Abstract Thermo-thickening copolymers have gained prominence in technological advancements due to its attractive properties and great potential to overcome the deficiency of viscosity of conventional copolymer upon increasing temperature and salinity. The work in this paper was devoted to examine the aqueous solution viscosity behavior of a new class thermo-thickening copolymer, poly(sodium 2-acrylamido-2-methylpropanesulfonic acid-co-N,N’-methylenebisacrylamide)-g-poly(acrylamide-co-N, N’-diethylacrylamide) denoted as CGBA in the presence of co-solutes. CGBA, which were reported in our previous work manifested notable viscosity enhancement macroscopically above the threshold temperature. However, the effect of small molecules on thermo-associative behavior was still unsettled. Based on structure/properties dependence of CGBA, this work aimed to explore the effect of small molecules and the role of molecular structure on aqueous solution viscosity behavior. The contributions of various added co-solutes such as anionic surfactant, acidic specie, monovalent and divalent salts were considered. For that purpose, three copolymers having distinctive composition of side-arms and length of side-arms were selected and their thermo-associating behaviors were followed by viscosity measurement. Results from rheological tests showed that these co-solutes induced notable modifications in the characteristic of thermo-thickening behavior. For all the co-solutes used, it was observed a strong dependence between the side-arms/water/co-solutes ternary system and the macroscopic property upon heating. Spectrofluorimetric and environmental scanning electron microscope (ESEM) tests were used to gain a deeper insight into the precise mechanism of phase transition process. Results from spectrofluorimetric experiment indicated that, only when the fraction of DEAm in CGBA was higher enough, it would appear strong abrupt macroscopic property above the threshold temperature, which could delay the offset of hydrophobic association phenomenon in the presence of anionic surfactant. Similar effect was also observed in the presence of added acidic specie. Conversely, the addition of monovalent and divalent salts showed dissimilar effects. ESEM revealed that, in comparison with monovalent salt, divalent salt favored the formation of larger and more condensed CGBA skeleton above the threshold temperature which led to an improved macroscopic response. This work demonstrates for the first time the micro-structure changes of copolymer, which was probably the main reason for the changes in magnitude of thermo-thickening effect in different divalent salt dosages.

中文翻译：

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基于交联 2-丙烯酰胺-甲基丙烷磺酸的热缔合聚合物，B 部分：共溶质对溶液行为的影响

摘要 热增稠共聚物由于其吸引人的性能和克服常规共聚物在增加温度和盐度时粘度不足的巨大潜力而​​在技术进步中获得突出地位。本文的工作致力于研究一种新型热增稠共聚物，聚（2-丙烯酰胺基-2-甲基丙磺酸钠-co-N,N'-亚甲基双丙烯酰胺）-g-聚（丙烯酰胺）的水溶液粘度行为。 -co-N, N'-二乙基丙烯酰胺）在共溶质存在下表示为 CGBA。在我们之前的工作中报道的 CGBA 在阈值温度以上宏观上表现出显着的粘度增强。然而，小分子对热缔合行为的影响仍未解决。基于CGBA的结构/性质依赖性，这项工作旨在探索小分子的影响和分子结构对水溶液粘度行为的影响。考虑了各种添加的共溶质的贡献，例如阴离子表面活性剂、酸性物质、一价和二价盐。为此，选择了三种具有不同侧臂组成和侧臂长度的共聚物，并通过粘度测量跟踪它们的热缔合行为。流变学测试结果表明，这些共溶质引起了热增稠行为特征的显着改变。对于所有使用的共溶质，观察到侧臂/水/共溶质三元体系与加热时的宏观性质之间存在很强的依赖性。荧光分光光度计和环境扫描电子显微镜 (ESEM) 测试用于更深入地了解相变过程的精确机制。荧光光谱实验结果表明，只有当 CGBA 中 DEAm 的比例足够高时，才会在阈值温度以上出现强烈的突变宏观特性，这可以延迟阴离子表面活性剂存在下疏水缔合现象的抵消。在添加的酸性物质存在下也观察到类似的效果。相反，一价和二价盐的添加显示出不同的效果。ESEM 显示，与单价盐相比，二价盐有利于在阈值温度以上形成更大、更凝聚的 CGBA 骨架，从而改善宏观响应。