The Preparation and Characterization of Amphiphilic Star Block Copolymer Nano Micelles Using Silsesquioxane As the Core

Amphiphilic star-shaped block copolymers of poly(epsilon-caprolactone-star-N-isopropylacrylamide) were synthesized by using hydroxyl-functionalized polyhedral oligomeric silsesquioxanes (POSS) as a core to initiate ring-opening polymerization of epsilon-caprolactone, followed by atom transfer radical polymerization of N-isopropylacrylamide. The sizes of the core and shell could be controlled through adjusting feed ratios of the reactants. The structure of the star block copolymers were confirmed by FTIR, (1)HNMR, (29)SiNMR, and DSC. Nano micelles were formed by adding water to the copolymer solution (DMF). The critical water concentration for the formation of the micelles were determined by UV. The results of TEM and DLS showed that the micelles were well-defined three-dimensional spherical particles with an average diameter of 155 nm. A hydrophobic drug ibuprofen could be loaded on the micelles effectively, and the release behavior was temperature dependent.