Synthesis of photoaddressable polymeric networks having azobenzene moieties and alkyl‐chain‐containing compounds

Abstract

AbstractWe discuss the synthesis of new optically active polymeric networks containing azobenzene moieties and different alkyl‐chain‐containing compounds. An epoxy resin based on diglycidyl ether of bisphenol A (DGEBA) was reacted with metaxylylenediamine (MXDA). An azo prepolymer (TAZ) was synthesized by reaction between Disperse Orange‐3 and DGEBA. Reaction between palmitic acid (PA) and DGEBA was performed using triphenylphosphine as catalyst of the epoxy–acid reaction employing variable molar ratios of epoxy to carboxyl groups (r = 1, 2, 4). These precursors were called PA1, PA2 and PA4. Crosslinked epoxy‐based azopolymers containing variable PA‐based precursor content and constant chromophore concentration equal to 20 wt% TAZ were synthesized. Their reversible optical storage properties were studied and compared. It was found that the optical response is a direct consequence of the morphologies generated, and that crystallization of PA‐based precursor can take place. When the PA‐based precursor is not covalently bonded to the matrix, e.g. PA1, the remaining birefringence is high. PA4‐modified materials present a completely different response, showing a behaviour that could be of great importance in the development of optical switchers. In this case, the organic tails remain dissolved in the matrix and unable to crystallize, giving a typical ‘on–off’ response. © 2012 Society of Chemical Industry