Latex 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). 

Complete recoveries are essential for the calculation of accurate particle size distributions from HDC data. In Small s work (O NaCl was used to increase the ionic strength of the eluant phase, however, quantitative results were not reported for any of the recoveries, especially at high ionic strengths, other than the statement that no latexes of 338 nm or 35T nm diameter were eluted at 0.1T6 M. In our case using SLS only in the mobile... 

Two different emulsion polymerization reactions were Investigated. One was the polymerization of acrylonitrile and methylacrylate (75/25 AN/MA) In the presence of an acrylonitrile elastomer (70/30 BD/AN) to produce a graft resin, llie second was the copolymerization oiE acrylonitrile and styrene (70/30 AN/S). Chromatographic analyses of latex solutions were conducted periodically during both types of polymerization reactions, using acetonitrile as latex solvent and chromatographic mobile phase. 

A unique anion-exchange column has been developed that has a thin (non-diffusion limited) anion-exchange phase coated onto a 10-/nm latex bead. When a mobile phase of 0.15 M NaOH is used, neutral carbohydrates are converted into anions, which are separated on the column. Although the resin has low capacity, and probably causes degradation of the carbohydrates, when it is coupled to a triple-pulsed, amperometric detector, the system provides extremely sensitive, high-resolution separations. 

Polystyrene latexes were similarly prepared by Ruckenstein and Kim [157]. Highly concentrated emulsions of styrene in aqueous solutions of sodium dodecylsulphate, on polymerisation, yielded uncrosslinked polystyrene particles, polyhedral in shape and of relative size monodispersity. Interestingly, Ruckenstein and coworker found that both conversions and molecular weights were higher compared to bulk polymerisation. This was attributed to a gel effect, where the mobility of the growing polymer chains inside the droplets is reduced, due to increased viscosity. Therefore, the termination rate decreases. 

Ferguson et al. [52] compared the behavior of a range of conventional alkyl ethoxylate surfactants in emulsion polymerizations with their acrylated analogues. This has allowed a direct comparison of identical surfactant structures, one of which remains kinetically mobile in the resultant lattices, while the other becomes chemically bound to the latex particles. The surfactants chosen for this study were C12 i4-(EO)30 with C12 14-(EO)30-A and C12 14-(EO)12 with C12 14-... 

Most technological suspensions consist of very polydisperse particles. In order to simplify his experimental system Stotz employed monodispersed latex suspensions (particle diameter = 6 or 30y). In an interesting comparative experiment, he also measured the particle mobilities using the simple... 

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. 

The H-form latex was converted to Na-form latex by adding either an excess or an exact amount of NaOH as determined by conductometric titration in order to eliminate the possible effect of the ion-exchange between the H+ ion on the latex particle and Na+ ion in the solution. The results showed that the Na-form latex had the same em (3.2 y.cm/sec. volt) with H-form latex (3.1 y.cm/sec. volt) in deionized water and same increasing dependency of mobility with increasing NaCl concentration, Figure 1. A reasonable explanation for the increase in zeta potential is the adsorption of negative chloride ion from solution to the surface of latex particle. The decrease in em above 10 M NaCl is associated with compression of the electrical double layer. 

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...

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