Nanosecond-Milisecond Dynamics of Phase Transition/Phase Separation of Thermo-Responsive Polymers.

我们想要证明激光是探索刺激响应性聚合物化学的强大工具。本研究的主要目标材料是具有代表性的热响应聚合物聚N-异丙基丙烯酰胺(PNIPAM)和聚乙烯基甲基醚(PVME)。在水溶液中，它们表现出从盘绕状态到球状状态的相变，然后根据较低临界溶液温度的升高进行相分离。本研究分为两类。第一个主题是(I)用激光T跳跃技术揭示的相变和相分离的动力学。测定过程的时间常数精度较高，且与聚合物的相对分子质量有很好的相关性。第二个主题是(II)聚焦激光束的光子压强引起的相变和相分离。将光学显微光谱与激光捕获技术相结合应用于聚合物，并详细分析了聚合物在光子压力作用下的局域结构。激光将是一种耐人寻味的、新颖的聚合物刺激。

We would like to demonstrate that laser is a powerful tool to explore chemistry of stimuli-responsive polymers. Main target materials of the present study are poly(N-isopropylacrylamide) (PNIPAM) and poly(vinyl methyl ether) (PVME) that are well known as representative thermo-responsive polymers. In aqueous solution, they exhibits phase transition from a coiled state to a globular state followed by phase separation in accordance to temperature elevation across the lower critical solution temperature. The present study falls into two categories. The first topic is (I) Dynamics of phase transition and phase separation as revealed by a laser T-jump technique. Time constants of the processes were determined with high accuracy and they were well correlated with molecular weight of the polymers. The second topic is (II) phase transition and phase separation induced by photon pressure of a focused laser beam. Optical micro-spectroscopy combined with laser-trapping technique was applied to the polymers and local structures of the polymer exerted with photon pressure were analyzed in details. Laser light would be an intriguing and novel stimulus to the polymers.