Effect of the Phobic Segregation between Fluorinated and Perhydrogenated Chains on the Supramolecular Organization in Ionic Aromatic Dendrimers

Abstract

Two novel series of codendrimers constituted by the grafting of poly(propylene imine) PPI-(NH2)16 (G = 3) with aromatic acids substituted with fluorinated and perhydrogenated chains in different proportions have been synthesized and their liquid crystalline properties have been investigated. Series I is generated by the ionic attachment of 4-decyloxybenzoic acid and 4-(1H,1H,2H,2H)-perfluorodecyloxybenzoic acid in different proportions. Series II results from the ionic junction of eight units of 3,4-didecyloxybenzoic acid or 3,4,5-tridecyloxybenzoic acid and eight units of 4-decyloxybenzoic acid or 4-(1H,1H,2H,2H)-perfluorodecyloxybenzoic acid. The liquid crystalline behavior has been investigated by means of differential scanning calorimetry (DSC), polarizing optical microscopy (POM), and X-ray diffractometry (XRD). All codendrimers exhibit smectic A mesomorphism. Besides, two compounds belonging to series I present uncommon mesophases originated by the incompatibility of the fluorinated and perhydrogenated chains. On the basis of the experimental results, a supramolecular model is proposed. AFM experiments on some of the compounds were also performed to investigate their surface aggregation behavior.