Adsorption Of Polyvinylpyrrolidone Research Articles

Effect of polyvinylpyrrolidone on the physical properties of titanium dioxide suspensions

The effect of polyvinylpyrrolidone (PVP) on the physical properties of aqueous and non-aqueous (methanol-based) TiO 2 suspensions was studied by measuring PVP adsorption and the rheological properties and dispersion stability of the suspensions. The amount of PVP adsorbed onto TiO 2 from the methanol solution is much larger than that from the aqueous solution and the effect on the dispersion stability of the suspension is much greater in the methanol-based suspension than in the aqueous suspension. The amount of adsorption of PVP is independent of the molecular weight, while the thickness of the adsorbed layer increases as the molecular weight increases. As the PVP concentration increases, the viscosity of the PVP solution increases, while the relative viscosity and the dynamic rheological parameters (G′, G″) of the suspension decrease, indicating that the network structure formed by dispersed TiO 2 particles in the absence of PVP diminishes with the increase in the PVP concentration. The dispersion stability of the methanol-based suspension increases with the increase in the concentration of PVP of high molecular weight, while the dispersion stability of the aqueous suspension is not significantly improved by PVP. It appears from the conformation of the adsorbed PVP molecules, determined by the measurement of the amount adsorbed and the thickness of the adsorbed layer, that the stabilization of the methanol-based suspension by PVP is due to entropic repulsion caused by the interaction of protruded tails of the adsorbed PVP molecules. It also appears from the measurement of the adsorption isotherm and the rheological properties that the increase in the dispersion stability with PVP at high PVP concentration is due to the increase in the concentration of non-adsorbing free PVP molecules.

Adsorption of non-ionic and cationic polymers on silica from their mixed aqueous solutions

The adsorption of polyvinylpyrrolidone (PVP) and poly(dimethyldiallylammonium chloride) (PDC) on silica from their mixed aqueous solutions has been investigated as a function of PVP concentration in the presence of PDC. The adsorption of PVP is almost unchanged with the feed concentration of PVP, while the adsorption of PDC decreases with increasing PVP concentration, especially at high concentrations of PDC. The conformation of PVP in the adsorbed layer on silica is relatively flat at low concentrations of PDC, but is extended in solution at high concentrations of PDC. The stability of the silica dispersion is low and the ζ potential is relatively small at low concentrations of PDC, whereas a stable dispersion is obtained at high concentrations of PDC and the ζ potential is large. Thus the stability of the dispersion is well correlated with the electrostatic repulsion and steric repulsion forces operating at the particles.

Aggregation/dispersion of amorphous silica particles by simultaneous adsorption of two polymers in an aqueous phase

The effect of simultaneous adsorption of two polymers on the mean diameter, d, of secondary particles of amorphous silica (Micon FN) was studied. The d value was decreased by the adsorption of sodium chondroitin-6-sulfate (Na 2Chs) or sodium carboxymethylcellulose (NaCMC), although the amount of Na 2Chs or NaCMC adsorbed was lower than that of polyvinylpyrrolidone (PVP), a flocculating agent. The amount of adsorbed Na 2Chs or NaCMC decreased in the presence of PVP due to competitive adsorption, but that of PVP increased, due to the disintegration of silica aggregates caused by the adsorption of Na 2Chs or NaCMC. The zeta potential of Micon FN became less negative on adsorption of PVP, due to the protrusion of the polymer loop, but became more negative by the adsorption of Na 2Chs or NaCMC in either the presence or absence or PVP, indicating that electrostatic ???ulsion is important for the dispersion of silica particles. In the case of PVP, non-electrostatic effects such as steric hindrance and interparticle bridging are dominant factors for the dispersion and flocculation.

