Latex surface charge excess

5 Layer-by-Layer Modification of Latex 8.5.5.1 Latex surface charge excess 

Based on UV absorbances measured after latex dissolution, it was found that the PAH PS ratio in the solid was 0.34, resulting in latexes that were highly hydrophobic. This meant that deprotonation only extended approx. 1.5 nm into the sphere, which for the diameter of 0.265 jxm means that of the total PAH in the particle 

To the best of our knowledge, the previous 1-b-l nanoparticle modifications of latex have all been directed at incorporation into the walls of hollow capsules, as described below. However, if metal nanoparticles are stabilized by a surface charge then they can be adsorbed to appropriately modified 1-b-l latex by electrostatic attraction, as shown in Fig. 8.1b. In this figure, the gold nanoparticles were produced by citrate reduction and so had a negative charge 

1- b-l deposition onto an organic core which is then dissolved, as shown in Fig. 8.10. T3q)ical latexes which have been used for the core are PSS and PSA, both of which have a negative surface charge, as explained earlier, that can be utilized for 1-b-l modibcation. Both cores can be dissolved by THF. Other organic cores which have been used for this method are melamine formaldehyde (MF), which dissolves at low pH, and polylactic acid (PLA) or polylactic-co-glycolic acid (PLGA), which can be dissolved in acetone/Af-methyl- 

2- p3nrolidinone mixtures. It should be noted that in this type of capsule formation, the incomplete removal of core material is 

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For serum replacement (6), the latex is confined in a cell with a uniform-pore-size Nuclepore filtration membrane. Distilled, deionized water is pumped through the latex until the conductance of the effluent stream is about the same as that of the distilled, deionized water. This serum replacement removes the adsorbed emulsifier and solute electrolyte quantitatively and allows recovery of the serum in a form suitable for further analysis however, it does not+replace the Na+ and K counterions of the surface groups with Vl ions. To do this, dilute hydrochloric acid (ca. 10 N) is pumped through the latex, followed by distilled, deionized water to remove the excess acid. The latex is then titrated conductometrically to determine the surface charge. 

On the other hand, activated carbon often has specific surface area in excess of 1000 nt /g, i.e. higher then most inorganic materials. Thus, even with relatively low affinity to the adsorbate, activated carbon can bring about substantial uptake. Polymeric materials in form of dispersion of nearly spherical (and often nearly raonodispersed) particles (size on the order of 100 nm) are termed latexes. Their specific surface area is typically on the order of a few m /g. The pFl dependent surface charging of some activated carbons and latexes, and their reactions with other inorganic adsorbates will be presented in this chapter. 

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