Observation of disclinations in the nematic state of a thermotropic aromatic copolyester by lamellar decoration

Abstract

The frozen nematic state of a thermotropic aromatic copolyester exhibits a schlieren texture with two and four dark brushes emanating from a point observed under a polarizing optical microscope; these correspond to disclination strengths s = ± ½ and s = ± 1, respectively. The combined techniques of lamellar decoration and ruthenium tetraoxide staining have been used to reveal the director orientation around disclinations in the frozen nematic state of polymers by transmission electron microscopy. All six disclinations in the nematic mesophase of a single liquid-crystalline aromatic copolyester have been observed. Every disclination interacts and is connected with its neighbouring disclination so that disclination exist in pairs usually of opposite sign in their disclination strengths. Some pairs with the same sign disclination have also been observed.