Leveraging catechol chemistry to tackle toughness-softness-work capacity tradeoff in reprogrammable liquid crystal actuators.

Abstract

Dynamic chemistry endows liquid crystal elastomers (LCEs) with reprogrammability, enabling the reversible modulation of actuation modes to adapt to diverse tasks and enhancing sustainability and lifecycle management. However, balancing toughness, softness, and work capacity remains challenging due to their inherent tradeoff, as these properties are essential for achieving high-performance and stable actuation. Here, inspired by mussel coordination chemistry, we design a macromolecular crosslinker that combines covalent crosslinking with coordination bonds to tackle this challenge. The optimized LCE achieves exceptional toughness of 28.5 MJ/m³ and low Young's modulus of 3.1 MPa, with high-temperature toughness exceeding 9.3 MJ/m³ at 90 °C (25 °C above phase transition temperature, Ti) and reaching 5.5 MJ/m³ at 120 °C (55 °C above Ti), while maintaining work capacity of 416 kJ/m³. Increasing coordination bond content further improves toughness (up to 67.0 MJ/m³) without significantly altering modulus or work capacity. Additionally, incorporating different metal ions provides a strategy akin to stem cell differentiation, transforming a single base material into variants with distinct properties. This enables spatially heterogeneous materials, paving the way for highly integrated actuators with multifunctionality.