X-rary studies on bilayer smectic A (A2) and bilayer smectic C (C2) phases

Abstract

Xray studies on the smectic A and smectic C phases of 4-n-heptacylphenyl-4'-(4"-cyano- benzoyloxy) benzoate show that both these phases are bilayer phases (A2 and C2) characterised by strong second order Bragg reflections and a large d/l, ratio (appro.1.8). Direct determination of the tilt angle from Xray photographs shows that the decrease in the layer spacing on going over from the A2 to the C2 phase is entirely due to the tilt of the molecular pairs and not due to any change in the interdigitation of the molecules.