High-strength thermochromic and mechanochromic liquid-crystal elastomers with responsive shape memory and dynamic adhesion

• Published in: Journal of materials chemistry. A, Materials for energy and sustainability Materials for energy and sustainability, 2024-07, Vol.12 (29), p.18117-18126
• Main Authors: Li, Lu, Yin, Xi, Zhao, Yu-Xi, Shi, Ling-Ying, Yang, Ke-Ke, Wang, Yu-Zhong
• Format: Article
• Language: English
• Subjects: Adhesion; Cholesteric liquid crystals; Crosslinking; Elastomers; Energy dissipation; External stimuli; Mechanical properties; Optical measuring instruments; Response functions; Robotics; Sensors; Shape effects; Shape memory; Soft robotics; Stimuli
• ISSN: 2050-7488; 2050-7496
• DOI: 10.1039/d4ta02010c

Soft materials with stimuli-responsive functionalities have crucial applications in advanced sensors and soft robotics. However, integrating multiple response functions into a single soft material poses significant challenges. In addition, striking a good tradeoff between achieving high mechanical performance and maintaining a highly sensitive response to external stimuli is crucial. Here, we present the design of cholesteric liquid-crystal elastomers (CLCEs) characterized by high mechanical performance and a diverse array of responsive functionalities including thermochromic, mechanochromic, shape memory, and dynamic adhesion behaviors. The strategy employed involves the creation of loosely crosslinked CLCEs with densely packed nematic and chiral LC mesogens suspended on the side chain, ensuring significant tunability in the ordering/orientation, coupled with notable energy dissipation across the nematic-isotropic transition. We systematically investigated the impact of the crosslinking density and chiral content on the thermal, photonic, and mechanical behaviors. The CLCE films exhibit superior mechanical properties ( σ b ∼ 19.7 MPa and b ∼ 300%), sensitive thermochromic and mechanochromic behaviors in the full visible light wavelength range, characteristic triple shape memory effects, and universal temperature-responsive adhesion. This study represents an effort toward developing mechanically robust CLCEs that integrate multiple stimuli-responsive functionalities, providing the foundation for advanced applications in anti-counterfeiting, optical sensors, and biomorphic robotics. Versatile CLCEs with a loosely crosslinking density were developed, which exhibit exceptional high mechanical performances and responsive functionalities including thermochromic, mechanochromic, shape memory, and dynamic adhesion behaviors.