Smectic Mesophases from Quaternary Amphiphilic Ammonium Salts Functionalized with Interacting Endgroups

The functionalization of amphiphilic quaternary ammonium salts with properly chosen interacting endgroups constitutes an easy way to produce novel liquid crystal-line materials with diversified physical properties.1 Additional cyano endgroups introduce dipole-dipole interactions susceptible to strongly affect the liquid crystalline behaviour. Thus, the dialkyldimethylammonium bromides were found to produce smectic mesophases in which, because of the strong coulombic interactions between the ionic species, the lateral packing of the molecules within the layers is ordered and tetragonal in symmetry.2 Introduction of a cyano endgroup attached to one of the alkyl chains, namely a propyl chain, was found to immediately transform the ordered smectic into a disordered smectic A structure.3 This is due to the fact that the cyano group induces supramolecular dimerization through its dipolar interactions. We thought it of interest to extend this study by taking quaternary alkyl(hexadecyldimethylammonium) bromides carrying a variety of endgroups X. This paper describes some preliminary, but encouraging, results along this line.