value.