Hydrophilic modification of silicone elastomer films: Thermal, mechanical and theophylline permeability properties

The improvement of the hydrophilicity of silicone rubber (SR) is sought in many biomedical applications. In the present work, we have prepared neat films coming from condensation-type SR, modified either through blending or end-linking reaction with low molecular weight poly(ethylene glycol) (PEG). The films were studied with respect to their water uptake capacity, stability of embedment of ethylenoxy moieties, and mechanical and thermal properties. Subsequently, we prepared drug-loaded films with theophylline, a relatively hydrophilic model drug, and studied the release performance of these systems. Results on neat films showed that blending increases significantly the overall water uptake of the films and, at the same time, has a limited detrimental effect on their mechanical properties. On the other hand, end-linked films loaded with theophylline exhibited better rate-controlling properties in vitro, due to better dispersion of the sorbed water.