Mechanism study of reversible transition between self-assembly and disassembly of ABC triblock copolymer micelles

Reversible transition of self-assembly and disassembly for PS720-P2VP200-PEO375 copolymer multicompartment micelles in solution induced solely by changing temperature has been studied. The large-sized shuttle-like micelles, formed from a second self-assembly of nano-sized spheres at 20 °C, will disassemble to small spherical micelles as the temperature increases to 40 °C, and then regenerate as the system is turned back to 20 °C. A critical temperature is found in the intermediate regime of 30 °C, at which the micelle dimension reaches the maximum size. However, the critical temperature is found to be varied with change of the composition of triblock copolymers and decreases to lower value with increase of the fraction of hydrophilic blocks. This reversible morphological change is considered as a result from the combination of the second-assembly of spherical micelles and the interaction parameter between the solvent and the hydrophobic block, and has great potential in drug release triggered by temperature.324