Morphology control of giant vesicles by manipulating hydrophobic-hydrophilic balance of amphiphilic random block copolymers through polymerization-induced self-assembly

The morphology of giant vesicles composed of amphiphilic poly(methacrylic acid)-block-poly(methyl methacrylate-random-methacrylic acid) random block copolymers, PMAA-b-P(MMA-r-MAA), was effectively controlled by manipulating the hydrophobic-hydrophilic balance of the P(MMA-r-MAA) blocks through the self-assembly induced by the nitroxide-mediated photo-controlled/living radical polymerization in an aqueous methanol solution. The morphology was transformed from spherical vesicles into fibers and finally into membranes as the molar ratio of the MAA units in the hydrophobic P(MMA-r-MAA) block increased at a constant block length. The membrane morphology reverted to spherical vesicles by exchanging the MMA units with more hydrophobic isopropyl methacrylate units at a constant MAA ratio. These morphology transitions were accounted for by the change in the critical packing shape of the random block copolymers based on the variation in the extent of the hydrophobic block chains.