Room temperature thermotropic liquid crystalline phases of catanionic surfactants derived from quaternary ammonium surfactants and bis(2-ethylhexyl)sulfosuccinate

Abstract

HypothesisProperties of catanionic surfactants can be tailored by the choice of appropriate headgroups and hydrocarbon tails. Thermal behavior of catanionic surfactants can be influenced by the length and number of alkyl chains. ExperimentsA series of eight catanionic surfactants were synthesized from quaternary ammonium surfactants as the cationic counterpart and bis(2-ethylhexyl)sulfosuccinate (AOT) as the anionic counterpart. The thermal properties and the liquid crystalline properties of these catanionic surfactants were studied by the following methods: Thermal Gravimetric Analysis (TGA), Differential Scanning Calorimetry (DSC), Hot-Stage Polarized Light Microscopy (HSPLM), and X-ray Diffraction (XRD). FindingsThe results indicate that transition temperatures, enthalpies of transition, and mesophase structures vary with the length and number of chains attached to the quaternary nitrogen. These compounds exhibit room temperature liquid crystalline (LC) textures that are predominantly “fan-like,” as observed by HSPLM, and phases that are hexagonal columnar, as observed by XRD, with the exception of one compound which exists as a nematic liquid crystal at 25°C. Additionally, all of the surfactants also exhibit thermal stability in the range of 256–300°C.