Polyelectrolytes characterization

Hinderberger. D. Jeschke. G. Spiess. H.W. Counterion condensation and conformational transitions of polyelectrolytes characterized by EPR spectroscopy. Macromolecules 2002. 35 (26). 9698-9706. 

To distinguish results for a free solution experiment, one conducted without a separation medium, the mobility in free solution is usually written as /u-o-When the value of E is low enough to avoid field-induced distortion of the polyelectrolyte s configuration, jx is independent of E. Measurements of fx have long been a cornerstone of polyelectrolyte characterization, especially for polyelectrolytes of biological origin. 

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. 

The reactivation of enzymes (after their partial inactivation in an acid medium) upon passing into a medium of pH 8 is also of great importance for oral use (Fig. 25). Enzymes immobilized in crosslinked polyelectrolytes are characterized by a structural memory even after considerable inactivation. Under changed conditions, this leads to a considerable or almost complete reactivation of the enzyme, whereas in the reactivation of a free enzyme in solution under similar conditions the enzymatic activity is restored on a lower level. 

In the following paper, the possibility of equilibration of the primarily adsorbed portions of polymer was analyzed [20]. The surface coupling constant (k0) was introduced to characterize the polymer-surface interaction. The constant k0 includes an electrostatic interaction term, thus being k0 > 1 for polyelectrolytes and k0 1 for neutral polymers. It was found that, theoretically, the adsorption characteristics do not depend on the equilibration processes for k0 > 1. In contrast, for neutral polymers (k0 < 1), the difference between the equilibrium and non-equilibrium modes could be considerable. As more polymer is adsorbed, excluded-volume effects will swell out the loops of the adsorbate, so that the mutual reorientation of the polymer chains occurs. 

One of the main characteristic of polyelectrolyte is the pK of the - COOH function as usually with polyelectrolyte only the intrinsic pK (pKo) extrapolated to zero charge characterizes the polymer [41] one gets 3.30 which is in same range as other carboxylic polymers the apparent values of pK (pKa) depends on the charge distribution, on the polymer concentration, on the ionic strength of the solution and on the nature of the counterions. 

In the classical theories of polyelectrolytes, the chain expansion is characterized by the electrostatic excluded volume parameter, zel with ... 

In conclusion one can say that SEC is a very powerful method for polymer characterization, especially in combination with other composition sensitive or absolute calibration methods. A big advantage is also that the sample amount is fairly small, typically 10 mg. For more complex polymers, such as polyelectrolytes, enthalpic effects often become dominant and also for rather high molecular weight polymers chromatographic methods such as field-flow fraction (FFF) techniques might be more suitable. For fast routine measurements linear columns are often used. 

Engelhardt, H. and Martin, H. Characterization of Synthetic Polyelectrolytes by Capillary Electrophoretic Methods. Vol. 165, pp. 211-247. 

The preparation of the FEDs, the experimental set-up and measuring conditions for the detection of DNA immobilization and hybridization as well as for the monitoring of the layer-by-layer adsorption of the polyelectrolyte multilayers are described in detail elsewhere [46-50], The attachment of these charged macromolecules to the FED surfaces has been systematically characterized by means of capacitance-voltage,... 

H. Kong, R Luo, C. Gao, and D. Yan, Polyelectrolyte-functionalized multiwalled carbon nanotubes preparation, characterization and layer-by-layer self-assembly. Polymer 46, 2472—2485 (2005). 

Steps 5 and 6 involved the characterization and optimization of multicomponent capsules based on blends containing up to four polyelectrolytes, often in the presence of a gelling agent or surface coating. While these results are part of the overall objective of this project, they are beyond the scope of this paper and will be reported elsewhere [61,62]. 

Further details of the theory and application of Raman spectroscopy in polymer studies can be found elsewhere (1. 9). However, vibrational frequencies of functional groups in polymers can be characterized from the spacing of the Raman lines and thus information complementary to IR absorption spectroscopy can be obtained. In addition, since visible radiation is used the technique can be applied to aqueous media in contrast to IR spectroscopy, allowing studies of synthetic polyelectrolytes and biopolymers to be undertaken. Conformation and crystallinity of polymers have also been shown to influence the Raman spectra Q.) while the possibility of studying scattering from small sample volumes in the focussed laser beam (-100 pm diameter) can provide information on localized changes in chemical structure. 

Nilsson KPR, Hammarstrdm P, Ahlgren F, Herland A, Schnell EA, Lindgren M, Westermark GT, Inganas O (2006) Conjugated polyelectrolytes-conformation-sensitive optical probes for staining and characterization of amyloid deposits. Chem Bio Chem 7 1096-1104... 

Although the theory of polyelectrolyte dynamics reviewed here provides approximate crossover formulas for the experimentally measured diffusion coefficients, electrophoretic mobility, and viscosity, the validity of the formulas remains to be established. In spite of the success of one unifying conceptual framework to provide valid asymptotic results, in qualitative agreement with experimental facts, it is desirable to establish quantitative validity. This requires (a) gathering of experimental data on well-characterized polyelectrolyte solutions and (b) obtaining the relationships between the various transport coefficients. Such data are not currently available, and experiments of this type are out of fashion. In addition to these experimental challenges, there are many theoretical issues that need further elaboration. A few of these are the following ... 

The rate of metal complex formation is often modified (usually enhanced) by the presence of a charged interface in the aqueous phase. This may be provided by ionic micelles, e. g., SDS, microemulsions or polyelectrolytes. jjjg reactions of Ni + and Co with hydrophobic ligands pan, pap and pad 14-16 are popular ones for examining effects, since they are well characterized in the bulk water. The simple model (4.126)... 

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