Hydrophobic energy estimation for giant vesicle formation by amphiphilic poly(methacrylic acid)-block-poly(alkyl methacrylate-random-mathacrylic acid) random block copolymers

The self-assembly induced by the photocontrolled/living radical polymerization mediated by 4-methoxy-2,2,6,6-tetramethylpiperidine-1-oxyl was performed for amphiphilic poly(methacrylic acid)-block-poly(alkyl methacrylate-random-methacrylic acid) containing ethyl, n-propyl, and n-butyl methacrylates in order to control the morphology based on the hydrophobic-hydrophilic balance. The morphology transformation from films to spherical vesicles via the transition was well-controlled by adjusting the ratio of the alkyl methacrylate unit to the methacrylic acid in the hydrophobic random copolymer block. The copolymers formed the respective morphologies at different ratios dependent on the alkyl chain length of the methacrylates; the ratio for the formation of the respective morphologies decreased as the alkyl chain length increased. The hydrophobic energy estimation of these copolymers demonstrated that the respective morphologies had definite hydrophobic energies independent of the alkyl chain length, indicating that the morphologies were determined only by the hydrophobic magnitude of the random copolymer block.