Polymer electrostatic interaction

In this chapter, we have presented an overview of the properties of solutions of charged polymers. Electrostatic interactions between charges lead to the rich behavior of polyelectrolyte and polyampholyte solutions qualitatively different from those of neutral polymers. " For example ... 

We also attempt to distinguish between surface physical chemistry and colloid and polymer physical chemistry. This distinction is not always possible, and clearly many of the features of physical chemistry of surfaces, such as the electrostatic interactions and adsorption of macromolecules, have a significant... 

How should a molecule be divided into groups In some cases there may appecir to be a chemically obvious way to define the groups, especially when the molecule is a polymer that is constructed from distinct chemical residues. A particularly desirable feature is that each group should, if possible, be of zero charge. The reason for this can be understood if we recall how the different electrostatic interactions vary with distance from Section 4.9.1 ... 

There are several methods of buffer and capillary surface modification used to prevent electrostatic interactions. Two modes have been examined mn buffer with pH >10 in the uncoated capillary and anionic polymer coating capillary, developed in lAI. 

Cationic samples can be adsorbed on the resin by electrostatic interaction. If the polymer is strongly cationic, a fairly high salt concentration is required to prevent ionic interactions. Figure 4.18 demonstrates the effect of increasing sodium nitrate concentration on peak shapes for a cationic polymer, DEAE-dextran. A mobile phase of 0.5 M acetic acid with 0.3 M Na2S04 can also be used. 

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. 

In pressing, the threshold concentration of the filler amounts to about 0.5% of volume. The resulting distribution of the filler corresponds, apparently, to the model of mixing of spherical particles of the polymer (with radius Rp) and filler (with radius Rm) for Rp > Rm as the size of carbon black particles is usually about 1000 A [19]. During this mixing, the filler, because of electrostatical interaction, is distributed mainly on the surface of polymer particles which facilitates the forming of conducting chains and entails low values of the percolation threshold. 

Note that when the concentration of added salt is very low, Debye length needs to be modified by including the charge contribution of the dissociating counterions from the polyelectrolytes. Because the equilibrium interaction is used, their theory predicts that the intrinsic viscosity is independent of ion species at constant ionic strength. At very high ionic strength, the intrachain electrostatic interaction is nearly screened out, and the chains behave as neutral polymers. Aside from the tertiary effect, the intrinsic viscosity will indeed be affected by the ionic cloud distortion and thus cannot be accurately predicted by their theory. 

The deposition-reduction (DR) method is based on the weak electrostatic interactions of polymer surfaces with the oppositely charged Au(III) complex ions, leading to the reduction of Au(III) exclusively on the polymer surfaces. Appropriate anionic or cationic Au(III) precursors are chosen based on the zeta potentials of polymer supports (Figure 3.6) [43]. 

Piletsky, SA Andersson, HS Nicholls, LA, Combined Hydrophobic and Electrostatic Interaction-Based Recognition in Molecularly Imprinted Polymers, Macromolecules 32, 633, 1999. 

The stability of colloids can also be dramatically altered by inclusion of polymeric materials. If the polymer interacts favourably with the particle surfaces, i.e. it adsorbs, then both an increase and a reduction in stability is possible, via modification of the electrostatic interaction of the polymer is charged or a reduction in the van der Waals attraction. 

M Ilavsky. Effect of electrostatic interactions on phase transition in the swollen polymeric network. Polymer 22 1687-1697, 1981. 

These behaviors are discussed from 27A1 NMR data giving the fraction of Al ions bound on the polymer and from of a model of electrostatic interactions. 

In fact this "unhydrolyzed" polyacrylamide sample is slightly charged and its low polyectrolyte character is confirmed by a slight difference of red values at pH 7 and 5, for salt free solutions. A really neutral polymer should be necessary to differentiate low effects of electrostatic interactions from non ionic interactions. coordination binding at low pH and hydrogen bonds at pH 7. Nevertheless, at this pH, the adsorption of the chain on Al(0H)3 aggregates can probably be considered as the main origin of the loss of viscosity. 

The effects of calcium on polymer-solvent and polymer-surface interactions are dependent on polymer ionicity a maximum intrinsic viscosity and a minimum adsorption density as a function of polymer ionicity are obtained. For xanthan, on the other hand, no influence of specific polymer-calcium interaction is detected either on solution or on adsorption properties, and the increase in adsorption due to calcium addition is mainly due to reduction in electrostatic repulsion. The maximum adsorption density of xanthan is also found to be independent of the nature of the adsorbent surface, and the value is close to that calculated for a closely-packed monolayer of aligned molecules. 

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