Synthesis and Properties of Alkylbetaine Zwitterionic Gemini Surfactants

A series of alkylbetaine zwitterionic gemini surfactants, 1,2-bis[N-methyl-N-carboxymethyl-alkyl-ammonium]ethane (C (n) Ab, n = 8, 10, 12, or 14), were synthesized by alkylation of N,N'-dimethylethylenediamine with an alkyl bromide, followed by reaction with sodium 2-bromoacetate. Their solution properties were characterized by surface tension, steady-state fluorescence, and rheological measurements. Surface-tension measurements showed C (n) Ab had lower critical micelle concentration (CMC) and higher efficiency in lowering the surface tension than their corresponding monomeric surfactants. The logCMC of C (n) Ab decreased linearly with increasing chain lengths up to 12. Viscosity measurements showed only C(10)Ab could enhance aqueous solution viscosity at high concentrations.