CRYSTALLIZATION OF AN INORGANIC PHASE CONTROLLED BY A POLYMER MATRIX

BIOLOGICAL composite materials such as bones, teeth and shells consist of a polymer matrix reinforced by an inorganic phase which forms in the matrix 1. These materials are distinguished from synthetic composites by the high degree of organization and regularity displayed by the inorganic phase: inorganic minerals of uniform size, morphology and crystallographic orientation can be formed in ordered arrays in living cells. Such a process has until now not been realized in synthetic systems, although the recent interest in nanoscience 2-6 has stimulated much research in the area. We report here an example of a synthetic process that produces composite materials analogous to those produced by natural biomineralization. The inorganic/organic in situ synthesized composites display controlled inorganic crystal size, morphology and orientation, which are determining features of type II, or matrix-mediated 7, biocomposites. The synthetic factors that must be optimized to give biomimetic properties to synthetic composites are strong binding of the inorganic reagents by the organic matrix (molecular complementarity); good 'solvation' of the inorganic reagents by the polymer; and an ordered, regular polymer environment in which to induce nucleation (matrix preorganization).