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Effects of t-butanol on micelle formation by a series of long chain alkyltrimethylamonnium bromides

1982; Elsevier BV; Volume: 88; Issue: 2 Linguagem: Inglês

10.1016/0021-9797(82)90284-3

1095-7103

David Oakenfull,

Chemical and Physical Properties in Aqueous Solutions

Micelles of decyl-, dodecyl-, and hexadecyltrimethylammonium bromide (C10TAB, C12TAB, C16TAB) were studied at 298°K in 0.5 mole dm−3 sodium bromide and in the presence of various concentrations of t-butanol. (1) A fluorescent probe, N-phenylnaphthylamine, was used to estimate critical micelle concentrations (CMC) and the polarity of the hydrocarbon core of the micelles. (2) The ultraviolet absorption spectrum of solubilized benzene was used to estimate the polarity of the headgroup region. (3) Viscosity measurements were used to derive information about micelle shapes and solvent penetration. (4) Low-angle laser light scattering was used to determine aggregation numbers. Added t-butanol lowers the CMC of C10TAB but increases that of C16TAB. When mole fraction of t-butanol reaches 0.03 the micelles have a looser structure with greaer solvent penetration than the classical detergent micelle. Micelles are not formed when the mole fraction of t-butanol exceeds 0.03. t-Butanol penetrates the hydrocarbon core of the micelles and is adsorbed at the head group region. The optimum surface area per head group is consequently increased with the result that the micelles are smaller in the presence of t-butanol than in water alone and they are spherical rather than ellipsoidal.