(588f) Polyacrylamide Induced Thinning and Increase in Head Group Area of Supported Cationic Bilayers

The interaction between supported cationic bilayers and the effect of uncharged polymer on theses interactions was studied using a surface forces apparatus (SFA) with a radius of curvature of the surfaces of  ~2 cm. Bilayers of the cationic surfactant di(tallow ethyl ester) dimethyl ammonium chloride (DEEDMAC) were deposited on molecularly smooth mica surfaces using the Langmuir-Blodgett technique and the forces between the bilayers were measured in a 4.5 mM CaCl₂ solution at pH=4. The forces between the bilayers were repulsive and followed DLVO theory with a modified Debye length to bilayer-bilayer separation of ~1nm. The addition of polyacryamide, an uncharged polymer, decreased the repulsive force of interaction between the bilayer surfaces. The polyacrylamide chain tends to lay on the surface of the bilayer due to hydrophobic force between the backbone of the polymer chain and the hydrocarbon chain of the DEEDMAC bilayer and caused thinning of the hydrocarbon chains and increase in the headgroup area.