Electrolytes poly

Micelle particles are usually spherical in shape due to the fact that the constituent ions tend to orientate themselves with lyophobic fragments pointing inwards away from the solvent. Consequently the distribution of charge will tend to be spherically symmetrical. Poly electrolytes, by contrast, are long- 

Measurements of conductance and transport numbers similar to those used for micelles confirm the importance of association of counter ions for polyelectrolytes. An interesting feature is that in an electric field such poly ions exhibit abnormally high induced dipoles. It is apparent that the associated counter-ions have considerable mobility along the length of the chain so that the field causes polarization and orientation of the chain along the field direction. 

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The earliest SFA experiments consisted of bringing the two mica sheets into contact m a controlled atmosphere (figure Bl.20.61 or (confined) liquid medium [14, 27, 73, 74 and 75]. Later, a variety of surfactant layers [76, 77], polymer surfaces [5, 9, fO, L3, 78], poly electrolytes [79], novel materials [ ] or... 

A similar approach, in spirit, has been proposed [212] for the study of two-component classical systems, for example poly electrolytes, which consist of mesoscopic, highly-charged, poly ions, and microscopic. 

R. S. Hadand, R. K. Pmd homme, Poly electrolyte Gels, Properties and Applications, American Chemical Society, Washiagton, D.C., 1992. 

A. Rembaum and E. Selegny, eds.. Poly electrolytes and Their Applications, Vol. 2, Reidl Publishing Co., Boston, 1975. 

Gutcho, Waste Treatment with Poly electrolytes Noyes Data Corp., Park Ridge, NJ, 1972. 

Usually the acid-base properties of poly electrolyte are studied by potentiometric titrations. However it is well known, that understanding of polyelectrolyte properties in solution is based on the knowledge of the thermodynamic properties. Up to now, there is only a small number of microcalorimetry titrations of polyelectrolyte solutions published. Therefore we carried out potentiometric and microcalorimetric titrations of hydrochloric form of the linear and branched polyamines at 25°C and 65°C, to study the influence of the stmcture on the acid-base properties. 

The polyelectrolyte catalysis of chemical reactions involving ionic species has been the subject of extensive investigations since the pioneering studies of Morawetz et al. [12] and Ise et al. [13-17]. The catalytic effect or the ability of poly-electrolytes to enhance or retard reaction rates is mainly due to concentration or exclusion of either or both of the ionic reactants by the polyions added to the reaction systems. For example, the chemical reaction between ionic species carrying the same charge is enhanced in the presence of polyions carrying the opposite charge. This enhancement can be attributed to an increase in the local concentration... 

A fuel cell is an electrochemical reactor with an anodic compartment for the fuel oxidation giving a proton and a cathodic compartment for the reaction of the proton with oxygen. Two scientific problems must be solved finding a low-cost efficient catalyst and finding a membrane for the separation of anodic and cathodic compartments. The membrane is a poly electrolyte allowing the transfer of hydrated proton but being barrier for the gases. 

The simple and clean polymerization of t-butyl methacrylate provides an opportunity to produce well defined, poly-electrolytes of uniform size, because this poly-ester, similarly to its Si(CH3)3 analogue i9), is readily hydrolysed by acids into polymethacry-lic acid. Furthermore, as pointed out by Muller 36), it becomes possible to produce... 

For poly electrolyte solutions with added salt, prior experimental studies found that the intrinsic viscosity decreases with increasing salt concentration. This can be explained by the tertiary electroviscous effect. As more salts are added, the intrachain electrostatic repulsion is weakened by the stronger screening effect of small ions. As a result, the polyelectrolytes are more compact and flexible, leading to a smaller resistance to fluid flow and thus a lower viscosity. For a wormlike-chain model by incorporating the tertiary effect on the chain... 

Surface force profiles between these polyelectrolyte brush layers have consisted of a long-range electrostatic repulsion and a short-range steric repulsion, as described earlier. Short-range steric repulsion has been analyzed quantitatively to provide the compressibility modulus per unit area (T) of the poly electrolyte brushes as a function of chain density (F) (Fig. 12a). The modulus F decreases linearly with a decrease in the chain density F, and suddenly increases beyond the critical density. The maximum value lies at F = 0.13 chain/nm. When we have decreased the chain density further, the modulus again linearly decreased relative to the chain density, which is natural for chains in the same state. The linear dependence of Y on F in both the low- and the high-density regions indicates that the jump in the compressibility modulus should be correlated with a kind of transition between the two different states. 

The density-dependent jump in the properties of poly electrolyte brushes has also been fonnd in the transfer ratio and the snrface potential of the brnshes [38], establishing the existence of the density (interchain distancej-dependent transition of polyelectrolytes in solntions. 

H Dautzenberg, W Jaeger, J Kotz, B Philipp, Ch Seidel, D Stscherbina. Poly electrolytes. New York Hanser, 1994. 

Polymers bearing electric charges, i.e., poly electrolytes, exhibit a very different behavior. See Chapter XIV. 

Exceptions occur in the case of polyelectrolytes where a, in the absence of added salts, may approach two. The difference arises here because at infinite dilution the charges cause the poly electrolyte chain to become nearly fully extended. 

While the condition of stoichiometric neutrality invariably must hold for a macroscopic system such as a space-network polyelectrolyte gel, its application to the poly electrolyte molecule in an infinitely dilute solution may justifiably be questioned. In a polyelectrolyte gel of macroscopic size the minute excess charge is considered to occur in the surface layer (the gel being conductive), which is consistent with the assumption that the potential changes abruptly at the surface. This change is never truly abrupt, for it must take place throughout a layer extending to a depth which is of the order of magnitude of the... 

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. 

In solutions, the counterions of poly electrolytes are HjO (for the polyacids) and OH (for the polybases), cations such as K+ and Na, or anions such as Cl (for the polysalts). The addition of polyvalent counterions (such as Ca, Mg, Cu, AT ) produces ionic cross-linking interfering with solubility The polyelectrolyte precipitates and may be redissolved upon addition of a strong acid (such as HCl). This can be regarded as a special case of ion exchange. 

The behaviour in solution of the first type of polyions compared with that of uncharged molecules is more involved in that the coil expansion is affected not only by the solvent but also by the electric field formed by the polyion itself, by the counterions and by the ions of other low-molecular-weight electrolytes, if present in the solution. Infinite charge dilution cannot be achieved by diluting the poly electrolyte solution, as a local high-intensity... 

Morawetz, H., Macromolecules in Solution, John Wiley Sons, New York, 1965. Oosawa, F., Poly electrolytes, M. Dekker, New York, 1971. 

RA Siegel, M Falamarzian, BA Firestone, BC Moxley. pH controlled release from hydrophobic poly electrolyte copolymer hydrogels. J Controlled Release 8 179-182, 1988. 

Tao C, Zheng S, Mohwald H, Li J (2003) CdS crystal growth of lamellar morphology within templates of poly electrolyte/surf actant complex. Langmuir 19(21) 9039-9042... 

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