Department of Chemistry, Faculty of Science, Mahidol University, Bangkok, 10400, Thailand.
Université de Lorraine, CNRS, LCPM, Nancy, F-54000, France.
Macromol Rapid Commun. 2020 May;41(9):e2000058. doi: 10.1002/marc.202000058. Epub 2020 Mar 18.
Currently, the phase transition of aqueous binary systems containing thermoresponsive (co)polymers, and exhibiting upper critical solution temperature (UCST), is exclusively investigated in dilute solutions, which can limit the knowledge of their UCST-type phase transition. Herein, a photo-RAFT polymerization approach, using acrylamide (AAm) and acrylonitrile (AN) as monomer models, is used to prepare well-controlled poly(AAm-co-AN) copolymers "in situ" in highly concentrated dispersions (60 wt%). The impact of the copolymer concentration and the chemical composition (as a variation of AN fraction in the copolymers) on the cloud point temperature (T ) are investigated using turbidity measurements. Importantly, the results show that upon increasing the polymer concentration, a sharp increase of T up to a maximum point is observed, representing the UCST, before the decrease of T at higher polymer concentrations. Finally, a model equation is developed to fit the UCST values of poly(AAm-co-AN), which can be useful to design new poly(AAm-co-AN) copolymers with a desired UCST for a specific application.
目前，仅在稀溶液中研究含有温敏（共）聚合物且表现出上临界溶解温度 (UCST) 的水基二元体系的相转变，这可能限制了人们对其 UCST 型相转变的了解。在此，使用丙烯酰胺 (AAm) 和丙烯腈 (AN) 作为单体模型的光 RAFT 聚合方法，“原位”在高浓度分散体（60wt%）中制备具有良好控制的聚（AAm-co-AN）共聚物。使用浊度测量研究了共聚物浓度和化学组成（作为共聚物中 AN 分数的变化）对浊点温度 (T) 的影响。重要的是，结果表明，随着聚合物浓度的增加，T 急剧增加至最大值，代表 UCST，然后在更高聚合物浓度下 T 下降。最后，开发了一个模型方程来拟合聚（AAm-co-AN）的 UCST 值，这对于设计具有特定应用所需 UCST 的新型聚（AAm-co-AN）共聚物可能很有用。
