EFFECT OF STEARIC-ACID ON THE SURFACE PRESSURE-GRADIENTS IN POLY(METHYL METHACRYLATE) MONOLAYERS

The surface pressure gradients that develop during the compression of poly(methyl methacrylate) (PMMA) monolayers are markedly reduced by the introduction of stearic acid into the monolayers. There is almost no gradient if the mole fraction of stearic acid (calculated on the basis of PMMA monomer) is greater than 0.3. At low surface pressures the stearic acid appears to cause a change in the conformation of PMMA molecules to a higher area form. High compressibilities of the mixed monolayers suggest that on compression there is a gradual return to the lower area form.