Thermal Behavior of Two Polar A-Smectics

Abstract

The experimental X-ray diffraction data reported recently in the literature for a cyano and a nitro smectogen¹ are used to calculate sane parameters of the smectic A phase, such as the molecular area of the paraffin tails and the degree of head to head association of the molecules. It is shown that the presence of a lateral methyl group on the aromatic cores enhances the head to head association of the molecules. It is, finally, suggested that the slight interruption observed in the temperature variation of the layer spacing could be related to a poor miscibility of the head to head and the side by side associated molecules.