Phase separation in polyelectrolyte solutions. Theory of complex coacervation

Overbeek, J. Th. G.; Voorn, M. J.

doi:10.1002/jcp.1030490404

Cited by 563 publications

(630 citation statements)

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“…In principle, ω can be obtained using the actual molecular volume of each species, but such data are generally not available for polyions and often unnecessary given the approximate nature of the theory. In the original VO theory [17], all species were assumed to be of the same size as water molecules, i.e., ω = 1 for all . Spruijt et al [10] also assumed that all species are of the same size but used that size as a fitting parameter instead of taking it equal to the size of water molecule.…”

Section: Theorymentioning

confidence: 99%

“…The thermodynamic description of polyelectrolyte coacervation was first developed by Overbeek and Voorn [17] using a mean-field approach, henceforth referred as VO (Voorn-Overbeek) theory. They argued that the tendency toward phase separation is governed by the competition of entropic forces that favor a single-phase solution (no phase separation) and electrostatic correlations that favor phase separation accompanied by the formation of a dense phase containing polyelectrolyte complexes.…”

Section: Introductionmentioning

confidence: 99%

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pH and Salt Effects on the Associative Phase Separation of Oppositely Charged Polyelectrolytes

et al. 2014

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Abstract:The classical Voorn-Overbeek thermodynamic theory of complexation and phase separation of oppositely charged polyelectrolytes is generalized to account for the charge accessibility and hydrophobicity of polyions, size of salt ions, and pH variations. Theoretical predictions of the effects of pH and salt concentration are compared with published experimental data and experiments we performed, on systems containing poly(acrylic acid) (PAA) as the polyacid and poly(N,N-dimethylaminoethyl methacrylate) (PDMAEMA) or poly(diallyldimethyl ammonium chloride) (PDADMAC) as the polybase. In general, the critical salt concentration below which the mixture phase separates, increases with degree of ionization and with the hydrophobicity of polyelectrolytes. We find experimentally that as the pH is decreased below 7, and PAA monomers are neutralized, the critical salt concentration increases, while the reverse occurs when pH is raised above 7. We predict this asymmetry theoretically by introducing a large positive Flory parameter (= 0.75) for the interaction of neutral PAA monomers with water. This large positive Flory parameter is supported by molecular dynamics simulations, which show much weaker hydrogen bonding between neutral PAA and water than between charged PAA and water, while neutral and charged PDMAEMA show similar numbers of hydrogen bonds. This increased hydrophobicity of neutral PAA at reduced pH increases the tendency towards phase separation despite the reduction in charge interactions between the polyelectrolytes. Water content and volume of coacervate are found to be a strong function of the pH and salt concentration.

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Section: Theorymentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

pH and Salt Effects on the Associative Phase Separation of Oppositely Charged Polyelectrolytes

et al. 2014

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“…[1][2][3] The dilute (supernatant) phase is in equilibrium with the dense (coacervate) phase which is easily observed by microscopy or by centrifugation. This coacervate phase, formed by desolvation 1 frequently occurs when electrostatic attractive forces overcome the hydration of the two particles.…”

Section: Introductionmentioning

confidence: 99%

Entering and Exiting the Protein−Polyelectrolyte Coacervate Phase via Nonmonotonic Salt Dependence of Critical Conditions

2009

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Critical conditions for coacervation of poly(dimethyldiallylammonium chloride) (PDADMAC) with bovine serum albumin were determined as a function of ionic strength, pH, and protein/polyelectrolyte stoichiometry. The resultant phase boundaries, clearly defined with this narrow molecular weight distribution PDADMAC sample, showed nonmonotonic ionic strength dependence, with the pH-induced onset of coacervation (at pH φ ) occurring most readily at 20 mM NaCl. The corresponding onset of soluble complex formation, pH c , determined using highprecision turbidimetry sensitive to changes of less than 0.1% transmittance units, mirrored the ionic strength dependence of pH φ . This nonmonotonic binding behavior is attributable to simultaneous screening of short-range attraction and long-range repulsion. The similarity of pH c and pH φ was explained by the effect of salt on protein binding, and consequently on the number of bound proteins relative to that required for charge neutralization of the complex, a requirement for phase separation. Expansion of the coacervation regime with chitosan, a polycation with charge spacing similar to that of PDADMAC, could be due to either the charge mobility or chain stiffness of the former. The pH φ versus I phase boundary for PDADMAC correctly predicted entrance into and egress from the coacervation region by addition of either salt or water. The ability to induce or suppress coacervation via protein/polyelectrolyte stoichiometry r was found to be consistent with the proposed model. The results indicate that the conjoint effects of I, r, and pH on coacervation could be represented by a three-dimensional phase boundary.

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“…Under appropriate conditions of charge density, solvent quality, and molecular weight, a phase transition can occur in such a system, with two phases being formed: one rich in both polymers and the other consisting of nearly pure solvent. 18,19,[34][35][36][37][38][39][40] This process is usually referred to as polyelectrolyte complexation in the physics community or as complex coacervation in the physical chemistry, colloid science, and biological communities. The resulting polymer-rich coacervate phase has two important properties: it is dense yet liquid, and it is charge neutral.…”

mentioning

confidence: 99%

“…18,19,[34][35][36][37][38][39] In addition to the direct electrostatic attraction between oppositely charged polyions, there are other factors playing an important role: electrostatic screening by small ions (salt or counterions), excluded volume interactions of polymer backbones mediated by the solvent, small ion translational entropy, and polymer conformational entropy. In many cases these factors are competitive rather than reinforcing, so it can be difficult to anticipate the conditions under which coacervate phases will form.…”

mentioning

confidence: 99%

Field‐theoretic simulations of polyelectrolyte complexation

Popov

Lee

Fredrickson

2007

J Polym Sci B Polym Phys

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This viewpoint article is intended as a brief introduction to the emerging subject of field-theoretic simulations (FTS) of charged polymers. While the direct numerical simulation of field theory models has begun to impact several traditional areas of polymer science, including blends and block copolymers, polyelectrolytes have hitherto not been the subject of field-theoretic simulations.Here we report on a preliminary FTS study of polyelectrolyte complexation that demonstrates the potential of this novel numerical approach.Polyelectrolytes are ubiquitous in nature and in applications ranging from personal care products to paints, coatings, and processed foods. Indeed, practically all biopolymers are polyelectrolytes. In the application context, the introduction of dissociable groups is one of the most powerful ways to confer water solubility on a polymeric material. Scientifically, the polymer bound charges, which are compensated by a sea of oppositely charged counterions, produce a coupling between chain conformations and electrostatics that leads to an incredible richness of polyelectrolyte phenomena. However, this richness comes with a price: charged polymers are among the most difficult polymer systems to study theoretically or to simulate on the computer [1,2,3,4]. The explanation lies in the long range nature of Coulomb interactions -charged segments feel each other at much larger distances than segments in neutral polymer systems.

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Phase separation in polyelectrolyte solutions. Theory of complex coacervation

Cited by 563 publications

References 9 publications

pH and Salt Effects on the Associative Phase Separation of Oppositely Charged Polyelectrolytes

pH and Salt Effects on the Associative Phase Separation of Oppositely Charged Polyelectrolytes

Entering and Exiting the Protein−Polyelectrolyte Coacervate Phase via Nonmonotonic Salt Dependence of Critical Conditions

Field‐theoretic simulations of polyelectrolyte complexation

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