DSC studies of neohexanol and its isomers

Abstract

DSC method has been used to establish a solid state polymorphism of four dimethyl butanols having CH 3 side groups:. Three isomers appear to be glass formers. Glass of liquid phase has been observed for 3,3-DM-1-B while glass of plastic phase for 2,2-DM-1-B and 3,3-DM-2-B. For 2,3-DM-2-B on cooling only crystallization has been found. Influence of location of the OH group in molecule on polymorphism is discussed. IR-spectra, measured in the liquid phase, have revealed hydrogen bonds in all isomers.

Solid State Polymorphism and Dynamics οf 2,2-Dimethylbutan-1-ol as Studied by Adiabatic Calorimetry and Dielectric Spectroscopy

“…Dworkin's DSC measurement showed a glass transition at 147 K, a spontaneous crystallization anomaly at 180 K, and melting at 224.5 K (onset value) [17]. In our DSC measurements [5] a previously nonobserved phase transition anomaly at about 235 K was found (see Fig. 1):…”

“…It is also valid for isomers of neohexanol, where systematic dierential scanning calorimetry (DSC) studies showed various sequences of mesophases [5]. It is worth to note that various isomers of neohexanol have dierent number of conformations.…”

“…Additionally, at melting some thermodynamical parameters are dierent for various isomers as calculated using extended Landau theory [8]. [15,16], DSC [5,6,17], dielectric relaxation [6,10,1520], and inelastic incoherent neutron scattering [6,7,9,1113] methods. The DT results published by Chan and Johari [18,19] showed a crystallization at 183 K and melting at 241 K. In DT studies of Edelmann [15,16] ve solid phases (with additional one at higher pressure) were found in the following phase transitions: C III…”

IINS, MIR, and DFT Investigations of Vibrational Spectra of 3, 3-Dimethyl-1-Butanol and 3, 3-Dimethyl-2-Butanol

“…For 3,3-DM-1B on cooling down to 13 K glass of isotropic liquid was formed and it softened (1131) during heating at 156 K. At 196 K the crystallization of the supercooled liquid occurred and at 234 K melting of the stable crystal was observed. On cooling of 3,3-DM-2B to liquid nitrogen temperatures a crystallization of the orientationally disordered plastic crystal C1 (ODIC) occurs at 260 K and it transforms into glass of plastic crystal at 210 K. On heating the ODIC phase C1 appeared at 210 K, and next solid-solid phase transitions took place at 245 K and 271 K, and at 275 K melting was observed [2]. At 20 K in 3,3-DM-1B glass of isotropic liquid phase (on fast cooling) or crystal phase (on slow cooling) were identified by the inelastic incoherent neutron scattering (IINS) spectra obtained using different temperature treatment of the sample [3,4] and only glassy crystal in 3,3-DM-2B.…”

“…These substances are isomers of neohexanol with the general chemical formula C 6 H 13 OH. Their solid phase polymorphism has been identified by the differential scanning calorimetry (DSC) and adiabatic calorimetry methods [1,2]. For 3,3-DM-1B on cooling down to 13 K glass of isotropic liquid was formed and it softened (1131) during heating at 156 K. At 196 K the crystallization of the supercooled liquid occurred and at 234 K melting of the stable crystal was observed.…”