Solvents polyelectrolytes

Polyelectrolyte films are comprised of the polyelectrolytes, solvent and ions, the latter mainly located at the film/solution interface, see below. Solvent content in PEMs can beaproximately40% ]94,95], being the actual value dependent on film history (drying and reswelling steps) and for dry films on environmental humidity ]95,96]. PEMs are therefore highly swollen structures, but its water content is below that found in... 

A vast number of applications in different fields of Nanotechnology (interfacial phenomena, colloids, and nanomateiials) have been described for the materials obtained following this approach [81]. The formation and growth of polyelectrolyte multilayers is the result of an intricate balance of interactions [82], among their components polyelectrolyte—polyelectrolyte, polyelectrolyte—solvent, polyelectrolyte-surface, etc. The different interactions involved are governed by the complex interplay between electrostatic and entropic contributions, as well as solvent quality. 

The linear regression coefficients (R ) for equations were determined. Parameters obtained by fitting the data in Fedors model are presented in Table 20.3 [44]. In our previous study we observed that the higher the DS, then the higher the intrinsic viscosity ([n]) at the same temperature, and [q] was also dependent on the properties of the solvent [44]. The polymer concentration parameter (Cni) in the Fedors correlation depends on solvent quality and molecular interaction, which shows that DMAc is a strong solvent for SPEEK (Table 20.2). The values of parameter B in the Fouss-Strauss correlation also depends on the polyelectrolyte-solvent interaction this again indicates strong interaction between SPEEK and DMAc. 

Polyelectrolyte complex membranes are phase-inversion membranes where polymeric anions and cations react during the gelation. The reaction is suppressed before gelation by incorporating low molecular weight electrolytes or counterions in the solvent system. Both neutral and charged membranes are formed in this manner (14,15). These membranes have not been exploited commercially because of then lack of resistance to chemicals. 

A variety of synthetic polymers, including polycarbonate resins, substituted olefins, and polyelectrolyte complexes, are employed as ultrafiltration membranes. Many of these membranes can be handled dry, have superior organic solvent resistance, and are less sensitive to temperature and pH than cellulose acetate, which is widely used in RO systems. 

Since the compartmentalization occurs as a result of microphase separation of an amphiphilic polyelectrolyte in aqueous solution, an aqueous system is the only possible object of study. This limitation is a disadvantage from a practical point of view. Our recent studies, however, have shown that this disadvantage can be overcome with a molecular composite of an amphiphilic polyelectrolyte with a surfactant molecule [129], This composite was dissolvable in organic solvents and dopable in polymer film, and the microphase structure was found to remain unchaged in the composite. This finding is important, because it has made it possible to extend the study on photo-systems involving the chromophore compartmentalization to organic solutions and polymer solid systems. 

The swelling pressure of polyelectrolyte gels is usually considered as a sum of the network (jtnct) and ionic contributions (nion) [4, 99, 101, 113, 114]. The former describes the uncharged gel while taking into account the interaction between the polymer segments and the solvent as well as the network elasticity [4] ... 

The linearity of L with N is maintained at the theta point. Relative to Eq. 5, the chains have shrunk by a factor of (a/d),/3 but the linear variation indicates that the chains are still distorted at the theta point and characteristic dimensions do not shrink through a series of decreasing power laws as do free chains [29-31]. Experimentally, Auroy [25] has produced evidence for this linearity even in poor solvents. Pincus [32] has recently applied this type of analysis to tethered polyelectrolyte chains, where the electrostatic interactions can produce even stronger stretching effects than those that have been discussed for good solvents. Tethered polyelectrolytes have also been studied by others [33-35],... 

Equations for the evaluation of formation constants of complexed ion species in cross-linked and linear polyelectrolyte systems. J. A. Marinsky, Ion Exch. Solvent Extr., 1973,4, 227-243 (18). 

Additional exchange of ion pairs and solvent molecules as in any other membrane formed by polyelectrolytes. 

