Molecular morphology and mesomorphism in dendrimers:: a competition between rods and discs

The synthesis and liquid crystalline behaviour of several sixteen-branched dendrimers based on poly(amidoamine) (PAMAM) and poly(propyleneimine) (DAB) are reported. Mono-, di- and trialkoxybenzoyloxysalicylaldehydes are used as mesogenic promotor moieties and are attached at the peripheral amino groups of the pre-existing dendrimers. All the compounds exhibit liquid crystalline properties which were studied by optical microscopy, DSC and X-ray diffraction. The relationship between the structure of the mesogenic units and the mesomorphic behaviour is discussed and models for the different supramolecular organizations are proposed.