Synthesis and Surface Active Properties of Novel Oligomer Betaine Surfactants

A new type of oligomer betaine surfactants pentasodium N,N',N ''-alkyl diethylene triamine pentaacetic acid containing five carboxylate groups, three quaternary ammonium groups and three hydrophobic groups was synthesized by alkaline neutralization reaction and quaternization with diethylene triamine pentaacetic acid, sodium hydroxide and long chain alkyl bromide as main raw materials. The chemical structures of the prepared compounds were confirmed by FTIR, H-1 NMR, MS spectroscopy and elementary analysis. With the increasing length of the carbon chain, the CMC of the synthesized compounds initially decreased. The surface active properties of these compounds were superior to that of the single chain betaine surfactants rich as decyl dimethyl betaine. The efficiency of adsorption at the water/air interface (pC(20)) of these surfactants was very high. It is found that the shorter hydrocarbon chain length of oligomer betaine surfactants, the faster the rate of reduction of surface tension, and the bigger the aggregation number of oligomer betaine surfactants are. Their foaming properties and wetting ability toward a felt chip, and lime-soap dispersing ability were investigated.