Photo-induced bending behaviour of side-on linear liquid crystal polymers with high molecular weight

Two photoresponsive side-on linear liquid crystal polymers (SLLCPs) with different spacer lengths have been synthesised through facile ring-opening metathesis polymerisation (ROMP). For the first time, high molecular weight SLLCPs with polynorbornene backbone and azobenzene side chains are obtained and processed into films by the melt shear-induced orientation method. These SLLCP films exhibit fast and large photo-induced bending behaviour, showing bend degree up to 72° in 3 s upon UV irradiation at ambient temperature. The shape of these films remains unchanged under visible light, demonstrating good shape stability against sunlight. Moreover, owing to their linear structure, the SLLCP films are recyclable through traditional melting or solution methods. Possessing these features, these SLLCP films show application prospects in the fields of light-controllable flexible actuators.