Silicone-based hydrogels prepared by interpenetrating polymer network synthesis: Swelling properties and confinements effects on the formation kinetics

In this work, interpenetrating polymer networks (IPNs) of polydimethylsiloxane (PDMS) and poly(acrylic acid) or poly(2-hydroxyethyl methacrylate) (PHEMA) have been synthesized employing a sequential method. Monomeric AAc or HEMA was introduced into the PDMS network by swelling the polymer in solutions of monomer. The polymerization of monomers was then conducted in the swollen network. The swelling properties of the IPNs were investigated by varying the monomer concentrations in the polymerization and more swelling was observed with low monomer concentrations due to the prevalence of cyclization reactions. Multi-step polymerization used to achieve IPNs with high hydrogel contents, did not improve their water uptake. The kinetics of acrylic acid polymerization was studied under various conditions. Specifically, in the presence of confinement effects imposed by the PDMS network a considerable drop in the rate of reaction was observed. The cross-linking density of the PDMS network was also studied how to affect the reaction rate. (C) 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2012