Dielectric constant of disordered phases of the smallest monoalcohols: Evidence for the hindered plastic crystal phase

• Published in: Chemical physics 2022-07, Vol.559, p.111554, Article 111554
• Main Authors: Kondrin, M.V., Pronin, A.A., Lebed, Y.B., Brazhkin, V.V.
• Format: Article
• Language: English
• Subjects: Deielectric spectroscopy; Ethanol; Metanol; Phase transition; Plastic crystal
• ISSN: 0301-0104
• DOI: 10.1016/j.chemphys.2022.111554

With gradual temperature increase in premelting regions of solid phase of methanol and high pressure phase of ethanol, and using novel procedure of separation of electrode polarization effects, we are able to register the contribution of relaxation process to low-frequency dielectric constant. This contribution is about half the liquid’s dielectric constant near temperature of solidification, and is almost an order of magnitude higher than reported earlier for ambient pressure phase of methanol. As opposed to dielectric constant of water at ambient pressure, which does not change much during crystallization, our finding indicates the hindrance of molecule rotation in orientationally disordered phases of monoalcohols. Similar dielectric responses of ambient pressure methanol and high-pressure phase of ethanol imply existence of hindered plastic crystal phase of ethanol (not observed at low pressures). We also have found some dynamic disorder in nominally fully ordered phase of these monoalcohols.