Propagation rate coefficient for sulfobetaine monomers by PLP-SEC

Abstract

Zwitterionic polymers have been extensively used in the biomedical field, however, the knowledge about the kinetics and mechanism of radical polymerization of their monomers is limited. This work introduces the first propagation rate coefficients, kp's, determined by pulsed-laser polymerization in conjunction with size-exclusion chromatography for the methacrylate-type sulfobetaine monomers N-(methacryloylaminopropyl)-N,N-dimethyl-N-(3-sulfopropyl) ammonium betaine (SBAm) and N-(methacryloyloxyethyl)-N,N-dimethyl-N-(3-sulfopropyl) betaine (SBE). The kp values are determined in aqueous solutions for monomer concentrations between 5 and 50 wt % and temperatures between 15 and 80 °C. The propagation rate for SBE is by about a factor of two higher than that for SBAm. The solvent effect manifested by the kp dependence on monomer concentration is stronger for SBAm than for SBE. The kp decreases upon increasing the monomer concentration up to 20 wt % followed by independence of kp on further increased monomer concentration. The anti-polyelectrolyte effect and the significance of hydrogen bonding interactions on kp values are illustrated by polymerizations in the presence of NaCl and organic co-solvents, respectively.