Synthesis and characterization of a poly(methyl methacrylate-acrylic acid) copolymer for bioimplant applications

This paper describes the development of a new crosslinked poly(methyl methacrylate-acrylic acid) copolymer for potential applications in bone implants. This copolymer, comprising hydrophobic and hydrophilic components, has been designed to provide small amounts of controllable swelling strains at saturation when exposed to an aqueous saline environment. The volume fraction of the hydrophobic methyl methacrylate monomer to the hydrophilic acrylic acid monomer strongly influenced the swelling behavior of the copolymer. Two different cross-linking agents, allyl methacrylate and diethylene glycol dimethacrylate, were evaluated for their effectiveness in cross-linking and limiting the saturated swelling levels. The influences of the amounts of crosslinking agents and other processing parameters on the swelling behavior of the copolymer were studied using differential scanning calorimetry measurements, solubility tests, and swelling measurements in saline solutions. These measurements provided a good understanding of the structure of the copolymer, the effectiveness of the crosslinkers, the swelling mechanisms in this system, and the factors that strongly affect the swelling weight gain levels in this copolymer. (C) 1997 John Wiley & Sons, Inc.