Effect of Pore Size on Adsorption of a Polyelectrolyte to Porous Glass

Abstract

The adsorption of quaternized poly(vinylpyridine) (QPVP) on controlled pore glass (CPG) size, over the ionic strength range 0.001-0.5 M was found to display nonmonotonic behavior as a function of pore size. Both adsorption kinetics and ionic strength effects deviated dramatically from behavior typical of adsorption on flat surfaces when the ratio of the pore radius Rp to the polymer hydrodynamic radius Rh became smaller than ca. 2. Ionic strength enhancement of adsorption for small pore sizes was observed at much higher salt concentrations than is typical for polycation adsorption on flat surfaces. The amount of polymer adsorbed per unit surface area of glass GammaA, in 0.5 M NaCl, exhibited a shallow maximum at Rp/Rh approximately 5. Since the value of GammaA for small pore size CPG is strongly depressed by the large surface area, an alternative and more interesting observation is that the amount of polymer adsorbed per gram of CPG, Gammaw, displays a strong maximum when Rp is equal to or slightly smaller than Rh. The efficiency with which QPVP binds anionic micelles to (negatively charged) CPG (grams of surfactant/grams of QPVP) increases strongly with diminishing pore size, indicating that the configuration of polycation bound to small pores favors micelle binding. Since the micelles are larger than small pores, the results indicate that when Rp < Rh, adsorbed polycation molecules reside only partially within the pore. The results of this study are supported by simulations of polyelectrolytes within cylindrical cavities.

Lysozyme binding to poly(4-vinyl-N-alkylpyridinium bromide)

“…These findings indicate that the adsorption of QPVP-C2 and QPVP-C5 onto Si wafers followed the screening enhanced adsorption regime [30,31], where the adsorbed amount increases with increasing salt concentration. Similar behavior has been observed for the adsorption of QPVP containing very short aliphatic side chains or none onto silica [4,6,7,12] or porous glass [5], and for the adsorption of hydrophobically modified polyelectrolytes [32]. In this regime of high salt concentration, the strong intrapolymer segment repulsion is screened and the polyelectrolyte chains behave more like uncharged polymers, adopting conformations such as loops and tails, thus increasing the adsorbed amount.…”

“…For QPVP carrying very short alkyl groups (H, methyl or ethyl) electrostatically driven adsorption onto negatively charged solid surfaces has been studied over the last 20 years [1][2][3][4][5][6][7][8][9][10][11][12]. Kawaguchi and co-workers [4] showed that the adsorption of QPVP onto nonporous silica increased with increasing KBr concentration due to a decrease in the excluded volume of polymer chains.…”

“…Kawaguchi and co-workers [4] showed that the adsorption of QPVP onto nonporous silica increased with increasing KBr concentration due to a decrease in the excluded volume of polymer chains. Recently Mishael and co-workers [5] reported that the adsorption of QPVP onto porous spherical glass depends strongly on the pore size and ionic strength. Partial confinement of QPVP in small oppositely charged pores is favored by electrostatic interaction and reduces the penalty of polyion compression [5].…”

“…Recently Mishael and co-workers [5] reported that the adsorption of QPVP onto porous spherical glass depends strongly on the pore size and ionic strength. Partial confinement of QPVP in small oppositely charged pores is favored by electrostatic interaction and reduces the penalty of polyion compression [5]. The adsorption of QPVP onto negatively charged flat surfaces (silicon oxide and mica) was investigated by means of surface force * Corresponding author.…”

PAA/alumina composites prepared with different molecular weight polymers and utilized as support for nickel‐based catalyst

“…PAA adsorption on alumina has been well documented to follow the Langmuir model, [42] in which the slope at the onset of adsorption isotherms represents the affinity of a polymer for the surface. In the work of Mishael et al, [43] when the polymer diameter is greater than the oxide pore size, the adsorption reached a plateau around 1.5 g/L polymer concentration. In the work of Mishael et al, [43] when the polymer diameter is greater than the oxide pore size, the adsorption reached a plateau around 1.5 g/L polymer concentration.…”