title: Mechanophores with a reversible radical system and freezing-induced mechanochemistry in polymer solutions and gels.
abstract: Visualization and quantitative evaluation of covalent bond scission in polymeric materials are highly important for understanding failure, fatigue, and deterioration mechanisms and improving the lifetime, durability, toughness, and reliability of the materials. The diarylbibenzofuranone-based mechanophore radical system enabled, through electron paramagnetic resonance spectroscopy, in situ quantitative evaluation of scission of the mechanophores and estimation of mechanical energy induced along polymer chains by external forces. The coagulation of polymer solutions by freezing probably generated force but did not cleave the mechanophores. On the other hand, cross-linking led to efficient propagation of the force of more than 80 kJ mol(-1) to some mechanophores, resulting their cleavage and generation of colored stable radicals. This mechanoprobe concept has the potential to elucidate other debated issues in the polymer field as well.
authors.affiliation: Department of Organic and Polymeric Materials, Tokyo Institute of Technology, 2-12-1 Ookayama, Meguro-ku, Tokyo 152-8550 (Japan).|Graduate School of Engineering, Kyushu University, 744 Motooka, Nishi-ku, Fukuoka 819-0395 (Japan).
authors.forename: Keiichi
authors.initials: K
authors.lastname: Imato
authors.affiliation: Graduate School of Engineering, Kyushu University, 744 Motooka, Nishi-ku, Fukuoka 819-0395 (Japan).
authors.forename: Atsushi
authors.initials: A
authors.lastname: Irie
authors.affiliation: Department of Organic and Polymeric Materials, Tokyo Institute of Technology, 2-12-1 Ookayama, Meguro-ku, Tokyo 152-8550 (Japan).
authors.forename: Takahiro
authors.initials: T
authors.lastname: Kosuge
authors.affiliation: Institute for Materials Chemistry and Engineering, Kyushu University, 744 Motooka, Nishi-ku, Fukuoka 819-0395 (Japan).
authors.forename: Tomoyuki
authors.initials: T
authors.lastname: Ohishi
authors.affiliation: Institute for Materials Chemistry and Engineering, Kyushu University, 744 Motooka, Nishi-ku, Fukuoka 819-0395 (Japan).
authors.forename: Masamichi
authors.initials: M
authors.lastname: Nishihara
authors.affiliation: Graduate School of Engineering, Kyushu University, 744 Motooka, Nishi-ku, Fukuoka 819-0395 (Japan). takahara@cstf.kyushu-u.ac.jp.|Institute for Materials Chemistry and Engineering, Kyushu University, 744 Motooka, Nishi-ku, Fukuoka 819-0395 (Japan). takahara@cstf.kyushu-u.ac.jp.
authors.forename: Atsushi
authors.initials: A
authors.lastname: Takahara
authors.affiliation: Department of Organic and Polymeric Materials, Tokyo Institute of Technology, 2-12-1 Ookayama, Meguro-ku, Tokyo 152-8550 (Japan). otsuka@polymer.titech.ac.jp.
authors.forename: Hideyuki
authors.initials: H
authors.lastname: Otsuka
keywords: cross-linked polymers; dynamic covalent chemistry; gels; mechanochemistry; mechanochromism