The use of computer simulations to study internal motions and thermodynamic properties is receiving increased attention. One important use of the method is to provide a more fundamental understanding of the molecular information contained in various kinds of experiments on these complex systems. In the first part of this paper we review recent work in our laboratory concerned with the use of computer simulations for the interpretation of experimental probes of molecular structure and dynamics of proteins and nucleic acids. The interplay between computer simulations and three experimental techniques is emphasized (1) nuclear magnetic resonance relaxation spectroscopy, (2) refinement of macro-molecular x-ray structures, and (3) vibrational spectroscopy. The treatment of solvent effects in biopolymer simulations is a difficult problem. It is not possible to study systematically the effect of solvent conditions, e.g. added salt concentration, on biopolymer properties by means of simulations alone. In the last part of the paper we review a more analytical approach we have developed to study polyelectrolyte properties of solvated biopolymers. The results are compared with computer simulations. 

Donnan-Type Equilibria in Polyelectrolyte Gels.—In a somewhat more rigorous fashion we consider the reduction of the chemical potential of the solvent in the swollen gel to be separable into three terms which severally represent the changes due to the mixing of polymer and solvent, to the mixing with the mobile ionic constituents, and to the elastic deformation of the network. Symbolically... 

If 0.6 N lithium bromide is added to the solution of the polyelectrolyte and also to the solvent on the opposite side of the osmometer membrane, the lowermost set of points in Fig. 145 (lower and left scales) is observed. The anion concentration inside and outside the coil is now so similar that there is little tendency for the bromide ions belonging to the polymer to migrate outside the coil. Hence the osmotic pressure behaves normally in the sense that each poly electrolyte molecule contributes essentially only one osmotic unit. The izjc intercept is lower than that for the parent poly-(vinylpyridine) owing to the increase in molecular weight through addition of a molecule of butyl bromide to each unit. 

Klooster, N. Th. M., van der Trouw, F. Mandel, M. (1984). Solvent effects in polyelectrolyte solutions. 3. Spectrophotometric results with (partially) neutralised poly(acrylic acid) in methanol and general conclusions regarding these systems. Macromolecules, 17, 2087-93. 

The viscosities were measured with an Ubbelohde Cannon 75-L, 655 viscometer. Formic acid was chosen as the solvent for the viscosity measurement because the polymer (VII) showed very low or no solubility in other common solvents. In a salt free solution, a plot of the reduced viscosity against the concentration of the polymer showed polyelectrolytic behavior, that is, the reduced viscosity ri sp/c increased with dilution (Figure 4). This plot passed through a maximum at 0.25 g/dL indicating that the expansion of the polyions reached an upper limit, and the effects observed on further dilution merely reflected the decreasing interference between the expanded polyions. 

The viscosity of the oxidized polymer (VIII) was determined using DMF as a solvent. Chloroform was not a good solvent because it was too volatile and resulted in poor reproducibility. The reduced viscosities are plotted against polymer concentration (Figure 6). Polymer VIII behaved like a polyelectrolyte, the reduced viscosities increased sharply on dilution in a salt free solution. The addition of 0.01 M KBr did not completely suppress the loss of mobile ions however, at 0.03 M KBr addition a linear relationship between the reduced viscosities and concentration was established. 

Poly(N-phenyl-3,4-dimethylenepyrroline) had a higher melting point than poly(N-phenyl-3,4-dimethylenepyrrole) (171° vs 130°C). However, the oxidized polymer showed a better heat stability in the thermogravimetric analysis. This may be attributed to the aromatic pyrrole ring structures present in the oxidized polymer, because the oxidized polymer was thermodynamically more stable than the original polymer. Poly(N-phenyl-3,4-dimethylenepyrroline) behaved as a polyelectrolyte in formic acid and had an intrinsic viscosity of 0.157 (dL/g) whereas, poly(N-pheny1-3,4-dimethylenepyrrole) behaved as a polyelectrolyte in DMF and had an intrinsic viscosity of 0.099 (dL/g). No common solvent for these two polymers could be found, therefore, a comparison of the viscosities before and after the oxidation was not possible. 

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