Latex electrophoretic mobility

Electroultrafiltration (EUF) combines forced-flow electrophoresis (see Electroseparations,electrophoresis) with ultrafiltration to control or eliminate the gel-polarization layer (45—47). Suspended colloidal particles have electrophoretic mobilities measured by a zeta potential (see Colloids Elotation). Most naturally occurring suspensoids (eg, clay, PVC latex, and biological systems), emulsions, and protein solutes are negatively charged. Placing an electric field across an ultrafiltration membrane faciUtates transport of retained species away from the membrane surface. Thus, the retention of partially rejected solutes can be dramatically improved (see Electrodialysis). 

Particle electrophoresis studies have proved to be useful in the investigation of model systems (e.g. silver halide sols and polystyrene latex dispersions) and practical situations (e.g. clay suspensions, water purification, paper-making and detergency) where colloid stability is involved. In estimating the double-layer repulsive forces between particles, it is usually assumed that /rd is the operative potential and that tf/d and (calculated from electrophoretic mobilities) are identical. 

Figure 7.7 Zeta potentials (calculated from electrophoretic mobility data) relating to particles of different ionogenic character plotted as a function of pH in acetate-veronal buffer at constant ionic strength of 0.05 mol dm 3, (a) Hydrocarbon oil droplets, (b) Sulphonated polystyrene latex particles, (c) Arabic acid (carboxylated polymer) adsorbed on to oil droplets, (d) Serum albumin adsorbed on to oil droplets...

Counterion nm-diameter polystyrene latex (0.35% solids) Electrophoretic Mobility, ym cm/volt sec a... 

Figure 2. Variation of electrophoretic mobility in distilled water with pH for polystyrene latex particles with different surface groups (1) 520 sulfate (2) 520 carboxyl (3) 520 hydroxyl (4) LS-1010-E sulfate (5) LS-1010-E hydroxyl.

The Relationship Between the Electrophoretic Mobility and the Adsorption of Ions on Polystyrene Latex... 

Characterization of the Polystyrene Latex Samples. The polystyrene, PS, latex samples under investigation were characterized according to particle size, concentration of surface sulphates and electrophoretic mobility, em, in deionized water. The results, Table I, show that all the samples were of similar size with the exception that the Dow latexes were monodisperse while... 

The Effect of NaCl on the Electrophoretic Mobility of PS Latex Particle. The em of the Dow 357 nm latex in the H-form and Na-form, along with two other Dow monodisperse latexes in the H-form with diameters of 795 and 1100 nm, was measured as a function of NaCl concentration. The results in Figure 1 show that the em for all three latexes increased with increasing concentration of NaCl to a maximum at about 1 x 10 "2 M NaCl followed by a rapid decrease. Converting the electrophoretic mobility to zeta potential, using tables derived by Ottewill and Shaw (6) from the results of Wiersma et al. in order to account for relaxation and retardation effects, led to the same dependency as shown in Figure 2. 

Figure 1. Electrophoretic mobility of PS latexes ((%) Na-form 357 nm (O) H-Form 357 nm (A) 795 nm (Q) 1100 nm) as a function of NaCl concentration...

Latex Particle Size, nm Surface Charge Density (sulfate group), yc/cm2 Electrophoretic Mobility in Deionized Water ym cm/sec volt... 

Figure 4. Electrophoretic mobility of 357-nm PS latex as a function of PH in 2 X 10 3M NaCl ((%) sulfate form (O) hydroxyl form)...

Figure 5. Electrophoretic mobility of the hydroxyl form 357-nm PS latex as a function of the concentration of electrolytes ((A) in NaOH ( A ) in NaCl (O) in...

The various latexes were characterized with respect to particle size and size distribution, surface charge and functional group density, and electrophoretic mobility behavior. As observed by transmission electron microscopy all latexes were found highly monodisperse with a uniformity ratio between 1.001 and 1.010, a property due to the short duration of the nucleation period involved in the various radical-initiated heterogeneous polymerization processes. The surface charge density was determined by a colorimetric titration method reported elsewhere [13]. 

Here, kd is the inverse of the Debye length. Even though the -potentials for latex spheres may exceed 25 mV and, therefore, require a more complex equation to relate to mobility (as per O Brien and White [265]), the low ionic strength (small kd) of El-FFF measurements should still ensure a proportionality between pe and . From the retention data, it is possible to obtain quantitative information regarding either the -potential of samples with known particle size eluting from the channel or the particle size, if the electrophoretic mobility is known. 

Figure 21.7 shows that the electrophoretic mobility of the latex particles was measured in a phosphate buffer solution at pH 7.4 at four different temperatures. 

Note that Makino et al. [57] found that Eq. (21.108) holds between the electro-osmotic velocity U o on a poly(N-isopropylacrylamide) hydrogel-coated solid surface and the electrophoretic mobility of a poly(N-isopropylacrylamide) hydrogel-coated latex particle. 

On basically hydrocarbon-hydrophobic substrates such as polystyrene, it is well established that even on the negatively charged particles there is adsorption of surfactant anions via the hydrocarbon chains. This is demonstrated in the work of Kayes (1976), who found a substantial increase in the electrophoretic mobility of polystyrene latices with increase in the concentration of dndecyl sulfate in the system, and in the work of Cebula et al. (1978) on the adsorption of dndecanoate ions on polystyrene latex particles. 

In the final paper of this important series (Machi et al., 1979d) the effect of tbe reaction conditions on the stability of the tetraBuoroethylene latices was studied. The stabilization was believed to be due to either carboxyl and groups or to the adsorbed hydrofluoric acid formed hy radiolysis of the monomer or to both. The surface charge densities, electrophoretic mobilities, and infrared spectra were all measured. The storage stability of tbe latices, measured by the appearance of coagulum, was found to be proportional to the total dose and the polymer concentration and not to depend on the dose rate. Since the stabilization results from the radiolysis of the monomer and wat this is quite reasonable as is the effect of concentration. The presence of monomer was necessary in the sense that irradiation of the latex in the absence of monomer did not improve the storage stability. 

Continuous decrease in the electrophoretic mobility when the ionic strength increases is observed for inorganic materials (Fig. 3.2) but not for latex. This anomalous behavior is attributed to the hairy structure of latex surfaces. 

Temperature has dramatic effect on the electrokinetic properties of thenno-sensitive polymers. A pH independent electrophoretic mobility of about -0.5x10 m" V s" (pH 3-11) in the presence of 0.1 mol dm NaCl was reported for synthetic poly (A-isopropylacrylamide) latex (persulfate initiator) at 20°C [17]. The same material has a mobility of about -5x10 m V s" (ten times greater ) at 50 C. This dramatic change occurs when the lowest critical solubility temperature is exceeded, and it is accompanied by substantial decrease in particle size (factor about two,... 

---