We have studied liquid-liquid phase transition systems from the view point of ‘fluctuations’. New experimental concept we have recently developed is used to detect ‘fluctuations’. The advantage of the method is the simplicity: just compare the two sound velocities, high-frequency one obtained by inelastic x-ray scattering technique and low-frequency one measured by ultrasonic method. We think it will make a substantial contribution to verify the liquid-liquid critical point hypothesis. In this article, we summarize the history of experimental verification of liquid-liquid critical point hypothesis at first. Then, we show some results of our ‘fluctuations’ measurements and explain the theoretical background of the method. Finally, perspective of the method will be given. We believe it will also play a crucial role to understand glass transition phenomena.
The effect of pressure on the phase transition behavior of tridecane, pentadecane and heptadecane has been investigated up to 489, 220 and 387 MPa, respectively, using Fourier transform infrared spectroscopy at 25℃. Short range positional order in the rotator phase is discussed on the basis of factor group splitting of the P1+P3 band of the methylene rocking mode. A large proportion of alkane molecules is found to possess herringbone-type short-range positional order in the high pressure rotator phase while a smaller proportion of alkane molecules is considered to possess herringbone-type short-range positional order in the high temperature rotator phase.
High pressure (HP) phase transition behavior of 1-alkyl-3-methylimidazolium-based ionic liquids ([Cnmim]-ILs) studied using optical spectroscopy was reviewed. On the whole, [Cnmim]-ILs under high pressure showed at least three transition patterns; (i) HP-glassy state, (ii) compression crystallization, and (iii) decompression crystallization. The glass transition pressure (pg) and compression or decompression crystallization pressure (pc or pd.c) throughout the reported [Cnmim]-ILs were observed in the pressure range from 1.0 to 3.0 GPa for pg, below 1.0 GPa for pc, and below 2.0 GPa for pd.c, respectively. We discussed the selectivity between the HP-glassy state and compression crystallization of [Cnmim]-ILs.
From a viewpoint of water polyamorphism, we examined the polyamorphic behaviors of the glass of dilute aqueous solutions, a glycerol-water system and a LiCl-water system, under pressure. The polyamorphic behaviors of aqueous solution are consistent with the water polyamorphism. The solvent water in the glassy aqueous solution is able to be classified as LDA-like or HDA-like solvent waters. A coexistent region of LDA-like and HDA-like solvent waters exists in the polyamorphic diagram of the aqueous solutions, and then the extent of the coexistence region depends on the solute concentration and the solute composition.
In this article, we review the recent advances made in our group in the analysis of the line shape of the vibrational spectra in supercritical water. The vibrational dynamics of water in supercritical states has been examined by means of the classical MD simulation by paying particular attention to the relation to the rotational dynamics. Through the analysis of the effects of the water density and the isotopes of hydrogen, we revealed that the rotational couplings are the dominant determining factors of the line shape of the O-H vibrational spectrum in supercritical water.
High pressure processing is an alternative technology for preservation of foods or causes detachment an adductor muscle of shellfish. This article describes the high pressure processing equipment which had been newly developed for oyster shucking and opening without heat-treatment.