Molecular morphology and mesomorphism in dendrimers: a competition betweenrods 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 gro ups of the pre-existing dendrimers. All the compounds exhibit liquid crysta lline properties which were studied by optical microscopy, DSC and X-ray di ffraction. The relationship between the structure of the mesogenic units an d the mesomorphic behaviour is discussed and models for the different supra molecular organizations are proposed.