Solubilization Behaviors of Nonpolar Substrates Using Double Tailed Cationic Surfactants

Abstract

A series of double hydrophobic tails of N-methyl diethanolammonium bromide cationic surface active agents were synthesized. Their chemical structures were elucidated using different analytical tools including elemental analyses, FTIR, mass fragmentation, and ¹H-NMR spectroscopy. Their surface parameters including critical micelle concentration (CMC), effectiveness (π _CMC ), efficiency (Pc ₂₀), maximum surface excess (Γ _max ), and minimum surface area (A _min ) were calculated. The behaviors of the synthesized molecules in their solutions were discussed based on the data of surface parameters, micellization and adsorption thermodynamics at 25°, 40°, and 55°C. The experimental data of surface activity showed that these molecules are tends to form micelles in the bulk of their solutions at lower temperatures. On contrarily, they prefer to adsorb at higher temperatures. The synthesized cationic surfactants were used as solubilizing agent for nonpolar substrate (paraffin oil) at 25°C. The results of solubilization measurements showed good ability for the used surfactants towards solubilizing paraffin oil in aqueous medium. The results showed that the chemical structure of the solubilizate plays an important rule in its solubilization. Several factors were found to influence the extent of solubilization including: number of alkyl chains within surfactant molecule, symmetry of molecules and chain length of hydrophobic parts. The results were rationalized by the Kraft point and HLB values of the used surfactants. Furthermore, solubilization curves showed the steady state solubilization of each surfactant used.

Keywords:

• Adsorption
• cationic surfactants
• CMC
• HLB
• hydrophobic length
• micellization
• solubilization
• surface activity

Notes

L.P = light petrol b.p (60–80°C); A = acetone.