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

自从Inoue等人在侧链型聚硅氧烷液晶聚合物（LCP）和二甲基硅氧烷（DMS）的共混物中观察到大的电流变（ER）效应以来，我们一直在进行深入的研究以阐明其机理。到目前为止，我们已经阐明了由高粘度的LCP液滴分散在低粘度的DMS中组成的聚合物共混物的基本机理，其在电场下拉伸和聚结以在电极之间形成桥，本文通过测量剪切应力和透射比，研究了在剪切流中施加阶跃电场后的瞬态过程。同时，通过样品的强度。结果发现，瞬态过程由两种模式组成;施加磁场后，应力急剧增加（第一种模式），然后缓慢增加（第二种模式）。从这个结果和高速摄像机的观察中，我们得出结论：第一种模式对应于液滴的拉伸和电极之间桥的形成，第二种模式对应于桥的生长。此外，我们还对液滴在电场和剪切流作用下的变形进行了计算机模拟，阐明了聚合物共混物中电流变效应的机理。根据所获得的结果，在不久的将来将开发出适用于实际器件的电流变液。

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.