Rwei Syang-Peng, Chiang Whe-Yi, Way Tun-Fun, Tuan Huynh Nguyen Anh, Chang Ya-Chin
Institute of Organic and Polymeric Materials and Research and Development Center for Smart Textile Technology, National Taipei University of Technology, Taipei 106, Taiwan.
Polymers (Basel). 2018 May 9;10(5):512. doi: 10.3390/polym10050512.
In this work, a smart copolymer, Poly(nipam-co-IAM) was synthesized by copolymerization of -isopropylacrylamide (nipam) and itaconamic acid (IAM) through reversible addition-fragmentation chain-transfer (RAFT) polymerization. Poly(nipam-co-IAM) has been studied previously synthesized via radical polymerization without stereo-control, and this work used cumyl dithiobenzoate and Ytterbium(III) trifluoromethanesulfonate as RAFT and stereo-control agents, respectively. The stereo-control result in this work shows that tacticity affects the lower critical solution temperature (LCST) and/or the profile of phase separation of Poly(nipam-co-IAM). In the pH 7 and pH 10 buffer solutions, the P(nipam-co-IAM) copolymer solutions showed soluble⁻insoluble⁻soluble transitions, i.e., both LCST and upper critical solution temperature (UCST) transitions, which had not been found previously, and the insoluble to soluble transition (redissolved behavior) occurred at a relatively low temperature. The insoluble to soluble transition of P(nipam-co-IAM) in alkaline solution occurred at a temperature of less than 45 °C. However, the redissolved behavior of P(nipam-co-IAM) was found only in the pH 7 and pH 10 buffer solutions and this redissolved behavior was more prominent for the atactic copolymers than in the isotactic-rich ones. In addition, the LCST results under our experimental range of meso content did not show a significant difference between the isotactic-rich and the atactic P(nipam-co-IAM). Further study on the soluble-insoluble-soluble (S-I-S) transition and the application thereof for P(nipam-co-IAM) copolymers will be conducted.
在本工作中，通过可逆加成-断裂链转移（RAFT）聚合反应，由N-异丙基丙烯酰胺（NIPAM）和衣康酸（IAM）共聚合成了一种智能共聚物聚（NIPAM-co-IAM）。聚（NIPAM-co-IAM）此前已通过无立体控制的自由基聚合反应合成，而本工作分别使用二硫代苯甲酸枯酯和三氟甲磺酸镱作为RAFT试剂和立体控制剂。本工作中的立体控制结果表明，立构规整性影响聚（NIPAM-co-IAM）的低临界溶液温度（LCST）和/或相分离曲线。在pH 7和pH 10缓冲溶液中，聚（NIPAM-co-IAM）共聚物溶液呈现出可溶-不溶-可溶转变，即同时存在LCST和上临界溶液温度（UCST）转变，这是此前未发现的，且不溶到可溶的转变（再溶解行为）在相对较低的温度下发生。聚（NIPAM-co-IAM）在碱性溶液中的不溶到可溶转变发生在低于45℃的温度下。然而，聚（NIPAM-co-IAM）的再溶解行为仅在pH 7和pH 10缓冲溶液中被发现，且这种再溶解行为对于无规共聚物比对于富含全同立构的共聚物更为显著。此外，在我们的内消旋含量实验范围内，LCST结果显示富含全同立构和无规的聚（NIPAM-co-IAM）之间没有显著差异。将对聚（NIPAM-co-IAM）共聚物的可溶-不溶-可溶（S-I-S）转变及其应用进行进一步研究。
