Entropy Driven Ordering in Colloidal Suspensions

这个新项目的目标是加深对(1)胶体的液晶有序性和(2)棒状和球形胶体混合物的相行为的基本理解。这些相互关联的项目涉及在三个层面上了解胶体物理，粒子及其相互作用的微观层面，有序相形成的介观层面，以及材料性质的宏观层面。我们研究的胶体的粒间势主要由空间和短程排斥相互作用决定，因此可以作为硬粒子悬浮的实验模型，其中相行为完全由熵决定。胶体具有良好的特性和均匀的颗粒，由于有一个了解其相行为的既定理论框架，因此我们对这些特殊体系的了解对于基本理解液晶、胶体聚合物混合物、蛋白质结晶和细胞内环境的生物物理以及分子有序性和自组装非常重要的复合材料的设计具有重要意义。这个新项目将对两个系统的结构、动力学和相行为进行一系列研究，(1)棒和球的胶体混合物，(2)棒的胶体悬浮液。我们研究的胶体的粒间势主要由空间和短程排斥相互作用决定，因此可以作为硬粒子悬浮的实验模型，其中相行为完全由熵决定。硬粒子理论是理解所有流体的基础，尤其是捕捉胶体悬浮液相行为的基本特征。胶体的研究很好地表征了均匀的颗粒，由于已经建立了了解其相行为的理论框架，因此我们对这些特殊体系的了解对于理解液晶、胶体-聚合物混合物、蛋白质结晶和生物细胞环境的基本性质以及分子自组装非常重要的新型材料的设计具有重要意义。***

w:\awards\awards97\fraden5336.doc 9705336 Fraden The objective of this new project is to develop fundamental understanding of (1) liquid crystal ordering of colloids, and (2) the phase behavior of mixtures of rodlike and spherical colloids. These inter-related projects involve understanding of the physics of colloids at three levels, the microscopic level of the particles and their interaction, the mesoscopic level of ordered phase formation, and the macroscopic level of materials properties. The interparticle potentials of the colloids we study are dominated by steric and short-range repulsive interactions, and thus serve as experimental models of hard particle suspensions, where phase behavior is determined solely by entropy. The colloids are well characterized, uniform particles and since there is an established theoretical framework for understanding their phase behavior, what we learn about these particular systems has implications for the fundamental understanding of liquid crystals, colloid - polymer mixtures, protein crystallization, and the biophysics of the intracellular environment, as well as the design of composite materials where molecular ordering and self-assembly is important. %%% This new project will carry out a series of studies of the structure, dynamics, and phase behavior of two systems, (1) colloidal mixtures of rods and spheres, and (2) colloidal suspensions of rods. The interparticle potentials of the colloids we study are dominated by steric and short-range repulsive interactions, and thus serve as experimental models of hard particle suspensions, where phase behavior is solely determined by entropy. Hard particle theories serve as a basis for the understanding of all fluids, and in particular capture essential features of the phase behavior of colloidal suspensions. The colloids w e study are well characterized, uniform particles and since there is an established theoretical framework for understanding their phase behavior, what we learn about these particular systems has implications for the understanding of fundamental properties of liquid crystals, colloid - polymer mixtures, protein crystallization, and the biological cellular environment, as well as for the design of novel materials where molecular self- assembly is important. ***