Characterization of polystyrene latexes by hydrodynamic and electrophoretic fingerprinting

Abstract

We report the first measurements of the new approach of hydrodynamic fingerprinting. The hydrodynamic fingerprint is the isothermal contour diagram of the hydrodynamic size as a function of pH and pX (the logarithm of the conductivity fitS/cm)). The general applications of fingerprinting are discussed, and we compare hydrodynamic fingerprints with electrophoretic fingerprints on similar systems. The electrophoretic fingerprint is the isothermal isomobility contour diagram in the pH-pX domain. Measurements are reported on five model polystyrene latexes with carboxyl or sulfate surface groups (ranging from 401 to 1050 nm) from the Interfacial Dynamics Corp. We find that the hydrodynamic size depends on pH, pX, and time, and is generally larger than the electron microscopy size. The hydrodynamic fingerprint, like the electrophoretic fingerprint, is a characteristic pattern of a particular colloidal system. The advantages of the colloid system variable pX over the classical ionic strength are illustrated. The fingerprinting approach is a correlation of variables that can be used to spot errors and assess the general

Surface Electrical Properties of Polystyrene Latex

“…Note the linear relationship between the conductivity and . This is also expected at low volume fractions, because the interesting parameter from these measurements is the conductivity increment ⌬K/K ϱ , defined as ⌬K/K ϱ ϭ ͑K/K ϱ Ϫ 1͒/, [7] where K is the suspension conductivity (at a given ) and K ϱ is the bulk electrolyte conductivity. The experimentally determined ⌬K/K ϱ as a function of ionic strength can be seen in Table 1.…”

“…The accuracy of the conductivity increment determination is about Ϯ0.15, because three parameters must be measured to evaluate ⌬K/K ϱ , as can be seen from Eq. [7]. Finally, it should be mentioned that all conductivity measurements were made on the aged latex.…”

“…Even if the geometrical dimensions are well defined the surface electrical properties are poorly understood. The electrical properties of latex particles have been investigated mainly by microelectrophoresis (1)(2)(3)(4)(5)(6)(7) and electrical conductivity measurements (8 -13), and in some cases dielectric response has been used also (14 -21). Comparison between the experimental results and standard theories based on the Gouy-Chapman Poisson-Boltzmann formalism shows unexpected anomalies.…”

Adsorption of Sodium Dodecyl Sulfate to Colloidal Titanium Dioxide: An Electrophoretic Fingerprinting Investigation

“…Fingerprinting (6)(7)(8), a means of representing colloidal variables as a function of pH and the log of the conductivity, pλ, was conceived at the University of Massachusetts in 1986. The conductivity is expressed in units of microsiemens per centimeter, which is convenient as it places the zero close to the conductivity of pure distilled water.…”

“…The conductivity is expressed in units of microsiemens per centimeter, which is convenient as it places the zero close to the conductivity of pure distilled water. Rowell and co-workers (6)(7)(8) have suggested that the solution conductivity is the experimental analogue to the ionic strength. It has the advantage of being a measured quantity that does not depend on a knowledge of the ions present in solution.…”