Polymers, polyelectrolyte dynamics

As discussed extensively in this chapter, most of the surprising properties of polyelectrolyte dynamics are due to the coupling of counterion dynamics with polymer dynamics. But, there is no adequate understanding of how much of the counterions are mobile and how much are effectively condensed on polymer chain backbone. Theoretical attempts [77, 78] on counterion condensation need to be extended to concentrated poly electrolyte solutions. 

Sedlak M, Konak C, Stepanek P, Jakes J. Influence of temperature on the polyelectrolyte dynamics. Partially neutralized solutions of poly(methacrylie acid). Polymer 1990 31 253-257. 

Interest in the chemistry of water-soluble polymers (polyelectrolytes) has been continually increasing during the past 45 years. The tremendous scope of utility for water-soluble polymers has led to a vigorous search for new materials and the rapid development of polyelectrolytes into a dynamic field of industrial research. Growth in this field has been especially rapid since 1960 and today, many companies are engaged in synthesis and applications research on polyelectrolytes that are primarily used in four main marketing areas water treatment, paper, textiles, and oil recovery [1]. Polyacrylamide gel was also used as soil conditioner [2-4]. 

In this article I review some of the simulation work addressed specifically to branched polymers. The brushes will be described here in terms of their common characteristics with those of individual branched chains. Therefore, other aspects that do not correlate easily with these characteristics will be omitted. Explicitly, there will be no mention of adsorption kinetics, absorbing or laterally inhomogeneous surfaces, polyelectrolyte brushes, or brushes under the effect of a shear. With the purpose of giving a comprehensive description of these applications, Sect. 2 includes a summary of the theoretical background, including the approximations employed to treat the equifibrium structure of the chains as well as their hydrodynamic behavior in dilute solution and their dynamics. In Sect. 3, the different numerical simulation methods that are appHcable to branched polymer systems are specified, in relation to the problems sketched in Sect. 2. Finally, in Sect. 4, the appHcations of these methods to the different types of branched structures are given in detail. 

In order to resolve these challenges, it is essential to account for chain connectivity, hydrodynamic interactions, electrostatic interactions, and distribution of counterions and their dynamics. It is possible to identify three distinct scenarios (a) polyelectrolyte solutions with high concentrations of added salt, (b) dilute polyelectrolyte solutions without added salt, and (c) polyelectrolyte solutions above overlap concentration and without added salt. If the salt concentration is high and if there is no macrophase separation, the polyelectrolyte solution behaves as a solution of neutral polymers in a good solvent, due to the screening of electrostatic interaction. Therefore for scenario... 

We have identified three diffusion coefficients. These are the self-translational diffusion coefficient D, cooperative diffusion coefficient Dc, and the coupled diffussion coefficient fly. fl is the cooperative diffusion coefficient in the absence of any electrostatic coupling between polyelectrolyte and other ions in the system, fly is the cooperative diffusion coefficient accounting for the coupling between various ions. For neutral polymers, fly and Dc are identical. Furthermore, we identify fly as the fast diffusion coefficient as measured in dynamic light scattering experiments. The fourth diffusion coefficient is the slow diffusion coefficient fl discussed in the Introduction. A satisfactory theory of flj is not yet available. 

The role of semiflexibility of the polymer backbone on the dynamical properties is necessary to explore the dynamical properties of biologically relevant polyelectrolytes. Orientational correlations among molecules are expected to enhance the richness of the dynamical properties. 

A new area that has been examined is that of molecular dynamics in polyelectrolytes,106 where the molecular motions responsible for the glass transition have been identified. Another interesting study is the effect of molecular motion upon the ingress of solvent into polymer material, as a function of cross-linking density.107 In the particular case studied, of dioxane... 

We shall consider only some results of investigation of complex polymer systems by method of EPR-spectroscopy obtained recently (results obtained earlier were considered in details in works [2, 3]). We shall discuss possibilities of method of EPR-spectroscopy of spin marks and probes for determination of macromolecules conformation in solid state, and also the results of investigation of molecular dynamics and organization of micelle systems -complexes polyelectrolyte-SAS. We shall also discuss some results obtained with the use of method of EPR-spectroscopy and its modification - the method of EPR-tomography for revealing of particularities of spatial distribution of active sites resulted from process of thermo-oxidative destruction of solid polymers. 

---