title: Electrocaloric and elastocaloric effects in soft materials.
abstract: Materials with large caloric effect have the promise of realizing solid-state refrigeration which has potential to be more efficient and environmentally friendly compared with current cooling technologies. Recently, the focus of caloric effects investigations has shifted towards soft materials. An overview of recent direct measurements of the large electrocaloric effect (ECE) in a composite mixture of a liquid crystal and nanoparticles (NPs) and large elastocaloric (eC) effect in main-chain liquid crystal elastomers is given. In mixtures of 12CB liquid crystal with functionalized CdSSe NPs, an ECE exceeding 5 K was found in the vicinity of the isotropic to smectic A phase transition. It is shown that the NPs smear the isotropic to smectic coexistence range in which a large ECE is observed due to latent heat enhancement. NPs acting as traps for ions reduce the moving-ion density and consequently the Joule heating. Direct eC measurements indicate that the significant eC response can be found in main-chain liquid crystalline elastomers, but at a fraction of the stress field in contrast to other eC materials. Both soft materials could play a significant role as active cooling elements or parts of thermal diodes in development of new cooling devices.This article is part of the themed issue 'Taking the temperature of phase transitions in cool materials'.
authors.affiliation: Jozef Stefan Institute, Jamova 39, 1001 Ljubljana, Slovenia.
authors.forename: Maja
authors.initials: M
authors.lastname: Trček
authors.affiliation: Jozef Stefan Institute, Jamova 39, 1001 Ljubljana, Slovenia.
authors.forename: Marta
authors.initials: M
authors.lastname: Lavrič
authors.affiliation: Jozef Stefan Institute, Jamova 39, 1001 Ljubljana, Slovenia.
authors.forename: George
authors.initials: G
authors.lastname: Cordoyiannis
authors.affiliation: Jozef Stefan Institute, Jamova 39, 1001 Ljubljana, Slovenia The Jozef Stefan International Postgraduate School, Jamova 39, 1001 Ljubljana, Slovenia.
authors.forename: Boštjan
authors.initials: B
authors.lastname: Zalar
authors.affiliation: Jozef Stefan Institute, Jamova 39, 1001 Ljubljana, Slovenia.
authors.forename: Brigita
authors.initials: B
authors.lastname: Rožič
authors.affiliation: Jozef Stefan Institute, Jamova 39, 1001 Ljubljana, Slovenia Faculty of Natural Sciences and Mathematics, University of Maribor, 2000 Maribor, Slovenia.
authors.forename: Samo
authors.initials: S
authors.lastname: Kralj
authors.affiliation: National Centre for Scientific Research 'Demokritos', 15310 Aghia Paraskevi, Greece.
authors.forename: Vassilios
authors.initials: V
authors.lastname: Tzitzios
authors.affiliation: National Centre for Scientific Research 'Demokritos', 15310 Aghia Paraskevi, Greece.
authors.forename: George
authors.initials: G
authors.lastname: Nounesis
authors.affiliation: Jozef Stefan Institute, Jamova 39, 1001 Ljubljana, Slovenia The Jozef Stefan International Postgraduate School, Jamova 39, 1001 Ljubljana, Slovenia zdravko.kutnjak@ijs.si.
authors.forename: Zdravko
authors.identifier: 0000-0002-3089-7993
authors.initials: Z
authors.lastname: Kutnjak
keywords: elastocaloric; electrocaloric; liquid crystal; liquid crystal elastomers