Photothermal-Responsive Crosslinked Liquid Crystal Polymers

Crosslinked liquid crystal polymers (CLCPs) are a promising type of smart polymer material with excellent two-way shape memory behavior under the stimulation of various external conditions. Among the various external stimuli, light with the advantages of instantaneity, high accuracy, remote controllability, pollution-free, etc., has been widely used in the control of CLCPs. Traditional photoresponsive CLCP systems based on photoisomerization are limited by the penetration depth of ultraviolet light, the number of useful photochemical reactions, and long-term stability. Recently, a strategy for designing photoresponsive CLCPs based on the photothermal effect has attracted scientific attention. Photothermal materials in the CLCP matrix can convert light into heat through plasma resonance or energy transition under the light irradiation of a certain wavelength, and locally heat the CLCP matrix to beyond the liquid crystal-to-isotropic phase transition temperature, thus achieving reversible macroscopic deformation. Combining photothermal materials and CLCPs can decrease the dependence on specific photosensitive groups such as azobenzene mesogens and endow photoresponsive CLCPs with design flexibility. Herein, the photothermal-responsive CLCPs under the stimulations of different light wavelengths and their application fields are reviewed. In addition, the current challenges in the field of photothermal-responsive CLCPs are summarized, and a brief outlook on future development is proposed.