NMR INVESTIGATION OF THE STRUCTURE OF SOME BIOACTIVE AND RELATED GLASSES

A magic angle spinning nuclear magnetic resonance (MAS-NMR) investigation of the environments of Si-29, (31)p and Na-23, in glasses from the Na2O-CaO-SiO2-(6 wt% P2O5) system, has shown that the distribution of non-bridging oxygens can be described by a binary distribution of Q(2) and Q(3) silicon species. The changes in the chemical shifts of these two species with composition are interpreted as resulting from the preferential association of Na+ with Q(3) and Ca2+ with Q(2). It is suggested that it is this partitioning that determines bioactivity by controlling the dissolution, hydrolysis and condensation reactions which occur at the interface between the glass and the physiological environment.