Morphological changes in polymer giant vesicles by intercalation of a segment copolymer as a sterol model in plasma membrane

Abstract

The morphological changes in polymer giant vesi- cles comprised of amphiphilic poly(methacrylic acid)-block- poly(methyl methacrylate-random-methacrylicacid),PMAA- b-P(MMA-r-MAA), were explored in the presence of a P(MMA-r-MAA) segment copolymer as the model for sterols in plasma membranes for the purpose of inventing a new biomembrane model using the polymer vesicles. PMAA-b- P(MMA-r-MAA) produced spherical vesicles with a 2.5-μm diameter by the photopolymerization-induced self-assembly in the absence of the segment copolymer in an aqueous meth- anol solution. The block copolymer formed a planar bilayer in the presence of the segment copolymer that had the MMA/ MAA ratio and length identical to those of the hydrophobic block composing the amphiphilic random block copolymer. The thermal analysis demonstrated that the segment copoly- mer was completely intercalated between the hydrophobic block chains forming the vesicle cores. This intercalation dis- ordered the vesicle surface of the hydrophilic PMAA blocks anddecreasedthecrystallinityofthehydrophilicblockchains.