Study of ionic surfactants by membrane osmometry

Abstract

CuSO4 in solutions of NaC103 and Bu4NC103 plotted against the molar concentrations of the added salts. I t can be seen that the curves essentially duplicate those of Figure 1. If anything, assuming constant absorptivity coefficients for CuS04 ion pairs, the demixing effect of Bu4NC103 may be greater than that of Bud- NETS.Spectra were run in 0.02 M CuS04 containing 0.1 M NaBr and 0.1 M Bu&Br. After rough empirical corrections for absorption by the CuBr+ complex, a t 250 mp, the residual absorbance in NaBr was 0.95 arid in Bu4NBr was 1.35. The same demixirig effect is qualitatively evident in this latter system.Up to this point, it has been assumed that the only significant antagonistic interaction is that between the organic cations and the sulfate anions. However, the remaining ions must also play some part, although it is probably less important in the present cases. The anions chlorate and bromide are water structure-breakers, with negative viscosity-B coefficients. l 2 The ethanesulfonate ion may also be a structure-breaker, or a weak structure-former of the organic type. A structurebreaking anion would exert a cooperative effect in the sense that it can provide loose water molecules to be organized around the quaternary ammoninm ion.2 The small differences between the ethanesulfonate and chlorate solutions may reflect differences in their compatibilities with the quaternary ammonium ion. One consequence of this hypothesis is that the demixirig effect would be very much smaller in solutions of CuSOl and Bu4NF, since both sulfate and fluoride ions are strong water-structure formers of the chargooriented type.Acknowledgment. We thank Professor S. Petrucci of this department for assistance and helpful sugges tions.The micellar weight of well-purified sodium dodecyl sulfate (NttDDS) was determined by means of an automatic osmometer in 0.03,0.1, and 0.342 ?il aqueous sodium chloride solutioii at 36.5'. The respective average numbers of monomer molecules in the micelles, N , were 58.9, 82.9, arid 115; in 0.03 .M NaCl at 3l0, N = 63.1.The solvent contained a specified amount of NaDDS in order to repress dissociation of the micelles and to minimize the monomer contribution to the osmotic pressure. The dialytic behavior of YaDDS is discussed, and the tnagnitude of the Staverman reflection coefficient is estimated. Saturation of the aqueous solution with benzene was found to increase N .

Luminescence Quenching in Supramolecular Systems: A Comparison of DNA- and SDS Micelle-Mediated Photoinduced Electron Transfer between Metal Complexes

“…) ([SDS] -cmc)/n ˜, where cmc is the critical micelle concentration and n ˜is the aggregation number (62 in water). 32,46,47 The cmc is not expected to change dramatically upon addition of metal complex and has been reported to drop from 8 to 7 mM when 200 µM Ru(bpy) 3 2+ is added. 38a Reasonable fits to time-resolved measurements on micelle samples were obtained by defining single-exponential decays without deconvolution or by assuming biexponential fits with deconvolution.…”

A study of aqueous systems of purified non-ionic surfactant by membrane osmometry

“…The application of the membrane osmometry to the determination of number average micellar molecular weights (%) has been reported by Coll (1969Coll ( , 1970 and Attwood, Elworthy & Kayne (1969, 1970. We report the value of R, of a purified sample of a non-ionic surfactant of pharmaceutical interest, polysorbate 80 and show that the effect of solubilizing nitrofurazone in micelles can be studied by membrane osmometry.…”

“…In the experiments with nitrofurazone, both the solutions in the solvent and solute side were saturated with nitrofurazone. The experimentally measured osmotic pressure, P, between a sample solution of concentration c g/litre and a solvent of concentration c' g/litre is given by (Coll, 1970;Attwood & others, 1970)…”

Conductance stopped-flow study on the micellar equilibria of ionic surfactants

“…As is clearly seen in figure 4, the r^1 of SLS was reduced by th e addition of NaCl. This m ay be due to th e increase of the aggregation num ber (n) of th e micelle on addition of NaCl (K ushner & H u b b ard 1955;A nacker 1964;Coll 1970). However, th e lowering of th e c.m.c.…”