Lamellar to columnar mesophase evolution in a series of PAMAM liquid-crystalline codendrimers

The synthesis, chemical characterization and liquid crystalline behavior of a series of seven poly(amidoamine) (PAMAM) codendrimers are described. These compounds were obtained by grafting two types of terminal promesogenic units, that carry either one or two decyloxy chains, in various proportions onto the third generation of PAMAM dendrimer. The average number of promesogenic units was determined by using an original interpretation of the NMR spectra. X-ray diffraction studies show that these compounds exhibit lamellar and/or columnar mesophases. The type of mesophase is determined by the number of each kind of promesogenic units present in a given codendrimer and by the temperature. The evolution of the supramolecular organization of the different molecules is explained as a function of the number of alkoxy chains present around the dendritic core and compared to the models developed for the homodendrimers totally functionalized by promesogenic units with either one or two decyloxy chains.