Electrostriction of the cubic blue phases

Abstract

ABSTRACT Under the influence of a weak electric field the unit cells of the cubix blue phases are continuously deformed. Wepropose a complete description of this phenomenon, known as electrostriction, within the frame of the standard Landau-Ginzburg-de Gennes theory for cholesteric liquid crystal.Keywords: cubic blue phase, electrostriction, external electric field 1. INTRODUCTION The cubic blue phases of chiral liquid crystals, i.e. the blue phase I (space group O8(I432)) and the blue phase II (space group 02(P4232)) have been intensively studied both experimentally and theoretically.' In particular, theinfluence of an external electric field has been examined.2 For increasing field strength three different effects areobserved. In a weak field the elementary cells of the cubic blue phases are aligned with their [001] crystallographicaxes parallel to the field direction. With increasing field strength the unit cells are deformed continuously. This phenomenon is called electrostriction and can be observed as a shift in wavelength of Bragg reflections in the visiblerange. Finally, when the field is strong enough, the blue phases transform into structures with different symmetries.