Tunability of the elastocaloric response in main-chain liquid crystalline elastomers

TL;DR

This study demonstrates that main-chain liquid crystalline elastomers exhibit a significant elastocaloric effect, which can be tuned by adjusting crosslinker density, offering promising applications in energy-efficient heat management technologies.

Contribution

The paper reveals how the elastocaloric response in liquid crystalline elastomers can be controlled via crosslinker density, highlighting their potential as soft cooling and heating materials.

Findings

Elastocaloric response is significant in liquid crystalline elastomers.

Transition character can be tuned from supercritical to first-order.

Latent heat enhances elastocaloric effect in certain regimes.

Abstract

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.