  Materials exhibiting a large caloric effect could lead to the development of
new generation of heat-management technologies that will have better energy
efficiency and be potentially more environmentally friendly. The focus of
caloric materials investigations has shifted recently from solid-state
materials toward soft materials, such as liquid crystals and liquid crystalline
elastomers. It has been shown recently that a large electrocaloric effect
exceeding 7 K can be observed in smectic liquid crystals. Here, we report on a
significant elastocaloric response observed by direct elastocaloric
measurements in main-chain liquid crystal elastomers. It is demonstrated that
the character of the nematic to paranematic/isotropic transition can be tuned
from the supercritical regime towards the first-order regime, by decreasing the
density of crosslinkers. In the latter case, the latent heat additionally
enhances the elastocaloric response. Our results indicate that a significant
elastocaloric response is present in main-chain liquid crystalline elastomers,
driven by stress fields much smaller than in solid elastocaloric materials.
Therefore, elastocaloric soft materials can potentially play a significant role
as active cooling/heating elements in the development of new heat-management
devices.
