Abstract: Palmitic acid and N,N-dimethyl-1,3-propane diamine were used as starting materials to synthesize the palmitic amide intermediate,which further reacted separately with sodium chloroacetate and sodium 3-chloro-2-hydroxy propane sulfonate via quaterization process to prepare palmitic amide dimethyl amino-carboxybetaine surfactant (C16ZC) and palmitic amide dimethyl amino hydroxy-propyl sulfobetaine surfactant (C16ZS) respectively.The effects of salts and temperature on the surface tension and critical micelle concentration (cmc) of the surfactants were measured and determined.The viscosity of solution of C16ZC and C16ZS were measured and discussed.The thermodynamic parameters were calculated in accordance with Gibbs micelle equations from the cmc of C16ZS and C16ZC at different temperature.Results showed that the cmc of C16ZC are lower than that of C16ZS while effect of inorganic salt on cmc and corresponding surface tension (γ_cmc) of C16ZC is higher than that of C16ZS,and effect of divalent salt (such as CaCl₂) is even more higher than that of monovalent salt (such as NaCl).As temperature rises,cmc and γ_cmc of both C16ZC and C16ZS decline slightly.The thermodynamic parameters showed that micellization process for both products is found to be entropy-driven and C16ZC is easy to form micelle as a result of much lower Gibbs free energy for micellization (ΔGmicθ) compared with that of C16ZS.Addition of suitable dosage of inorganic salt can increase the viscosity of both products,and viscosity of C16ZC is more sensitive to inorganic salt than that of C16ZS.

Key words: betaine, synthesis, property, inorganic salt, viscosity