Doctoral Dissertations

Date of Award

8-1986

Degree Type

Dissertation

Degree Name

Doctor of Philosophy

Major

Chemistry

Major Professor

Linda J. Magid

Abstract

Hexadecyltrimethylammonium surfactants with a number of mono- and dlchlorobenzoate counterions were prepared by ion-exchange methods. Solutions of these surfactants were characterized by a number of techniques. Small-angle neutron scattering experiments were carried out to determine the size and shape of the micelles formed by several of the surfactants in water. Measurements of the electrical conductivity of the surfactant solutions were performed to determine their critical micelle concentrations and extents of counterion binding. Viscosity measurements, as a function of concentration, shear rate, and pH were made; proton and Carbon-13 nuclear magnetic resonance spectra of the solutions were recorded.

The results of these experiments indicate a strong dependency of the properties of the micellar solutions on the precise structure of the counterion of the surfactant. Solutions of a number of the sur factants exhibited strongly viscoelastic behavior; these solutions had low CMC values, high extents of counterion binding, and contained long cylindrical micelles. Solutions of the other surfactants exhibited normal viscometric behavior, contained approximately spherical micelles and had relatively low extents of counterion binding. Suggestions were advanced as to the cause of the observed counterion specificity.

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