Synthesis of monodisperse glycerol dimethacrylate-based microgel particles by precipitation polymerization

Abstract

A new, single-stage precipitation polymerization was proposed for the synthesis of monodisperse crosslinked glycerol dimethacrylate (GDMA)-based microgel particles carrying hydroxyl and carboxyl functionalities, from nanometer to micrometer size range. The synthesis of monodisperse microgel spheres in the size range of 30-1500 nm was possible by the proposed method. In the polymerizations, glycerol dimethacrylate was copolymerized with methacrylic acid (MAA) in the medium containing toluene and acetonitrile without using a stabilizing agent. The effects of polymerization conditions on the final monomer conversion, polymerization kinetics, and MAA distribution in the microgel particles were investigated. The hydrodynamic size, the size distribution characteristics, and the mass charge density of microgel particles were also determined. Highly monodisperse and spherical microgel particles were obtained particularly with low GDMA feed concentrations. A marked increase in the hydrodynamic size was observed with the decreasing polarity (i.e., increasing toluene concentration) in the continuous medium. The distribution of MAA in the particles and the effect of pH on the swelling behavior in the aqueous medium indicated that the microgel particles contained a swellable shell and a nonswellable core. Most of the MAA charged was buried within the core part of the microgel particles. The swelling of microgel was controlled by the ionization of the carboxyl groups located on the shell layer. The swellable character, the presence of functional groups for surface derivatization, and the similarity of microgel to a biocompatible structure, poly(hydroxyethyl methacrylate), make the new microgel a promising material for biomedical applications. © 2009 American Chemical Society.