Self-Assembly of Block Copolymer as Biomaterials

This new research project, in collaboration with Professor Jimmy Mays, University of Tennessee/ORNL Distinguished Scientist, investigates the synthesis, self-assembly, characterization, and properties of amphiphilic block copolymers as biomaterials. Block copolymers that have the potential to form micellar structures and vesicles in aqueous media are the initial focus of this work, because of their ability to compartmentalize additives into different domains, to be environmentally responsive (temperature and pH), and to encapsulate large molecules. These structures, particularly when they are based upon poly(ethylene oxide) (PEO), are of great interest in biomedicine and biotechnology for the delivery and controlled release of drugs or genes to specific targets. Living anionic and free radical polymerization techniques will be used to construct amphiphilic block copolymers. Since the impact of nonlinear block copolymer architectures, such as star blocks and comb multigrafts (see Figure 1), on the structure and properties of biomaterials has not been extensively investigated, this will be a major focus of the research. The goal of this research is to gain insight into the structure-property relationships of amphiphilic block copolymers (particularly for nonlinear architectures) so that materials can be synthesized with desired structure, properties, and function, and to develop new, potentially less demanding, synthetic methodologies for the construction of novel polymer architectures.

Initially, anionic polymerization methods will be used in the synthesis of nonlinear block copolymers based on poly(ethylene oxide) (PEO) and hydrogenated and non-hydrogenated polybutadiene (PBD). Miktoarm star polymers with compositions of (PEO)₂(PBD)₂ and (PEO)₂PBD will be synthesized, followed by more elaborate architectures. Crew-cut block copolymers, in which the insoluble block is longer than the soluble block, composed of polystyrene and poly(acrylic acid) will also be synthesized by living radical polymerization methods, such as atom transfer radical polymerization (ATRP) and nitroxide-mediated radical polymerization. The impact of core structure and branching on micelle formation and stability will be investigated.