Material highlights (Issue 1): Liquid crystal polymers a digest of the recent literature

A key issue in the area of side-chain liquid crystal polymers concerns the conformation of the backbone within the mesophase. In order to resolve this matter, Noirez and co-workers (Liquid Crystals, 1995, 18 129) have studied a wide range of polymers exhibiting both nematic and smectic behaviour using small angle neutron scattering. Their results combined with a survey of those in the literature reveal that if the polymer is solely nematogenic, then the backbone adopts a prolate conformation in which on average it lies along the director. By contrast, in a smectic phase the backbone adopts an oblate shape and on average lies perpendicularly with respect to the director. This arises from a microphase separation in which the backbones are distributed between the mesogenic layers. However, the backbones can cross the mesogenic layers although their ability to do so depends on, amongst other factors, the degree of polymerization. If the polymer exhibits both nematic and smectic behaviour, then in the nematic phase the backbone adopts a slightly oblate shape resulting from smectic fluctuations.