Study of the Dilution-Induced Deposition of Concentrated Mixtures of Polyelectrolytes and Surfactants (original) (raw)
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Langmuir, 2018
Polyelectrolyte(PE)/surfactant(S) mixtures play a distinguished role in the efficacy of shampoos and toiletries, primarily due to the deposition of PE/S precipitates on the hair surface upon dilution of the formulations. The classical interpretation of this phenomenon is a simple composition change during which the system enters into the two-phase region. Recent studies, however, indicated that the phase properties of PE/S mixtures could be strongly affected by the applied solution preparation protocols. In the present work, we aimed at studying the impact of dilution on the nonequilibrium aggregate formation in the sodium poly(styrenesulfonate)(NaPSS)/dodecyltrimethylammonium bromide (DTAB)/NaCl system. Mixtures prepared with hundredfold dilution of concentrated NaPSS/DTAB/NaCl solutions in water were compared with those ones made by rapid mixing of dilute NaPSS/NaCl and DTAB/NaCl solutions. The study revealed that the phase-separation concentration range as well as the composition, morphology and visual appearance of the precipitates was remarkably different in the two cases. These observations clearly demonstrate that the dilution/deposition
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 ...
Colloid particle deposition on heterogeneous surfaces produced by polyelectrolyte adsorption
Colloids and Surfaces A: Physicochemical and Engineering Aspects, 2009
The kinetics of polystyrene latex deposition on mica surface covered by mono-and bilayers of polyelectrolytes has been studied using the optical microscopy and the AFM methods. In these investigations the cationic poly(ethylene imine) (PEI) having an averaged molecular weight of 70 kD was used and the anionic poly(acrylic acid) (PAA) having a linear structure and an average molecular weights of 12 and 70 kD. Formation and stability of polyelectrolyte layers on mica was characterized in terms of streaming potential measurements carried out using a parallel-plate channel arrangement. These polyelectrolyte layers have been exploited as substrates of controlled heterogeneity and charge density for deposition of colloid particles. Positively charged polystyrene latex particles having an average size of 450 nm (determined by laser diffractometry, PCS and AFM) were used in these experiments. Latex deposition kinetics was studied under convection-controlled transport conditions using the impinging-jet cell and the optical microscopy method. The AFM method was also used to confirm maximum coverage of latex particles. The dependence of the initial deposition rate of particles on the coverage of PAA in the PEI/PAA bilayer was systematically studied. It was found that the initial deposition rate increased monotonically with the density of the adsorbed polyelectrolyte layer. These experimental results, deviating from the DLVO theory predictions, were successfully interpreted in terms of a theoretical model, which considered charge fluctuations within the adsorbed polyelectrolyte layers. It was concluded that the particle deposition method can be applied as a sensitive tool for quantitatively determining the presence of polyelectrolyte layers on solid surfaces, at a coverage degree inaccessible for other methods.
Colloids and Surfaces A-physicochemical and Engineering Aspects, 2005
The very slow equilibration time in oppositely charged systems makes it necessary to control not only the concentration of the species but also the details of the mixing process. This has been demonstrated for processes occurring at interfaces where order of addition effects can be of great importance. In this investigation we set out to study the bulk properties of aqueous mixtures of a highly charged cationic polyelectrolyte mixed with an anionic surfactant with the aim to learn if long-lived non-equilibrium states were formed also in this case, and thus if the details of the mixing procedure would affect the structure of the aggregates formed. For simplicity we chose two mixing protocols, denoted “PTS” and “STP”. In the PTS-method the polyelectrolyte is added to the surfactant solution whereas in the STP-method the surfactant is added into the polyelectrolyte solution. The properties of the mixtures in aqueous solutions, with different NaCl concentrations and as a function of time, were followed by conducting turbidity, electrophoretic mobility and dynamic light scattering measurements. The results demonstrate that the mixing protocol indeed has a great impact on the size of the aggregates initially formed and that this size difference persists for long times. Hence, trapped non-equilibrium states do play an important role also in the bulk solution. We found that in excess surfactant solutions the smaller aggregates formed by the STP-method are more resistant than the larger ones formed by the PTS-method to colloidal instability induced by electrolytes (NaCl). Based on our results we suggest that for producing small and stable polyelectrolyte–surfactant aggregates in systems with excess surfactant, the surfactant should be added last, while the opposite should be applied for systems with excess polyelectrolyte.
