Mechanophores with a reversible radical system and freezing-induced mechanochemistry in polymer solutions and gels

Keiichi Imato; Atsushi Irie; Takahiro Kosuge; Tomoyuki Ohishi; Masamichi Nishihara; Atsushi Takahara; Hideyuki Otsuka

doi:10.1002/anie.201412413

Mechanophores with a reversible radical system and freezing-induced mechanochemistry in polymer solutions and gels

Angew Chem Int Ed Engl. 2015 May 18;54(21):6168-72. doi: 10.1002/anie.201412413. Epub 2015 Mar 30.

Authors

Keiichi Imato^{1

2}, Atsushi Irie², Takahiro Kosuge¹, Tomoyuki Ohishi³, Masamichi Nishihara³, Atsushi Takahara^{4

5}, Hideyuki Otsuka⁶

Affiliations

¹ Department of Organic and Polymeric Materials, Tokyo Institute of Technology, 2-12-1 Ookayama, Meguro-ku, Tokyo 152-8550 (Japan).
² Graduate School of Engineering, Kyushu University, 744 Motooka, Nishi-ku, Fukuoka 819-0395 (Japan).
³ Institute for Materials Chemistry and Engineering, Kyushu University, 744 Motooka, Nishi-ku, Fukuoka 819-0395 (Japan).
⁴ Graduate School of Engineering, Kyushu University, 744 Motooka, Nishi-ku, Fukuoka 819-0395 (Japan). takahara@cstf.kyushu-u.ac.jp.
⁵ Institute for Materials Chemistry and Engineering, Kyushu University, 744 Motooka, Nishi-ku, Fukuoka 819-0395 (Japan). takahara@cstf.kyushu-u.ac.jp.
⁶ 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.

PMID: 25823899
DOI: 10.1002/anie.201412413

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.

Keywords: cross-linked polymers; dynamic covalent chemistry; gels; mechanochemistry; mechanochromism.