Interactions and Self-Assembly of Particles in Complex Fluids

University Of Texas At Austin, Austin TX

Investigators

Abstract

This award supports theoretical and computational research on complex fluids. The PI aims to combine field-theoretic and particle-based approaches to develop hybrid simulation tools that can be used to study the thermodynamics and self-assembly of particles in complex fluids. These hybrid techniques can account for the disparate length scales accompanying particle dispersions in complex fluid media, while efficiently incorporating steric and short-range interactions. Two classes of studies and tools are proposed: (1) Field-Theoretic Simulations (FTS), an approach recently developed by the PI, will be used to systematically evaluate the interactions between particles of arbitrary geometries in different complex fluids. The results may yield fundamental insights into the different factors that influence fluctuation-induced forces, in particular, their nonpairwise additive nature, as well as the interplay between energetic (arising from a physical interaction between the complex fluid and the surface of the particle) and entropic interactions. The results from these studies will also be used in effecting an in vacuo simulation of the particles, in order to glean insights into the self-assembly features of the particles. (2) The PI will develop a hybrid multibody simulation approach to the self-assembly of particles in complex fluids. A combination of FTS and mean-field equations for the fields at every step determines the effective interactions between the rigid units. These effective interactions will be used to "evolve" the rigid units through a particle-based simulation. The studies are aimed to clarify the role of multibody interactions, nonpairwise additivity of forces and excluded volume interactions in modulating the self-assembly of a variety of mixtures of complex fluids and particles. The research will be effected in the context of studies of the interactions and self-assembly in polymer-particle mixtures, charge stabilized colloidal dispersions, and multiblock rod-coil copolymers. These are ideal model systems in which to study effects pertaining to fluctuations, self-assembly, and dynamics. Each of these can be tuned independently and in a controlled way by tailoring the synthesis conditions. This capability allows for a synergistic interaction with experimental studies to compare predictions and experiments. In each of these model systems, the PI plans to carry out studies, linked by a common objective, to discern the self-assembly arising from a competition between steric and energetic interactions, as well as the interplay between nematic/smectic ordering, crystallization and microphase separation. The successful implementation of these hybrid simulation approaches is expected to have significant impact on the development of multiscale computational approaches to the design of advanced materials. %%% This award supports theoretical and computational research and education on complex fluids. The PI aims to combine distinct and powerful computational approaches to develop hybrid simulation tools that can be used to study the thermodynamics and self-assembly of particles in complex fluids. These tools will be used to study the interactions and self-assembly in polymer-particle mixtures, charge stabilized colloidal dispersions, and multiblock rod-coil polymers to elucidate important issues in the physics of complex fluids. The simulation tools also contribute to efforts to use theoretical methodology to predict the morphological characteristics and properties of advanced materials that result from specific molecular parameters. ***