Macroion

Kinetics. Details of the kinetics of polymerization of THF have been reviewed (6,148). There are five main conclusions. (/) Macroions are the principal propagating species in all systems. (2) With stable complex anions, such as PF , SbF , and AsF , the polymerization is living under normal polymerization conditions. When initia tion is fast, kinetics of polymerizations in bulk can be closely approximated by equation 2, where/ is the specific rate constant of propagation /is time [I q is the initiator concentration at t = 0 and [M q, [M and [M are the monomer concentrations at t = 0, at equiHbrium, and at time /, respectively. 

For counterions that can form esters with the growing oxonium ions, the kinetics of propagation are dominated by the rate of propagation of the macroions. For any given counterion, the proportion of macroions compared to macroesters varies with the solvent—monomer mixture and must be deterrnined independentiy before a kinetic analysis can be made. The macroesters can be considered to be in a state of temporary termination. When the proportion of macroions is known and initiation is sufftcientiy fast, equation 2 is satisfied. 

A. M. Walsh, R. D. Coalson. Lattice field theory for spherical macroions in solution Calculation of equilibrium pair correlation function. J Chem Phys 700 1559-1566, 1994. 

R. D. Coalson, A. Duncan. Systematic ionic screening theory of macroions. J Chem Phys 97 5653-5661, 1992. 

The parameter n reflects the measure of deviation of the system from the behavior of the monomeric acid where n = 1, i.e., it characterizes the degree of interaction between the neighboring functional groups of the macroion. The value of n depends on the structure of the polyelectrolyte and the nature of the counterion pK = pK0 — log (1 — a)/a is the negative decadic logarithm of the effective dissociation constant of the carboxylic CP depending on a. 

As no long-lasting absorption was detected with pure dioxane, the transient absorptions found with PBS solutions are due to macroradicals or macroions. 

Figure 13. (a) Substituted polypyrrole, (b) self-doped polypyrrole, (c) heteroaromatic polymer showing the monomer unit, (d) composite polypyrrole-polyelectrolyte, and (e) hybrid material. (Polyaniline macroion photo supplied by Gomez-Romero and M. Lira.)... 

Polypyrrole hybrids [Fig. 13(e)], electrogenerated from solutions containing the monomer and a salt of an inorganic macroion or a polyoxide.90-92... 

A.Malovikova, M.Milas, M.Rinaudo, R.Borsali, in "Macroions Characterization from dilute solution to complex fluids", ACS Symposium series 548, Edit. K.S.Schmitz, (1994)297. 

The apparent dissociation constant pK is strongly dependent on the electrical potential on the surface of the macroion, according to the well known equation [11]... 

Polyelectrolytes are polymers having a multiplicity of ionizable groups. In solution, they dissociate into polyions (or macroions) and small ions of the opposite charge, known as counterions. The polyelectrolytes of interest in this book are those where the polyion is an anion and the counterions are cations. Some typical anionic polyelectrolytes are depicted in Figure 4.1. Of principal interest are the homopolymers of acrylic acid and its copolymers with e.g. itaconic and maleic adds. These are used in the zinc polycarboxylate cement of Smith (1968) and the glass-ionomer cement of Wilson Kent (1971). More recently, Wilson Ellis (1989) and Ellis Wilson (1990) have described cements based on polyphosphonic adds. 

Polymer molecules with just one or a few ionic groups, in most cases terminal and anionic, are called macroions. They are encountered primarily in living polymers, polymer molecules present in a polymerizing reaction system that will grow as long as monomers (e.g., esters or nitriles of methacrylic acid) continue to be supplied. The ionic charge of the macroion always transfers to the last monomer added, keeping the macroion ready for the next such addition. 

By definition, in a solution all ions belong to the same phase, even though counterions may cluster more or less diffusely around the macroions. When significant amounts of a simple 1 1 electrolyte (such as KCl) are added to a polyelectrolyte solution, dissociation of the polyelectrolyte macromolecule is repressed in an extreme case the polyelectrolyte may be salted out. An undissociated polyacid may be precipitated by generous addition of a simple acid such as HCl. 

Shklovskii BI. 1999. Screening of a macroion by multivalent ions Correlation-induced inversion of charge. Phys Rev E 60 5802-5811. 

The results of the simple DHH theory outlined here are shown compared with DH results and corresponding Monte Carlo results in Figs. 10-12. Clearly, the major error of the DH theory has been accounted for. The OCP model is greatly idealized but the same hole correction method can be applied to more realistic electrolyte models. In a series of articles the DHH theory has been applied to a one-component plasma composed of charged hard spheres [23], to local correlation correction of the screening of macroions by counterions [24], and to the generation of correlated free energy density functionals for electrolyte solutions [25,26]. The extensive results obtained bear out the hopeful view of the DHH approximation provided by the OCP results shown here. It is noteworthy that in... 

Polyelectrolytes are macromolecular substances whose molecules have a large number of groups that are ionized in solution. They are termed macroions or poly ions and are studied most often in aqueous solutions. 

K. S. Schmitz, Macroions in Solution and Colloid Suspension, VCH Publishers, New York, 1993. 

Polymerization Equilibria. As mentioned earlier, esters of strong acids, e.g. trifluoromethane sulfonic acid ("triflates"), are excellent initiators for the polymerization of THF. With such initiators, however, a complication arises. In addition to the normal propagation i depropagation equilibria of oxonium ions, Smith and Hubin postulated that the macroion ( ) may also convert into a corresponding nonpolar macroester ( ) by attack of the anion (14). ... 

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