E. Juszyńska

DSC studies of neohexanol and its isomers

DSC method has been used to establish a solid state polymorphism of four dimethyl butanols having CH3 side groups: 2,2-dimethyl-1-butanol [CH3CH2C(CH3)2CH2OH)], 3,3-dimethyl-1-butanol [(CH3)3CCH2CH2OH], 3,3-dimethyl-2-butanol [(CH3)3CCH(OH)CH3] and 2,3-dimethyl-2-butanol [(CH3)2CHCOH(CH3)2]. 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.

Signatures of glass transition in partially ordered phases

Features of glass transition in liquid crystalline nematic and smectic E, B and IA phases of selected materials observed by means of the polarising microscopy and Fourier transform infrared spectroscopy (FTIR) are reported. Evolution of cracking in the glass and a coincidence of its disappearance temperature with the glass transition temperature (Tg) on heating is shown and discussed in the context of processes that occur in the glass. The shape of temperature dependencies of absorption bands is shown as the signature of the glass transition.

Phase Transition and Structure Studies of a Liquid Crystalline Schiff-Base Compound (4O.8)

Calorimetric and X-ray powder diffraction studies of N-(4-n-butyloxybenzylidene)-4′-n′-octylaniline are presented. Heat capacity measurements have been performed by adiabatic calorimetry in the temperature range from 5 K to 375 K. Three liquid crystalline phases, i.e., nematic, smectic A and smectic B, and an ordered crystal of triclinic structure and two new metastable crystal phases were observed. In addition, the crystalline smectic B phase of different sequence of molecular layers than liquid crystalline smectic B, has been found. Both smectic B phases have been vitrified. For the smectic B phase a hexagonal unit cell has been identified by X-ray diffraction. The diffraction pattern of glass of crystalline smectic B phase is shown.

Description of isomorphous transformations in materials with various kinds of molecular disorder

The Landau-type expansion of the free energy density function up to the eighth order with respect to the order parameter is used to describe the specific heat in structural transformations, where the symmetry does not change. This model implies three generic scenarios of phase transitions: (i) single discontinuous; (ii) one discontinuous (isomorphous) and one continuous (symmetry breaking transition); (iii) two continuous (the first transformation-like anomaly with no symmetry change, the second – symmetry breaking transition), depending on the value of the only negative coefficient of the sixth order. The specific heat data in MAPCB, 2,2-DM-1-B, 3,3-DM-2-B and 3TCB are analysed within proposed theory.