Effect of counterions on surface and foaming properties of dodecyl sulfate.

The influence of counterions of surfactant on interfacial properties is studied by measuring foamability, foam stability, equilibrium and dynamic surface tension, and surface viscosity. The surfactant chosen is anionic dodecyl sulfate with various counterions, Li(+), Na(+), Cs(+), and Mg(++). Surface tension measurements show a decrease in the following order: LiDS > NaDS > CsDS > Mg(DS)(2).

Effect of degree, type, and position of unsaturation on the pKa of long-chain fatty acids.

Titration of a series of C(18) fatty acids yields pK(a) values that decrease with an increasing degree of unsaturation in the fatty acid chain. The pK(a) values of stearic, elaidic, oleic, linoleic, and linolenic acids were studied and compared to values of area per molecule in a spread monolayer of these acids. The decrease in pK(a) was found to relate to melting point temperature and area per molecule in the spread fatty acid monolayer.

A Dynamic Model for the Attachment of a Brownian Particle Mediated by Discrete Macromolecular Bonds.

A model is presented for the attachment of a Brownian particle to a surface mediated by both the conservative colloidal forces and the formation of macromolecular bonds. By considering Brownian motion and bond formation as coupled stochastic processes, the model derives a governing equation for the time-dependent probability density of having a given number of bonds and separation distance from the surface. The model predicts the deposition rate of particles to a surface as a function of the physicochemical parameters of the binding molecules, including the density, interaction length, stiffness, and formation and dissociation kinetic rate constants.