Sub-layer adequacy in smectic ordering : structural charcterization of new low molar mass liquid-crystalline siloxanes

(Received 13 July 1993, Received in final form 26 August 1993, accepted 1 September 1993)

Abstract
This paper deals with the structural characterization of a new series of smectogens the molecules of which contain three distinct parts, a cyanobiphenyl aromatic core, a central paraffin chain and a siloxane endgroup. Incompatible with one another, these parts tend to locate themselves in three seprate sub-layers superposed in a partially bilayered smectic A structure. Because the siloxane endgroups have an important lateral extension as compared with the other two molecular moieties, the head to head association of the cyano endgroups is smaller than usual and the smectic layering of the aromatic cores closer to a single layer arrangement. This behaviour illustrates the necessity for the sub-layers to adapt their internal structure so as to be adequate for superposition.