Abstract: The dilational rheological properties of a pair of structural isomers: sodium 2-propyl-4,5-dihexyl benzene sulfonate (366) and sodium 2,5-dipropyl-4-nonyl benzene sulfonate(393) at the air/water and decane/water interfaces were investigated by drop shape analysis method. The influences of concentration on dilational modulus were expounded. The experimental results showed that the 5-alkyl played an important role in the surface dilational modulus, while the dimension of surfactant molecule dominated the interfacial dilatinal modulus.

Key words: Sodiumalkyl benzene sulfonate, Surface, Interface, Dilational modulus