Approach, latex

In an example by the Ballauff group, which follows essentially a very similar strategy but with a different synthetic approach, latex particles with a... 

Mixed anionic and nonionic surfactant systems have been widely used in industry to manufacture latex products. Anionic surfactants can provide electrostatic repulsion force between two similarly charged electric double layers. By contrast, nonionic surfactants can impart two approaching latex particles... 

Anotlier model system consists of polymetliylmetliacrylate (PMMA) latex, stabilized in organic solvents by a comb polymer, consisting of a PMMA backbone witli poly-12-hydroxystearic acid (PHSA) chains attached to it [10]. The PHSA chains fonn a steric stabilization layer at tire surface (see section C2.6.4). Such particles can approach tire hard-sphere model very well [111. 

Mechanical whipping of polymers in a liquid form and subsequent setting in the whipped state. The manufacture of latex rubber foam is the best-known example of this approach. 

The latex may then either be concentrated to about 60% DRC, usually by centrifuging or evaporation, or alternately coagulated and dried. The two approaches lead to two quite distinct branches of rubber technology, namely latex technology and dry rubber technology. 

An early approach was to use butadiene as the comonomer but the resultant copolymers have largely been used only in latex form in paper and board finishes and are no longer believed to be important. 

Figure 3 shows calibration plots of log (particle diameter) vs. elution voliame difference (AV) between marker and particle using three different monodisperse latexes at a low eluant ionic strength of 1.29 mM SLS. These results illustrate the featiire of universal calibration behavior predicted by the capillary bed model as mentioned earlier. Of note also is the fact that the curve deviates from linearity for the 38 nm particle and begins to approach the origin as also indicated by the model calculations. 

The parameters K1/ K2/ and K3 are defined by the refractive indices of the crystal and sample and by the incidence angle [32]. If the sample has uniaxial symmetry, only two polarized spectra are necessary to characterize the orientation. If the optical axis is along the plane of the sample, such as for stretched polymer films, only the two s-polarized spectra are needed to determine kz and kx. These are then used to calculate a dichroic ratio or a P2) value with Equation (25) (replacing absorbance with absorption index). In contrast, a uniaxial sample with its optical axis perpendicular to the crystal surface requires the acquisition of spectra with both p- and s-polarizations, but the Z- and X-axes are now equivalent. This approach was used, through dichroic ratio measurements, to monitor the orientation of polymer chains at various depths during the drying of latex [33]. This type of symmetry is often encountered in non-polymeric samples, for instance, in ultrathin films of lipids or self-assembled monolayers. 

Protective Colloids. Another approach in preparing and stabilizing metal colloids is by adsorption of macromolecules on their surfaces. A wide variety of materials have been used including gummy gelatinous liquids,(J 0) albumin,(27) Icelandic moss,(28) latex,(22) polyvinylpyrrolidone, (29) antibodies, ( 30 ) carbowax 20M, ( 31 ) polyvinylpyridine, (31 ) and various polymer-water/oil-water mixtures.( 2) These studies clearly indicate that "steric stabilization of metal colloids is also important (along with electronic stabilization).(33)... 

Another approach to producing latexes with chemically bound surface-active groups is to use a reactive surfactant—a surfactant with a polymerizable double bond, such as sodium dodecyl allyl sulfosuccinate [Wang et al., 2001a,b,c]. Copolymerization of the reactive surfactant with the monomer of interest binds the surface active groups into the polymer chains. 

Adsorption on Polystyrene Latex. Figure 3 shows the adsorption isotherms of the two single surfactants, NP-EO q and SDS, on the polystyrene latex surface. Both isotherms reach a limiting value when the cmc is approached. The lines drawn in the figure are calculated from the fitting Equation 19. The adsorption free energies, as obtained from Equation 21, are shown in Table I. The table also shows the two contributions to Ap, according to Equation 21, where the first contribution is obtained from the cmc s and the second from the difference between the two terms in Equation 21. 

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