Surface phase separation and morphology of stimuli responsive complex micelles

Complex micelles with a P4VP core surrounded by a mixed PNIPAM/PEG shell were prepared by comicellization of PNIPAM(93)-b-P4VP(58) and PEG(114)-b-P4VP(58) in aqueous solutions. Increasing the temperature above the LCST of the PNIPAM induced a phase separation of the mixed shell due to the collapse of the PNIPAM block. The morphology of the collapsed PNIPAM was dependent on the composition of the mixed shell; a lower content of the PNIPAM resulted in separately distributed domains on the surface of the P4VP core, while a higher content of the PNIPAM led to the formation of continuous membrane around the P4VP core. When the continuous membrane was formed, the hydrophilic PEG block could connect the inner P4VP core and the outer milieu to form channels across the PNIPAM membrane for water and other small molecules to pass through.