Title

Thermotropic Mesomorphism in Catanionic Surfactants Synthesized from Quaternary Ammonium Surfactants and Sodium Dodecylbenzenesulfonate: Effect of Chain Length and Symmetry

Publication Title

Colloids and Surfaces A: Physicochemical and Engineering Aspects

Publication Date

7-31-2014

Document Type

Article

DOI

10.1016/j.colsurfa.2014.07.037

Keywords

Catanionic surfactant, Mesophase structure, Hexagonal columnar phase

Disciplines

Physics

Abstract

Thermotropic properties of catanionic surfactants are influenced by the headgroups as well as hydrocarbon chains. A series of eight catanionic surfactants were synthesized from quaternary ammonium surfactants as the cationic counterpart and dodecylbenzenesulfonate (DBS) as the anionic counterpart and their structures and purities established. Thermal Gravimetric Analysis (TGA), Differential Scanning Calorimetry (DSC), Hot-Stage Polarized Light Microscopy (HSPLM), and X-ray Diffraction (XRD) were used to characterize the thermal and liquid crystalline properties of the derived catanionic surfactants. These surfactants form hexagonal columnar (Colh) phase before isotropization. Their phase behavior is rather complex depending on the chain length, symmetry, and number of chains. In all these surfactants, the thermal stability is influenced by the nature of the headgroup. Mesomorphism on the other hand is a result of the interplay between headgroup interactions and chain interactions. In general, formation of mesophases at lower temperature is favored as the number of CH2 groups per molecule is increased.