Ion Entropy in Phase-Separated Aqueous Mixtures of Polyelectrolyte and Neutral Polymer

Vis, Mark; Peters, Vincent F. D.; Erné, Ben H.; Tromp, R. Hans

doi:10.1021/acs.macromol.5b00324

Cited by 19 publications

(22 citation statements)

References 39 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…A linear correlation of the electrical potential difference is observed with the tie-line length. This is as expected, since the Donnan potential scales linearly with the difference in polyelectrolyte concentration, according to 9,28 ψ ≃ Δ kT e z c c 2 D p s (31) and the tie-line length is a direct measure of the compositional difference between the two phases. For increased magnitudes of the polyelectrolyte charge z, the magnitude of the Donnan potential is also increased (at a fixed tie-line length), resulting in an increased slope of the plot of |ψ D | against the tie-line length.…”

Section: ■ Resultssupporting

confidence: 77%

Effects of Electric Charge on the Interfacial Tension between Coexisting Aqueous Mixtures of Polyelectrolyte and Neutral Polymer

et al. 2015

Self Cite

View full text Add to dashboard Cite

Upon demixing, an aqueous solution of a polyelectrolyte and an incompatible neutral polymer yields two phases separated by an interface with an ultralow tension. Here, both in theory and experiment, we study this interfacial tension in detail: how it scales with the concentrations of the polymers in the two phases and how it is affected by the interfacial difference in the electrical potential. Experiments are performed on an aqueous model system of uncharged dextran and charged nongelling gelatin. The experimental tension scales to the power ∼3 with the tie-line length in the phase diagram of demixing, in agreement with mean-field theory where space is filled with a binary mixture of polymer blobs. The interfacial electrical potential difference is experimentally found to decrease the interfacial tension in a way that is consistent with Poisson−Boltzmann theory inspired from Frenkel and Verwey−Overbeek. ■ INTRODUCTIONWhen aqueous solutions of polymers are mixed, phase separation is a commonly observed phenomenon. 1−4 It yields phases that differ in the concentrations of the polymers. The interface between the phases is not abrupt, but there are gradients in the relative composition and the total concentration of the polymers. A particularity of phase separating solutionsas opposed to phase separated blendsresults from the osmotic compressibility of the solutions: compared to the bulk phases, the interfacial region is diluted by uptake of solvent. 5 In the case of charged polymers, there is also an interfacial gradient in the electric charge density, corresponding to an interfacial electric potential step. This is the so-called Donnan potential, 6,7 and its effect on the interfacial tension is the subject of this paper.The main conditions for phase separation are a sufficient concentration and a sufficient degree of polymerization. These two factors often make the unfavorable mixing enthalpy dominate over the small mixing entropy of two types of polymer. Phase separation is also affected by the presence of charge on the polymers. 8 For instance, when one of the polymers is charged and the other is uncharged, phase separation becomes entropically more unfavorable due the accumulation of counterions in one of the phasesnecessary for charge neutrality. In order to increase entropy, the positive and negative salt ions spread across the interface to different extents; the buildup of charge separation halts the spreading.The accompanying electric potential difference is the Donnan potential. It has the same origin as the well-known membrane potential found in living cells and dialysis membranes. However, in our case, the charged interface is formed spontaneously and in equilibrium with the bulk phases; moreover, the interfacial electric potential step is relatively small, typically less than 10 mV, 9 as compared to 40−60 mV for the membranes of living cells.The electric interfacial potential step contributes negatively to the interfacial tension due to the spontaneous formation of interfacial electrical double layer...

show abstract

Section: ■ Resultssupporting

confidence: 77%

Effects of Electric Charge on the Interfacial Tension between Coexisting Aqueous Mixtures of Polyelectrolyte and Neutral Polymer

et al. 2015

Self Cite

View full text Add to dashboard Cite

show abstract

“…2, and the critical demixing mass fraction shifts by a factor of 2. Such a shift has been observed also in similar systems [44,45] and can be understood in terms of the loss in translational entropy of the salt ions [41]. The polyelectrolyte-rich phase has the highest concentration of counterions, which stems from the condition of macroscopic electroneutrality, and this unequal distribution of the ions over the two phases has an entropic cost.…”

