Adsorption of toluene‐soluble polymers at the toluene–water interface

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) (M̄n = 420,000) and ethyl cellulose (EC) (M̄n = 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.