Light-induced healing in azobenzene bridged silsesquioxanes

MARÍA JOSÉ GALANTE; ILEANA A. ZUCCHI; PATRICIA A. OYANGUREN; LUCIANA M. SÁIZ

EUROPEAN POLYMER JOURNAL

PERGAMON-ELSEVIER SCIENCE LTD

Lugar: Amsterdam; Año: 2019 p. 382 - 390

0014-3057

Intrinsic healable polymers are materials capable of repairing itself through its chemical nature, in order toimprove stability and durability and to restore the lost functionalities or properties.In this study, azobenzene (AZO) moieties were incorporated into a previously reported bridged silsesquioxanebased on the reaction of isocyanatepropyltriethoxysilane (IPTS) with bisphenol A (BPA), by replacing a smallfraction of BPA by a bisazophenol (4,4′-dihydroxyazobenzene, AZOH). The incorporation of these AZO moietiesled to a material with UV light-induced healing abilities. The underlying healing mechanism is attributed to theintra-molecular conformational changes of the azo-chromophores that are induced by the trans to cis photoisomerizationof the azobenzene. These changes temporary increased its mobility and allowed the material toflow in the damaged area, followed by a process of restoring the physical hydrogen bonds. This process wasmonitored 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 theoriginal one.