Ionic Liquid Crystal Dendrimers with Mono-, Di- and Trisubstituted Benzoic Acids

The synthesis and characterization of a new family of ionic liquid crystal dendrimers consisting of the ammonium salts of the commercially available poly(propylene imine) (G = 1−5) dendrimers and 4-decyloxy-, 3,4-didecyloxy-, and 3,4,5-tridecyloxybenzoic acids are reported. The liquid crystalline behavior was investigated by means of differential scanning calorimetry, polarizing-light optical microscopy, and X-ray diffractometry. Dendrimers with mono- and didecyloxybenzoate moieties show lamellar mesomorphism, namely, smectic A, whereas those with tridecyloxybenzoate units show columnar mesomorphism:  rectangular for G = 1 and hexagonal for G = 2−5. On the basis of the experimental results, we propose models both at the molecular level and in the mesophase for all the materials.