Gibbs polyelectrolytes, aqueous solutions

By the systematic work on the complexation equilibrium analyses of both weak acidic and weak basic polyelectrolytes, the Gibbs-Donnan approach is validated to provide deep insights into the complexation behaviors of linear polymer ligands. This concept does not need any adjustable parameter it only uses the logic of phase separation of polyelectrolyte aqueous solutions. The electrostatic nonideality (polyelectrolytic effect) observed in the acid dissociation equilibria of a polyion can directly be used to correct for the electrostatic nonideality for metal complexation. The potentiometric titration technique with concurrent measurements of pH and pM is most suit-... 

Takahashi et al.67) prepared ionene-tetrahydrofuran-ionene (ITI) triblock copolymers and investigated their surface activities. Surface tension-concentration curves for salt-free aqueous solutions of ITI showed that the critical micelle concentration (CMC) decreased with increasing mole fraction of tetrahydrofuran units in the copolymer. This behavior is due to an increase in hydrophobicity. The adsorbance and the thickness of the adsorbed layer for various ITI at the air-water interface were measured by ellipsometry. The adsorbance was also estimated from the Gibbs adsorption equation extended to aqueous polyelectrolyte solutions. The measured and calculated adsorbances were of the same order of magnitude. The thickness of the adsorbed layer was almost equal to the contour length of the ionene blocks. The intramolecular electrostatic repulsion between charged groups in the ionene blocks is probably responsible for the full extension of the... 

Gibbs monolayers are widespread. The simplest system is that of the surface of a fully miscible binary liquid. More complex ones are monolayers of uncharged molecules adsorbed from dilute solutions (example aliphatic alcohols from aqueous solution) electrolytes surfactants (non-ionic or ionic) polymers and polyelectrolytes and yet more. On the other hand, the methods for characterizing... 

Abstract This chapter reviews the thermodynamic properties of aqueous solutions of polyelectrolytes, concentrating on properties that are related to phase equilibrium phenomena. The most essential phenomena as well as methods to describe such phenomena are discussed from an applied thermodynamics point of view. Therefore, the experimental findings concentrate on the vapor liquid phase equilibrium phenomena, and the thermodynamic models are restricted to expressions for the Gibbs energy of aqueous solutions of polyelectrolytes. 

Keywords Aqueous solutions Counterion condensation Excess Gibbs energy Osmotic coefficient Polyelectrolytes Salt effects Thermodynamics Vapor liquid equilibrium... 

There are many well-established models for the Gibbs energy of nonelectrolyte solutions and also several methods to describe conventional polymer solutions. However, the state of the art for modeling thermodynamic properties of aqueous solutions of polyelectrolytes is far less elaborated. This is partly due to the particular features of such solutions but is also caused by insufficiencies in the knowledge of the parameters that characterize a polyelectrolyte, for example, the polydisper-sity and the different stmctures (primary, secondary etc.) of the polyelectrolytes. The development and testing of thermodynamic models has always been based on reliable experimental data for solutions for which all components are well characterized. Such characterization is particularly scarce for biopolymers and biopolyelectrolytes. Furthermore, such polymers are generally more complex than synthetic polymers. Therefore, the present contribution is restricted to a discussion of the thermodynamic properties of aqueous solutions of synthetic polyelectrolytes that consist of only two different repeating units that are statistically distributed. Furthermore, it is restricted to systems where sufficient information on the polyelectrolyte s polydispersity is available. 

As an example, we discuss here an aqueous solution of one polyelectrolyte P and one strong electrolyte S (=Mv Xv ), where P and S share a common counterion X. Some of the counterions that originate from the polyelectrolyte are assumed to be located in a small volume Vp around the polyelectrolyte backbone (the phenomenon is called counterion condensation ). The polyelectrolyte, condensed counterions, free counterions, free coions, and water contribute to the Gibbs energy of the solution ... 

When a neutral salt S is dissolved in the aqueous polyelectrolyte solution there is also a contribution to the Gibbs energy of the aqueous solution by the other ions, here called coions. When vcoi is the stoichiometric coefficient of that coion in S, following the same ideas as explained before for the free counterions, that contribution is ... 

The aqueous phase contains free (or dissolved ) counterions. These ions are either dissociated from the polyelectrolyte or result from the dissolution of the salt S. Their contribution to the Gibbs energy of the solution is ... 

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