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) surf actants 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 wa s estimated. The plateau values of the interfacial tension at the CMC (sigma(c)) are independent of temperature and almost independent of ad ded electrolyte in the decane/water system. The ability of the surfact ants 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 observe d break point of the interfacial tension after equilibration of the tw o phases. In decane/water, k(c) is nearly zero for all surfactants stu died. 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 octyldodecano l/water. The values of sigma(c) in the different oil/water systems app ear to be correlated with k(c) and exhibit a minimum near k(c) = 1.