Adsorption of anionic polymers

The method of action of the polymers is thought to be encapsulation of drill cuttings and exposed shales on the borehole wall by the nonionic materials, and selective adsorption of anionic polymers on positively charged sites of exposed clays which limits the extent of possible swelling. The latter method appears to be tme particularly for certain anionic polymers because of the low concentrations that can be used to achieve shale protection (8). 

Fig. 4.16 provides an illustration of the adsorption of a neutral polymer, polyvinyl alcohol, on a polar surface, and the resulting effects on the double layer properties. Adsorption of anionic polymers on negative surfaces - especially in the presence of Ca2+ or Mg2+ which may act as coordinating links between the surface and functional groups of the polymer - is not uncommon (Tipping and Cooke, 1982). 

The kinetics and the equilibrium of adsorption of anions PoCl62" by ionized monolayers of cationic soaps have been studied and both phenomena are analogous to those observed with the polymer ion exchangers... 

The absolute value of the zeta potential decreases until a plateau is reached at a certain polyanion concentration. A contrary effect is obtained in the case of adding a polycation. A partial stabilization of the kaolin particles can be realized due to an adsorption of anionic charged macromolecules at the edges of the kaolin platelets. By adding a polycation to the kaolin dispersion, an adsorption at the negative basal surface becomes possible, and the iep of the particles is reached very quickly at low PEI concentrations. A further addition of PEI leads to an increase of the zeta potential while flocculation was observed. This is because the adsorption of cationic polymer can cause a face-to-face association that can generate polymer-kaolin complexes. 

Despite the low levels of adsorption, the anionic polymers have a significant effect on the rheology of the bentonite suspensions. Figure 22 shows the dependence of the Bingham yield stress rG on bentonite concentration with and without added dispersants. Rabaioli et al. found the dependence of rG on the volume fraction of bentonite 0 to be... 

Dulman V, Simion C, Barsanescu A, Bunia I, Neagu V. Adsorption of anionic textile dye Acid Green 9 from aqueous solution onto weak or strong base anion exchangers. J Appl Polymer Sci 2009 113 615-627. 

Titanium dioxide is the most used white pigment in the plastic industiy. This pigment is hydrophilic and the dispersibility in non-polar polymers such as polyethylene is not easy. In the previous work, the adsorption of anionic surfactant has been used to modify the hydrophilicity of titania. " It was found that the surfactant treatment improves the dispersibility of titania in non-polar media. 

A different effect occurs with the use of polycarboxy-lates in combination with zeolites. Small amounts of polycarboxylates or phosphonates can retard the precipitation of sparingly soluble calcium salts such as CaCOs (the threshold effect ). As they behave as anionic polyelectrolytes, they bind cations (counterion condensation), and multivalent cations are strongly preferred. Whereas the pure calcium salt of the polymer is almost insoluble in water, mixed Ca/Na salts are soluble, i.e. only overstoichiometric amounts of calcium ions can cause precipitation. Polycarboxylates are also able to disperse many solids in aqueous solutions. Both dispersion and the threshold effect result from the adsorption of the polymer on to the surfaces of soil and CaCOs particles, respectively. 

Figure 44 Repeated adsorption of anionic and cationic polyelectrolyte polymers onto colloidal particle templates followed by excavation of the core domain gives micro-Znanocapsules. Reproduced with permission from Quinn, J. F. Johnston, A. P. R. Such, G. K. etal. Chem. Soc. Rev. 2007, 36, 707-718,and Wang, Y. Angelatos, A. S. Caruso, F. Chem. Mater. 2008,20,848-858. ...

Ihara Y (1992) Adsorption of anionic surfactants and related compounds from aqueous solution onto activated carbon and synthetic adsorbent. J Appl Polym Sci 44(10) 1837-1840... 

An analysis presented of the forces contributing to the attraction and repulsion interactions between macromolecules in acrylate latices. The electrostatic repulsion forces, enthalpy and entropy effects, and the attraction forces from the expanded Hamaker equation are analysed. The influence of the structure of copolymers consisting of monomeric units of alkyl acrylate or methacrylate (methyl to n-butyl) and acryhc or methacryhc acid on the physico-chemical properties of the latices and their stabihty were determined. On the basis of experiments and calculations it was established that the stability of latices is decided by two mechanisms. The first (ionic stabilisation) consists in adsorption of anionic emulsifier particles, and the second (ionic-steric stabilisation) involves adsorption of such an emulsifier on an adsorption layer formed by the polymer macromolecules forming the latex. 25 refs. Articles from this journal can be requested for translation by subscribers to the Rapra produced International Polymer Science and Technology. 

Direct evidence of the adsorption of cationic polymers on skin from an anionic surfactant system has been reported by Goddard and Leung (20). The authors determined the uptake of Polymer JR 125, on stratum corneum (SC) in the presence of three anionic surfactants [SDS, alfa olefin sulfonate (AOS), and alkyl 2EO sulfate] and a coco-betaine surfactant. Even though the conditions involved 30 min of exposure to the substrate, the results obtained are indicative of the trends that can be expected under normal conditions. The results reproduced in Figure 3 show that the uptake of the polymer is initially reduced markedly by the surfactants. Interestingly, at surfactant concentrations above about 10%, the polymer uptake in fact increases and at 20% the extent of uptake is in fact higher than that obtained in the absence of the surfactant. Note that the surfactant concentrations are... 

Shubin V. Adsorption of cationic polymer onto negatively charged surfaces in the presence of anionic surfactant. Langmuir 1994 10 1093-1100. 

Bolt, G. H., and B. P. Warkentin. 1958. The negative adsorption of anions by clay suspensions. Colloid and Polymer Science (Kolloid-Zeitschrift) 156, no. 1 41 6. doi 10.1007/ BF01812361. 

It has been hypothesized that interaction of chitosan with multivalent anions (such as sodium citrate which acts as anion cross-linker) leads to the formation of bridges between polymeric chains, resulting in cross-linking (due to electrostatic interaction) between the polymer molecules.This facilitates efficient adsorption of the polymer on the drug molecule. 

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