Stability of dispersions of iron oxide in mixed solutions of polyvinylpyrrolidone and sodium alkyl sulfate

The stability of dispersions of iron oxide in mixed solutions of polyvinylpyrrolidone and sodium alkyl sulfate has been investigated. The results show that polyvinylpyrrolidone and sodium alkyl sulfate alone cannot stabilise the iron oxide dispersions effectively. However, the presence of low concentrations of sodium alkyl sulfate enhances the stabilizing effect of polyvinylpyrrolidone markedly, while the presence of a high concentration of sodium alkyl sulfate deminishes this enhanced stabilizing effect. This phenomenon is suggested to be a consequence of the interaction between polyvinylpyrrolidone and sodium alkyl sulfate. The formation of surface complexes of polyvinylpyrrolidone and sodium alkyl sulfate at low concentrations of sodium alkyl sulfate enhances the adsorption of polyvinylpyrrolidone and hence the stability of the dispersions, while the decrease of polyvinylpyrrolidone adsorption at high concentrations of sodium alkyl sulfate, due to the formation of polyvinylpyrrolidone/sodium alkyl sulfate in solution, leads to a depression of the enhanced stability of iron oxide dispersions.

Graft polymerization of polyvinylpyrrolidone onto silica

AbstractA new technique is reported for the surface grafting of polyvinylpyrrolidone (PVP) to hydroxylated solid surfaces. Free radical graft polymerization of vinylpyrrolidone onto vinylsilane–modified impermeable silica particles was carried out in an aqueous slurry reactor. The graft yield and the monomer conversion were determined by thermogravimetric analysis and UV spectroscopy, respectively. The graft yield was shown to increase by increasing the initial monomer concentration. A comparison of the graft polymerization reaction with the adsorption of polyvinylpyrrolidone onto untreated, vinylsilane‐modified, and PVP‐grafted silica was performed.

The adsorption of polyvinylpyrrolidone and polyethylene oxide onto chemically modified silica

Polyvinylpyrrolidone (PVP) adsorption onto silica is shown to be strongly dependent on surface chemistry whereas polyethylene oxide adsorption exhibits less dependence on surface chemistry. The surface of silica was modified with four different chemical treatments: surface grafting of polymer, silylation with vinyltriethoxysilane, silylation with ethyltriethoxysilane, and silylation with isobutyltrimethoxysilane. Isotherms for PVP adsorption were measured on the untreated surface and the four treated surfaces. Both large increases and large decreases in the amount adsorbed relative to the untreated surface were recorded. Adsorption of polyethylene oxide was conducted in the plateau region on untreated silica and on polymer-grafted silica.

A New Packing for Aqueous Size Exclusion Chromatography Polyvinylpyrrolidone-Coated Silica

Abstract Adsorption of polyvinylpyrrolidone on silica in aqueous medium is studied. Adsorption isotherms, thermogravimetry and elementary analysis show that a complete surface coverage is reached with large pore microbeads. The coating stability and its ability to prevent non-steric effects when used as packing in exclusion chromatography are demonstrated. Four different pore size packings were prepared for chromatographic evaluations. It is shown that water soluble polymers like polyethylene oxide, polyvinylalcohol, polyacrylamide and hydroxyethylcellulose can be chromatographied in pure water according to the steric exclusion mechanism.

Adsorption characteristics of polyvinylpyrrolidone at solid-liquid interface

Adsorption studies of polyvinylpyrrolidone (PVP) on the surface of colloidal silicas, Aerosil 300 and Aerosil R-972 are reported. The adsorption isotherms of PVP at the hydrophilic silica/aqueous solution interface were greater than that at the hydrophobic silica R-972. The PVP adsorption shows that the amount adsorbed decreases with the concentration.

Interlayer adsorption of polyvinylpyrrolidone on montmorillonite

Two methods (x-ray diffraction and desorption of 109Cd and 85Sr) were used to provide indirect evidence for the adsorption of polyvinylpyrrolidone (PVP) on the surface of montmorillonite. It was shown that by decreasing the number of solvent layers in the interlayer distance the amount of adsorbed PVP was decreased, indicating that attachment of the polymer to the tetrahedral sheets is likely to occur. Desorption of radio-nuclides from calcium and sodium montmorillonites confirmed this hypothesis.

Adsorption of Organic Polymers on Platinum Electrode

Abstract The adsorption behavior of polyvinylpyrrolidone (PVP), polyethyleneglycol (PEG), and alkylphenoxy polyethoxy ethanols (Triton X) on a smooth platinum electrode was investigated by observation of the inhibition effect on the electrosorption of hydrogen and oxygen in the potential range between hydrogen and oxygen evolution. The adsorption of PVP, PEG, and Triton X on platinum always took place within the potential range from −0.20 to 1.25 V vs. SCE, the inhibition effect on the electrosorption of hydrogen and oxygen being distinctly shown. The order of inhibition of these adsorbates was Triton X>PVP>PEG. The inhibition effect became larger in most cases with decreasing mean molecular weight of adsorbate. In contrast to the case with a mercury, the adsorbates were oxidized or reduced on the platinum electrode in the adsorption range, the anodic peak due to oxidation being distinctly revealed in the case of PEG.

