Molecular Dynamics Simulations of the Spontaneous Deformation and Auxetics Behavior During Tensile Test of a Nematic Liquid Crystal Elastomer Model

Nematic liquid crystal elastomers (LCEs) are advanced materials known for their shape-changing capability in response to external stimuli such as heat, light and electromagnetic fields. This makes them excellent candidates for applications like soft robotics and energy harvesting. While studies on their physical behavior have shed light on the complex nonlinear mechanics of LCEs, investigations through all-atom molecular dynamics (MD) simulations remain an underutilized avenue compared to experimental and theoretical analyses. This limited use is primarily due to the lack of well-established frameworks for conducting high-fidelity atomistic simulations of LCEs. To bridge this gap, we introduce an all-atom MD simulation framework based on the Polymer Consistent Force-Field (PCFF), which models the polymerization and crosslinking processes for a category of acrylate LCEs and captures their synthesis history- and composition-dependent properties. Our computational framework empowers us to simulate the spontaneous deformations and shape memory behavior upon temperature changes and enables us to observe the auxetic effect under elastic strains by generating models that closely replicate experimental findings. Moreover, this study not only validates the numerical models but opens up new avenues to explore the intricate behaviors of LCEs through their molecular structures and facilitate computational design advancements.