title: Dynamic photoinduced realignment processes in photoresponsive block copolymer films: effects of the chain length and block copolymer architecture.
abstract: A series of block copolymers composed of an amorphous poly(butyl methacrylate) (PBMA) block connected with an azobenzene (Az)-containing liquid crystalline (PAz) block were synthesized by changing the chain length and polymer architecture. With these block copolymer films, the dynamic realignment process of microphase separated (MPS) cylinder arrays of PBMA in the PAz matrix induced by irradiation with linearly polarized light was studied by UV-visible absorption spectroscopy, and time-resolved grazing incidence small angle X-ray scattering (GI-SAXS) measurements using a synchrotron beam. Unexpectedly, the change in the chain length hardly affected the realignment rate. In contrast, the architecture of the AB-type diblock or the ABA-type triblock essentially altered the realignment feature. The strongly cooperative motion with an induction period before realignment was characteristic only for the diblock copolymer series, and the LPL-induced alignment change immediately started for triblock copolymers and the PAz homopolymer. Additionally, a marked acceleration in the photoinduced dynamic motions was unveiled in comparison with a thermal randomization process.
authors.affiliation: Department of Molecular Design and Engineering, Graduate School of Engineering, Nagoya University, Furo-cho, Chikusa, Nagoya 464-8603, Japan. tseki@apchem.nagoya-u.ac.jp.
authors.forename: Masami
authors.initials: M
authors.lastname: Sano
authors.forename: Feng
authors.initials: F
authors.lastname: Shan
authors.forename: Mitsuo
authors.initials: M
authors.lastname: Hara
authors.forename: Shusaku
authors.initials: S
authors.lastname: Nagano
authors.forename: Yuya
authors.initials: Y
authors.lastname: Shinohara
authors.forename: Yoshiyuki
authors.initials: Y
authors.lastname: Amemiya
authors.forename: Takahiro
authors.initials: T
authors.lastname: Seki