Langmuir, 2004
We have examined the polymer/surfactant interaction in mixed aqueous solutions of cationic surfactants and anionic polyelectrolytes combining various techniques: tensiometry, potentiometry with surfactantselective electrodes, and viscosimetry. We have investigated the role of varying polymer charge density, polymer concentration, surfactant chain length, polymer backbone rigidity, and molecular weight on the critical aggregation concentration (Cac) of mixed polymer/surfactant systems. The Cac of these systems, estimated from tensiometry and potentiometry, is found to be in close agreement. Different Cac variations with polymer charge density and surfactant chain length were observed with polymers having persistence lengths either smaller or larger than surfactant micelle size, which might reflect a different type of molecular organization in the polymer/surfactant complexes. The surfactant concentration at which the viscosity starts to decrease sharply is different from the Cac and probably reflects the polymer chain shrinkage due to surfactant binding.
International Journal of Molecular Sciences, 2021
The formation of coffee-ring deposits upon evaporation of sessile droplets containing mixtures of poly(diallyldimethylammonium chloride) (PDADMAC) and two different anionic surfactants were studied. This process is driven by the Marangoni stresses resulting from the formation of surface-active polyelectrolyte–surfactant complexes in solution and the salt arising from the release of counterions. The morphologies of the deposits appear to be dependent on the surfactant concentration, independent of their chemical nature, and consist of a peripheral coffee ring composed of PDADMAC and PDADMAC–surfactant complexes, and a secondary region of dendrite-like structures of pure NaCl at the interior of the residue formed at the end of the evaporation. This is compatible with a hydrodynamic flow associated with the Marangoni stress from the apex of the drop to the three-phase contact line for those cases in which the concentration of the complexes dominates the surface tension, whereas it is r...
Polyelectrolyte adsorption layers studied by streaming potential and particle deposition
Journal of Colloid and Interface Science, 2006
Adsorption of a cationic polyelectrolyte, polyallylamine hydrochloride (PAH), having a molecular weight of 70,000 on mica was characterized by the streaming potential method and by deposition of negative polystyrene latex particles. Formation of PAH layers was followed by determining the apparent zeta potential of surface ζ as function of bulk PAH concentration. The zeta potential was calculated from the streaming potential measured in the parallel-plate channel formed by two mica plates precovered by the polyelectrolyte. The experimental data were expressed as the dependence of the reduced zeta potential ζ /ζ 0 on the PAH coverage Θ PAH , calculated using the convective diffusion theory. It was found that for the ionic strength of 10 −2 M, the dependence of ζ /ζ 0 on Θ PAH can be reflected by the theoretical model formulated previously for surfaces covered by colloid particles. The electrokinetic measurements were complemented by particle deposition experiments on PAH-covered mica surfaces. A direct correlation between the polymer coverage and the initial deposition rate of particles, as well as the jamming coverage, was found. For Θ PAH > 0.3 the initial deposition rate attained the value predicted from the convective diffusion theory for homogeneous surfaces. The initial deposition rates for surfaces modified by PAH were compared with previous experimental and theoretical results obtained for heterogeneous surfaces formed by preadsorption of colloid particles. It was revealed that negative latex deposition occurred at surfaces exhibiting negative apparent zeta potential, which explained the anomalous deposition of particles observed in previous works. It was suggested that the combined electrokinetic and particle deposition methods can be used for detecting adsorbed polyelectrolytes at surfaces for coverage range of a percent. This enables one to measure bulk polyelectrolyte concentrations at the level of 0.05 ppm. .pl (M. Zembala). of electrophoretic mobility of colloid particles covered by multilayers or of streaming potential and streaming current determined by exploiting channel flows . Using this method, PE multilayer formation and degradation were studied using mica as model substrate .