Calorimetric and Dielectric Investigations of the Phase Transformations and Glass Transition of Triphenyl Phosphite

Abstract

The phase transformations and the glass−liquid transition on heating of supercooled liquid triphenyl phosphite (TPP) were studied by differential scanning calorimetry and fixed frequency dielectrometry, and the nature of its various states was discussed. The dielectric behavior of the so-called “glacial” phase shows that the slow rise in its apparent heat capacity on heating is a reflection of its exceptionally broad glass-softening transition, due to a multiplicity of relaxation times, and not its premelting. The static permittivity near its freezing point is 3.6, and the change in both the permittivity and loss shows the temperature range of the supercooled liquid → “glacial” → crystal → liquid phase transformations. These transformations are illustrated by the free energy plots, and calorimetry was done to determine their merits. The heat capacity of the glass is comparable with that of the crystal phase, which indicates that the anharmonic phonon contributions to C p in the glass and crystal phase are comparable, but that of the glacial phase is more than that of both the glass and crystal phases. In its thermal and dielectric manifestations, the “glacial” phase appears to be similar to an orientationally disordered crystal formed by a first-order transformation of a supercooled metastable liquid such as ethanol, but fails to reveal whether or not that phase is of liquid-crystal type.

Micro-structural investigations in the glacial state of triphenyl phosphite

“…The discovery of an apparently amorphous state (glacial state) by Ha et al [4,5] at ambient pressure and in a very accessible temperature range (above 200 K) has given the opportunity to analyze a supposed example of polyamorphic transformation by usual laboratory equipments. However different descriptions of the glacial state emerge from extensive investigations: a defect-ordered phase [4][5][6][7][8] inherent to the development of a locally preferred structure which is not space-tiling [8][9][10], plastic or liquid crystal [11], strong liquid [12], highly correlated liquid [13], a second glassy state corresponding to a second liquid [14], and liquid/crystallites mixed system [15][16][17][18][19][20][21][22][23].…”

On the number of amorphous phases in n-butanol

“…At present, this is, probably, the only compound, which has no threedimensional network of bonds for which the existence of two solid amorphous phases is assumed. The ÔglacialÕ phase of TPP has been studied actively by various methods [9][10][11][12][13][14][15][16][17]. Despite all attempts, there is no unambiguous description of the structure of the new state.…”

Structure Determination for the Crystalline Phase of Triphenyl Phosphite by Means of Multi-Dimensional Solid-State NMR and X-Ray Diffraction

“…[18] favoured the possibility that this phase is a second supercooled liquid with, however, unusual dynamical properties. Johari et al [19] discussed that phase all could be a 0932-0776/01/1100-1089 $ 06.00 (c) 2001 Verlag der Zeitschrift für Naturforschung, Tübingen • www.znaturforsch.com K Brought to you by | New York University Bobst Library Technical Services Authenticated Download Date | 6/13/15 12:41 AM liquid crystalline state. This possibility is also men tioned by Dvinskikh et al [8].…”