Vesicular and monolayer properties of diastereomeric surfactants (original) (raw)

Three diastereomeric, quaternary ammonium surfactants, [3-(~-4,~-5-dihexadecyl-r-2-methyl-l,3-dioxolan-2-yl)propyl]trimethylammonium bromide (la) and its t-4J-5-(lb) and c-4,t-5-(IC) isomers, were prepared and the properties of their vesicles and monolayers compared. The vesicles were characterized by dynamic laser light scattering, differential scanning calorimetry, and [14C]sucrose entrapment and release studies. Clear differences among the three systems were found in the latter two studies. The phase transition temperature order for both sonicated and vortexed vesicles was la > IC > lb, and for sonicated vesicles the permeability order was l b > IC > la. The three surfactants also displayed different monolayer characteristics. The degrees of expansion in the surface pressure-area isotherms, the monolayer stability limits, and the propensities of the films to spread from their crystals followed the same order: l b > IC > la. Overall, the results suggest that in both vesicular and monolayer form l a has the tightest and l b the loosest surfactant packing.