Cationic Amphiphilic Polyelectrolytes and Oppositely Charged Surfactants at the Silica−Aqueous Interface

Abstract

The influence of sodium dodecyl sulfate (SDS) on the interfacial behavior of two amphiphilic polyelectrolytes, which are copolymers of the cationic monomers triethyl(vinylbenzyl)ammonium chloride and dimethyldodecyl(vinylbenzyl)ammonium chloride, at the silica-aqueous interface was studied. The fraction of amphiphilic monomers was varied, where 0DT, 40DT, and 80DT contained 0, 40, and 80 mol % monomers with dodecyl side chains, respectively. We used in situ ellipsometry to follow the kinetics of adsorption, in terms of adsorbed amount and adsorbed layer thickness, as well as the response of the adsorbed layers to changes in ionic strength and surfactant concentration. Different results were obtained when surfactant was added to the preadsorbed layers compared to the cases when complexes were preformed in the solution prior to the adsorption. In the whole range of concentrations studied, SDS interacts with 40DT and 80DT noncooperatively, whereas for 0DT cooperativity of binding is observed. The amount adsorbed increased significantly as the SDS concentration was close to the cmc. At high SDS concentrations, a lowering of the layer density was observed. For the amphiphilic polyelectrolytes, 40 DT and 80DT, no desorption from the interface was detected for the range of SDS concentrations studied, while 0DT features a maximum in adsorbed amount at concentrations close to the cmc of SDS. Adsorption of 40DT and 80DT from their mixtures with SDS is found to be path dependent with respect to the variation in SDS concentration, where the reversibility decreases with increasing SDS concentration above the expected charge neutralization point. The coadsorption of 80DT and SDS is highly irreversible with respect to changes in the ionic strength within the time scale of the experiment. In this study, we attempt to illustrate both general mechanisms and specific effects. With regard to the general behavior, it is important to note the charge regulation of both the silica surfaces and the polyion/surfactant complexes; an interplay between the two charge-regulating effects is the key to understanding our observations.

The Adsorption Layer in the System: Carboxymethylcellulose/Surfactants/NaCl/MnO2

“…They found out that complexes are formed between the above-mentioned polysaccharides and SDS molecules. This was also confirmed by Samoshina et al [31]. Moreover, Liu and et al [32] proved the existence of complexes between sodium carboxymethylcellulose and C12mimBr (1-dodecyl-3-methylimidazolinum bromide) using the isothermal titration microcalorimetry, turbidimetric titration and surface tension measurements.…”

Complexation of Polycations to Anionic Liposomes: Composition and Structure of the Interfacial Complexes

“…An “S-shape” of the Δ R versus N max profile (Figure ) could, in principle, result from a conformational change of the adsorbed macromolecules when the fraction of polymer-occupied surface is increased. Although such an effect was described previously for the adsorption of polymers on solid supports, the systems involve rather dense polymer layers in close contact with each other. − For this reason, such a model is hardly suitable for our case, because in our experiments the fraction of CL 2- in the membrane, and hence the fraction of PEVP-occupied liposome surface, never exceeded 20% (40% following PEVP-induced lipid flip-flop).…”

“…Although such an effect was described previously for the adsorption of polymers on solid supports, the systems involve rather dense polymer layers in close contact with each other. [26][27][28][29] For this reason, such a model is hardly suitable for our case, because in our experiments the fraction of CL 2in the membrane, and hence the fraction of PEVP-occupied liposome surface, never exceeded 20% (40% following PEVP-induced lipid flip-flop).…”

Interaction of sodium dodecyl sulfate and high charge density comb polymers at the silica/water interface

“…18,22 One way to tune these interactions is to change the molecular architecture of the polyelectrolyte, for instance by incorporating amphiphilic groups (sometimes named polysoaps) that increase intramolecular interactions and the affinity towards surfactant. 23,24 The subject of the present work is polycations that have been modified by adding hydrophilic side-chains. We have studied two methacrylate comb polymers, in which either 90 or 75 mol% of the backbone units are positively charged in the form of the quaternary ammonium groups (methacryloxyethyl trimethylammonium chloride, METAC) and the remainder are uncharged but bear poly(ethylene oxide) (PEO) side-chains (poly(ethylene oxide) methyl ether methacrylate, PEO 45 MEMA).…”