(582c) Synthesis and Characterization of Cyclic Poly(vinylmethylsiloxane)-b-Poly(methyl methacrylate)s

Cyclic polymers exhibit physical properties that differentiate them from linear counterparts, including lower viscosity/greater chain mobility, lack of glass transition temperature depression in thin films, and potentially enhanced thin film stability at equivalent molecular weights. Cyclic block copolymers (BCPs) also exhibit nanostructure domain sizes 20-50% smaller than linear counterparts of equivalent molecular weight. In this work, we synthesize and characterize the nanoscale self-assembly of cyclic poly(vinylmethylsiloxane-block-methyl methacrylate)s (c-PVMS-b-PMMAs), using theoretical calculations of the Flory-Huggins interaction parameter and dissipative particle dynamics simulations of domain spacing scaling laws as guides to select synthetic targets. c-PVMS-b-PMMA synthesis involved first independently synthesizing bifunctional PVMS and PMMA homopolymers and then cyclizing these homopolymers using copper-catalyzed azide-alkyne click coupling under highly dilute conditions to form a block copolymer. PVMS was prepared by anionic polymerization and PMMA by atom transfer radical polymerization (ATRP); both synthesis schemes involved initiation from a bifunctional initiator. We explored various cyclization conditions and evaluated the outcomes of the cyclization reaction with different molecular weight homopolymers in an effort to minimize the generation of linear impurities in the final reaction product; additionally, we characterized the types of impurities present in the cases where they could not be eliminated.