Effects of Small Molecule Additives on Liquid Crystal Elastomer Network Phase Behavior

Due to their actuation and soft elastic properties, liquid crystal elastomers (LCEs) hold promise for a wide variety of applications, ranging from electrocalorics to artificial muscles. To tune these properties, a comprehensive understanding of the relationship between LCEs' properties and their network structure is required. While theoretical models have been developed to explain LCE behavior, as-synthesized LCE networks are affected by the inevitable presence of small molecule additives; little work has been done to explicitly understand their impact. Notably, crosslinkers can lead to two opposing effects to the LCE network: an increase in the crosslinker concentration increases the crosslinking density, however the crosslinker can also act as a defect in the LCE system prior to crosslinking. Here, by probing the thermal and mechanical properties of LCEs utilizing complimentary techniques, we quantify the effects of crosslinking molecules as a function of concentration and functionality both prior to and following crosslinking. Through this study, we highlight factors and additives that perturb LCE phase behavior, allowing for a more controlled design of LCE networks.