Work

Theoretical and experimental study of elastocaloric responses in liquid crystalline elastomers

Year: 2024

Type: article

Abstract: • Relatively large temperature changes occur near the phase transition temperature. • A responsivity of a few 10 K/MPa is achieved for a relatively small external stress. • Qualitative agreement between experiments and simple mesoscopic modeling. • Response can be manipulated with cross-linker density and cross-linking stress. • Proximity to critical point enables strong responsivity to an external stimuli. We carry out systematic experimental and theoretical study of elastocaloric (eC) response in nematic liquid crystal elastomers (LCEs), which possess the elastic properties of elastomers combined with the orientational order of liquid crystals. The chemical linking of mesogens to the polymer backbone enables thermomechanical response yielding a large spontaneous change in the LCE geometry on varying the temperature. In LCEs, a relatively large eC effect could be obtained upon adiabatic application or removal of a stress field in the isotropic state near phase transformation to the more ordered state. In these cases a change in the isothermal entropy or adiabatic temperature is compensated with the temperature change of liquid crystal elastomers. This effect could be exploited towards soft condensed state cooling technologies that gain increasing interest due to environmental issues, low-cost and low stimuli field. In the present study we measure directly the elastocaloric temperature change. Experimental measurements are interpreted using a modified Landau-de Gennes mesoscopic model taking into account both internal and external stress fields. Our systematic study identifies conditions yielding responsivity of a few K/MPa, which is two orders of magnitude larger than in the shape memory alloys, the most intensively studied materials for this effect.

Source: Journal of Molecular Liquids

DOI: 10.1016/j.molliq.2024.126058

Authors: Dejvid Črešnar, Brigita Rožič, Zdravko Kutnjak, Samo Kralj

Institutions: Institute of High Pressure Physics, Polish Academy of Sciences, Jožef Stefan Institute, Jožef Stefan International Postgraduate School, University of Maribor

Language: English

Topic: Advanced Materials and Mechanics

Subfield: Mechanical Engineering

Field: Engineering

Domain: Physical Sciences

Open Access status: hybrid

Estimated APC paid: $3,380

Funders: North Atlantic Treaty Organization, Javna Agencija za Raziskovalno Dejavnost RS, European Research Executive Agency