Supramolecular Micelles and Reverse Micelles Based on Cyclodextrin Polyrotaxanes

A new supramolecular self-assembly approach to construct micelles and reverse micelles was reported. Double-hydrophilic block copolymers poly(ethylene oxide)-b-poly(N-isopropylacrylamide) (PEO-b-PNIPAAm) was synthesized via atom transfer radical polymerization (ATRP) using PEO macroinitiator. Because of the lower critical solution temperature (LCST) phase behavior of PNIPAAm, PEO-b-PNIPAAm block copolymers self-assembled to form PNIPAAm-core micelles at 40 degrees C. The PNIPAAm-core micelles were disassembled to unimers when the temperature was decreased to 25 degrees C. But the addition of -cyclodextrins (-CDs) could induce the formation of PNIPAAm-shell micelles because of the channel-type crystallities induced by PEO/-CDs polyrotaxanes. The assembly and disassembly procedure of micelles and reverse micelles were investigated by dynamic light scattering (DLS), X-ray diffraction (XRD), H-1 NMR and transmission electron microscopy (TEM).