Selective Fundamental Problems in Supramolecular Assembly and Phase Stability of Homopolymer Mixtures

University Of Chicago, Chicago IL

Investigators

Abstract

Karl Freed at the University of Chicago is supported by an award from the Chemical Theory, Models and Computational Methods Program to study self-assembly and related phenomena. Equilibrium self-assembly involving the spontaneous organization of molecules into larger structures that show order is a ubiquitous phenomenon pervading chemistry, materials science, and biology. Hence, the ability to control this self-assembly has numerous applications for industry and medicine. The vast array of complex functional structures formed through equilibrium self-assembly suggests that an understanding of the underlying principles can be transformative in designing truly novel materials and medical therapies. This has motivated numerous advanced experimental studies of synthetic self-assembling systems such as nanoparticles, peptides and DNA complexes, the development of transformative strategies for synthesis of macromolecular systems, the synthesis of supramolecular systems with specific properties, and computer simulations of the self-assembly of molecular and larger-scale particles. The last is a focus of the work in the current project. The rapid growth of analytical modeling of self-assembly promises to drive applications forward as one learns to exploit the rich palette of principles, long utilized by nature, to create highly responsive and functional self-organizing and self-healing materials. These advances can greatly improve knowledge concerning diverse problems in soft matter, nanotechnology, biotechnology, medicine, and, when extended to non-equilibrium self-assembly, allow addressing basic processes such as the development of living systems and cell locomotion and communication. The current proposal represents the culmination of a long term research program devoted to developing fundamental theories for predicting thermodynamic properties of homopolymer mixtures and of solutions containing species that can associate with each other or with solvent. Both types of association lead at chemical equilibrium to the formation of clusters of variable size. The theoretical approaches are based either on extensions of Flory-Huggins (FH) theory to self-assembly or on the more detailed lattice cluster theory (LCT), which includes a description of molecular features neglected by FH theory, such as monomer size and shape, chain stiffness, and compressibility effects. The LCT has recently been extended to describe solutions of strongly interacting telechelic polymers (polymers with sticky end groups). The theory aims at elucidating the generic effects of many structurally important binding processes in living systems that are greatly influenced by surrounding chains, confining surfaces, and binding molecules (e.g., proteins that modulate the stability of assemblies). The common general mechanism of mutual association, polymer solubility and hydrophobicity stresses the fundamental nature of the proposed studies of solvation/binding. Competitive molecular binding is also of central significance in elution chromatography, materials synthesis, and biological processes. The proposed research outlines a broad theoretical framework for developing theories that can assist in the rational design of new materials, new drug systems, and physical therapies to mitigate against diseases associated with malfunctioning self-assembly.