Entropy Driven Ordering in Colloidal Suspensions

这个新项目的目标是发展对(1)胶体的液晶有序和(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对胶体物理的三个层面的理解，微观层面的粒子及其相互作用，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子间势由位阻和短程排斥相互作用主导，因此可以作为硬粒子悬浮液的实验模型，其中相行为仅由熵决定。胶体具有良好的特征，均匀的颗粒，由于有一个已建立的理论框架来理解它们的相行为，我们对这些特殊系统的了解对液晶，胶体-聚合物混合物，蛋白质结晶和细胞内环境的生物物理学的基本理解具有重要意义。以及复合材料的设计，其中分子有序和自组装是重要的。这个新项目将对两种系统的结构、动力学和相行为进行一系列的研究，(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子间势是由位阻和短程排斥相互作用主导的，因此可以作为硬粒子悬浮液的实验模型，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，特别是捕捉胶体悬浮液相行为的基本特征。我们研究的胶体具有很好的特征，均匀的颗粒，由于有一个既定的理论框架来理解它们的相行为，我们对这些特殊系统的了解对理解液晶的基本性质、胶体-聚合物混合物、蛋白质结晶和生物细胞环境具有重要意义。同时也适用于设计分子自组装很重要的新材料。＊＊＊

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. ***