Trioxatruxenes: A New Family of Disc-Like Mesogens with a Complex Polymorphism

Abstract

A homologous series of hexa-n-alkanoyloxytrioxatruxenes has been prepared with n=7 t o n=15 in order to check the influence upon the mesomorphic properties exerted by the substitution of the three methylenes of the truxene core by oxygen atoms. Interphase transitions between solid, mesomorphic and isotropic phases were studied by hot stage microscopy and DSC. One of the homologs (R=C₁₃H₂₇CO-) was previously identified by X-Ray investigations and used as t h e reference substance to confirm the structure of the various mesophases by contact method. A new example of the socalled inverted sequence (crystal-N_D nematic-D columnar-isotropic) and several examples of the new oblique disordered columnar phase (Dobd) are reported. Trioxatruxenes can be quoted as able to exhibit the most complex polymorphism found in disc-like liquid crystals with the sequence: K - N_D - D_obd - D_rd - D_hd - I.