Chapter 3 89 surface with the nonionic and/or anionic blocks in the lamellar liquid. Alternatively, formation of phase-separated coacervates between the cationic polymer and the anionic surfactant could result in blockage of the plateau border. Of course, if the interaction of the cationic polymer was strong enough to form “inverse micellar” structures, then there would be a possibility that the phase-separated particles could cause a local reversal of the curvature in the lamellae and this in turn would result in breakage of the lamellar film and subsequent foam destabilization. This type of foam destabilization mechanism has been extensively reported by Peter Garrett. Solid Foams Cationic conditioners that would normally be incompatible with liquid shampoos can be delivered from solid foams. Solid foams also make it possible to have one scent for the solid and then to allow a second different fragrance to bloom when the solid was wetted by water.35 The porous solids are made by mixing the surfactants, glycerin as plasticizer, and water in the presence of a water-soluble polymer. The image in Figure 14 shows a solid foam in which poly(vinyl alcohol) is the water-soluble polymer. After a heating and mixing cycle, the porous solid is formed by aeration. Figure 14. Micrograph showing solid foam structure (reproduced from US Patent Application 20110195098).