上临界溶液温度
高分子化学
哌啶
聚合物
聚合
部分
材料科学
链式转移
化学
低临界溶液温度
共聚物
有机化学
自由基聚合
标识
DOI:10.1002/marc.202100208
摘要
Abstract In this study, poly( N ‐acryloyl‐nipecotamide) (PNANAm), poly( N ‐acryloyl‐isonipecotamide) (PNAiNAm), and poly( N ‐acryloyl‐ N , N ‐diethylnipecotamide) (PNADNAm) are synthesized as novel temperature‐responsive polymers using reversible addition‐fragmentation chain‐transfer polymerization. Aqueous solutions of these three polymers are examined via temperature‐dependent optical transmittance measurements. The PNANAm sample with a hydrophilic terminal group shows an upper critical solution temperature (UCST) in phosphate‐buffered saline (PBS) when its molecular weight ( M n ) is 7600 or higher, whereas PNANAm ( M n < 7600) is soluble. The UCST is influenced by molecular weight and the polymer concentration. In contrast, PNANAm sample with nonionic terminal group shows UCST, when M n is below 7600, suggesting that the terminal nonionic group possibly increases UCST of PNANAm. The urea addition experiment suggests that the driving force for expression of UCST of PNANAm is the formation of inter‐and intramolecular hydrogen bonds among the polymer chains. PNAiNAm is soluble in PBS but exhibits an UCST in an appropriate concentration of ammonium sulfate. In contrast, PNADNAm exhibits a lower critical solution temperature. Comparing the chemical structure of these polymers and their phase transition behaviors suggests that the carboxamide group position in the piperidine ring could determine the UCST expression. These results could help design temperature‐responsive polymers with a desired the cloud point temperature.
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