Polymer/Surfactant Complexes at the Air/Water Interface Detected by a Simple Measure of Surface Viscoelasticity

The rheology of the air/water interface of mixed polymer/surfactant systems has been examined by the talc particle test. Polymer/surfactant pairs studied range from strongly interacting polyelectrolytes/oppositely charged surfactant systems, such as sodium hyaluronate/alkyltrimethylammonium halides, carboxymethylcellulose/hexadecyltrimethylammonium chloride (HTAC), and an alternating copolymer of acrylamide and diallyldimethylammonium chloride (Merquat-550)/sodium dodecyl sulfate (SDS) to less strongly interacting systems of neutral polymers and charged surfactants, such as ethylhydroxyethyl cellulose/SDS or /HTAC, hydroxypropyl cellulose/SDS, poly( N -isopropylacrylamide)/SDS and poly-( N -vinylpyrrolidone)/SDS. Clear indications of surface viscoelasticity at the air/water interface were obtained over a wide range of compositions for several, but not all, polymer/surfactant pairs examined. These results extend our previous findings (Regismond, S. T. A.; Winnik, F. M.; Goddard, E. D. Colloids Surf., A 1996, 119, 221−228.) on mixed solutions of SDS and a cationic derivative of hydroxyethyl cellulose (polymer JR400). Generally, viscoelasticity provides evidence of a synergistic adsorption of the two components. Factors influencing the development of surface viscoelasticity are assessed.