Ultra-high molecular weight polymer synthesis via aqueous dispersion polymerization

Abstract

The synthesis of ultra-high molecular weight (UHMW, Mn ≥ 106 g mol−1) polymers is generally complicated by the high viscosity of the resulting polymer solution. We report the synthesis of UHMW double-hydrophilic block copolymers (DHBCs) by leveraging polymerization-induced self-assembly (PISA) to obtain concentrated but free-flowing dispersions of UHMW water-soluble particles. By polymerizing N-acryloylmorpholine (NAM) from a poly(N,N-dimethylacrylamide) (PDMA) macroiniferter in the presence of a kosmotropic salt ((NH4)2SO4), the salt sensitivity of the resultant poly(NAM) (PNAM) block induced self-assembly to result in free-flowing dispersions of polymeric particles (η < 6 Pa·s), despite the UHMW and high concentration of the newly formed block copolymer. To retrieve the UHMW polymer products, simple dilution with water lowered the (NH4)2SO4 concentration sufficiently to resolubilize the PNAM chains, affording a highly viscous solution of fully dissolved DHBCs. The simplicity of this synthetic route has important implications for the facile production of UHMW materials on an industrial scale.