INTERACTIONS BETWEEN POLY(ACRYLAMIDE) AND SURFACTANTS OF DIFFERENT HEADGROUP CHARGE

Air/water surface tensions and oil/water interfacial tensions are reported for aqueous mixtures of poly(acrylamide) (PAAm) and three different surfactants, i.e. sodium dodecyl sulfate (SDS), cetyltrimethylammonium bromide (CTAB), and a commercial non-ionic surfactant, Triton X-100 (TX-100). Results show a synergistic effect between these surfactants and the polymer. Oil-in-water emulsification experiments using PAAm-surfactant mixtures showed that the TX-100-PAAm mixture was the most effective emulsifier. The emulsification ability of TX-100-PAAm was not affected by pH in the range pH 3-10, implying that hydrophobic interactions between TX-100 and PAAm dominate over other mechanisms. At low pH, SDS has an emulsification ability similar to TX-100, and at high pH the effect of CTAB is comparable to that of TX-100. Pressure-area (pi-A) curves and Brewster angle microscopy are used to gain insight into the interaction mechanism between PAAm and these three surfactants.