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A Series of Bisamide‐Substituted Diacetylenes Exhibiting a Terminal Alkyl Odd/Even Parity Effect on Mechanoactivated Photopolymerization
Author(s) -
Qi Jiajun,
Kim Yuna,
Takahashi Kiyonori,
Aoki Ken'ichi,
Hisaki Ichiro,
Nakamura Takayoshi,
Tamaoki Nobuyuki
Publication year - 2021
Publication title -
chemistry – a european journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.687
H-Index - 242
eISSN - 1521-3765
pISSN - 0947-6539
DOI - 10.1002/chem.202004768
Subject(s) - polydiacetylenes , photopolymer , diacetylene , alkyl , polymerization , photochemistry , chemistry , monomer , intermolecular force , thermochromism , polymer chemistry , steric effects , hydrogen bond , crystallography , polymer , molecule , stereochemistry , organic chemistry
Diacetylene derivatives exhibit solid‐state polymerization to polydiacetylene initiated by UV light or γ‐ray irradiation. The activation of the photopolymerization relies on the monomer diynes arrangement. Recently, it has been demonstrated that the first mechanoresponsive bisamide substituted diacetylenes (DAs) show dramatic switching from light‐inert to light‐reactive states at a given pressure. The origin of this unique phenomenon was apparently related to the pressure‐sensitive crystalline transition in DAs, but the molecular mechanism remains elusive. To obtain more insight, herein a series of DAs with varying terminal alkyl spacer length is presented, and their molecular structural effect on the intermolecular hydrogen bonding and steric repulsion is examined. In pristine states, even‐parity DAs were inactive upon UV irradiation ( λ =254 nm) unless external pressure was applied. By contrast, odd‐parity DAs were easily polymerized upon UV irradiation without pressure application. However, the pressure‐induced crystalline phase transition exhibiting photopolymerization was valid for all DAs regardless of their alkyl spacer length. A systematic investigation revealed that the terminal alkyl spacer length, especially its odd/even parity plays a key role in determining the intrinsic intermolecular hydrogen‐bonding nature of DA crystals and the resultant molecular packing. In addition, the relevant thermochromic behavior was also observed from photopolymerized polydiacetylenes.