Effect of gold and graphene oxide nanoparticles on the thermo- and photo-actuation of monodomain liquid crystal elastomers

Monodomain liquid crystal elastomers (m-LCEs) were synthesized from polymethylhydrosiloxane (PMHS), two distinct vinyl-functionalized mesogens (benzoate and azobenzene) and one crosslinking monomer, using the hydrosilylation reaction. Gold or amino-functionalized graphene oxide nanoparticles (NP) were in-situ incorporated into the m-LCEs, aiming to enhance their response to thermal and optical stimuli. All m-LCEs exhibited a degradation temperature of similar to 310 degrees C and a mesomorphic behavior over a wide temperature range (clearing temperature around 100 degrees C). The inclusion of nanoparticles stiffened the m-LCEs, although they induced a highly randomized ordering of mesogens at the nematic to isotropic transition, resulting in a higher specimen contraction; a schematic model is proposed in this concern. The photo-actuation (bending) of the m-LCEs/NP composites resulted rather diminished as they became stiffer than the neat m-LCEs, although the increasing content of azobenzene units allowed higher bending angles that could be suitable for remote actuation applications.