Ultra-high molecular weight polymer synthesis via aqueous dispersion polymerization

Abstract

The synthesis of ultra-high molecular weight (UHMW, M_n ≥ 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.