Development of Transient Viscosity Measurement Method and Improvement of Polymer-Blended Electrorheological Fluids

自从Inoue等人观察到侧链型聚硅氧烷液晶聚合物（lps）和二甲基硅酮（DMS）的聚合物共混物中存在较大的电流变效应以来，我们一直在进行深入的研究以阐明其机理。至此，我们已经明确了高粘度LCP液滴分散在低粘度DMS中的聚合物共混物的基本机理，这些液滴在电场作用下从电极间的桥上拉伸并聚结，从而导致表观粘度的增加。本文通过测量试样的剪切应力和透射强度，研究了在剪切流作用下施加阶跃电场后的瞬态过程。结果表明，瞬态过程由两种模式组成；在施加电场后，应力急剧增加（第一模态），然后缓慢增加（第二模态）。根据这一结果和高速摄像机的观察，我们得出结论，第一模式对应于液滴的拉伸和电极之间桥的形成，第二模式对应于桥的生长。此外，我们还进行了计算机模拟来研究液滴在电场和/或剪切流下的变形。通过本项目的研究，阐明了共混聚合物中ER效应的机理。在此基础上，将在不久的将来开发出适用于实际设备的电流变流体。

Since the observation of a large electrorheological (ER) effect in polymer blends of sidechain type polysiloxane liquid crystalline polymers (LCPs) and a dimethylsilicone (DMS) by Inoue et al, we have been making an intensive investigation to elucidate the mechanism. So far, we have clarified the fundamental mechanism of the polymer blend consisting of LCP droplets with high viscosity dispersed in DMS with low viscosity, which stretch and coalesce to from bridges between electrodes under an electric field, resulting in the increase of the apparent viscosity.This year we have investigated the transient process after applying a step electric field under shear flow by measuring the shear stress and the transmitted intensity through the sample at the same time. As a result, it was found that the transient process consists of two modes ; just after applying the field the stress steeply increases (the first mode) and then slowly increases (the second mode). From this result and observations with a high speed video camera, we concluded that the first mode corresponds to the stretch of droplets and the formation of bridges between electrodes, and the second mode to the growth of the bridge. In addition, we have performed computer simulations to investigate the deformation of the droplets under an electric field and/or a shear flow.Through the present project the the mechanism of ER effect in polymer blends have been clarified. On the basis of the obtained results ER fluids applicable to actual devices will be developed in the near future.