BIODEGRADABLE AND BIOCOMPATIBLE INORGANIC-ORGANIC HYBRID MATERIALS - 4 - EFFECT OF ACID CONTENT AND WATER-CONTENT ON THE INCORPORATION OF ALIPHATIC POLYESTERS INTO SILICA BY THE SOL-GEL PROCESS

The extent of poly epsilon-caprolactone (PCL) incorporation into silic a networks prepared by the sol-gel process depends on the HCl:tetraeth oxysilane (TEOS) molar ratio and the H2O:TEOS molar ratio, as well. Th e PCL incorporation increases with the concentration of the acid used as the catalyst. Dynamic mechanical analysis (DMA) indicates that incr easing the acid concentration or decreasing the water content results in a higher glass transition temperature for the organic component in the hybrid materials, whereas the modulus does not change significantl y. Small-angle X-ray scattering (SAXS) data agree with a nanoscopic ph ase separation of the two constitutive components: the organic polymer and the silica network. The characteristic length of this two-phase s tructure increases with acid content (except for the lower HCl:TEOS mo lar ratio of 0.05) and with water content (except for the higher H2O:T EOS molar ratio of 2.0). The structure of the PCL/SiO2 interface is ma ss fractal and the structure is more open when the acid content is low er or the water content higher. (C) 1998 Elsevier Science Ltd. All rig hts reserved.