A review of the early development of the thermodynamics of the complex coacervation phase separation

Arthur Veis*

*Corresponding author for this work

Research output: Contribution to journalReview articlepeer-review

100 Scopus citations


Coacervation was defined as the phenomenon in which a colloidal dispersion separated into colloid-rich (the coacervate), and colloid-poor phases, both with the same solvent. Complex coacervation covered the situation in which a mixture of two polymeric polyions with opposite charge separated into liquid dilute and concentrated phases, in the same solvent, with both phases, at equilibrium, containing both polyions. Voorn and Overbeek provided the first theoretical analysis of complex coacervation by applying Flory-Huggins polymer statistics to model the random mixing of the polyions and their counter ions in solution, assuming completely random mixing of the polyions in each phase, with the electrostatic free energy, ΔG elect, providing the driving force. However, experimentally complete randomness does not apply: polyion size, heterogeneity, chain stiffness and charge density (σ) all affect the equilibrium phase separation and phase concentrations. Moreover, in pauci-disperse systems multiple phases are often observed. As an alternative, Veis and Aranyi proposed the formation of charge paired Symmetrical Aggregates (SA) as an initial step, followed by phase separation driven by the interaction parameter, χ 23, combining both entropy and enthalpy factors other than the ΔG elect electrostatic term. This two stage path to equilibrium phase separation allows for understanding and quantifying and modeling the diverse aggregates produced by interactions between polyampholyte molecules of different charge density, σ, and intrinsic polyion structure.

Original languageEnglish (US)
Pages (from-to)2-11
Number of pages10
JournalAdvances in Colloid and Interface Science
Issue number1-2
StatePublished - Sep 14 2011


  • Aggregate structure models
  • Collagen
  • Electrostatic free energy
  • Free energy of mixing
  • Gelatin-gelatin coacervates
  • Phase diagrams
  • Phase separation
  • Polyelectrolyte complexes

ASJC Scopus subject areas

  • Surfaces and Interfaces
  • Physical and Theoretical Chemistry
  • Colloid and Surface Chemistry


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