Investigation of the Origin and The Domain Growth Mechanism of Viscoelastic Phase Separation

粘弹性相分离的起源和域增长机制的研究

基本信息

批准号：
12440109
负责人：
TANAKA Hajime
金额：
$ 8.9万
依托单位：
The 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：
2000
资助国家：
日本
起止时间：
2000 至 2001
项目状态：
已结题

来源：
https://kaken.nii.ac.jp/en/grant/KAKENHI-PROJECT-12440109/
关键词：
viscoelastic phase separation polymer solution molecular weight dependence tansient gel destructiion pallem concentriation dependence Quench depth dependence dynamic asymmotry

项目摘要

This study aims at revealing the overall features of viscoelastic phase separation of polymer solutions on a quantitative level. In particular, we focus on how the molecular weight of polymer affects the phase-separation behavior of a polymer solution. We found that the formation of a transient gel plays a crucial role in viscoelastic phase separation.We study how viscoelastic phase separation proceeds in a macroscopic length scale, focusing on the similarity and difference between a transient gel and a permanent gel. We found that upon phase separation the volume of the polymer-rich phase shrinks as in the volume-shrinking of chemical gel. However, a transient gel keeps deforming after the volume shrinking and relaxes to a shape determined by the interface tension. In other words, a transient gel behaves as a fluid in the final stage. This is fully consistent with what we observed with microscopy. We also found that just at the time when a transient gel stops shrinking, the transparency of the polymer-rich phase also changes drastically. This indicates that the internal phase-separated structure changes drastically at that time. This behavior should be induced by the transformation of the polymer-rich phase from an elastic body to a fluid, which makes it difficult for the polymer-rich phase to support its own weight. We also found that the characteristic time when the polymer-rich phase starts to loose its elastic properties increases in proportional to the quench depth. The temperature which this time becomes zero coincides well with the temperature below that a transient gel appears, Tt, which support our picture.This study clearly indicates the similarity between phase separation in polymer solutions and volume phase transition in polymer gels. This fact is important in understanding not only viscoelastic phase separation, but also the static and dynamic phase behavior of polymer solutions.

这项研究旨在揭示聚合物溶液在定量水平上的粘弹相分离的总体特征。特别是，我们关注聚合物的分子量如何影响聚合物溶液的相分离行为。我们发现瞬态凝胶的形成在粘弹性相分离中起着至关重要的作用。我们研究粘弹相分离如何以宏观长度尺度进行，重点是瞬态凝胶与永久凝胶之间的相似性和差异。我们发现，在相位分离时，富含聚合物的相的体积像化学凝胶的体积缩短一样收缩。但是，瞬态凝胶在体积收缩后不断变形并放松到由界面张力确定的形状。换句话说，瞬态凝胶在最后阶段表现为流体。这与我们在显微镜下观察到的完全一致。我们还发现，在瞬时凝胶停止收缩时，富含聚合物相的透明度也发生了巨大变化。这表明当时内相分离的结构发生了巨大变化。这种行为应是通过从弹性体到流体的富含聚合物相的转化来引起的，这使得富含聚合物的相很难支持其自身的重量。我们还发现，富含聚合物相的特征时间与淬灭深度成正比增加了其弹性特性的增加。这段时间零的温度与瞬时凝胶的温度很好，TT支持我们的图片。这项研究清楚地表明了聚合物溶液中相位分离与聚合物凝胶中体积相变的相似性。这个事实对于不仅理解粘弹性相分离至关重要，而且还要理解聚合物溶液的静态和动态相行为。