ADSORPTION OF NONIONIC SURFACTANTS ON LATEXES

Adsorption isotherms of ethoxylated nonylphenols on poly(styrene) and poly(vinyl chloride) latexes have been measured. The isotherms all reach a limiting adsorption at concentrations somewhat higher than the critical micellar concentrations of the surfactants. The relative affinity of the surfactants to the latex surfaces was found to decrease with increased ethylene oxide chain length. Analysis of the isotherms indicates some affinity of the ethylene oxide chain to the latex surface. This affinity may possibly be attributed to the presence of surface carboxylic groups

Some of the isotherms were obtained using the serum replacement technique developed by S.M. Ahmed et. al. (S.M. Ahmed, M.S. El-Aasser, G.H. Pauli, G.W. Poehlein and J.W. Vanderhoff, J. Coll. Interface Sci., 73 388 (1980). In the application of this technique to the adsorption of nonionic surfactants it was found that polydispersity of the surfactant plays an important role since surfactant species with high affinity to the latex surface will continuously replace other species with lower affinity.