Adsorption of surfactant on polystyrene‐styrene interfaces

The adsorption of sodium dodecyl sulfate on polystyrene‐styrene interfaces has been studied. Polystyrene interfaces of 20 and 60% were considered. Initial surfactant concentrations used in the study were 0.0004, 0.0008, and 0.004 mole/l. Two temperature levels, 25 and 75°C., were studied. Results showed no effect of initial surfactant concentration for a 20% interface at 25°C. However, the data for the 60% interface at 25°C. showed an effect of initial surfactant concentration. The apparent anomaly in the results regarding effect of initial surfactant concentration was explained in terms of the behavior of polystyrene‐styrene as a mixed absorbent and the work of Harkins and co‐workers, which showed that surfactant adsorption was a function of initial surfactant concentration over certain concentration ranges. Rate of surfactant adsorption appeared to be a function of surfactant adsorption raised to a power. The order of the adsorption appeared to be first‐order for the 20% interface and second‐order for the 60% interface.