| Abstract: | The adsorption of several toluene-soluble polymers at the toluene–water interface has been investigated by using the duNouy ring method of measuring interfacial tension γT /W . Polystyrene and poly(ethylene-co-vinyl acetate) (11.1 mole-% vinyl acetate) have little affinity for this interface at 29°C, but poly(methyl methacrylate) (PMMA) (M?n = 420,000) and ethyl cellulose (EC) (M?n = 50,100; 49.1% ethoxyl) adsorb significantly at concentrations as low as 1.0 × 10?4 g/100ml. A plot of interfacial tension lowering versus initial logarithm of initial bulk phase polymer concentration is linear from 1.0 × 10?4 to 1.0 × 10?1 g/100 ml for EC and 1.0 × 10?4 to 1.0 × 10?2 g/100 ml for PMMA. When the PMMA concentration increases to 1.15 × 10?1 g/100 ml, its adsorption behavior changes markedly. Prolonged time effects occur and adsorption becomes dependent upon dissolved water content of the toluene prior to formation of the toluene/water interface. Such effects are not observed with the other solutions studied. Increasing temperatures have variable effects on values of γT /W for the polymer solutions studied. Experiments with various polymer mixtures indicate that the polymer lowering T /W the most is preferentially adsorbed at the toluene–water interface and rapidly displaces less strongly adsorbed polymers. |
