Guest molecule dynamics and ferroelectric transition in a clathrate compound

• Published in: Physical chemistry chemical physics : PCCP Vol. 27; no. 15; pp. 7833 - 7839
• Main Authors: Erkoreka, Aitor, Du, Zi-Yi, Oleaga, Alberto, Huang, Rui-Kang, Martinez-Perdiguero, Josu
• Format: Journal Article
• Language: English
• Published: England Royal Society of Chemistry 09.04.2025
• Subjects: Broadband; Clathrates; Ferroelectric materials; Ferroelectricity; Imidazole; Low molecular weights; Molecular motion; Molecular relaxation; Quantum chemistry
• DOI: 10.1039/d5cp00100e
• ISSN: 1463-9076; 1463-9084

Low molecular weight glass formers encapsulated within clathrate structures offer a singular testground to study the intricate interplay of confined molecular motion and ferroelectric properties. Using broadband dielectric spectroscopy (BDS), we investigate the dynamic behavior of 1-propyl-1 H -imidazole within a supramolecular enclosure formed by duad semicage p-tert -butylcalix[4]arene. Unlike the bulk liquid, where the dielectric spectrum is dominated by the structural relaxation, the clathrates paraelectric phase reveals two distinct molecular relaxation processes. Aided by quantum chemical calculations, the slow process is assigned to head-to-tail reorientations of the guest molecule, while the faster process arises from intramolecular fluctuations of the imidazole ring. These dynamics freeze as the system transitions to the ferroelectric state via a second-order phase change that has been characterized by photopyroelectric calorimetry. The confinement of a low molecular weight glass former in a clathrate system leads to a significant change in its dynamics and to the emergence of long-range polar order.