Multiscale approach of photomechanical thin films based on the supramolecular assembly of bistable photoswitch and thermoplastic elastomer

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 photo-responsive molecules. Dithienylethenes 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 (carbon-carbon electrocyclization) 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 Dithienylethenes (Ureidopyrimidinone-functionalized dithienylethenes 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 where the subunits are connected to each other 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 drastic macroscopic deformations.