Conformational Behavior of Polyelectrolyte Complexes at the Solid/Liquid Interface

Abstract

Conformation of polymers at solid/liquid interface is an important property that determines their effectiveness in processes such as dispersion, deposition, adhesion, and wettability. In this work, conformational behavior of pyrene labeled poly(maleic acid-co-propylene), MS-P*, in solution and at the alumina surface and its changes upon perturbation in solution pH or addition of a second oppositely charged polymer than the ones in solution were studied using fluorescence spectroscopy. Conformation of this weak polyanion, both in solution and at the solid/liquid interface was found to be strongly pHdependent. The degree of coiling on alumina depended on the solution state immediately before the adsorption. The conformation of the polymers in solution and on the solid were the same above pH 4, but, interestingly, the adsorbed polymer was more stretched at low pH. When the polymer is in the coiled form, changes in pH caused partial conformational adjustments of the adsorbed species. However, in the stretched form, the adsorbed polymer was unable to adopt the coiled conformation on the surface even with pH perturbation. Addition of polycations, poly(ethyleneimine) and poly(diallyldimethylammonium) chloride, to systems containing the preadsorbed polyanion led to conformational changes due to the formation of complexes between them at the surface. While the polyelectrolyte adsorbed in the stretched form undergoes very little conformational rearrangement, the re-conformation of the polymer adsorbed in the coiled form depends on the charge density of the second polymer and the solid. These results are compared with the behavior of polyelectrolyte complexes in solution and analyzed to elucidate possible conformational dynamics of polymers at interfaces.

Fluorescence and ESR studies of the conformational behavior of oppositely charged polyelectrolytes at solid/liquid interfaces

“…Fluorescence and total organic carbon measurements of the supernatant indicated absence of detectable free polymer in solution or desorption of preadsorbed polyanion or polycation. It is important to note that former studies have shown irreversibility of certain relaxation and reconformation processes of the polyanion in the polyelectrolyte complex or adsorbed on alumina [39]. Evidently, once the polyanion is anchored on the surface or bound in a polyelectrolyte complex, its behavior is dependent on the already altered conformation with possibly only partial reconformation to reach an energetic minimum.…”

“…The result of the reaction is a covalently attached label to the polymer via a cyclic imide bond. The behavior of the labeled MS-P * in solution and adsorbed on the surface has been described in detail elsewhere [39]. Aminopyrene and amino-TEMPO were purchased from Aldrich and used as received.…”

“…The details of the adsorption experiment and the polyelectrolyte complexation are given elsewhere [39]. Fluorescence and total organic carbon measurements of the supernatant indicated absence of detectable free polymer in solution or desorption of preadsorbed polyanion or polycation.…”

Atomic force microscopy study on the microtopography of natural organic matter and newly formed hydrous MnO2

“…Molecular conformations of sphere, sponge, sheets [7], globule [10], ring [8] and, cone [12] were observed. The NOM origin and solution properties, as two major factors, controlled the conformation of NOM [13,14]. Diverse structures with respect to NOM concentration [7,9], solution pH [10,11], ionic strength [9,10], and cation electrolyte identity [9] were also reported.…”

Pyrene partition behavior to the NOM: Effect of NOM characteristics and its modification by ozone preoxidation

“…At the same time, positive [9] or inverse [10] correlation between K oc and the molecular weight were reported depending on the origin and/or fractional composition of the aggregated humic materials. Besides the investigation on NOM structures, solution properties including pH value, ionic strength, and cationic electrolyte characteristics had been demonstrated to greatly alter the structure of NOM [4,12]. However, only few researches were focused on the impact of solution property on HOCs' partition to NOM.…”