Micellization Behavior of Conventional Cationic Surfactants within Glycerol-Based Deep Eutectic Solvent

Ramesh Kumar Banjare; Manoj Kumar Banjare; Kamalakanta Behera; Siddharth Pandey; Kallol K Ghosh

doi:10.1021/acsomega.0c00866

Micellization Behavior of Conventional Cationic Surfactants within Glycerol-Based Deep Eutectic Solvent

ACS Omega. 2020 Jul 27;5(31):19350-19362. doi: 10.1021/acsomega.0c00866. eCollection 2020 Aug 11.

Authors

Ramesh Kumar Banjare¹, Manoj Kumar Banjare^{1

2}, Kamalakanta Behera³, Siddharth Pandey⁴, Kallol K Ghosh²

Affiliations

¹ MATS School of Sciences, MATS University, Pagariya Complex, Pandari, Raipur, C.G. 492009, India.
² School of Studies in Chemistry, Pt. Ravishankar Shukla University, Raipur, C.G. 492010, India.
³ Amity University, Gurugram, Manesar, Panchgaon, Gurugram, Haryana 122413, India.
⁴ Department of Chemistry, Indian Institute of Technology Delhi, Hauz Khas, New Delhi 110016, India.

Abstract

The aggregation behavior of two cationic surfactants, i.e., cetyldimethylethanolammonium bromide (CDMEAB) and cetyltributylphosphonium bromide (CTBPB), within an aqueous deep eutectic solvent (DES) is studied. The synthesized DES is composed of 1:2 mole ratio of choline chloride and glycerol and is further characterized by Fourier transform infrared (FTIR) and ¹H NMR spectroscopy techniques. The critical micellar concentration (CMC), micellar size, and intermolecular interaction in surfactants within Gly-based DES solutions are investigated by various techniques including surface tension, conductivity, fluorescence, dynamic light scattering (DLS), FTIR, ¹H NMR, and two-dimensional (2D) nuclear Overhauser effect spectroscopy (NOESY). The various interfacial properties and thermodynamic parameters are determined in the presence of 5 wt % glyceline (Gly)-based DES in an aqueous solution. The CMC, aggregation number (N _agg), and Stern-Volmer constant (K _sv) have also been determined by a steady-state fluorescence method. DLS is used to obtain information regarding the size of the aggregates formed by the cationic surfactants in DES solutions. FTIR spectroscopy is used to study the surfactant-DES interactions that tune the micellar structure of the surfactants within the Gly-based DES solution. The functional groups involved in the interactions (H-bonding and electrostatic) are the head groups (HO-CH₂-CH₂-N⁺ ion for CDMEAB and quaternary phosphonium (P⁺) ion for CTBPB) of the surfactants with the -OH-containing Gly DES. The hydrophobic moieties are involved in the hydrophobic interactions. The ¹H NMR data show that differences in chemical shifts can provide significant information about the interactions taking place within the system. ¹H NMR and NOESY techniques are further employed to strengthen our claim on the feasible structural arrangements within the aqueous surfactant-DES self-assembled structures. It is observed that both the cationic surfactants, i.e., CDMEAB and CTBPB, form self-assembled nanostructures in the Gly-based DES solutions. The present results are expected to be useful for colloidal solutions of DES and their mixtures with water.