Nanometer-Scaled Hollow Spherical Micelles with Hydrophilic Channels and the Controlled Release of Ibuprofen

PS-b-PAA spherical micelles with a liquid core and a PAA shell are prepared with the assistance of 1,2-dichloroethane. During the process of adding a mixture of PNIPAM-b-P4VP and PEG-b-P4VP, multi-layered micelles with a mixed corona that consists of both PNIPAM and PEG chains are constructed through the electrostatic interaction and hydrogen bonding between the PAA block and the P4VP block. When heating above the LCST, the PNIPAM chains collapse onto the PAA/P4VP complex layer while the PEG chains still stretch into the solution through the collapsed PNIPAM layer, which leads to the formation of hydrophilic channels around the PEG, chains. The ibuprofen encapsulated in the hollow space can diffuse through the channels and its release rate can be controlled by changing the ratio of PEG chains to PNIPAM chains in the corona.