ON THE COLLAPSE OF POLY(ETHYLENE OXIDE) MONOLAYERS. SUBPHASE OF AQUEOUS ELECTROLYTE.

Surface pressure, pi , has been measured as a function of surface concentration for poly(ethylene oxide) (PEO) surface films, spread onto 1 M MgCl//2 and onto 1 M MgSO//4 aqueous substrates at several temperatures. The former liquid is a solvent for PEO. The latter is a non-solvent. At large surface coverages, pi rose with increasing temperature on both substrates. This unusual observation was also observed previously for PEO films on deionized water; the present experiments indicate that it does not appear to reflect ionic strength or solubility in the subphase. The absolute surface tension for films spread to high coverage onto aqueous MgCl//2 was similar at every temperature to that for films spread onto deionized water. This indicates that the enhancing influence of electrolyte on water surface tension was screened by the PEO surface film, and suggests that electrolyte was not excluded from the interface it would be on pure water.