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 (CnAb, 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 CnAb had lower critical micelle concentration (CMC) and higher efficiency in lowering the surface tension than their corresponding monomeric surfactants. The logCMC of CnAb decreased linearly with increasing chain lengths up to 12. Viscosity measurements showed only C10Ab could enhance aqueous solution viscosity at high concentrations.