COVALENT BONDING OF PMMA, PBMA, AND POLY(HEMA) TO HYDROXYAPATITE PARTICLES

In our earlier study, we showed that the surface hydroxyl groups of hy droxyapatite have the ability to react with organic isocyanate groups. In this study, the feasibility of grafting poly(methyl methacrylate) (PMMA), poly(n-butyl methacrylate) (PBMA), and Poly(hydroxyethyl metha crylate) [poly(HEMA)] by using the reaction of isocyanate groups with the hydroxyl groups on the surface of HA was investigated. Double bond s were introduced to the surface of HA via the coupling reaction of is ocyanateoethyl methacrylate (ICEM) with HA, or through hexamethylene d iisocyanate (HMDI) with hydroxyethyl methacrylate (HEMA) and HA, follo wed by radical polymerization in MMA, BMA, or HEMA. Infrared spectra i ndicated the existence of polymers on the surfaces of HA. Thermogravim etric analysis also confirmed the presence of grafted polymers on the surface of HA powder particles (20-26 wt%). The polymers gave typical PMMA, PBMA, or poly(HEMA) infrared spectra, with the exception of amid e bands, a result of the coupling reaction of ICEM or HMDI with hydrox y groups of HA or HEMA. Therefore it is concluded that the polymers we re chemically bonded to the surface of HA through the isocyanate group s of ICEM or HMDI. (C) 1998 John Wiley & Sons, Inc.