Solid-Phase Transitions of Catanionic Surfactants

✍ Scribed by N. Filipović-Vinceković; I. Pucić; S. Popović; V. Tomašić; Đ. Težak

• Publisher: Elsevier Science
• Year: 1997
• Tongue: English
• Weight: 558 KB
• Volume: 188
• Category: Article
• ISSN: 0021-9797
• DOI: 10.1006/jcis.1997.4767

✦ Synopsis

characteristics similar to those of zwitterionic phospholipids A series of catanionic surfactants were prepared by making and their phase behavior parallels that of a lecithin-water an equimolar mixture of cationic (alkylammonium chloride) and system (6).

anionic (sodium alkyl sulfate) surfactants, both containing an iso-

The purpose of the present study was to provide an initial mer of the same chain length, namely, C 10 , C 12 , or C 14 . The preinsight into the thermal behavior of catanionic surfactants, pared compounds exhibited complex thermal behavior, characteralkylammonium alkyl sulfates of the general formula ized by several successive phase transitions in the solid state as

C n H 2n/1 NH 3 SO 4 C n H 2n/1 , with n between 10 and 14, using proved by differential scanning calorimetry, X-ray diffraction, and differential scanning calorimetry (DSC), X-ray diffraction optical birefringence observation using a polarizing microscope.

(XRD), and polarizing microscopy. Three endothermic tran-On heating, three main phase transitions were observed for all compounds; solid crystalline-solid crystalline, solid crystalline-sitions were observed by heating all samples: (1) a polymorliquid crystalline, and liquid crystalline-isotropic liquid. On coolphic transition between two solid crystalline forms; (2) solid ing, all three compounds underwent reversibly the isotropic crystalline-liquid crystalline, and (3) liquid crystalline-isoliquid-liquid crystalline phase transition, while the liquid crystaltropic liquid. Below the melting point two polymorphic line-solid crystalline phase transition displayed peculiar properforms were confirmed by XRD. The basic lamellar thickness, ties. Phase transition temperatures increased with an increase in which is dependent on molecular chain length, appears to hydrocarbon chain length.