Toward mechanically robust liquid crystal elastomers: multiscale strategies from molecular engineering to hierarchical integration

Liquid crystal elastomers (LCEs) uniquely couple the orientational order of mesogens with the elasticity of polymer networks, enabling reversible shape transformation under diverse stimuli. However, their practical deployment is limited by intrinsic mechanical weaknesses, including low modulus, poor toughness, and fatigue under cyclic loading. This review article discusses recent progress and design principles for achieving mechanically robust LCEs through multiscale strategies. At the molecular level, backbone engineering, mesogen design, functional crosslinkers and chain extenders, and dynamic covalent chemistry can enhance intrinsic strength and adaptability of LCEs. At the network level, crystallizable segments, chain entanglements, supramolecular interactions, along with interpenetrating structures, can introduce efficient energy dissipation and toughness. At the hierarchical level, the incorporation of nanofillers and fiber architectures enables scalable, high-load-bearing, and multifunctional actuators. The synergy between these structural hierarchies establishes a foundation for LCEs to possess high mechanical strength, large reversible strain, and energy-efficient actuation. Finally, we highlight emerging challenges and opportunities in developing mechanically adaptive, recyclable, and multifunctional LCE systems for soft robotics, wearable devices, and biomedical actuation.