In this article we present an investigation of the liquid crystal properties of nonchiral and racemic branched alkyl chain (swallow-tailed) molecules and some chiral analogues based on a cinnamic acid core group, It was found in these systems that increasing the extent of the branching of the terminal alkyl chain increased the incidence of alternating tilt smectic phases, whereas smectic C-alpha and smectic C-gamma phases were suppressed. X-ray studies of the effect on the layer spacing in the smectic A phase of increasing the long alkyl branch of one series of compounds are included. Results of polarisation studies on some chiral analogues are also reported.