Density measurements on liquid-crystalline side-chain polysiloxanes

Abstract
We have studied the behaviour of the density, ϱ, as a function of temperature for a number of side-chain liquid-crystalline polymers. The polymers have a polysiloxane backbone and a benzoate ester side group with different tails or flexible spacers. From the values of ϱ in the smectic A phase and from the layer thickness obtained from X-ray experiments we have determined a molecular area in the plane of the layers. The evolution of this parameter shows clearly the asymmetrical role of the tail and the spacer.