Silicone rubber films modified by ethylenoxy moieties: Characterization and drug delivery properties

We present a comparative study between two different types of modification applied on a highly hydrophobic, yet biocompatible polymer, aiming to increase its hydrophilicity. More specifically, silicone rubber (SR) was modified by the introduction of low-molecular weight poly(ethylene glycol), through either (a) blending or (b) addition-grafting reaction. The modifications were first evaluated in neat films with respect to their water sorption capacity, stability of ethylenoxy groups' embedment, mechanical and thermal properties. The results from this series of tests showed that blending offered better results in terms of hydrophilicity, both surficial and in the bulk, while the films maintained better mechanical properties. Subsequently, the release kinetics of a relatively hydrophilic drug (theophylline) along with the concurrent water uptake was examined in drug-loaded, pure and modified SR films. As in the case of the drug-free films, blending appeared to offer better possibilities in controlling the drug's release rate through increased water sorption. (c) 2013 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 129: 874-883, 2013