Aggregation-assisted induced electric order in the nematic phase of a metallorganic complex

Abstract

The family of nematic liquid crystals has been recently enlarged with the class of metallorganic molecules. Among them, AZPAC ͓4,4Ј-bis͑hexiloxy͒-azoxybenzene-palladium complex͔ presents some unusual behavior as a transitory ''ferroelectric'' state, which we explain by considering bound multimers of AZPAC of peculiar steric conformation.

The Validity of an Aggregation-Assisted Induced Electric Order in a Metalloorganic Complex

“…In a recent paper, 10 we discussed the aggregation-assisted induced electric order in the nematic phase of AZPAC by comparing records of depolarization currents to measurements of clearing point transition temperatures under different applied electric fields on different widths of the cells. In that paper, we interpreted the somewhat contradictory measurements on AZPAC, i.e., the fact that the maxima of the depolarization curves depend strongly on the applied electric field whereas the transition temperatures do not, in terms of an electric order set in liquid crystal which is, geometrically, orthogonal to the nematic order and, in many respects, independent of it.…”

“…We suggested that this was due to two main facts, i.e., AZPAC is not entirely rodlike as usual nematics but rather semidiscotic, which prevents a free rotation about the long molecular axis, and also there is a possibility of Pd-O(N) bonding, considered as being responsible for a transitory ferroelectric order in a direction orthogonal to the nematic director. The suggestion of aggregation-assisted induced electric order 10 was inferred only by analyzing the depolarization currents and the clearing point transition temperatures. Later, we obtained new evidence for this suggestion by measuring directly the polarization of AZPAC and its dependence on the temperature.…”