title: Design amphiphilic dipolar π-systems for stimuli-responsive luminescent materials using metastable states.
abstract: π-Conjugated compounds that exhibit tunable luminescence in the solid state under external mechanical stimuli have potential applications in sensors and imaging devices. However, no rational designs have been proposed that impart these mechano-responsive luminescent properties to π-conjugated compounds. Here we demonstrate a strategy for mechano-responsive luminescent materials by imparting amphiphilic and dipolar characteristics to a luminescent π-conjugated system. The oligo(p-phenylenevinylene) luminophore with a didodecylamino group at one end and a tri(ethylene glycol) ester group at the other end yields segregated solid structures by separately aggregating its hydrophobic and hydrophilic moieties. The segregated structures force the molecules to align in the same direction, thereby generating a conflict between the side-chain aggregation and dipolar stabilization of the π-system. Consequently, these metastable solid structures can be transformed through mechanical stimulation to a more stable structure, from a π-π stacked aggregate to a liquid crystal and further to a crystalline phase with variable luminescence.
authors.affiliation: 1] Graduate School of Engineering, Chiba University, 1-33 Yayoi-cho, Inage-ku, Chiba 263-8522, Japan [2] Japan Science and Technology Agency (JST), Core Research for Evolutional Science and Technology (CREST), Chiyoda-ku, Tokyo 102-0076, Japan.
authors.forename: Shiki
authors.initials: S
authors.lastname: Yagai
authors.affiliation: Graduate School of Engineering, Chiba University, 1-33 Yayoi-cho, Inage-ku, Chiba 263-8522, Japan.
authors.forename: Satoru
authors.initials: S
authors.lastname: Okamura
authors.affiliation: Graduate School of Engineering, Chiba University, 1-33 Yayoi-cho, Inage-ku, Chiba 263-8522, Japan.
authors.forename: Yujiro
authors.initials: Y
authors.lastname: Nakano
authors.affiliation: Graduate School of Engineering, Chiba University, 1-33 Yayoi-cho, Inage-ku, Chiba 263-8522, Japan.
authors.forename: Mitsuaki
authors.initials: M
authors.lastname: Yamauchi
authors.affiliation: Graduate School of Engineering, Chiba University, 1-33 Yayoi-cho, Inage-ku, Chiba 263-8522, Japan.
authors.forename: Keiki
authors.initials: K
authors.lastname: Kishikawa
authors.affiliation: Graduate School of Engineering, Chiba University, 1-33 Yayoi-cho, Inage-ku, Chiba 263-8522, Japan.
authors.forename: Takashi
authors.initials: T
authors.lastname: Karatsu
authors.affiliation: Graduate School of Engineering, Chiba University, 1-33 Yayoi-cho, Inage-ku, Chiba 263-8522, Japan.
authors.forename: Akihide
authors.initials: A
authors.lastname: Kitamura
authors.affiliation: Microjet Corporation, 5-79-2 Daimon, Shiojiri, Nagano 399-0732, Japan.
authors.forename: Akira
authors.initials: A
authors.lastname: Ueno
authors.affiliation: Graduate School of Material Science, Nara Institute of Science and Technology (NAIST), 8916-5, Takayama-cho, Ikoma, Nara 630-0192, Japan.
authors.forename: Daiki
authors.initials: D
authors.lastname: Kuzuhara
authors.affiliation: 1] Japan Science and Technology Agency (JST), Core Research for Evolutional Science and Technology (CREST), Chiyoda-ku, Tokyo 102-0076, Japan [2] Graduate School of Material Science, Nara Institute of Science and Technology (NAIST), 8916-5, Takayama-cho, Ikoma, Nara 630-0192, Japan.
authors.forename: Hiroko
authors.initials: H
authors.lastname: Yamada
authors.affiliation: Division of Chemical Process Engineering and Frontier Chemistry Center (FCC), Graduate School of Engineering, Hokkaido University, Kita 13 Nishi 8, Kita-ku, Sapporo 060-0810, Japan.
authors.forename: Tomohiro
authors.initials: T
authors.lastname: Seki
authors.affiliation: Division of Chemical Process Engineering and Frontier Chemistry Center (FCC), Graduate School of Engineering, Hokkaido University, Kita 13 Nishi 8, Kita-ku, Sapporo 060-0810, Japan.
authors.forename: Hajime
authors.initials: H
authors.lastname: Ito