Grant: Discovery Grants Program - Individual

The remarkable progress in the understanding of the rheology of branched and hyperbranched macromolecules have been catalyzed by the ability to synthesize well-defined polymers of complex architectures. Developing functionalized polymers is an important and challenging theme, especially in the research and development of polyolefins. The presence of functional groups in the non-polar polyolefin chains imparts functionalized polyolefins with some enhanced materials properties such as toughness, barrier properties, surface properties, miscibility with other polar polymers, etc. One potential area of interest is to combine catalytic olefin polymerization with successive living/controlled polymerization of polar monomers (such as anionic polymerization, atom transfer radical polymerization or ATRP, nitrogen-mediated radical polymerization or NMRP, and reversible addition fragmentation techniques or RAFT) to prepare functionalized polyolefins containing blocks of functional comonomer and having well-defined architectures such as star-shaped, comb-shaped, and block olefin copolymers. The primary focus of this proposal will be development and rheological behavior of chain-topology-controlled functionalized hyperbranched polymers (HBP) that have unique dendrimer-like branched structure with lack of chain entanglements, resulting in dramatically reduced melt viscosity. The objectives of the proposed research are (a) to synthesize hyperbranched polyolefins containing blocks of functional comonomer having well-defined architectures and block olefin copolymers catalyzed by novel functionalized catalysts using controlled free radical polymerization with successive living/controlled polymerization of polar monomers, (b) to characterize the synthesized polymers, and (c) to study the linear rheological properties of the synthesized polymers and relate it to the topology by combining different models of relaxation with the concept of hierarchical motion.