Vesicle–surfactant interactions: effects of added surfactants on the gel to liquid-crystal transition for two vesicular systems

Abstract

Interactions of both cationic and anionic surfactants with vesicles formed by dimethyldioctadecylammonium bromide (DOAB) and by sodium didodecylphosphate (DDP) have been probed using differential scanning microcalorimetry. The scans show that the surfactants are incorporated into the vesicle bilayers. The change in the melting temperature, Tm, characterising the gel to liquid-crystal transition depends on whether the charges on the head groups of surfactant ion and vesicular ion have either similar or opposite signs.

Aggregation properties of aqueous casein hydrolysate solutions at different pH

“…Thus, the sharp peak at 62.4 C at pH 2.0 and at 56.7 C at pH 7.0 might be assigned to the melting of the main 'crystal-like' state to a 'liquid-like' state. The smaller peaks at 56.7 C at pH 2.0 and 50.8 C at pH 7.0 may be linked to the melting of the patches perturbed by aggregates-aggregates interaction/aggregation (Blandamer, Briggs, & Cullis, 1995). At these two temperatures, the three-dimensional network of the macroaggregates dissociates.…”

Formation and stability of micelles and vesicles

“…Finally, we note that the addition of SDS to DOAB vesicles results in an increase of T m by approximately 20 K, but the eventual melting process is much less clearly defined [47]. The authors presume that the incorporation of the dodecyl chains into the vesicle, containing octadecyl chains, leads to some disruption of the chain packing, but the negatively charged headgroups of SDS diminish the electrostatic repulsion between the ammonium headgroups.…”

“…Blandamer et al [47] have employed differential scanning microcalorimetry to monitor the influence of micelleforming surfactant on the phase transition temperature of vesicle bilayers at surfactant/lipid ratios below R e,SAT . Two features are clear-cut.…”

Rheological investigation of thermal transitions in vesicular dispersion

“…It includes differential scanning calorimetry [6][7][8][9][10][11][12][13][14], turbidity [14,16], static light scattering [17], fluorescence [9], surface pressure [18], and electron spin resonance (ESR) [10,18,19]. In general, the DSC thermograms of the unsonicated DODAB dispersions are dominated by two endotherms; the pre-and main transition peaks.…”