Colossal Barocaloric Effect in Liquid Crystals via Cascade Order–Disorder Transitions

The order–disorder transition plays a pivotal role in the exploration of barocaloric materials, exemplified by the recent discovery of colossal barocaloric plastic crystals. Among the various candidates undergoing order–disorder transitions, liquid crystals stand out as a particular category with cascade solid-smectic-nematic-liquid phase transitions, which endow them with great potential as high-performance barocaloric materials. Herein, we report the barocaloric properties and the underlying entropy change mechanism of a series of length-tunable liquid crystals (4′-alkyl-4-cyanobiphenyl, nCB, n = 5, 6, 7, and 8). These liquid crystals exhibit large isothermal entropy changes (200–540 J K^–1 kg^–1) and substantial adiabatic temperature changes up to 20 K at 1000 bar. Raman spectroscopy confirms enhanced intermolecular interactions and more ordered molecular packing under pressure with a notable peak narrowing and red shift. These liquid crystals also exhibit stable thermodynamic properties over multiple pressurization cycles, with an average entropy change of 275 J K^–1 kg^–1. Compared with other known barocaloric materials, liquid crystals show superior performance in terms of both pressure response and thermal stability, highlighting the significance of cascade order–disorder phase transitions in achieving colossal barocaloric performance.