Investigation of the Release of Bioactive Volatiles from Amphiphilic Multiarm Star-Block Copolymers by Thermogravimetry and Dynamic Headspace Analysis

Amphiphilic multiarm star-block copolymers with a hydrophobic inner and a hydrophilic outer shell have been used to encapsulate hydrophobic bioactive volatiles in aqueous media under realistic application conditions. The release rates of the bioactive compounds have been investigated for a series of fragrances by thermogravimetry and dynamic headspace analysis. An increasing amount of ethanol present in an aqueous solution linearly reduces the long-lastingness of the fragrance evaporation, which seems to particularly affect nonencapsulated fragrances. An improved controlled release effect is also obtained in the presence of surfactants, where a boosting effect was observed for the fragrance evaporation. Amphiphilic core-shell structures based on hyperbranched polymers were thus found to be suitable delivery systems for the controlled release of bioactive volatiles under typical application conditions. The fundamental understanding of the parameters influencing the release of bioactive compounds is of major interest for the development of tailor-made core-shell structures as efficient delivery systems in various areas of life-science research.