Programming photoactuation by modulating the degree of charge-separation in DASA-based liquid crystal elastomers

Photoresponsive soft actuators enable light-driven shape changes with spatial and temporal control, typically achieved by integrating molecular photoswitches into liquid crystal elastomers (LCEs). Commonly, the structure-property relationship of photoswitches is well explored in dilute solution phase. However, connecting solution-phase molecular electronic structure to function in crosslinked LCEs remains challenging. Here, we use donor-acceptor Stenhouse adducts (DASAs) as a tunable photoswitch family to engineer an electronically diverse DASA-LCE platform with varied charge separation. A series of five DASAs spanning neutral to strongly zwitterionic character were incorporated into siloxane-based LCEs via late-stage functionalization. The solution-phase solvatochromic slope serves as a spectroscopic descriptor for ground-state push-pull character and reveals a strong linear correlation with solid-state reversible photofading rate coefficients, establishing a unique molecular-level predictor for DASA-based LCE switching. Increasing charge separation produces a continuum of LCE responses: neutral DASAs undergo efficient photoisomerization that drives reversible uniaxial contraction. In contrast, zwitterionic DASAs drive photothermal bending, enabling bilayer actuators with biomimetic crawling (0.2 cm s^-1) and jumping. These results establish a design rule linking DASA electronic structure to macroscopic actuation and provide a practical screening metric for white-light-responsive LCE actuators.