GLASS TRANSITIONS IN CONFINED GEOMETRY AND DYNAMICAL CROSSOVER OF POLYMER CHAIN DYNAMICS

1)用介电弛豫谱研究了顺式-1，4-聚异戊二烯（PIP）薄膜的动力学过程.在PIP薄膜中，可以观察到α过程和正常模式的动力学。α过程与玻璃化转变有关，正常模式是整个聚合物链的运动（爬行动力学）。目前的测量结果表明，α-过程的动态几乎保持不变，减少膜厚度。另一方面，正常模式的动力学通过共存状态转变为另一种更快的动力学。这一结果意味着，在膜内有一些区域的聚合物的有效链长是较短的原始链长，和这样的区域的贡献，通过介电弛豫光谱观察到的弛豫动力学变得更加显着，随着膜厚度的减小。2）在聚甲基丙烯酸甲酯（PMMA）薄膜中，我们可以观察到α-过程动力学的立构规整度依赖性，而β-过程动力学的立构规整度依赖性则没有观察到。此外，α-过程的立构规整度依赖性随着膜厚度的减小而变弱。这一结果表明立构规整度序列的长度尺度与α-过程的特征长度之间存在竞争。3）研究了PMMA玻璃态在低于玻璃化转变温度下的老化动力学。可以观察到令人惊讶的记忆和恢复效果。这表明，不仅对于聚合物玻璃，而且对于自旋玻璃，存在着普遍的老化动力学物理规律。为了理解玻璃化转变的机制，应该阐明普遍的行为。为此，在JSPS Kakenhi的支持下，一个新项目刚刚开始。

1) The dynamics of thin films of cis-1, 4-polyisoprene (PIP) has been investigated by using dielectric relaxation spectroscopy. In thin films of PIP, dynamics of alpha-process and normal mode can be observed. The alpha-process is related to glass transitions and the normal mode is the motion of entire polymer chains (reptation dynamics). The present measurements show that the dynamics of the alpha-process remains almost unchanged with decreasing film thickness. On the other hand, the dynamics of the normal mode changes into another faster dynamics via a coexistent state. This result implies that within the films there are some regions where the effective chain length of polymers is shorter that the original chain length, and that the contributions of such regions to relaxation dynamics observed by dielectric relaxation spectroscopy become more significant with decreasing film thickness. As a result, the crossover of dynamics from the normal mode to another faster mode could be observed.2) In thin films of poly (methyl methacrylate) (PMMA), we could observe the tacticity dependence of the dynamics of alpha-process, while no tacticity dependence of the beta-process could be observed. Furthermore, the tacticity dependence of alpha-process becomes weaker with decreasing film thickness. This result suggests that there is a competition between the length scale of tacticity order and the characteristic length of the alpha-process.3) The aging dynamics below the glass transition temperature has been investigated for the glassy states of PMMA. Surprising memory and rejuvenation effects could be observed. This suggests that there is a universal physical law of aging dynamics not only for polymer glasses but also for spin glasses. The universal behavior should be elucidated in order to understand the mechanism of glass transitions. For this purpose, a new project has just started under the support from JSPS Kakenhi.