Induced Crystallization of Polyelectrolyte-Surfactant Complexes at the Gas-Water Interface (original) (raw)
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Phase behavior of polyelectrolyte-surfactant complexes at planar surfaces
Physical Review E, 2006
We investigate theoretically the phase diagram of an insoluble charged surfactant monolayer in contact with a semidilute polyelectrolyte solution ͑of opposite charge͒. The polyelectrolytes are assumed to have long-range and attractive ͑electrostatic͒ interaction with the surfactant molecules. In addition, we introduce a short-range ͑chemical͒ interaction which is either attractive or repulsive. The surfactant monolayer can have a lateral phase separation between dilute and condensed phases. Three different regimes of the coupled system are investigated depending on system parameters. A regime where the polyelectrolyte is depleted due to short range repulsion from the surface, and two adsorption regimes, one being dominated by electrostatics, whereas the other by short range chemical attraction ͑similar to neutral polymers͒. When the polyelectrolyte is more attracted ͑or at least less repelled͒ by the surfactant molecules as compared with the bare water-air interface, it will shift upwards the surfactant critical temperature. For repulsive short-range interactions the effect is opposite. Finally, the addition of salt to the solution is found to increase the critical temperature for attractive surfaces, but does not show any significant effect for repulsive surfaces.
The Journal of Physical Chemistry B, 2002
The internal structure of the solid phase formed in mixtures of the anionic surfactant sodium dodecyl sulfate (SDS) and a range of oppositely charged polyelectrolytes with different side chains and charge density has been investigated using small-angle X-ray scattering. Polyelectrolytes with short side chains ([3-(2methylpropionamido)propyl]trimethylammonium chloride, MAPTAC, and poly{[(2-propionyloxy)ethyl]trimethylammonium chloride}, PCMA) form a 2-dimensional hexagonal structure with SDS, whereas a polyelectrolyte without side chains (poly(vinlyamine), PVAm) forms a lamellar structure. The hexagonal structure of MAPTAC is retained either when a neutral monomer (acrylamide, AM) is included in the polymer backbone to reduce the charge density or when a nonionic surfactant is admixed to the SDS/polyelctrolyte complex. The unit cell length of AM-MAPTAC increases with decreasing charge density from a ) 47.7 Å (MAPTAC, 100% charge density) to 58.5 Å (AM-MAPTAC, 30% charge density). The unit cell length in the lamellar SDS/PVAm complex (a ) 36.1 Å) is significantly smaller than for the different hexagonal structures. It is conjectured that the cylinders in the hexagonal structure and the bilayers in the lamellar structure are based on self-assembled surfactant aggregates with the polyelectrolyte mainly located in the aqueous region adjacent to the charged surfactant headgroups.
Physical Chemistry Chemical Physics, 2000
We report dynamic surface tension and X-ray reÑectivity studies on mixed polyelectrolyteÈsurfactant solutions. We have studied two di †erent polyelectrolytes, polyacrylamide sulfonate, with a Ñexible backbone and xanthan, with a rigid backbone. We compare the results with the surface rheology and foaming behaviour of the same solutions. The static and dynamic properties of the mixed surface layers are similar for the solutions with the two polymers, only the behaviour upon large compressions is di †erent. This might be at the origin of the di †erences in foamability and foam Ðlm stability observed with the two systems. Fig. 1 Chemical structure of the polymers (a) xanthan and (b) PAMPS ( f \ 0.1).°1 Da (dalton) B 1.660 54 ] 10~27 kg.
The Journal of Physical Chemistry B, 2009
Polyelectrolyte/surfactant complexes formed between well-defined linear flexible polyelectrolytes, namely, quaternized poly[3,5-bis(dimethylaminomethylene)hydroxystyrene] (Q-N-PHOS), bearing two cationic sites on each repeating unit, and two different anionic surfactants, namely, sodium dodecyl sulfate (SDS) with one hydrocarbon tail and sodium bis(2-ethylhexyl) sulfosuccinate (AOT) with two hydrocarbon chains, are studied by means of fluorescence spectroscopy, electrophoretic, dynamic and static light scattering, and atomic force microscopy. Depending on the surfactant state in initial solutions (i.e., below or above nominal critical micelle concentration, cmc) and final (-/+) charge ratio, self-assembly in nanoparticles of variable size, stability, and effective charge is possible. Spherical, rather polydispserse complexes are formed in all cases. Critical aggregation concentrations (cac) depend on the surfactant type, while hydrophobicity of the main polyelectrolyte chain plays a role in colloidal stability of the complex nanoparticles.
