Synthesis and liquid-crystalline properties of polyacrylates containing prochiral sulfide substituents

The synthesis and thermal behaviour of a new series of side-chain liquid-crystalline polyacrylates 1a-h containing prochiral alkyl sulfide substituents with a variable number n of carbon atoms are described. No liquid-crystalline behaviour was exhibited in the melt by the relevant monomers and intermediate compounds. In contrast, all polymers displayed thermotropic properties. The lower homologues 1a-f(n less than or equal to 6) displayed smectic B1 and smectic A1 mesophases, while the higher homologue 1h (n = 10) formed a bilayer, partly interdigitated smectic C mesophase. A special position was held by 1g with a sulfide substituent of intermediate length (n = 8), for which monolayer and bilayer smectic mesophases coexisted over a wide temperature range.