Adaptive Structural Regulation of Disulfide Contained Liquid Crystal Elastomers for Mild Temperature-Induced Two-Way Shape Memory Effects

Liquid crystal elastomers (LCEs) have emerged as promising candidates for flexible actuators due to their unique combination of synergistic anisotropic, responsive feature, and excellent elasticity. However, achieving desirable stress-free two-way shape memory effects (2W-SMEs) under mild thermal conditions remains a key challenge. In this study, we present a molecular engineering strategy that not only incorporates dynamic disulfide bonds, but also systematically regulates molecular chain architecture and network topology to realize structurally adaptive main-chain LCEs with superior stress-free 2W-SMEs. Our approach involves (1) the adaptive design of disulfide-containing monomers, (2) the strategic selection of chain extenders and flexible regulators, and (3) the implementation of two distinct cross-linking strategies to modulate network rigidity and density. This comprehensive design enables precise tuning of the liquid-to-isotropic phase transition temperature of prepolymers, lowering it close to room temperature and allowing thermal programming at just 80 °C. The resulting LCE demonstrated remarkable 2W-SME performance, achieving an actuating strain (Ract) of 53.6% and an exceptional shape recovery ratio (Rrec) of 99.9% at 50 °C under stress-free conditions. Furthermore, the incorporation of ultraviolet-responsive disulfide bonds facilitated the localized programming via photomask lithography, paving the way for the creation of complex shape-morphing actuators. This work achieves molecular engineering and programming of mild-temperature-responsive LCEs with outstanding 2W-SMEs performance, offering promising applications in smart materials for advanced technologies.