School of Chemistry and Chemical Engineering, State Key Laboratory of Metal Matrix Composites , Shanghai Jiao Tong University , 800 Dongchuan Road , Shanghai 200240 , China.
Langmuir. 2018 Mar 6;34(9):3058-3067. doi: 10.1021/acs.langmuir.7b04255. Epub 2018 Feb 23.
A novel thermoresponsive hyperbranched multiarm copolymer with a hydrophobic hyperbranched poly[3-ethyl-3-(hydroxymethyl)oxetane] core and many poly(acrylamide- co-acrylonitrile) (P(AAm- co-AN)) arms was for the first time synthesized through a reversible addition-fragmentation chain-transfer polymerization. These copolymers show reversible, sharp, and controlled temperature-responsive phase transitions at the upper critical solution temperature (UCST) in water and electrolyte solution. It is the first report on the hyperbranched copolymers with a UCST transition. Two series copolymers with variable AN content (series A) and variable arm length (series B) were synthesized to study the influence of molecular structure on the UCST transition. It was found that the UCST of copolymers could be raised by increasing the AN content or decreasing the arm length. Most interestingly, the amplification effect of the hyperbranched topological structure leads to a broad change of the UCST from 33.2 to 65.2 °C with the little change of AN content (5.9%). On the basis of variable temperature nuclear magnetic resonance, dynamic light scattering, and transmission electron microscopy, a UCST transition mechanism, in combination with hydrophilic/hydrophobic balance and multimicelle aggregate (MMA), was proposed. This work enriches the UCST copolymer topology and may extend the knowledge on the structure-activity relationship as well as the mechanism of the UCST polymers.
一种新型的温敏超支化多臂共聚物，具有疏水超支化聚[3-乙基-3-(羟甲基)恶唑烷]核和许多聚（丙烯酰胺-共-丙烯腈）（P（AAm-co-AN））臂，首次通过可逆加成-断裂链转移聚合合成。这些共聚物在水中和电解质溶液的上临界溶解温度（UCST）下表现出可逆、尖锐和可控的温度响应相转变。这是关于具有 UCST 转变的超支化共聚物的首次报道。合成了两个系列的具有可变 AN 含量（系列 A）和可变臂长（系列 B）的共聚物，以研究分子结构对 UCST 转变的影响。结果发现，通过增加 AN 含量或降低臂长可以提高共聚物的 UCST。最有趣的是，超支化拓扑结构的放大效应导致 UCST 从 33.2°C 到 65.2°C 的宽范围变化，而 AN 含量的变化很小（5.9%）。基于变温核磁共振、动态光散射和透射电子显微镜，提出了一种 UCST 转变机制，结合亲水/疏水平衡和多胶束聚集（MMA）。这项工作丰富了 UCST 共聚物的拓扑结构，并可能扩展 UCST 聚合物的结构-活性关系以及 UCST 聚合物的机制方面的知识。
