アニオン重合の基礎から最近の進歩 : 5. 異相系高分子の自己組織化と分子集合体 Fundamental Studies and Recent Advances in Anionic Polymerization : 5. Assembly and Self-organization of Macromolecules with Hetero-phase Structures
Morphological studies of well-defined polymers with heterophase structures including AB diblock copolymers, ABC triblock terpolymers, and 3-arm asymmetric ABC star-branched polymers are reviewed. Among them, ABC triblock terpolymers and asymmetric ABC star-branched polymers have been recently synthesized by means of living anionic polymerization. It has been well established as Molau's rule for a long time that the microphase-separated structures observed for AB diblock copolymers are successively changed from spherical, cylindrical, gyroid, to lamellar, depending on the composition <i>f</i> and combination parameter <i>X N</i> where <i>X</i> and <i>N</i> are the segment-segment interaction energy and the degree of polymerization, respectively. On the other hand, in ABC triblock terpolymers, there are additional several parameters (<i>X</i><sub>AB</sub>, <i>X</i><sub>AC</sub>, <i>X</i><sub>BC</sub>, <i>f</i><sub>A</sub>, <i>f</i><sub>B</sub>, <i>N</i>) that can be varied by the sequential order (ABC, ACB, and BAC). Their morphologies are dependent on the relative magnitude of three segment-segment interaction parameters: a lamellar morphology that minimizes both interfacial contact energy and chain stretching with <i>X</i><sub>AB</sub>=<i>X</i><sub>BC</sub><<i>X</i><sub>AC</sub>, a core-shell cylindrical morphology that reduces the overall free energy with <i>X</i><sub>AB</sub><<i>X</i><sub>BC</sub><<i>X</i><sub>AC</sub>, and a cylinder-at-the-wall and a sphere-at-the-wall that accommodate the most energetically favorable contact with <i>X</i><sub>AB</sub>=<i>X</i><sub>BC</sub>>><i>X</i><sub>AC</sub>. Moreover, 3-arm asymmetric ABC star-branched polymers potentially develop several super lattice structures including tricontinuous gyroid ones based on the arm length ratios and interaction parameters. Such characteristic morphologies are of particularly interest to produce novel and unique self-organized nano architectures potentially applicable to nano-devices.
日本ゴム協會誌 80(7), 266-272, 2007-07-15
THE SOCIRETY OF RUBBER SCIENCE AND TECHNOLOGYY, JAPAN