A compendium of phase change enthalpies published in 2010 is updated to include the period 1880–2015. Phase change enthalpies including fusion, vaporization, and sublimation enthalpies are included for organic, organometallic, and a few inorganic compounds. Part 1 of this compendium includes organic compounds from C1 to C10. Part 2 of this compendium, to be published separately, will include organic and organometallic compounds from C11 to C192. Sufficient data are presently available to permit thermodynamic cycles to be constructed as an independent means of evaluating the reliability of the data. Temperature adjustments of phase change enthalpies from the temperature of measurement to the standard reference temperature, T = 298.15 K, and a protocol for doing so are briefly discussed.

Phase Transition Enthalpy Measurements of Organic and Organometallic Compounds. Sublimation, Vaporization and Fusion Enthalpies From 1880 to 2015. Part 1. C1-C10

–OH) is revealed to be a complexproblem and only two stable solid phases, denoted on cooling from the liquid as phases I and II, are foundusing static ~thermodynamic and x-ray diffraction! as well as dynamic ~dielectric spectroscopy! experimentaltechniques. Both solid phases are known to exhibit glass transitions if they are cooled down fast enough toprevent transition to ordered crystalline states. Although glass transitions corresponding to both phases hadbeen well documented by means of speciﬁc heat measurements, x-ray measurements constitute, as far as weknow, the ﬁrst evidence from the structural point of view. In addition, a great amount of dielectric worksdevoted to phase I and its glass transition, were published in the past but next to nothing relating to thedielectric properties of phase II and its glass transition. The nature of the disorder of phase II will be discussed.DOI: 10.1103/PhysRevB.69.224202 PACS number~s!: 61.43.2j, 64.70.Pf, 65.60.1a, 77.22.2dI. INTRODUCTION

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Thermodynamic, crystallographic, and dielectric study of the nature of glass transitions in cyclo-octanol.

The results of mid-infrared spectroscopy and X-ray studies of the third member of the 4-n-alkyl-4'-isothiocyanatobiphenyl (nTCB) homologous series are presented. Correspondence between the phase transitions observed by means of the IR spectroscopy and those given by the adiabatic calorimetry was found. The structure of five solid phases was obtained by X-ray measurements. IR spectroscopic and X-ray data give the arguments supporting the identification of the glass of smectic E phase. Assignment of the IR vibrational bands, in the smectic E, in the glass of smectic E, and in one of the crystalline phases, with help of the hybrid B3LYP/6-311++G(d,f) functional calculations is presented.

Infrared spectroscopic and X-ray studies of the 4-propyl-4'-isothiocyanatobiphenyl (3TCB).

In the present communication, dielectric relaxation investigations on three interesting supercooled plastic crystalline substances, i.e., isocyanocyclohexane (ICNCH), cyanocyclohexane (CNCH), and 1-cyanoadamantane (CNADM) are reported. All of these have the main dipole moment situated in their side group- C[Triple Bond]N or- N[Triple Bond]C. Differential scanning calorimetry (DSC) was also employed as a supporting technique. Glassy crystal were easily formed in the first two samples by slowly cooling the plastic phase, but in CNADM it was formed by rapidly quenching the room temperature plastic phase. In addition to the so called alpha process that can reasonably be described by a Havriliak-Negami (HN) shape function, a secondary (or beta) relaxation process is found in all the materials. The beta process in CNADM has an activation energy (DeltaE(beta)) of about approximately 13.8+/-1 kJmol, and is present even in the corresponding ordered crystalline phase, i.e., in its monoclinic phase. On the other hand, the magnitude of DeltaE(beta) in both the isomers of cyanocyclohexane, i.e., ICNCH and CNCH, is similar and is about 21.1 and 23.4 kJmol, respectively. Unlike CNADM, the cyclohexane derivatives are capable of exhibiting additional intramolecular process due to chair-chair conversion (i.e., in addition to the rotational motion of the side group- C[Triple Bond]N or- N[Triple Bond]C). Therefore, the secondary process of these systems is compared to that occuring in the binary liquid glass formed by dispersing a small quantity of these dipolar liquids in nearly nonpolar orthoterphenyl (OTP). Measurements were also made in the supercooled binary mixures of other cyclohexyl derivatives like cyclohexylchloride and cyclohexylbromide with OTP which lack a flexible side group. The sub-T(g) relaxation process exhibited in all these cases have almost similar activation energy as in case of pure ICNCH and CNCH. These observations together with the fact that the activation energy for this process is much below that of chair-chair conversion which is about 43 kJmol leads us to the conclusion that sub-T(g) relaxation process in the binary mixtures is JG type, and perhaps beta relaxation process in phase I of ICNCH and CNCH is also similar. With the help of semiemperical calculations of the dipolemoments for the axial and equitorial confirmers, it is concluded that the process associated with the chair-chair may not be dielectrically very active and, hence, should be relatively weaker in magnitude. The beta process in CNADM has an activation energy (DeltaE(beta)) of about 13.8+/-1 kJmol, and is present even in the corresponding ordered crystalline phase indicating that it may not be characteristic of the glass formation of phase I. The molecular structure of CNADM is such that it does not possess other intramolecular degrees of freedom of the type equitorial to axial (or chair-chair) transformation. Our experimental finding that JG relaxation for CNADM dispersed in glassy OTP matrix is about 31 kJmol, indicating that the well resolved sub-T(g) process in CNADM is due to the small side group, i.e., -C[Triple Bond]N and JG relaxation in phase I of CNADM is perhaps not resolvable or too small to be detected.

