Universality of Viscoelastic Phase Separation and its application to the material design

粘弹性相分离的普遍性及其在材料设计中的应用

基本信息

批准号：
08455007
负责人：
TANAKA Hajime
金额：
$ 5.25万
依托单位：
University of Tokyo
依托单位国家：
日本
项目类别：
Grant-in-Aid for Scientific Research (B)
财政年份：
1996
资助国家：
日本
起止时间：
1996 至 1997
项目状态：
已结题

项目摘要

We have improved a general model of phase separation in isotropic condensed matter, namely, a viscoelastic model. We propose that the bulk mechanical relaxation modulus that has so far been ignored in previous theories plays an important role in viscoelastic phase separation in addition to the shear relaxation modulus. In polymer solutions, for example, attractive interactions between polymers under a poor-solvent condition likely cause transient gel-like behavior, which makes both bulk and shear modes active. Although such attractive interaction between molecules of the same component exist universally in the two phase region of a mexture, the stress arising from attractive interactions is asymmetrically diveded between the components only in dynamically asymmetric mixtures such as polymer solutions and colloidal suspensions. Thus the interaction network between the slower components, which can store the elastic energy against its deformation through bulk and shear moduli, is formed. This unique feature originates from the difference in mobility between two components of a mixture. It is the bulk relaxation modulus associates with this interaction network that is primarily responsible for the appearance of the sponge structure to viscoelastic phase separation and the phase inversion. It suppresses short-wavelength concentration fluctuation in the initial stage, and causes the volume shirinking of a more viscoelastic phase. We also propose a simple general law of stress division between the two components of a mixture, as a straightforward extension including this new effect is a general model that can describe all types of isotropic phase separation. The physical origin of volume shrinking behavior during viscoelastic phase separation and the universality of the resulting sponge like structure are also discussed.

我们改进了各向同性凝聚态相分离的通用模型，即粘弹性模型。我们提出，除了剪切松弛模量之外，迄今为止在先前理论中被忽略的体积机械松弛模量在粘弹性相分离中也发挥着重要作用。例如，在聚合物溶液中，贫溶剂条件下聚合物之间的吸引相互作用可能会导致短暂的凝胶状行为，从而使本体和剪切模式都变得活跃。尽管同一组分的分子之间的这种吸引相互作用普遍存在于混合物的两相区域中，但仅在动态不对称混合物（例如聚合物溶液和胶体悬浮液）中，由吸引相互作用产生的应力在组分之间不对称地分配。因此，形成了较慢组件之间的相互作用网络，该网络可以通过体积模量和剪切模量存储弹性能以抵抗其变形。这种独特的特性源于混合物中两种成分之间的流动性差异。与该相互作用网络相关的体积松弛模量是造成海绵结构出现粘弹性相分离和相转化的主要原因。它抑制了初始阶段的短波长浓度波动，并导致更粘弹性相的体积收缩。我们还提出了混合物两种成分之间应力分配的简单一般定律，作为包括这种新效应的直接扩展，是可以描述所有类型的各向同性相分离的通用模型。还讨论了粘弹性相分离过程中体积收缩行为的物理起源以及所得海绵状结构的普遍性。