Synergism between betaine surfactants under high-salt conditions

Abstract

Foam properties and surface dilational rheology of single and mixed LHSB (lauramidopropyl hydroxyl sulfobetaine)-OAB (oleic amide propyl betaine) surfactants were measured to investigate the synergism between the two components. Experimental results showed obvious synergistic effects in foam stability, dilational modulus, and phase angle between LHSB and OAB. Moreover, interaction parameters were calculated to quantitatively characterize the synergism. The negative interaction parameters between LHSB and OAB demonstrated that there was an attractive interaction between LHSB and OAB, and the attractive interaction contributed to forming the dense surfactant layer at the liquid/air layer, which in turn improved foam stability. The negative values of parameters reached their maximum when the LHSB: OAB molar ratio ranged from 1:1 to 1:2, the same time the foam stability reached its maximum. The interaction between LHSB and OAB was confirmed by 2D NOSEY (two-dimensional nuclear overhauser enhancement spectroscopy) experiments, the interaction between LHSB and OAB could be attributed to the hydrogen bonding or the electrostatic interaction between the hydrophilic groups of the two surfactants.