Association and structure formation in oppositely charged polyelectrolyte–surfactant mixtures
Investigations dealing with association behaviour and structure formation in oppositely charged polyelectrolytesurfactant mixtures in aqueous solutions are reviewed. Discussion is limited to a selection of vinyl based anionic polyelectrolytes that, when completely ionized, posses the same structural value of the linear charge density parameter. Particular emphasis is placed on the role of polymer chain properties in aggregates with surfactants. Chain characteristics are varied by changing the nature of the charged group, its ionization degreewhen possible, the spatial distribution of these groups along the chain, i.e. the tacticity, and the hydrophobic character of other substituents attached to the chain. Quantitative information on the degree of binding in the form of binding isotherms is obtained using surfactant-sensitive membrane electrodes and microstructures of polyelectrolytesurfactant complexes are determined by synchrotron small angle X-ray scattering. Considerable differences in the degree of binding (including the critical association concentration, CAC, values) and in structures are found. It is concluded that strong interactions in these systems arise from the electrostatic attraction, but this only forms the basis for initial extensive accumulation (anchoring) of surfactant ions in the vicinity of the polyion chain. When this is accomplished, additional specific interactions and effects may come into play. The most powerful of these interactions, the hydrophobic association between the chain and the micelle core, were found in polystyrenesulfonate, PSS, solutions. Other properties are less influential but still lead to CAC values that differ by more than one order of magnitude. These differences are explained by taking into account the chain conformation, flexibility, and hydrophobic character. Specific interactions between PSS and cetylpyridinium, CP, cations result in a soluble non-stoichiometric PSS-CP complex that could be characterized by measuring various solution properties as a function of polymer concentration and degree of complexation. The review is supplemented by including studies of complexation between the spherical fullerene hexamalonate anion and cationic surfactants, which demonstrate a high association tendency with characteristics similar to those found in binding of surfactants by linear polyelectrolytes.
Structure and dynamics of polyelectrolyte surfactant mixtures under conditions of surfactant excess
The Journal of chemical physics, 2016
Oppositely charged polyelectrolyte (PE) surfactant mixtures can self-assemble into a large variety of mesoscopic structures, so-called polyelectrolyte surfactant complexes (PESCs). These structures directly affect the macroscopic behavior of such solutions. In this study, we investigated mixtures of the cationically charged PE JR 400 and the anionic surfactant SDS with the help of different neutron scattering and fluorescence methods. While an excess of PE charges in semi-dilute solutions causes an increase of viscosity, it has been observed that an excess of surfactant charges reduces the viscosity while precipitation is observed at charge equilibrium. The increase in viscosity had been investigated before and was attributed to the formation of cross links between PE chains. In this publication we focus our attention on the reduction of viscosity which is observed with an excess of surfactant charges. It is found that the PE chains form relatively large and densely packed clusters ...
Polyelectrolyte-surfactant association at solid surfaces
Berichte der Bunsengesellschaft für physikalische Chemie, 1996
The interferometric surface force technique has been utilized for studying the interaction between negatively charged surfaces coated with a cationic polyelectrolyte across solutions of anionic surfactant, sodium dodecyl sulphate (SDS). The polyelectrolyte used was poly ([2-(propionyloxy)ethyl]trimethylammonium chloride), PCMA, which has one positive charge per segment. At low ionic strength the polyelectrolyte adsorbs in a flat conformation and neutralizes the negative mica surface charge. The interaction forces between the polyelectrolyte-coated surfaces are dominated by a strongly attractive force at distances shorter than about 150 A.
Polyelectrolyte–surfactant complexes (synthesis, structure and materials aspects)
Progress in Polymer Science, 2002
Self-assembled polyelectrolyte -surfactant complexes in the solid state and as nanoparticles are the topic of this review. These materials combine the properties of polymers (mechanical stability) and surfactants (formation of highly ordered mesophases). Their building principle is modular which allows a great variety in their designing as well as their structural and functional properties. Typical examples discussed in this review are complexes of fluorinated surfactants. Thin and ultra-thin films of these polyelectrolyte -fluorosurfactant complexes form different smectic structures with low surface energies. The critical surface energies are in the range 6 -18 mN/m. Optically functionalized complexes form rigid-rod, smectic A, B and turbostratic layered mesophases. Electroluminescent complexes with low turn-on points are described. It is reported that complexes of hexaperi-hexabenzocoronene with polysiloxanes and poly(ethylene imine) form different columnar discotic structures with columns as long as 200 nm. These materials behave as viscoelastic solids. q