(6by) Structure, Deformation, and Flow of Soft Materials

Soft materials are the basic components of biological systems and form an integral part of our modern lifestyle. Advances in the design of supramolecular systems that can mimic the structure of innate biological matter and recent progress in the synthesis of polymers for display and lighting technologies (light-emitting polymers), together with the advancements in the ability to design and assemble materials such as colloids, hydrogels, molecular electrolytes, and polymeric lubricants demonstrate that soft materials will rapidly become the foundation of future devices and applications in medicine, energy, and electronics. Simulations and theory have an important role in guiding this emerging field by assisting the design of soft materials and accurately evaluating their properties as well as providing predictions of their behavior in applications. I have explored the fundamental physics associated with the structure, deformation and flow of soft materials by examining a number of model soft-matter systems such as flexible membranes, colloidal suspensions, polymeric lubricants, and electrolytic solutions. At the same time, I have evaluated the prospects of these systems as applied materials.

I have demonstrated how long-range repulsive interactions can be used as a tool to manipulate shapes of soft membranes formed in emulsions and synthetic nanocontainers by tuning environmental conditions such as the electrolyte concentration. The proposed shell-design mechanism can be used as a template to synthesize nanoparticle-based drug-delivery carriers, and it can help understand shape changes in micelles and emulsions that form during metal-extraction processes. I have developed a variational formulation and an associated simulation procedure that can accurately and efficiently predict the structural and dynamical behavior of ions in biological and synthetic materials that often exhibit varying dielectric response. Applications of this method accurately described the non-monotonic structural features in the ionic density near dielectric surfaces and showed how these features can significantly alter the inter-surface interactions. I have also advanced our understanding of flow in disordered systems which many soft materials can be identified as. I investigated the shear-thinning response of simple binary Lennard-Jones fluids and lubricant squalane over a wide range of strain rates and uncovered the underlying mechanism responsible for shear thinning as the systems are driven through the glass transition. In addition, I showed the shortcomings of methods such as time-temperature superposition that are frequently employed to understand such phenomena. These results are important to models of elastohydrodynamic lubrication and will be useful in superior polymeric lubricant design.

My poster will present the key aspects and results of my research summarized above along with an outline of future projects which will use the aforementioned investigations as a platform. A few questions that I anticipate will influence my future project designs include: Given a particular set of tunable environmental parameters and constraints, what are the typical morphologies that can be tailored in a soft material? How does a soft material adapt to changes in its shape and composition; are there ways to make the material more robust and/or functional by controlling its environmental properties such as pH or salt concentration? How can we accurately extract and then efficiently exploit the dynamical behavior of soft materials that are often amorphous in nature and are characterized with rheological properties that lie in between liquids and solids? In the investigations of these problems I envision the development and application of both computational and theoretical methods that will encompass a wide range of concepts from statistical mechanics, supramolecular chemistry, electrostatics, polymer science, and rheology.