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The complex polymorphism and vibrational dynamics of three glass-forming single-phenyl-ring alcohols (with and without fluorine atoms) have been studied by complementary methods. Glass of isotropic...

The appearance of reentrant nematic phase was identified in nCB/8CB (n = 1–6) binary mixtures using differential scanning calorimetry, small-angle X-ray diffraction and polarising microscopy with photomonitor. Phase diagrams can roughly be unified if plotted against the average number of alkyl chain length. Distinction was recognised for the phase boundaries between nematic and smectic A phases of even and odd n of the minor component nCB. The character of 8CB as ‘SmA former’ is briefly discussed.

The phase behaviour of the thermotropic cubic mesogen 1,2-bis(4′-n-hexyloxybenzoyl)hydrazine [BABH(6)] was investigated under pressure up to about 55 MPa using a polarising optical microscope equipped with a high-pressure optical cell. BABH(6) shows the crystal (Cr)–cubic (Cub)–isotropic liquid (I) phase transition at ambient pressure on heating. The smectic C (SmC) phase was induced above 32 MPa, showing the unusual phase sequence of Cr–Cub–SmC–I, similar to those in BABH(n) (n = 8–10). The boundary between the Cub and SmC phases exhibited a negative slope dT/dP of about –1.0 oC MPa−1.

Molecular dynamics in the soft crystal, E phase of 6-octyl-2-phenylazulene was studied by X-ray diffraction, and dielectric and Fourier transform infrared spectroscopies. Clear dielectric dispersion is observed due to the head-to-tail disordering in a kHz range around 400 K. The CH stretching frequencies exhibit more pronounced shifts at the phase transition point from the high-temperature ordered crystal to the E phase than that at the melting from the E phase to the isotropic liquid. The results are discussed in comparison with a typical E series, 4-n-alkyl-4′-isothiocyanatobiphenyl (n being the number of carbon atoms in the alkyl group).

The thermal behaviour of 4‐propyl‐4′‐thiocyanatobiphenyl (3TCB) was studied by adiabatic calorimetry. In addition to the isotropic liquid and smectic E (SmE) phases, five crystalline phases were detected. Such a rich polymorphism was not observed for the other low‐n members of the nTCB homologous series (n = 2–5). The observed anomalies are analysed and the possible origin for their existence is suggested. The temperature quench of the SmE phase leads to a metastable crystalline state with a multiple‐stage relaxation process.

Physical properties up to 600 K are studied for (TMTSF) 2 PF 6 , (TMTTF) 2 PF 6 , (DMET) 2 I 3 , (DMET) 2 AuI 2 , (DIMET) 2 I 3 , (DIMET) 2 AuI 2 and κ-(ET) 2 Cu(NCS) 2 . It has been found that all the compounds decompose between 450 and 500 K by TG-DTA measurement. Electric resistivity and thermopower of the TMTSF and DMET salts are metallic as were expected from their temperature dependence below 300 K. The TMTTF and DIMET salts show constant thermopower, though their resistivity is metallic. This suggests that the TMTTF and DIMET salts are intrinsically non-metallic even above room temperature. Rapid decrease in resistivity found for many of the Q1D salts before their decomposition suggests the partial escape of anions and change in the carrier concentration. κ-(BEDT-TTF) 2 Cu(NCS) 2 shows hysteretic temperature dependence of the resistivity above 300 K.

Heat capacities of optically isotropic mesogens, BABH(8), ANBC(16) and ANBC(18), have been measured by adiabatic calorimetry. The existence of solid-solid phase transitions with large entropy chang...

Raman scattering spectra and magnetic susceptibility are measured in intercalation compounds FexNbS2 (0.159≤x≤0.325). A strong modification of Raman spectra is observed in a sample with x=0.239 (∼ 0.25) which is accompanied by 2a × 2a structural change and antiferromagnetic ordering. Some correlations between magnetic ordering (antiferromagnetic or spin glass) and structural change are also discussed for wide range of Fe contents x.

Heat capacity measurements have been made on ANBC(18) at temperatures from 8 to 490 K by adiabatic calorimetry. All known phases were detected. The temperatures, enthalpies and entropies of transition were determined for the phase transitions observed. On the basis of the entropy of transition to the SmC phase from the D or cubic phases, it is pointed out that the D phase of ANBC and the cubic phase of BABH might be identical in nature. It is shown that the arrangement of 'molecular' cores has a higher degree of order in the isotropic (D and cubic) phases than in the SmC phase, whereas the terminal alkoxy chains are more disordered in the isotropic phases than in the SmC phase. The degrees of disorder in the D and cubic phases relative to the SmC phase are very similar in terms of the entropy of transition per methylene group. The inverted phase sequence in ANBC (SmC D on heating) and BABH (cubic SmC) can be accounted for in terms of the competing roles in the entropy between the molecular core and the ch...