A Statistical Approach to the Effect of Sol-Gel Process Variables on the Physical Properties of Polymer [PLLA]-Silica Hybrid Materials for Use as Biomaterials

Abstract

AbstractHybrid poly(L-lactic acid)-silica materials for potential use in orthopaedic applications have been prepared by a sol-gel method using an experimental design approach to investigate the effect of synthesis variables separately and together on the physical form of the organic polymer. The five factors investigated were the molar ratios of tetraethyl orthosilicate (TEOS)/Poly(Llactic acid) (PLLA), Toluene/PLLA, EtOH/TEOS, Water/TEOS and HCl (catalyst)/TEOS. All other synthesis conditions were kept constant. X-Ray powder diffraction (Statton's graphical method) and differential scanning calorimetry were used to assess the extent of polymer crystallinity in the hybrid materials. In accordance with other studies, increasing the molar ratio of TEOS/PLLA lead to increasing incorporation of the organic polymer into the silica network. Increase of the toluene/PLLA molar ratio lead to an increase in the crystallinity of the polymer phase. As our studies investigated the effect of synthesis variables simultaneously it was possible to identify, for the first time, that interactions between specific reactants are important in the development of the two structural components of this hybrid system. The most important of these was the TEOS/PLLA*H2O/TEOS interaction that may indicate that silica species from hydrolysed TEOS interact with the PLLA phase possibly via hydrogen bonding and leads to the lowering of the crystalline order of the polymer The results from this study give useful information on the ability of the organic polymer and the silica phase to form interpenetrating networks, an important requirement for the generation of a potential hybrid polyester-silica biomaterial for orthopaedic applications.