Self-diffusion and NMR studies of chloride and bromide ion binding in aqueous hexadecyltrimethylammonium salt solutions

Abstract

A combination of tracer self-diffusion and NMR techniques was used to study mixed solutions of hexadecyltrimethylammonium chloride (C16TAC) and bromide (C16TAB). The degree of counterion association with the micelles, 03x), and the relative strength of counterion binding was obtained from ^Cl and 82Br self-diffusion studies. A slight increase in ¡8Br occurs at the transition from spherical to rodlike Ci6TAB micelles and is markedly greater than ß of ClgTAC solutions at all concentrations. For C16TAC/C16TAB mixtures there is a pronouncedly preferential binding of Br" ions for both spherical and rodlike micelles. For pure C16TAC or C16TAB solutions there is a marked increase in 35C1 or 81Br quadrupole relaxation on the formation of rods.For mixtures the quadrupole relaxation rate of 81Br~is strongly influenced by the presence of rodlike micelles while that of 36C1~is not. This can be interpreted either as the presence of two binding sites in the micelles with preferential Br" binding close to the head groups or as a coexistence of spheres and rods and a preferential binding of Br" to rods. For hexagonal liquid crystals of C16TAC/C16TAB mixtures, 3SC1 quadrupole splittings demonstrate a preferential binding of Br" ions.

Effects of urea and a nonionic surfactant on the micellization and counterion binding properties of cetyltrimethyl ammonium bromide and sodium dodecyl sulfate

“…The nature of the equation is such that algebraic solution of a and lg from the intercept and the slope is not possible. This and similar works [16][17][18][19] have evidenced parallel effects. A conceptual analysis of the utility of Eq.…”

“…Urea is known to have important physicochemical properties, it reduces hydrophobic interaction and also the micellization extents of surfactants [9,10,12,14,[25][26][27][28][29][30]. A few studies on the counterion binding by the ionic-nonionic mixed micelles have recently appeared [16][17][18][19][20][21][22]. Besides this, counterion binding charac-teristics of CTAB-sodium cholate (NaC) and CTAB-NaC1 have also been studied.…”

Self-aggregation of binary mixtures of alkyltriphenylphosphonium bromides: a critical assessment in favor of more than one kind of micelle formation

“…There are reports that pure surfactants (both anionic and cationic) can form two kinds of micelles registering two cmc's [3][4][5][6][7][8][9]. Triener and Makayssi [9] have reported it confirmatively from conductance measurements for alkyltrimethylammonium bromides and their binary mixtures and have concluded that the phenomenon of two-cmc formation can be shown for surfactants having alkyl chains containing carbon numbers 16 or more.…”

Counting ions and other nucleophiles at surfaces by chemical trapping

“…Several experimental methods are available to estimate the distributions of ions between these interfaces and the bulk phase, including solubility, conductivity, potentiometric studies and nuclear magnetic resonance, UV/visible and fluorescence spectroscopy. Most of these methods rely on adjustable parameters to describe the measured property of the ion when bound to the interface, monitoring only one component at a time, and some are limited to narrow ranges of solution compositions (Fabre et al 1980;Tanford 1980;Zana 1985).…”