Facile synthesis and thermoresponsive behaviors of a well-defined pyrrolidone based hydrophilic polymer
Facile synthesis and thermoresponsive behaviors of a well-defined pyrrolidone based hydrophilic polymer
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DOI：
10.1021/ma800145s
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发表时间：
2008-05-13
期刊：
影响因子：
5.5
通讯作者：
Cai, Yuanli
中科院分区：
文献类型：
--
作者：
Deng, Junjie;Shi, Yi;Cai, Yuanli
通过N-(2-甲基丙烯酰氧乙基)吡咯烷酮单体在甲醇中的可逆加成-断裂链转移自由基聚合或RAFT聚合，在30℃温和的可见光照射下合成了一种基于吡咯烷酮的热响应性聚合物聚[N-(2-甲基丙烯酰氧乙基)吡咯烷酮](PNMP)。动力学研究表明，该RAFT聚合反应具有良好的可控性。将合成的PNMP聚合物作为大分子链转移剂，在30℃的温和可见光照射下，通过RAFT聚合，简单地合成了一系列定义良好的基于PNMP的嵌段共聚物，证实了这种RAFT聚合的活性。变温H-1核磁共振明确表明，重均相对分子质量(M-w)为105.4 kgmol(-1)、多分散指数(M-w/M-n)为1.11的PNMP聚合物在常温下(如22℃)以分子形式溶解在D2O中，随着溶液温度的升高，这种完全水合的PNMP聚合物的脱水过程在46.1C被触发，导致PNMP的质子共振信号与D2O的积分比急剧下降。进一步将溶液温度提高到51.9摄氏度，导致PNMP聚合物从水溶液中急剧相分离。激光光散射分析表明，PNMP聚合物的浊点随分子量的增加而降低，分子量在20.6-105.4 kg摩尔(-1)范围内。此外，这种PNMP聚合物在水溶液中表现出显著的可逆热响应性脱水/水化和相变行为。与在PNIPAM水溶液中观察到的不同，PNMP水溶液在一次加热和冷却循环中没有观察到滞后现象。
A well-defined pyrrolidone based thermoresponsive polymer, poly [N-(2-methacryloyloxyethyl) pyrrolidone] (PNMP), was synthesized via reversible addition-fragmentation chain transfer radical polymerization or RAFT polymerization of N-(2-methacryloyloxyethyl) pyrrolidone monomer in methanol under a mild visible light radiation at 30 degrees C. The average molecular weights and polydispersity indices of PNMP polymers were characterized by gel permeation chromatography (GPC) and static light scattering analysis. The kinetic studies indicated that this RAFT polymerization exhibited a well-controlled behavior. The living character of this RAFT polymerization was confirmed by the facile synthesis of a series of well-defined PNMP-based block copolymers via RAFT polymerization under this mild visible light radiation at 30 degrees C using the above-synthesized PNMP polymer as a macromolecular chain transfer agent. Temperature-variation H-1 NMR unambiguously revealed that the PNMP polymer with weight-average molecular weight (M-w) of 105.4 kg mol(-1) and polydispersity index (M-w/M-n) of 1.11 was molecularly dissolved in D2O at ambient temperature, e.g. 22 degrees C. Upon elevating the solution temperature, the dehydration process of this fully hydrated PNMP polymer was triggered at 46.1 degrees C, leading to a dramatic decrease of integral ratios of proton resonance signals of PNMP to that of D2O. Further elevating the solution temperature to 51.9 degrees C led to a sharp phase separation of PNMP polymer from aqueous solution. Laser light scattering analyses demonstrated that the cloud point of the PNMP polymer decreased with molecular weight in the M-w range of 20.6-105.4 kg mol(-1). Moreover, this PNMP polymer exhibited a remarkably reversible thermoresponsive dehydration/hydration and phase transition behaviors in aqueous solution. Unlike what was observed in PNIPAM aqueous solution, no hysteresis phenomenon was observed in PNMP aqueous solution during one heating-and-cooling cycle.