The self-assembly of block copolymers has attracted attention for many decades because it can yield polymeric nanoobjects with a wide range of morphologies. Membrane emulsification is a fairly novel technique for preparation of various types of emulsions, which relies on the dispersed phase passing through a membrane in order to effect droplet formation. In this study, we have prepared polymeric nanoparticles of different morphologies using self-assembly of asymmetric block copolymers in connection with membrane emulsification. Shirasu Porous Glass (SPG) membranes has been employed as the membrane emulsification equipment, and poly (oligoethylene glycol acrylate)-block-poly (styrene) (POEGA-b-PSt) copolymers prepared via RAFT polymerization. It has been found that a number of different morphologies can be achieved using this novel technique, including spheres, rods, and vesicles. Interestingly, the results have shown that the morphology can be controlled not only by adjusting experimental parameters specific to the membrane emulsification step such as membrane pore size and pressure, but also by changing the nature of organic solvent. As such, this method provides a novel route to these interesting nanoobjects, with interesting prospects in terms of exercising morphology control without altering the nature of the block copolymer itself.
The role of cooling rate in crystallization-driven block copolymer self-assembly
