Light-induced healing in azobenzene bridged silsesquioxanes

GALANTE, M.J.; I. A. ZUCCHI; PATRICIA A. OYANGUREN; LUCIANA SAIZ

EUROPEAN POLYMER JOURNAL

PERGAMON-ELSEVIER SCIENCE LTD

Lugar: Amsterdam; Año: 2019

0014-3057

Intrinsic healable polymers are materials capable of repairing itselfthrough its chemical nature, in order to improve stability anddurability and to restore the lost functionalities or properties.In this study, azobenzene (AZO) moieties were incorporated into apreviously reported bridged silsesquioxane based on the reaction ofisocyanatepropyltriethoxysilane (IPTS) with bisphenol A (BPA), byreplacing a small fraction of BPA by a bisazophenol (4,4´-dihydroxyazobenzene, AZOH). The incorporation of these AZOmoieties led to a material with UV light-induced healing abilities.The underlying healing mechanism is attributed to the intramolecular conformational changes of the azo-chromophores that areinduced by the trans to cis photoisomerization of the azobenzene.These changes temporary increased its mobility and allowed thematerial to flow in the damaged area, followed by a process of restoring the physical hydrogen bonds. This process was monitoredfollowing the viscoelastic properties during successive cycles ofturning ON and OFF the UV irradiation. Remarkably, the resultanthealed material has not significant observed mechanical differenceswith the original one.