Novel Cationic Gemini Surfactants Based on Piperazine: Synthesis, Surface Activity, and Foam Ability

A series of novel Gemini surfactants C-n-pi-C-n with piperazine moiety as spacer was synthesized and characterized by IR, H-1 NMR, and mass spectra. Their surface activities were evaluated by surface tension, electrical conductivity, and steady-state fluorescence. The obtained results indicated that the synthesized Gemini surfactants exhibited lower critical micelle concentration (cmc) and surface tension (gamma cmc) compared with traditional surfactants. The steady-state fluorescence measurement and electrical conductivity were recorded to demonstrate the accuracy of cmc values. In addition, the micellization was evaluated using conductivity measurement in the temperature range of 298-308 K. The foamability and foam stability of these Gemini surfactants were also examined. In which, the Gemini surfactant with the shortest chain (C-12) showed the best foamability but the poorest foam stability. Hydrophile-lipophile balance and emulsifying ability were studied and a comparatively poor emulsifying ability displayed.