Effect of dicationic ionic liquids on cloud points of tergitol surfactant and the formation of aqueous micellar two-phase systems


A cloud point evaluation was performed for the nonionic surfactant Tergitol 15-S-7 in aqueous solutions of McIlvaine buffer (pH 7.0). Cloud point temperatures of the selected nonionic surfactant were studied in relation to the effect that the addition of dicationic ionic liquids (ILs) had on the systems. The dicationic ILs with different alkyl spacer lengths were derived from 1, n-bis(3-methylimidazolium-1-yl)alkane bromide ([BisAlk(MIM)(2)][2Br]) - in which Alk=But, Hex, Oct, and Dec. The dicationic ILs with longer alkyl spacer chains (Alk >= 6) led to an increase in the Tergitol's cloud point values, due to their ability to fold their structures in solution, which increase the interactions of ILs with tergitol in the mixed micelles. This increase was even more pronounced when the concentration of the dicationic ILs was increased. Furthermore, the addition of dicationic ILs increased the micelles size; however, the hydrodynamic diameter of mixed micelles did not depend on the length of the ILs' alkyl spacer chains. The Tergitol/IL systems with lower critical micellar concentration values will result in higher cloud point values, due to the greater colloidal dispersion stability.

subject category

Materials Science, Multidisciplinary


Bender, CR; Vicente, FA; Kuhn, BL; Frizzo, CP; Villetti, MA; Carvalho, PJ

our authors


The authors acknowledge the financial support from CNPq, CAPES, and FAPERGS (edital 04/2019 Auxilio Recem Doutor (ARD); grant no 19/25510001242-0), as well as the research fellowships from CNPq (C. P. F. and M. A. V.) and CAPES (B.L.K). This work was also developed within the scope of the CICECO-Aveiro Institute of Materials project (UIDB/50011/2020 and UIDP/50011/2020), financed by national funds from Portugal's Foundation for Science and Technology (Fundacao para a Ciencia e a Tecnologia -FCT) of the Ministry of Science, Technology, and Higher Education (Ministerio da Ciencia, Tecnologia e Ensino Superior -MCTES). The authors are also grateful for the national funds from the FCT for the doctoral grant (SFRH/BD/101683/2014) of F.A.V. Also, P.J.C. acknowledges the FCT/MCTES for research contract IF/00758/2015 as part of the Investigador FCT'' program.

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