INTERFACIAL-TENSION OF ALKYLGLUCOSIDES IN DIFFERENT APG/OIL/WATER SYSTEMS

The interfacial performance of pure alkylglucosides (C(8)G(1), C(10)G(1) and C(12)G(1)) and of technical grade alkylpolyglucoside (APG) surfactants was investigated in three different water/oil systems (decane, isopropylmyristate and 2-octyldodecanol). From the dependence of the interfacial tension on the surfactant concentration below the CMC the cross-sectional area of the molecules at the decane/water interface was estimated. The plateau values of the interfacial tension at the CMC (sigma(c)) are independent of temperature and almost independent of added electrolyte in the decane/water system. The ability of the surfactants to lower the oil/water interfacial tension is most pronounced for the nonpolar oil. The partition coefficient of the surfactant between oil and water phase (k(c)) was estimated from the CMC and the observed break point of the interfacial tension after equilibration of the two phases. In decane/water, k(c) is nearly zero for all surfactants studied. For the polar oils, k(c) increases with the chain length of the surfactant up to k(c) approximate to 10 for C(12)G(1) in octyldodecanol/water. The values of sigma(c) in the different oil/water systems appear to be correlated with k(c) and exhibit a minimum near k(c) = 1.