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

ABSTRACT

Materials exhibiting a large caloric effect could lead to the development of a 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 towards soft materials, such as liquid crystals and liquid crystalline elastomers. It has been shown recently that a large electrocaloric effect exceeding 6 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.

Graphical abstract

KEYWORDS:

• Elastocaloric
• liquid crystal elastomers
• caloric materials
• solid-state cooling

Disclosure statement

No potential conflict of interest was reported by the author(s).

Supplementary material

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Additional information

Funding

This work was supported by the European Commission [778072 H2020-MSCA-RISE-2017, European Regional Development Fund]; Javna Agencija za Raziskovalno Dejavnost RS [J1- 9147, NAMASTE Centre of Excellence, P1-0099, P1-0125, Space-SI Centre of Excellence].