Multiple melting phenomena in low mass mesogenic compound†

†This article is dedicated to Professor Jerzy A. Janik on the occasion of his 80th birthday.

Abstract

Nematogenic trans 4′-n-hexyl-4-cyclohexyl-1-thiocyanophenyle was studied using differential scanning calorimetry (DSC) and polarizing microscopy. Melting was observed in DSC at two peaks with various intensities depending upon the thermal history of the sample. After cooling to temperatures lower than 262 K double melting at 283.4 K (more intense) and 285.4 K (weaker) was noticed. The cooling to temperatures slightly higher than 262 K resulted in two peaks of equal intensity, further increasing of this temperature showed the domination of melting at the higher peak. Observations of melting starting from 269 to 276 K were leading to a single peak at 286 K. DSC results were confirmed by polarizing microscopy observations: three different textures were observed for the crystal, intermediate (also crystalline) and nematic phases. Moreover at lower temperatures on heating one could observe two extra coupled transitions (endothermic and exothermic ones).

†This article is dedicated to Professor Jerzy A. Janik on the occasion of his 80th birthday.

Keywords:

• Multiple melting
• Metastable phases
• DSC measurements
• Thermal polarizing microscopy

Acknowledgement

This work was supported in part by Polish Ministry of Higher Education and Science as the research grant No. 1 P03B 060 28.

Notes

†This article is dedicated to Professor Jerzy A. Janik on the occasion of his 80th birthday.