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LIGHT SCATTERING STUDY OF SPINODAL DECOMPOSITION AND ELASTIC INSTABILITY OF POLYMER GELS

聚合物凝胶旋节线分解和弹性不稳定性的光散射研究

基本信息

批准号：
63540272
负责人：
HIROTSU Shunsuke
金额：
$ 1.15万
依托单位：
TOKYO INSTITUTE OF TECHNOLOGY
依托单位国家：
日本
项目类别：
Grant-in-Aid for General Scientific Research (C)
财政年份：
1988
资助国家：
日本
起止时间：
1988 至 1989
项目状态：
已结题

项目摘要

1. Dynamical mechanism of spinodal decomposition (SD) in NIPA gel. By combining multi-channel photodetectors and a personal computer, we made a time- and position-sensitive light-scattering photometer. With this apparatus, evolution of the unstable fluctuation in NIPA gel brought into an unstable region was investigated. It was found that at least two kinds of SD coexists in this gel, which were tentatively assigned as the surface SD and the bulk SD. On the basis of the Flory-type phenomenological theory, it was pointed out that three types of SD, i.e. those between swollen phase-shrunken phase, swollen phase-pure solvent, and shrunken phase-pure solvent, exist in NIPA gel. To make correspondence between the theoretical prediction and the experimental results, further detailed studies will have to be made.2. High-frequency elastic measurements by Brillouin scattering. Velocity and attenuation of hyper sound near the volume phase transition in NIPA gel were measured by means of Brillouin scattering. Large step-like anomalies in both quantities were found at the transition point.3. Evolution of patterns on the surface of gels during swelling. It was found on AA and NIPA gels that the evolution of honey-comb like pattern on gel surface follows a power law, the index of which is nearly 1.0.4. Development of a new method to impose a homogeneous uniaxial tension on gels and some measurements utilizing this technique. (1) Dependence of the volume phase transition on external stresses. (2) Measurements of softening of the bulk modulus and the negative Poisson's ratio. It is remarkable that this measurement is the first report to confirm the existence in nature of a material with negative Poisson's ratio. (3) Light-scattering measurement of the dependence of concentration fluctuation of gel network upon external stresses.

1. NIPA凝胶中独立分解（SD）的动力学机制。将多通道光电探测器与个人计算机相结合，制成了时间和位置敏感的光散射光度计。利用该装置，研究了NIPA凝胶进入不稳定区域时不稳定波动的演化过程。结果表明，该凝胶中至少存在两种类型的SD，暂定为表面SD和本体SD。根据flory型现象学理论，指出NIPA凝胶中存在膨胀相—收缩相、膨胀相—纯溶剂、收缩相—纯溶剂三种类型的SD。为了使理论预测与实验结果相吻合，还必须进行进一步的详细研究。布里渊散射的高频弹性测量。用布里渊散射法测量了NIPA凝胶在体积相变附近的声速和衰减。在过渡点发现两个量都有较大的阶梯状异常。凝胶在膨胀过程中表面图案的演变。在AA和NIPA凝胶上发现，凝胶表面蜂窝状图案的演化遵循幂律，幂律指数接近1.0.4。在凝胶上施加均匀单轴张力的新方法的发展和利用该技术的一些测量。(1)体积相变对外应力的依赖性。(2)体模量和负泊松比软化量的测量。值得注意的是，这一测量是证实自然界中存在负泊松比物质的第一份报告。(3)凝胶网络浓度波动随外应力变化的光散射测量。