Deconvoluting the Contribution of Polymerization Temperature to Liquid Crystalline Elastomer Actuation

Liquid crystalline elastomers (LCEs) are increasingly considered as advanced materials that prospectively may enable distinctive functional utility in medical devices, consumer goods, and aerospace. This report details the contribution of the polymerization conditions within the thermotropic phase behavior of material compositions and systematically illustrates the substantive contributions of nematic genesis to the resulting thermomechanical response. Compositionally identical LCEs were polymerized in the monodomain orientation over a range of temperatures in the nematic phase of the formulations. Upon polymerization, the thermomechanical response of the compositionally identical LCEs prepared over a range of temperatures had a 15% increase in the nematic to isotropic transition temperature (T_NI), 50% decrease in the magnitude of the thermomechanical response, and 25% decrease in total actuation stroke. X-ray scattering was utilized to elucidate the correlation of polymerization temperature (e.g., nematic genesis) to the orientational order of LCEs. These measurements show, in addition to differences in mechanical properties between the LCEs, the nematic genesis of the polymerization reaction affects the overall degree of liquid crystallinity, the coherence length of the cybotactic nematic domains, and the orientation parameter of the LCE.