Studies on surface films of soybean lecithin III: The effect of lysolecithin on lecithin monolayers at the air-water interface

The influence of lysolecithin on lecithin monolayers has been studied. Evidence that lysolecithin, when in the subsolution, appears to expand lecithin films to a greater extent than expected is presented. It has been postulated that the increased expansion over the amount expected is due to the enhancement of migration of the lysolecithin to the air-water interface in the presence of the lecithin film. Compression of such films results in what appears to be the loss of material from the lecithin-lysolecithin film. Studies in which the lysolecithin concentration in the subsolution was varied while the lecithin concentration layered at the surface was held constant indicate that an optimum lysolecithin concentration exists at which the initial film pressure generated reaches a maximum. Time dependent behavior of compressed films at lysolecithin subsolution concentrations exceeding the critical concentration indicate that one, both, or possibly some combination of the two components may be leaving the interface.