(561b) Interactions Between Cationic Bilayers In the Presence of Polyelectrolytes with Implications to the Stability of Vesicle Dispersions

Colloidal vesicle dispersions are commonly used in both consumer products and medical applications. Often additives such as polyelectrolytes are added to the dispersions to stabilize the dispersions or give desired consumer affects to the product. The colloidal properties of these dispersions are determined by interactions between the vesicles and polyelectrolytes making up the dispersion. We have used a Surface Forces Apparatus (SFA) to measure the interactions between positively charged di (tallowethyl-ester) dimethyl ammonium chloride bilayers in the presence and absence of positively charged poly (diallyldimethylammonium chloride) (polyDADMAC) in calcium chloride solutions. The effects of salt concentration, electrolyte concentration and molecular weight have been studied for this system. In colloidal vesicle dispersions of this kind we have found that the addition of polyelectrolyte has been shown to destabilize the suspension. This is due to a depletion attraction interaction between the vesicles in the dispersion as well as a decrease in the electrostatic repulsion between the vesicles due to the presence of the polyelectrolyte. This study has implications for anticipating the behavior of vesicle dispersions in complex mixtures.