Phase Behavior of Colloidal Suspensions of Rods and Spheres

本研究主要研究棒状胶体、棒状胶体与球形胶体混合物的相行为。棒状胶体的生物学例子包括肌动蛋白和微管、DNA和丝状病毒等蛋白质。在这项工作中感兴趣的棒状胶体由基因工程丝状噬菌体FD病毒组成。球形粒子是聚苯乙烯胶乳或水溶性聚合物，如聚环氧乙烷。从这些具有良好特性的材料中获得的知识对于基本理解液晶、胶体-聚合物混合物、细胞内环境的生物物理以及分子有序和自组装非常重要的复合材料的设计具有重要意义。主要目标将是确定纯棒悬浮液的液晶相的基本性质，然后是棒和球的混合物、不同长度的棒的混合物以及不同直径的棒的混合物。具体地说，将得到棒状胶体的角分布函数、共存浓度和维里系数。这些实验旨在确定吸引和排斥在控制相行为中的作用，以及探索在前一次NSF拨款期间在棒和球的混合物中发现的进一步丰富和意想不到的微相行为。将研究棒状和球状混合物中的相变动力学，包括亚稳相的鉴定。最后，将研究被视为示踪剂的单个棒和球的动力学。参与研究的学生接受跨学科培训，为他们在学术界、工业和政府的各种职业做好准备。%本研究的重点是确定棒状胶体以及棒状胶体和球形胶体的混合物所表现出的物质状态。棒状胶体虽然比球形胶体研究得少，但却具有相当重要的意义。杆状胶体的生物学例子是蛋白质，如肌动蛋白和微管、DNA和丝状病毒。本项目中研究的棒状胶体由基因工程丝状噬菌体FD病毒组成。对于球体，使用众所周知的聚苯乙烯乳液或水溶性聚合物聚环氧乙烷。所有这些胶体都是表征良好的、均匀的颗粒，对于这些颗粒，存在着理解其相行为的既定理论框架。对这些特殊体系的了解对基本理解液晶、胶体-聚合物混合物、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。这项研究是化学、生物学和物理学的交叉学科。生物分子和过程越来越多地被理解在机械水平上，物理学在理解非平衡和无序系统方面取得了重大进展。因此，这两个传统上相距甚远的领域正迅速向对方发展。参与研究的学生接受跨学科培训，为他们在学术界、工业界和政府部门的各种职业做好准备。

This research focuses on determining the phase behavior of rodlike colloids, and mixtures of rodlike and spherical colloids. Biological examples of rodlike colloids include proteins such as actin and microtubules, DNA, and filamentous viruses. The rodlike colloids on interest in this work consist of genetically engineered filamentous phage fd virus. The spherical particles are , either polystyrene latex or water soluble polymers such as poly(ethylene) oxide. Knowledge gained from these well characterized materials has implications for the fundamental understanding of liquid crystals, colloid-polymer mixtures, and the biophysics of the intracellular environment, as well as the design of composite materials where molecular ordering and self-assembly is important. A primary goal will be determining fundamental properties of the liquid crystalline phase of pure rod suspensions, then mixtures of rod and spheres, mixtures of rods of different lengths, and mixtures of rods of different diameters. Specifically, the angular distribution function of the rodlike colloids, co-existence concentrations, and virial coefficients will be obtained. These experiments are designed to determine the roles of attraction and repulsion in governing phase behavior, as well as to explore further rich and unexpected microphase behavior discovered in mixtures of rods and spheres during the previous NSF grant. The kinetics of phase transformation in mixtures of rods and spheres will be examined, including the identification of metastable phases. Finally, the dynamics of individual rods and spheres seen as tracers will be studied. Students participating in the research receive interdisciplinary training that will prepare them for a variety of careers in academe, industry, and government.%%%This research focuses on determining the states of matter exhibited by rodlike colloids and by mixtures of rodlike and spherical colloids. Rodlike colloids, though less studied than spherical colloids, are of considerable importance. Biological examples of rodlike colloids being proteins such as actin and microtubules, DNA, and filamentous viruses. The rodlike colloids studied in this project consist of genetically engineered filamentous phage fd virus. For spheres, the well known polystyrene latex or water soluble polymer poly(ethylene) oxide are employed. All these colloids are well characterized, uniform particles for which an established theoretical framework exists for understanding their phase behavior. What is learned about these particular systems has implications for the fundamental understanding of liquid crystals, colloid-polymer mixtures, the biophysics of the intracellular environment, as well as the design of composite materials where molecular ordering and self-assembly is important. This research lies at the intersection of chemistry, biology, and physics. Biological molecules and processes are increasingly being understood at a mechanistic level, and physics is making significant gains in understanding non-equilibrium and disordered systems. Thus these two fields, which traditionally have been widely separated, are swiftly growing towards each other. Students participating in the research receive interdisciplinary training that will prepare them for a variety of careers in academe, industry, and government.