Light-induced healing in azobenzene bridged silsesquioxanes

[Display omitted] •The incorporation of azobenzene moieties into a bridged silsesquioxane led a material with light-induced healing ability.•The photoisomerization of the azobenzene increases the mobility and allows the material to flow in the damaged area.•A complete recovery of the damage was obse...

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Bibliographic Details
Published in:European polymer journal 2019-08, Vol.117, p.382-390
Main Authors: Galante, María J., Zucchi, Ileana A., Oyanguren, Patricia A., Sáiz, Luciana M.
Format: Article
Language:English
Subjects:
Azo compounds
Azobenzene
Bisphenol A
Bridged silsesquioxane
Chromophores
Healable materials
Healing
Hydrogen
Hydrogen bonds
Maintenance
Organic chemistry
Photoisomerization
Polymers
Ultraviolet radiation
Viscoelasticity
Wound healing
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Summary:[Display omitted] •The incorporation of azobenzene moieties into a bridged silsesquioxane led a material with light-induced healing ability.•The photoisomerization of the azobenzene increases the mobility and allows the material to flow in the damaged area.•A complete recovery of the damage was observed after only 30 s of UV irradiation. Intrinsic healable polymers are materials capable of repairing itself through its chemical nature, in order to improve stability and durability and to restore the lost functionalities or properties. In this study, azobenzene (AZO) moieties were incorporated into a previously reported bridged silsesquioxane based on the reaction of isocyanatepropyltriethoxysilane (IPTS) with bisphenol A (BPA), by replacing a small fraction of BPA by a bisazophenol (4,4′-dihydroxyazobenzene, AZOH). The incorporation of these AZO moieties led to a material with UV light-induced healing abilities. The underlying healing mechanism is attributed to the intra-molecular conformational changes of the azo-chromophores that are induced by the trans to cis photoisomerization of the azobenzene. These changes temporary increased its mobility and allowed the material to flow in the damaged area, followed by a process of restoring the physical hydrogen bonds. This process was monitored following the viscoelastic properties during successive cycles of turning ON and OFF the UV irradiation. Remarkably, the resultant healed material has not significant observed mechanical differences with the original one.
ISSN:0014-3057
1873-1945
DOI:10.1016/j.eurpolymj.2019.05.025