Phase separation dynamics of aqueous solutions of thermoresponsive polymers studied by a laser T-jump technique.
Phase separation dynamics of aqueous solutions of thermoresponsive polymers studied by a laser T-jump technique.
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DOI：
10.1021/jp711128s
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发表时间：
2008-02
期刊：
影响因子：
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通讯作者：
Yasuyuki Tsuboi;Y. Yoshida;K. Okada;N. Kitamura
中科院分区：
文献类型：
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作者：
Yasuyuki Tsuboi;Y. Yoshida;K. Okada;N. Kitamura
聚（N-异丙基丙烯酰胺）和聚（乙烯基甲基醚）是公知的温敏聚合物。这些聚合物的水溶液在LCST约305-310 K时表现出相转变，然后相分离。在本研究中，相分离的动态行为进行了分析，通过激光T-跳跃方法。采用两种不同的T-跳跃方法：第一种是使用532 nm激光脉冲的染料光敏T-跳跃技术（间接加热），而另一种是使用1.2 μ m激光脉冲的直接加热T-跳跃技术。两种方法得到了相似的结果。系统地测定了1- 10wt%聚合物水溶液的相分离时间常数（τ），并清楚地观察到τ的流体动力学半径（R）依赖性。τ值随R的平方增加而线性增加。目前的行为是可以解释的Tanaka的凝胶的体积相变模型的框架中，因为每个聚合物链纠缠在本样品溶液中，这可以被视为近似于溶液中的凝胶。
Poly(N-isopropylacrylamide) and poly(vinyl methyl ether) are well-known thermoresponsive polymers. The aqueous solutions of these polymers exhibit a phase transition followed by phase separation with LCST approximately 305-310 K. In the present study, the dynamic behavior of the phase separation was analyzed by a laser T-jump method. Two different T-jump methodologies were employed: the first was a dye-photosensitized T-jump technique (indirect heating) using 532 nm laser pulses, while the other was a direct heating T-jump technique using 1.2 mum laser pulses. Both methods gave similar results. The time constants (tau) of the phase separation were systematically determined for 1-10 wt % aqueous solutions of the polymers, and a hydrodynamic radius (R) dependence for tau was clearly observed. The values of tau increased linearly with increasing square of R. The present behavior is interpretable in the framework of Tanaka's model for the volume phase transition of a gel, since each of the polymer chains are entangled in the present sample solutions, which can be regarded as approximating to a gel in solution.