Ionic liquids (ILs) present unique physicochemical properties such as negligible vapour pressure and high solubility in different solvents; therefore, they have been used in several areas of chemistry with success.1
Some ILs show amphiphilic character2 presenting better surface-active properties than conventional surfactants.3 Because of this, ILs have emerged as a superior class of surfactants.4
In this communication, the design and synthesis of new task-specific amino acid based ILs to be used as surfactants is reported; for this purpose, long alkyl chains were introduced into their structures. The selected ILs were designed aiming low toxicity and viscosity and high biodegradability as well as high thermal stability. Due to the low toxicity of amino acids, cations derived from proline were selected; 5 in addition, these cations allow simple variations on the side chain and nitrogen quaternization. Taking into account the known application of dodecylsulfate and dodecylbenzenesufonates surfactants, they were selected as anions.
The general procedure used to synthesize these ILs involves two steps: esterification and quaternization of the amino acid using different alcohols and later anion exchange.
Reference:
[1] Plechkova, N.V.; Seddon, K.R., Chem. Soc. Rev., 2008, 37, 123-150.
[2] Singh, G.; Singh, G.; Zhang, S.; Kang, T.S., J. Phys. Chem. B, 2016, 120, 1092-1105.
[3] Cognigni, A.; Gaertner, P.; Zirbs, R.; Peterlik, H.; Prochazka, K.; Schroder, C., Bica, K., Phys. Chem. Chem. Phys, 2016, 18, 13375-13384.
[4] Huang, B.; Huang, C.; Jinging, C.; Xiaoqui , S., J. Alloys Compd., 2017, 712, 164-171.
[5] Trivedi, T. J.; Srinivaa Rao, K.; Singh, T.; Kumar Mandal, S.; Sutradhar, N.; Panda, A.B.; Kumar, A., ChemSusChem, 2011, 4, 604-608.
