Molecular-Scale Simulation of Auxetic Behavior in Side-Chain Liquid Crystalline Polymers (SCLCPs)

Auxetic materials, characterized by a negative Poisson’s ratio (NPR), exhibit unique mechanical properties with applications in medical and military technologies. Recent experimental and theoretical studies have demonstrated bulk auxetic behavior in liquid crystal elastomers (LCEs), highlighting the molecular reorientation mechanisms involved. However, side-chain liquid crystalline polymers (SCLCPs) remain underexplored for intrinsic molecular auxeticity. Using coarse-grained molecular dynamics simulations, we investigate SCLCPs inspired by Griffin’s architecture, focusing on their phase transitions and Poisson’s ratio. One-arm and two-arm SCLCP variants were simulated, revealing NPR in one-arm systems at low lateral monomer volume fractions (R < 6%), driven by the swirling motion of longitudinal monomer domains. Phase transitions from amorphous to polycrystalline smectic-like configurations were analyzed using a cooling process, with properties evaluated below the transition threshold (∼400 K). To enhance accuracy, the ab initio calculations on energy interactions between different configurations of ellipsoids and beads were performed. Our findings elucidate molecular mechanisms underlying auxetic behavior in SCLCPs, complementing existing LCE studies and offering insights for designing tailored auxetic polymers.