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Solubilization, Surface Active and Thermodynamic Parameters of Gemini Amphiphiles Bearing Nonionic Hydrophilic Spacers
Author(s) -
Negm Nabel A.
Publication year - 2007
Publication title -
journal of surfactants and detergents
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.349
H-Index - 48
eISSN - 1558-9293
pISSN - 1097-3958
DOI - 10.1007/s11743-007-1014-x
Subject(s) - chemistry , micelle , enthalpy , amphiphile , critical micelle concentration , adsorption , aqueous solution , alkyl , surface tension , pulmonary surfactant , lamellar structure , ethylene oxide , gibbs isotherm , thermodynamics , organic chemistry , crystallography , copolymer , physics , biochemistry , polymer
Abstract A series of novel nine symmetric diquaternary gemini amphiphiles was synthesized having the formula:Br ‐ [ RRR 1N + CH 2 COO ‐ ( − CH 2 CH 2 O − ) n COCH 2N + RRR 1 ]Br −where R 1 = C 11 H 23 COOCH 2 CH 2 , C 15 H 31 COOCH 2 CH 2 and/or C 17 H 35 COOCH 2 CH 2 alkyl chain, R = CH 2 CH 2 OH and n = 10, 15 and 25 ethylene oxide units. Surface active properties at air‐aqueous solution were determined using Gibb's adsorption equations including critical micelle concentration (CMC), effectiveness ( π CMC ), efficiency ( p C 20 ) and minimum surface area ( A min ). The effects of hydrophobic and hydrophilic chain length on the surface and thermodynamic parameters of the diquaternary surfactants were discussed. Surface tension–concentration profiles of diquaternary amphiphiles display the formation of various aggregative structures, e.g., spherical micelles and lamellar shapes, as well as bearing lower critical micelle concentration than the expected values for the corresponding N + /CH 2 ratio of monoquaternary amphiphiles. The calculations of minimum surface area ( A min ) appear to have higher values for the molecules at the interface, reinforcing the idea of air–water interface attachment of both positively charged nitrogen atoms. Thermodynamic data including, free energy, entropy and enthalpy changes (Δ G , Δ S , Δ H ) for adsorption at the air–water interface and also for micellization in the bulk of surfactant solutions were calculated. The data showed a great tendency of the synthesized molecules for adsorption at the interfaces rather than micellization in the bulk of their solutions. Solubilization behaviors of the prepared amphiphiles were described as a vital application of these compounds. The effect of their structures on the solubilization process towards polar and nonpolar solubilizates was also explained.