Synthesis and Surface Active Properties of tri[(N-alkyl-N-ethyl-N-Sodium carboxymethyl)-2-Ammonium bromide ethylene] Amines

Trimeric betaine surfactants tri[(N-alkyl-N-ethyl-N-sodium carboxymethyl)-2-ammonium bromide ethylene] amines were prepared with raw materials containing tris(2-aminoethyl) amine, alkyloyl chloride, lithium aluminium hydride, sodium chloroacetate, and bromoethane by alkylation, Hoffman degradation reaction, carboxymethylation and quaternary amination reaction. The chemical structures of the prepared compounds were confirmed by FTIR, 1H NMR, MS and elemental analysis. With the increasing length of the carbon chain, the values of their critical micelle concentration initially decreased. Surface active properties of these compounds were superior to general carboxylate surfactants C10H21CHN+(CH3)2COONa. The minimum cross-sectional area per surfactant molecule (A min), standard Gibbs free energy adsorption (ΔG ads) and standard Gibbs free energy micellization (ΔG mic) are notably influenced by the chain length n, and the trimeric betaine surfactants have greater ability to adsorb at the air/water interface than form micelles in solution. The efficiency of adsorption at the water/air interface (pC20) of these surfactants increased with the increasing length of the alkyl chain. Their foaming properties, wetting ability of a felt chip, and lime-soap dispersing ability were also investigated.