Microsegregating blends of ethyl cellulose and poly(vinyl pyrrolidone): a combined thermo-mechanical and positron annihilation spectroscopy study

Polymer blends are a versatile playground for studying phase separation and its effect on the development of morphology and mechanical properties of the resulting materials. Blends obtained from two immiscible polymers, ethyl cellulose (EC) and poly(vinyl pyrrolidone) (PVP), are especially relevant for their practical applications as coatings for pharmaceutical preparations and controlled drug release. Here, films of EC-PVP blends are studied by means of thermal analysis, dynamic-mechanical analysis as well as positron annihilation lifetime spectroscopy. The morphology of the microstructures generated by phase separation is investigated by means of scanning electron microscopy. The effect of both components' ratio and of molecular mass of PVP on the final properties of the blends is determined in a systematical way. The results obtained are not only of theoretical interest but will prove useful for the optimization of industrial formulations based on these polymers.