Biodegradable hybrid poly(3-hydroxyalkanoate)s networks through silsesquioxane domains formed by efficient UV-curing

New bridged silsesquioxanes derived from poly(3-hydroxyalkanoate)s were synthesized, according to the sol-gel process, by conventional acidic, basic hydrolysis or by UV-curing in presence of cationic photo-initiator to compare the properties of the resulting networks. First, microwave assisted alcoholysis in the presence of ethylene glycol provided an efficient method for engineering PHA-diols. These well-defined oligoesters have been derivatized into telechelic bis-triethoxysilyl precursors and sol gel chemistry was employed as cross-linking reaction method. The thermal stability of PHA was improved by incorporation into the silica network, except in basic condition, due to simultaneous formation of the network and the degradation of the PHA backbone. The glass-transition temperatures of the networks prepared in acidic conditions increased from −14 °C up to +16 °C. 29Si NMR measurements also showed that UV curing catalyzed by cationic photo-initiator promotes a high degree of condensation in the organic network that became totally amorphous. This method is a straightforward way applied at room temperature in a very short reaction time (i.e., 300 s) to obtain crosslinked network that remain partially biodegradable by lipase.