Effect of Long-Chain Length on the Surface Activities of Zwitterionic Imidazolium-Based Surfactants: 1-Carboxymethyl-3-alkylimidazolium Inner Salts

摘要

Zwitterionic imidazolium-based surfactants, namely 1-carboxymethyl-3-alkyl imidazolium inner salts (C n imCM, n = 10, 12, and 14), were synthesized. Their molecule structures were characterized by means of electrospray ionization mass spectrometry (ESI–MS), 1H nuclear magnetic resonance (1H NMR) and elemental analysis. Compared to the structurally related N-alkylbetaines (C n H2n+1N+(CH3)2CH2COO−), the CMCs of C n imCM are smaller than those of N-alkylbetaines. The effect of the long-chain length on the typical physicochemical properties of C n imCM was studied. It is found that the lengthening of the long-chain enhances the surface activity of C n imCM. The tendency for C n imCM surfactants is similar to the case of the structurally related traditional zwitterionic N-alkylbetaines.