微凝膠引起的膠體分散體系的固—液轉變

趙傳壯+袁光萃+韓志超

摘 要：該報告中以PS微球和PNIPAM微凝膠的混合分散液為研究對象，細致地考察了這種硬球和軟球的混合分散液的凝膠化和玻璃化的行為，其主要結論包括：（1）隨著微凝膠濃度的上升，PS微球先通過微凝膠的橋聯而聚集，然后又被足量的微凝膠所穩定，最后被游離的微凝膠產生的滲透壓推動產生聚集，因此出現了混合分散液從橋聯凝膠到液體到耗盡效應的凝膠的轉變；（2）由于PNIPAM微凝膠在高溫下的收縮，微球表面在高溫下比在低溫下可以吸附更多的微凝膠，改變溫度導致吸附了微凝膠的微球的聚集方式和凝膠化方式發生變化，這一結果同時也說明PS微球之間的橋聯鍵是“動態”的。

關鍵詞：微凝膠 短程吸引 膠體 液體-凝膠轉變

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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