Enhancement of catansome formation by means of cosolvent effect: Semi-spontaneous preparation method

Some short-chained alcohols have been found to be good vesicle-promoting agents for both mixed cationic–anionic surfactant systems through spontaneous formation and ion-pair amphiphiles (IPAs) through classic mechanical dispersion preparation. The promotion is mainly due to the cosolvent effects based on the medium dielectric constant. Such prepared vesicle will be referred as “catansome” in this work. A semi-spontaneous method for preparing catansomes through a simple process, that is, dissolving the IPA in a liquid alcohol and then adding water with mixing by using of a homogenizer, is proposed here. This preparation method has the advantage over the preceding ones in purity and simplicity, in the sense that no counterions exist in the solution and no film preparation is needed, respectively. Effects of four homologous cosolvents (methanol, ethanol, 1-propanol, and 1-butanol) on the stability of catansomes formed from three IPAs (decyltrimethylammonium dodecylsulfate, DeTMA-DS; decyltrimethylammonium tetradecylsulfate, DeTMA-TS; dodecyltrimethylammonium dodecylsulfate, DTMA-DS) were systematically studied. Successful preparations of stable catansomes were established for both DeTMA-DS and DeTMA-TS with the four alcohols used and for DTMA-DS with 1-propanol and 1-butanol. An explanation of cosolvent effects based on the medium dielectric constant was found to be still appropriate.