The homologous series of some new six-ring double-swallow-tailed compounds

Recently we reported three homologous six-ring double-swallow-tailed compounds. For one homologue we observed the unusual phase sequence re-entrant smectic C-D_ob-smectic C-nematic. For this reason, results for a more complete homologous series are now presented. It was found that the phase behaviour can be compared with some series of biforked compounds. The lower members of the series exhibit nematic and smectic C phases, whereas the long-chain homologues form columnar phases. For three members of the series with intermediate lengths of the terminal chains, lamellar (S_c) and columnar (D_ob) phases occur for the same substance.