UC Riverside

ABSTRACT OF THE THESIS

Designed assembly of biomimetic membrane from amphiphilic copolymers

by

Chun-Che Tseng

Master of Science in Chemical and Environmental Engineering

University of California, Riverside, March 2011

Dr. Jianzhong Wu, Chairperson

At appropriate condition amphiphilic block copolymers may self-assemble into well-organized mesoscopic structures such as micelles, vesicles, microscopic sheets and rods useful for practical applications. Vesicles of charged amphiphilic block copolymers have been utilized for fabrication of biomimetic membranes that exhibit properties similar to those of biological cell membranes but with exceptional durability and mechanical strength. Such membranes are suitable for embedding proteins/enzymes for various industrial applications.

In this work, amphiphilic block copolymers of complementary charges are used in a cascade self-assembly process that involves sequential formation of vesicles in solution and their fusion on a charged substrate. Each copolymer chain links a strong polyelectrolyte (hydrophilic) block with a hydrophobic polymer that provides the driving force of the vesicle self-assembly in an aqueous environment. Biomimetic membranes are formed by layer-by-layer deposition/fusion of oppositely charged vesicles at a strongly charged mica surface. The cascade self-assembly process allows us to have a precise control of the membrane microscopic structure, thickness and composition. We have identified optimal solution conditions for formation of various mesoscopic block copolymer structures. The morphologies of cationic and anionic block copolymer structures at dry and at wet conditions are characterized by, respectively, atomic force microscopy (AFM) and by dynamic light scattering (DLS) measurements. Moreover, the thicknesses of these biomimetic membranes on the substrate have been measured by AFM scratching experiments. While the practical utility of these biomimetic membranes is yet to be demonstrated, this work provides deeper understanding of the size variation and spreading of amphiphilic block copolymer vesicles on mica surface and the selection of appropriate conditions for membrane fabrication.