Study of secondary relaxation in disordered plastic crystals of isocyanocyclohexane, cyanocyclohexane, and 1-cyanoadamantane.

High pressure dielectric studies on the H-bonded liquid D-glucose and Orientationally Disordered Crystal (ODIC) 1,6-anhydro-D-glucose (levoglucosan) were carried out. It was shown that in both compounds, the structural relaxation is weakly sensitive to compression. It is well reflected in the low pressure coefficient of the glass transition and orientational glass transition temperatures which is equal to 60 K/GPa for both D-glucose and 1,6-anhydro-D-glucose. Although it should be noted that ∂Tg(0)/∂p evaluated for the latter compound seems to be enormously high with respect to other systems forming ODIC phase. We also found that the shape of the α-loss peak stays constant for the given relaxation time independently on the thermodynamic condition. Consequently, the Time Temperature Pressure (TTP) rule is satisfied. This experimental finding seems to be quite intriguing since the TTP rule was shown to work well in the van der Waals liquids, while in the strongly associating compounds, it is very often violated. We have also demonstrated that the sensitivity of the structural relaxation process to the temperature change measured by the steepness index (mp) drops with pressure. Interestingly, this change is much more significant in the case of D-glucose with respect to levoglucosan, where the fragility changes only slightly with compression. Finally, kinetics of ODIC-crystal phase transition was studied at high compression. It is worth mentioning that in the recent paper, Tombari and Johari [J. Chem. Phys. 142, 104501 (2015)] have shown that ODIC phase in 1,6-anhydro-D-glucose is stable in the wide range of temperatures and there is no tendency to form more ordered phase at ambient pressure. On the other hand, our isochronal measurements performed at varying thermodynamic conditions indicated unquestionably that the application of pressure favors solid (ODIC)-solid (crystal) transition in 1,6-anhydro-D-glucose. This result mimics the impact of pressure on the crystallization of fully disordered supercooled van der Waals liquids.

High pressure dielectric studies on the structural and orientational glass

Static and dynamic studies on cycloheptanol as two-orientational glass-former

The two-component system cycloheptanol (C7) + cyclooctanol (C8) has been studied by means of thermal analysis, X-ray powder diffraction, and dielectric spectroscopy. In a first step, the polymorphi...

Two-component system cycloheptanol (C7) + cyclooctanol (C8): An extraordinary system

The stable solid polymorphism of cycloheptanol (C 7 H 14 O, for short C 7 –OH) is revised in the present paper. Four solid stable phases, denoted on cooling from the liquid as phases I, II, III and IV are identified from X-ray diffraction measurements. Lattice symmetry of phase III has been unambiguously stated as orthorhombic. Diffraction patterns corresponding to phase IV have been also indexed as orthorhombic, but only in a tentative way. A detailed broadband dielectric spectroscopy study devoted to these phases has been made. Such an experimental technique has no revealed differences between phases III and IV and from specific-heat measurements, the III–IV phase transition has not been observed yet. Dielectric results seem to evidence that the dynamic disorder of phase III and/or IV should be intra-molecular attributed to changes between the possible distinguishable molecular conformations along with possible hydroxyl group rotations. The possibility of C 7 –OH as conformational glass - forming material is discussed.

R. Puertas

Papers

Static and dynamic studies on cycloheptanol as two-orientational glass-former

Two-component system cycloheptanol (C7) + cyclooctanol (C8): An extraordinary system

Solid phases in cycloheptanol: Dynamic disorder and glass transitions