THE MOLECULAR ORIENTATION OF POLYETHER-TYPE SURFACTANTS AT THE INTERFACES II, THE SURFACE FILMS OF POLYOXYETHYLENE-POLYOXYPROPYLENE TYPE POLYOLS AT AIR/WATER INTERFACE

The film pressure vs, area curves of the surface films of three PLURONIC polyoxyethylene-polypropylene polyols (with molecular weight in the range 2 x 10(3)-8 x 10(3)), three all haterio polyoryethylene polypropylene polyols (with molecular weignt in the range 1.5 x 10(3)-2.5 x 10(5)), and two polypropylene glycols (with molecular weight of 2025 and 2 x 10(5)) have been determined on a saturated sodium nitrate (46%) aqueous solution substrate. Based on the analysis of experimental data, it is proposed that the polyoxyethylene polyoxypropylene polyols molecule orients at the air/water interface with the EO chain partially lies in the interface and partially immerses in the water phase, The fraction of the number of EO unit lain in the interface increases progressively with film pressure, but independent of n(EO), the ethylene oxide chain length, The same is tore for propylene oxide (PO) chain, except the fraction of the number of PO unit lain in the interface is much smaller than that of the number of EO unit lain in the interface at the same film pressure, With this model and the assumption that the fractions of the number of EO and PO units lain in the interface are independent each other, the surface film data of PLURONIC payola and all heterie polyoryethylene polyoxypropylerte polyols can be related with the results of polypropylene glycols and TRITON type surfactants quantitatively, Based on the experimental data of the surface films of three all heteric polyoryethylene-polyoxypropylene polyols on a pure water surface, it is suggested that in this ease the EO chain of the molecule not only is easily soluble in water, but also trends to bring part of PO chain to penetrate the water phase.