Solubilization,Surface Active and Thermodynamic Parameters of Gemini Amphiphiles Bearing Nonionic Hydrophilic Spacers

摘要

A series of novel nine symmetric diquaternary gemini amphiphiles was synthesized having the formula:Br-[RRR1N+CH2COO-(-CH2CH2O-)_n COCH2N+RRR1]Br-where R1=C11H23COOCH2CH2,C15H31COOCH2CH2 and/or C17H35COOCH2CH2 alkyl chain,R=CH2CH2OH 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(pi_(CMC))efficiency(pC20)and minimum surface area(A_(min)).The effects of hydrophobic and hydrophilic chain length on the surface and thermodynamic parameters of the diquaternary surf actants 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 mi celle concentration than the expected values for the cor responding N+/CH2 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(DELTA G,DELTA S,DELTA 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 to wards polar and nonpolar solubilizates was also explained.