Poly(styrene/pentafluorostyrene)-block-poly(vinyl alcohol/vinylpyrrolidone) amphiphilic block copolymers for kinetic gas hydrate inhibitors: Synthesis, micellization behavior, and methane hydrate kinetic inhibition

摘要

Amphiphilic block copolymers of short poly(styrene) (PS) or poly(2,3,4,5,6-pentafluorostyrene) (PPFS) segments with comparatively longer poly(vinyl acetate) or poly(vinylpyrrolidone) (PVP) segments are synthesized using a 2-cyanopropan-2-yl N-methyl-N-(pyridin-4-yl)dithiocarbamate switchable reversible addition-fragmentation chain transfer (RAFT) agent toward application as kinetic gas hydrate inhibitors (KHIs). Polymerization conditions are optimized to provide water-soluble block copolymers by first polymerizing more activated monomers such as S and PFS to form a defined macro chain-transfer agent (linear degree of polymerization with conversion, comparatively low dispersity) followed by chain extensions with less activated monomers VAc or VP by switching to the deprotonated form of the RAFT agent. The critical micelle concentrations of these amphiphilic block copolymers (after VAc unit hydrolysis to vinyl alcohol units) are measured using zeta surface potential measurements to estimate physical behavior once mixed with the hydrates. A PS-poly(vinyl alcohol) block copolymer improved inhibition to 49% compared to the pure methane-water system with no KHIs. This inhibition was further reduced by 27% by substituting the PS with a more hydrophobic PPFS. A block copolymer of PS-PVP exhibited 20% greater inhibition than the PVP homopolymer and substituting PS with a more hydrophobic PPFS resulted in a 35% further decreased in methane KHI. (c) 2018 Wiley Periodicals, Inc.