Photoresponsive thin film based on photochromic diarylethene blended with thermoplastic elastomer: Structural and morphological analysis

An increasing attention has been paid to photo-deformable polymeric materials that can convert light energy into mechanical energy without contact or electrical wires, using photoresponsive molecules. Diarylethenes known for their thermal stability and their fatigue resistance are one of the best studied compounds that exhibit photomechanical response. Upon alternating irradiation with UV and visible light, a change in molecular volume occurs between open- and close-ring during the photochromic reaction which induces photomechanical motions. In order to develop a light-driven polymer actuator, we investigate a novel system based on the mixture of a derivative diarylethene (Ureidopyrimidinone-functionalized diarylethene denoted UPy-DTE) and a thermoplastic elastomer (Ureidopyrimidinone -functionalized poly(ethylene-co-butylene) denoted UPy-PEB). In solution, the UPy-DTE/UPy-PEB system leads to a supramolecular assembly via quadrupole hydrogen bonding. The thin films are elaborated using different techniques such as drop casting or melt molding. Under illumination, a photomechanical response of the film is observed. Our strategy is to establish a correlation between the structural and morphological properties responsible for the macroscopic deformations.