The structure of smectic A phases of compounds with cyano end groups

2014 The smectic layer spacings (d) have been determined for a number of cyano derivatives which have an anomalous d/l ratio of ~ 1.4, where l is the molecular length. It is shown that the quantity (d 2014 l) is directly related to the length of the alkyl or alkoxy tail of the molecule but is not simply related to the length of the aromatic core. This is consistent with a bimolecular layer structure having overlapping molecular cores at the layer centre. Using a combination of X-ray and neutron diffraction measurements of the intensity of the layer reflections on several isotopically substituted forms we have positively confirmed and quantified this model for one compound (4-cyano4’-n-octylbiphenyl, 8CB). LE JOURNAL DE PHYSIQUE TOME 40, AVRIL 1979, Classification Physics A bstracts 61. 30