Competitive Adsorption of Polyvinylpyrrolidone with n-Alkyl Alcohols at the Mercury/Solution Interface

Abstract Competitive adsorption of polyvinylpyrrolidone (PVP, \barM=10000) with n-hexanol, n-pentanol, or n-butanol was examined by observation of the differential capacity at the mercury interface in 1 n sulfuric acid. Adsorption of PVP coexistent with alcohol hardly differed from the single adsorption1) controlled by its diffusion. The competitive adsorption curve of C (differential capacity) vs. t1⁄2 (adsorption time) was expected from the sum of the individual capacity depressions by the single adsorption at −0.5 or −0.6 V (SCE) and the expected curve of C vs. t1⁄2 was compared with the curve observed. The competitive behavior of alcohol coexistent with PVP was examined by the relation “θAlccom (coverage of coexistent alcohol) vs. t1⁄2” at −0.5 or −0.6 V (SCE), where θAlccom was estimated from the difference between the differential capacities with and without PVP, in view of the fact that behavior of PVP is nearly independent of the coexistent alcohol. The results are discussed in terms of four types of models assumed for the competitive behavior of coexistent alcohols with different adsorbability. It is considered that the alcohol is replaced with PVP as soon as the latter reaches the interface by diffusion, the adsorption equilibrium of an alcohol being achieved immediately. The relation θAlccom=(1−θpvp)θAlc holds in the case of n-butanol coxistent with PVP, where θPVP, θAlc, and θAlccom are coverages due to the single adsorption of PVP and butanol and to the competitive adsorption of butanol, respectively. The tendency of alcohol to be replaced with PVP is inversely proportional to its adsorption coefficient. n-Butanol was most sensitive to the coexistence of PVP.

The Adsorption of Polyvinylpyrrolidone at the Mercury/Solution Interface

Abstract The adsorption of polyvinylpyrrolidone (PVP), known as a water-soluble polymer, at the electrolyte/DME interface was examined by observing the differential capacity vs. the time relation, under conditions where the adsorption process was mainly controlled by diffusion. In the case of a relatively low bulk concentration and a short adsorption time, the adsorption rate of PVP at−500 mV(SCE) was controlled almost wholly by the diffusion of the adsorbate to the DME. The relation between the time required to attain the saturated adsorption and the bulk concentration was explained approximately by the Koryta equation, based on the linear diffusion. PVP showed no tendency to form multi-layers within the range of bulk concentrations and adsorption times observed. The maximum surface concentration of PVP decreased almost linearly with the increase in its mean molecular weight. The number of constitutive segments adsorbed per unit of area to form a monolayer at the interface was almost constant, independent of the mean molecular weight. The activation energy for the diffusion was found to be ca. 4.7 kcal/mol. On the basis of the results obtained, the configuration of PVP adsorbed at the interface was discussed.

The effect of adsorption of polyvinylpyrrolidone on the stability of chloramphenicol suspension

The effect of adsorption of polyvinylpyrrolidone on the stability of chloramphenicol suspension

The Adsorption of Polyvinyl Pyrrolidone on Silver Iodide Surfaces

Abstract Adsorption isotherms for four kinds of polyvinyl pyrrolidone (PVP), having different molecular weights, on the sol particles and the powder of silver iodide at 25°C were obtained. Further, the adsorption of PVP on the sol particles was investigated by means of the electrophoresis method. All of the PVP materials give approximate adsorption isotherms of the Langmuir type, at least up to the PVP concentration of 0.4 g/l At higher concentrations, the amounts of PVP adsorbed gradually increase with the increase in the PVP concentration. The effect of the molecular weight on the PVP adsorption is not observed except for the lowest-molecular-weight material, which displays a lower adsorption. The tendency for the ζ-potential of the sol particles to increase with an increase in the PVP concentration almost coincides with that of the amount of PVP adsorbed.