Solid-Phase Transitions of Catanionic Surfactants

• Published in: Journal of colloid and interface science Vol. 188; no. 2; pp. 396 - 403
• Main Authors: FILIPOVIC-VINCEKOVIC, N, PUCIC, I, POPOVIC, S, TOMASIC, V, TEZAK, D
• Format: Journal Article
• Language: English
• Published: San Diego, CA Elsevier Inc 15-04-1997; Elsevier
• Subjects: catanionic surfactants; Condensed matter: structure, mechanical and thermal properties; Equations of state, phase equilibria, and phase transitions; Exact sciences and technology; liquid crystals; Physics; polymorphism; Solid-liquid transitions; Solid-solid transitions; Specific phase transitions; thermal analysis; X-ray diffraction; X-ray diffraction; catanionic surfactants; polymorphism; liquid crystals; thermal analysis; Liquid solid transition; Solid-state phase transformations; Phase transformations; Surfactants; Experimental study; Liquid crystals
• ISSN: 0021-9797; 1095-7103
• DOI: 10.1006/jcis.1997.4767

A series of catanionic surfactants were prepared by making an equimolar mixture of cationic (alkylammonium chloride) and anionic (sodium alkyl sulfate) surfactants, both containing an isomer of the same chain length, namely, C10, C12, or C14. The prepared compounds exhibited complex thermal behavior, characterized by several successive phase transitions in the solid state as proved by differential scanning calorimetry, X-ray diffraction, and optical birefringence observation using a polarizing microscope. On heating, three main phase transitions were observed for all compounds; solid crystalline–solid crystalline, solid crystalline–liquid crystalline, and liquid crystalline–isotropic liquid. On cooling, all three compounds underwent reversibly the isotropic liquid–liquid crystalline phase transition, while the liquid crystalline–solid crystalline phase transition displayed peculiar properties. Phase transition temperatures increased with an increase in hydrocarbon chain length.