Growth of toric domains in the smectic phase of oxadiazoles

TL;DR

This paper investigates how toric domains grow in the smectic phase of oxadiazoles, focusing on the role of defects and comparing compounds with different terminal substituents.

Contribution

It provides new insights into the growth mechanisms of toric domains in oxadiazoles and compares the effects of Cl and Br terminal substituents on phase textures.

Findings

Toric domain growth behavior is similar in Cl- and Br-substituted oxadiazoles.

Defects play a significant role in the development of domain structures.

Smectic and nematic textures evolve with temperature changes.

Abstract

In a previous paper (Phase Transitions, 80(9), 987, 2007) we discussed the smectic and nematic textures of some mesomorphic oxadiazole compounds with terminal Cl-substituent. Optical microscope investigations showed a very interesting behaviour of smectic and nematic phases; the smectic phase has fan-shaped and toric textures and the nematic phase has spherulitic domains, which disappear as the sample is further heated, the texture changing into a smooth one. Here, we investigate four oxadiazole compounds with the same structure but terminal Br-substituent. The behaviour of the smectic and nematic phases is like that observed in the compounds with Cl. The focus of the paper is on the growth of toric domains from the nematic melt and on the role of defects in the domain structure.