Surface films of polymers. Part I. Films of the fluid type

Abstract

Many linear polymers containing water-attracting groups, such as polyesters, polyethers, polyalcohols and polyacids, may be spread uniformly at the air-water and oil-water interface. Polymers with the least internal cohesion spread most easily, those with high internal cohesion do not spread well. The character of the resulting film depends on the balance between the lateral attractions at the surface and the water-attracting properties of the polar groups. The specific area occupied per monomer unit is independent of the molecular weight in high polymers. Fluid films gelating only at high surface pressure are termed “fluid amorphous type.” They exhibit a low pressure region in which there is free space between the chains, a high pressure region where an increasing proportion of the groups are formed into an “overfilm,” and a collapse pressure or pressure range where the “overfilm” is complete and has properties of the bulk polymer. Segments in the overfilm are in equilibrium with segments in the monolayer, the process being reversible. Certain films appear to have a small proportion of residues distributed into an “over-film” at zero pressure. Estimations of the limiting area from the FA and Δ V A curves are in reasonable agreement with known intermolecular dimensions and probable molecular configurations. The values of apparent surface moments are comparable to those in long chain films, and the dipoles are, in the majority of vinyl derivatives, free to orientate fully.