Equilibrium and dynamics of PEO/PPO/PEO penetration into DPPC monolayers

The data suggests that the adsorption of polymer into the lipid monolayer is reversible and that upon compression of the surface, the lipid can eject the macromolecule from the surface. A comparison of the equilibrium surface pressure of the penetrated monolayer with the surface pressure of the polymer alone shows that interactions in the adsorbed layer are non-ideal and consistent with polymer-lipid repulsion. Both desorption of the polymer from a suddenly compressed interface and response to oscillatory perturbation of the interface show that a characteristic timescale in the kinetics of monolayer relaxation is in the order of 100 s. Because of the elevated concentration of polymer in the bulk phase, this suggests a kinetic barrier to macromolecule adsorption/desorption.