Fabrication of Anastomosed Tubular Networks Developed out of Fenestrated Sheets through Thermo Responsiveness of Polymer Giant VesiclesAuthor(s): Eri Yoshida
The thermo responsive behavior of spherical vesicles and worm-like vesicles composed of amphiphilic poly (methacrylic acid)-blockpoly (methyl methacrylate-random-methacrylic acid) diblock copolymer, PMAA-b-P(MMA-r-MAA), was investigated in order to elucidate their morphological transformation and thermal stability. The spherical vesicles comprised of PMAA195-b-P(MMA0.817- r-MAA0.183)224 were disrupted into smaller spherical vesicles by an increase in temperature, followed by much smaller micelles, and finally into planar aggregates consisting of the micelles. A decrease in the temperature produced spherical vesicles smaller than the original ones. A rapid temperature decrease of the planar aggregates, followed by the ripening simultaneously provided anastomosed tubular networks and fenestrated sheets as seen in some organelles. The tubular networks consisted of round swollen tubules and were continuous with the fenestrated sheets. The worm-like vesicles of PMAA351-b-P (MMA0.826-r-MAA0.174)372 were transformed into shorter and spherical vesicles and finally into fused aggregates by the temperature increase. By decreasing the temperature, the worm-like vesicles were reproduced from the fused aggregates through the formations of partial sheets and branched tubules, however, they were round and shorter than the original vesicles. It was found that the worm-like vesicles were more thermally stable than the spherical vesicles at the same vesicle concentration and retained the vesicle structure even at the high temperature.