微凝胶引起的胶体分散体系的固—液转变

赵传壮+袁光萃+韩志超

摘 要：该报告中以PS微球和PNIPAM微凝胶的混合分散液为研究对象，细致地考察了这种硬球和软球的混合分散液的凝胶化和玻璃化的行为，其主要结论包括：（1）随着微凝胶浓度的上升，PS微球先通过微凝胶的桥联而聚集，然后又被足量的微凝胶所稳定，最后被游离的微凝胶产生的渗透压推动产生聚集，因此出现了混合分散液从桥联凝胶到液体到耗尽效应的凝胶的转变；（2）由于PNIPAM微凝胶在高温下的收缩，微球表面在高温下比在低温下可以吸附更多的微凝胶，改变温度导致吸附了微凝胶的微球的聚集方式和凝胶化方式发生变化，这一结果同时也说明PS微球之间的桥联键是“动态”的。

关键词：微凝胶 短程吸引 胶体 液体-凝胶转变

Abstract：The mechanism of solid-liquid transition of colloidal suspension is of great importance in the development of many industrial fields， and is also an important question in fundamental area such material science， life science and condensed-matter physics. The study on this subject will help us finally understand the nature of disordered solid such as gel and glass. In this report， we studied the gelation and glass transition of PS microsphere and PNIPAM microgel mixed suspension. With the increasing of the concentration of PNIPAM microgel， the microspheres are firstly bridged by the adsorptive microgel， then are stabilized by the adsorptive microgel， and finally are aggregated due to osmotic pressure of the free microgels. Theregore， the mixed suspension gelates through bridging mechanism or depletion mechanism depending on whether the microgel concentration was lower or higher than the concentration of saturation adsorption. Due to the shrinking of the microgel at high temperature， the aggregation of the microsphere and the gelation of the mixed suspension is strongly influenced by the temperauture. It was also founded that the bridging bonds between the microspheres are dynamic bonds.

Key Words：Microgel； Short-range attraction； Colloid； Liquid-gel transition

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