Polymer-Surfactant Interactions

Deposition from oppositely charged polyelectrolyte/surfactant (P/S) systems has numerous industrial applications such as detergency, paints, oil recovery, the pharmaceuticals, food, and biotechnology. Deposition is a delicate balance between the bulk-solution phase behavior of the system and the forces that control the interaction with the surface. Generally, maximum surface excess from polyelectrolyte surfactant mixtures coincides with this phase separation region, and this process is often kinetically controlled. We will discuss how the molecular properties of a range of polymers can be used to tune the properties. If the polymer is not hydrophobic enough, the surfactant binding is too limited to ensure attachment, whereas surfactant binding will be too strong and the phase separation range too limited if the polymer is too hydrophobic. No phase separation will occur if the charge density is too low, but a too-high charge density will cause so strong an association between surfactant and polymer that deposition does not occur. It is important to bear in mind that during the timescale of the application of a formulation, nonequilibrium effects can be significant and utilized to form a layer that is trapped in a nonequilibrium state, which gives the desired surface functionality