Effect of binary solvents on the critical micelles concentration by using1-methyl-4-[4 '-aminostyryl]pyridinium iodide

The influence of preferential solvation of 1-methyl-4-[4'-aminostyryl]pyrid inium iodide (M-NH2) on critical micelles concentration (c.m.c) has been st udied by using sodium dodecyl sulfate (SDS) in the binary aqueous mixtures of protic and aprotic co-solvents including glycerol, ethylene glycol, dime thyl sulfoxide (DMSO), and acetone. The results reveal that the c.m.c depen ds on the polarity, in addition to the dielectric constant of the co-solven ts. The lower the polarity as well the dielectric constant (epsilon), the m ore effective the breaking of the micelles. Acetone which has a low polarit y (Z), low dielectric constant (epsilon), and large hydrophobic surface is shown to be the strongest denaturant for micelles. On the other hand DMSO, which has relative hydrophobic effect with large (epsilon), in addition wit h glycerol and ethylene glycol which has large (epsilon) and small hydropho bic surface have the weakest effect. (C) 2001 Elsevier Science B.V. All rig hts reserved.