Poly adsorption isotherms

Adsorption Isotherm The details of the technique used have been described before (15). Basically,0.5 g of the dilute latex was added to poly(vinyl alcohol) (PVA) solutions covering the range 50-1000 ppm. These were then rotated end-over-end for 24 hours at room temperature (22+2°C) for equilibration. 

Recent investigations have shown that the behavior and interactions of surfactants in a polyvinyl acetate latex are quite different and complex compared to that in a polystyrene latex (1, 2). Surfactant adsorption at the fairly polar vinyl acetate latex surface is generally weak (3,4) and at times shows a complex adsorption isotherm (2). Earlier work (5,6) has also shown that anionic surfactants adsorb on polyvinyl acetate, then slowly penetrate into the particle leading to the formation of a poly-electroyte type solubilized polymer-surfactant complex. Such a solubilization process is generally accompanied by an increase in viscosity. The first objective of this work is to better under-stand the effects of type and structure of surfactants on the solubilization phenomena in vinyl acetate and vinyl acetate-butyl acrylate copolymer latexes. 

Adsorption Isotherms of Nitrogen ond Argon on Reduced Poly crystal line Copper... 

In the case of fibrinogen, the slow time course of adsorption onto poly(HEMA)/Silastic and Silastic make attempts at obtaining true equilibrium adsorption isotherms difficult because the fibrinogen solutions will undergo slow fiber formation unless protected from bacterial degradation. Also, storage of such solutions is a problem since fibrinogen... 

Figure 6. Fibrinogen adsorption isotherms on Silastic, poly(NVP)/Silastic, and poly(H EM A)/Silastic. Untreated Silastic and Silastic grafted with poly-(NVP) (2.7 mg/cm ) or poly(HEMA) (5.8 mg/cm ) were equilibrated at 37°C for 20 hrs in fibrinogen solution of the depicted concentration in O.OJM HEPES, 0.147M NaCl, 0.02% azide, pH 7.4 and then rinsed by dilution displacement and extensive soaking with buffer at room temperature.

In the initial studies carried out to date, poly-s tyrene-supported dimethylamine polymers crosslinked with 2 and 15% divinylbenzene (DVB) were complexed with m-chlorobenzoic acid and the adsorption isotherms defined. The corresponding binding constants were calculated to be 126.19 and 67.99 m", respectively. It is thus evident that the polymer support affects the strength of the binding interaction between the ligand and substrate. Mechanistic studies to understand the basis for this influence and its use in the design of polymers for selective molecular complexation reactions are in progress. 

Churaev, Nikologorodskaya, and co-workers (33) investigated the Brownian and electrophoretic motion of silica hydrosol particles in aqueous solutions of an electrolyte at different concentrations of poly(ethylene oxide) (PEO) in the disperse medium. The adsorption isotherms of PEO on the surface of silica particles were obtained. The thickness of the adsorption layers of PEO was determined as a function of the electrolyte concentration and the pH of the dispersed medium. The results can be used in an analysis of the flocculation and stabilization conditions for colloidal dispersions of silica (with non-ionogenic water-soluble polymers of the PEO type). 

Figure 21. Adsorption isotherms of sodium poly aery late, sodium ligno-sulphonate, ferrochrome lignosulphonate, and the copolymer PAA-AMES on bentonite at various ionic strengths. (Reproduced with permission from reference 78. Copyright 1993 Society of Petroleum Engineers.)...

Adsorption isotherms for Silastic, poly(NVP)/Silastic, and poly(HEMA)/Silastic obtained after 20 hrs of adsorption were approximately "Langmuirian" but a Freundlich fit is also possible. 

Figure 2 Adsorption isotherms of four serum proteins to poly-tetrafluorethylene. Proteins dissolved at various bulk concentrations in phosphate buffered saline, pH 7.3 surface tension =72.0 ergs/cm. Proteins as indicated. (Reproduced with permission from Ref. 18. Copyright 1981, Elsevier/North Holland Press).

Figure 6.13 shows the adsorption isotherms for PAM on poly Si and Si02 as a function of PAM concentration. Adsorption of PAM on oxide surfaces increases and reaches a plateau level of approximately 0.23 mg/m. However, PAM is scarcely adsorbed on poly Si surfaces. This is driven by the difference in hydrophobicity, which affects the interaction between PAM and each surface. At high pH, the negative site MO of metal oxide (MO) surface bonds with the weakly acidic NH2 function. Therefore, the interaction between SiO of Si02 surface and NH2 group of PAM led to the selective adsorption of PAM on Si02. 

Figure 7.10. Adsorption isotherms for different narrow-molecular-weight poly(vinyl alcohol) at the polystyrene-water interface. The molecular weights used are 8000 (filled diamonds), 28 000 (open triangles) and 67 000 (open circles). (Redrawn from ref. (13))...

Figure 16.6 shows the adsorption isotherms (at 20°C) of two graft copolymers based on a poly(methyl methacrylate-methacrylic acid) backbone and PEO chains, namely Atlox 4913 and Hypermer CG-6(a) (17). The latter has a higher proportion of poly(methacrylic acid) and hence contains a lower PEG chain density than Atlox 4913. Two latex particles with diameters of 427 and 867 nm were used for these measurements. The adsorption isotherms are of a Langmuir type and the plateau value does not seem to depend on the particle size. However, the adsorption plateau value of Hypermer CG-6(a) (1.2mg m ) is lower than that obtained when using Atlox 4913 (1.6mg m ). This is due to the... 

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