mentioning

confidence: 70%

“…Our fish gelatin has a net zero charge at pH 7.5, is positively charged at low pH, and is negatively charged at higher pH [40]. In the linear regime (jψ D j ≤ 10 mV), the Donnan potential ψ D ¼ ψ α − ψ β is given by [40,41]…”

mentioning

confidence: 98%

“…Dextran is a neutral polymer and gelatin is a weak polyelectrolyte with a charge adjustable via the pH. This model system has been featured in several earlier studies [10,11,[29][30][31][40][41][42]. The compositions of the phases, the difference in electrical potential, the salt concentration, and the charge on the gelatin were determined as described previously [40,41].…”

mentioning

confidence: 99%

“…z = +20 (pH 4.8) z = +5 (pH6.2) Mass fraction of polyelectrolyte (%) color online). Measured phase diagrams[40,41] of demixing of aqueous solutions of dextran (uncharged) and nongelling fish gelatin (charged), under conditions where the Donnan potential is small (pH 6.2, 5 mM salt) and where it is large (pH 4.8 with 9 mM salt, 20 charges per gelatin chain).w a t e r /w a te r int erfa ce color online). Determination of the interfacial tension of a demixed aqueous solution of 5% dextran and 5% nongelling fish gelatin from image analysis of the profile of the liquid-liquid interface at a vertical polystyrene surface: (top) micrograph and (bottom) extracted profile and fit.…”

mentioning

confidence: 99%

See 2 more Smart Citations

Decreased Interfacial Tension of Demixed Aqueous Polymer Solutions due to Charge

et al. 2015

Self Cite

View full text Add to dashboard Cite

Electric charge at the water-water interface of demixed solutions of neutral polymer and polyelectrolyte decreases the already ultralow interfacial tension. This is demonstrated in experiments on aqueous mixtures of dextran (neutral) and nongelling fish gelatin (charged). Upon phase separation, electric charge and a potential difference develop spontaneously at the interface, decreasing the interfacial tension purely electrostatically in a way that can be accounted for quantitatively by Poisson-Boltzmann theory. Interfacial tension is a key property when it comes to manipulating the water-water interface, for instance to create novel water-in-water emulsions.

show abstract

Synthetic Membraneless Droplets for Synaptic‐Like Clustering of Lipid Vesicles

Li,

Song,

Guo

et al. 2023

Angewandte Chemie

View full text Add to dashboard Cite

In eukaryotic cells, the membraneless organelles (MLOs) formed via liquid‐liquid phase separation (LLPS) are found to interact intimately with membranous organelles (MOs). One major mode is the clustering of MOs by MLOs, such as the formation of clusters of synaptic vesicles at nerve terminals mediated by the synapsin‐rich MLOs. Aqueous droplets, including complex coacervates and aqueous two‐phase systems, have been plausible MLO‐mimics to emulate or elucidate biological processes. However, neither of them can cluster lipid vesicles (LVs) like MLOs. In this work, we develop a synthetic droplet assembled from a combination of two different interactions underlying the formation of these two droplets, namely, associative and segregative interactions, which we call segregative‐associative (SA) droplets. The SA droplets cluster and disperse LVs recapitulating the key functional features of synapsin condensates, which can be attributed to the weak electrostatic interaction environment provided by SA droplets. This work suggests LLPS with combined segregative and associative interactions as a possible route for synaptic clustering of lipid vesicles and highlights SA droplets as plausible MLO‐mimics and models for studying and mimicking related cellular dynamics.

show abstract

Ion Entropy in Phase-Separated Aqueous Mixtures of Polyelectrolyte and Neutral Polymer

Cited by 19 publications

References 39 publications

Effects of Electric Charge on the Interfacial Tension between Coexisting Aqueous Mixtures of Polyelectrolyte and Neutral Polymer

Effects of Electric Charge on the Interfacial Tension between Coexisting Aqueous Mixtures of Polyelectrolyte and Neutral Polymer

Decreased Interfacial Tension of Demixed Aqueous Polymer Solutions due to Charge

Synthetic Membraneless Droplets for Synaptic‐Like Clustering of Lipid Vesicles

Contact Info

Product

Resources

About