Elastocaloric effect in amorphous polymer networks undergoing mechanotropic phase transitions

Abstract

Deformations of amorphous polymer networks prepared with significant concentrations of liquid crystalline mesogens have been recently reported to undergo mechanotropic phase transitions. Here, we report that these mechanotropic phase transitions are accompanied by an elastocaloric response ($\Delta T = 2.9 \text{ K}$). Applied uniaxial strain to the elastomeric polymer network transitions the organization of the material from a disordered, amorphous state (order parameter $Q=0$) to the nematic phase ($Q=0.47$). Both the magnitude of the elastocaloric temperature change and mechanically induced order parameter are dependent on the concentration of liquid crystal mesogens in the material. While the observed temperature changes in these materials are smaller than those observed in shape memory alloys, the responsivity, defined as the temperature change divided by the input stress, is larger by an order of magnitude.