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Orientational Transition in a Liquid Crystal Triggered by the Thermodynamic Growth of Interfacial Wetting Sheets
Published on: May 15, 2017
Pressure-Induced Solid-Solid Phase Transitions in Barocaloric Organic Ionic Plastic Crystals
Samantha L Piper1, Amith Kumar Murali2, Marian Paluch2
1Institute for Frontier Materials, Deakin University, Burwood, Victoria 3125, Australia.
ACS Applied Materials & Interfaces
|June 19, 2026
Summary
Organic ionic plastic crystals show promise as eco-friendly refrigerants. High-pressure dielectric spectroscopy reveals their pressure-dependent phase transitions and hysteresis, crucial for designing better barocaloric materials.
Area of Science:
- Materials Science
- Thermodynamics
- Solid-State Physics
Background:
- Barocaloric (BC) materials offer a sustainable alternative to traditional gas refrigerants.
- Understanding solid-solid phase transitions (SSTs) under pressure is key for designing effective BC materials.
- Organic ionic plastic crystals (OIPCs) are promising BC candidates, but their pressure-dependent phase behavior is difficult to characterize.
Purpose of the Study:
- To utilize high-pressure broadband dielectric spectroscopy (HP-BDS) to map the phase diagrams of three OIPCs.
- To investigate the pressure sensitivity and transition hysteresis of SSTs in OIPCs.
- To understand the ion-dependent nature of phase transitions and hysteresis in OIPCs.
Main Methods:
- High-pressure broadband dielectric spectroscopy (HP-BDS) was employed.
- Isobaric cooling/heating and isothermal compression/decompression experiments were conducted.
- The real part of the complex dielectric permittivity (ε') was monitored to detect SSTs.
Main Results:
- The real part of dielectric permittivity (ε') effectively detects SSTs in OIPCs, linked to dipolar reorientation.
- Direct measurements of pressure sensitivity (dTSS/dP) and transition hysteresis were obtained for three OIPCs.
- Hysteresis behavior was found to be unique to each OIPC and strongly ion-dependent, with [C2mmor][FSI] showing lower pressure hysteresis than predicted.
Conclusions:
- HP-BDS is a valuable tool for characterizing pressure-dependent phase behavior in OIPCs.
- The ion structure significantly influences SSTs and hysteresis in OIPCs.
- [C2mmor][FSI] exhibits favorable hysteresis properties, enhancing its potential as a barocaloric material.
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