Formation and Properties of Vesicles from Cyclic Amphiphilic PS-PEO Block Copolymers.
Linear polystyrene-poly(ethylene oxide)-polystyrene (PS-PEO-PS) block copolymers and corresponding cyclized PS-PEO counterparts with three different PS molecular weights were synthesized and self-assembled to investigate the effects arising from the topology. Linear PS5-PEO45-PS5(L1) and cyclic PS10-PEO45(C1) formed micelles. As previously reported for poly(n-butyl acrylate) and PEO block copolymers, the micelles from C1 showed more than 30 °C higher phase transition temperature (cloud point, Tc) than those from L1. Linear PS10-PEO45-PS10(L2) and cyclic PS20-PEO45(C2) resulted in the formation of a structure called large compound micelles. Self-assembly of linear PS40-PEO48-PS40(L3) and cyclic PS86-PEO48(C3) lead to the formation of vesicles. The vesicles were characterized by TEM, DLS, and SLS. Remarkably, the vesicles from L3 (Tc= 69, 59, and 48 °C in the presence of 1, 5, and 10 wt % of NaCl, respectively) were found to be somewhat more thermally stable than those from C3 (Tc= 62, 52, and 43 °C in the presence of 1, 5, and 10 wt % of NaCl, respectively). This trend of the thermal stability was counterintuitively opposed to the case of the micelles. Moreover, Tcof the vesicles was controlled by the ratio of L3 and C3.
Department of Organic and Polymeric Materials, Tokyo Institute of Technology , O-okayama, Meguro-ku, Tokyo 152-8552, Japan.
Eisuke
E
Baba
Department of Organic and Polymeric Materials, Tokyo Institute of Technology , O-okayama, Meguro-ku, Tokyo 152-8552, Japan.
Toshiaki
T
Yatsunami
Department of Organic and Polymeric Materials, Tokyo Institute of Technology , O-okayama, Meguro-ku, Tokyo 152-8552, Japan.
Yasuyuki
Y
Tezuka
Department of Organic and Polymeric Materials, Tokyo Institute of Technology , O-okayama, Meguro-ku, Tokyo 152-8552, Japan.|Division of Applied Chemistry, Faculty of Engineering, Hokkaido University , Sapporo, Hokkaido 060-8628, Japan.
Takuya
T
Yamamoto