Polymer melt polyelectrolyte

Since the ions in ionic polymers are held by chemical bonds within a low dielectric medium consisting of a covalent polymer backbone material with which they are incompatible, the polymer backbone is forced into conformations that allow the ions to associate with each other. Because these ionic associations involve ions from different chains they behave as crosslinks, but because they are thermally labile they reversibly break down on heating. lonomers therefore behave as cross-Unked, yet melt-processable, thermoplastic materials, or if the backbone is elastomeric, as thermoplastic rubbers. It should be noted that it is with the slightly ionic polymers, the ionomers, where the effect of ion aggregation is exploited to produce meltprocessable, specialist thermoplastic materials. With highly ionic polymers, the polyelectrolytes, the ionic cross-linking is so extreme that the polymers decompose on melting or are too viscous for use as thermoplastics. 

This section could have followed section 1 in this chapter. The reason for placing it here is that the concepts and derivations developed in section 2 are needed for deriving the viscosity equation for polymeric electrolytes (polymer solutions) and polymer melts. Similar to the previous two sections, the viscosity of polyelectrolytes and polymer melts without an external electric field are discussed first, and then the viscosity of those materials under an external electric field or having strong surface charges are focused upon thereafter. 

Viscosity of the polyelectrolyte and polymer melt (the free volume of polymeric materials)... 

In the following, we will discuss some microscopic dynamical models. We begin with the Rouse model, which describes the dynamics of chains in a non-entangled polymer melt. The effects of entanglements on the motion can be accounted for by the reptation model, which we will treat subsequently. Then we shall be concerned with the motion of polymer chains in a solvent, when the hydrodynamic interaction between the segments of a chain plays a prominent role. At the end of this chapter, we briefly discuss the modes of motion in polyelectrolyte solutions, which are strongly affected by Coulomb forces. 

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. 

W. A. Henderson, Solid State Ionics 2012, 217, 1-5. Influence of polymer chain length and chains ends on polyelectrolyte solvate structure and melting point. 

Zhu Y, Shah NH et al (2002) Influence of thermal processing on the properties of chlorpheniramine maleate tablets containing an acrylic polymer. Phaim Dev Technol 7(4) 481-489 ZhuY, Shi J et al (2005) Stimuli-responsive controlled dmg release from a hollow mesoporous silica sphere/polyelectrolyte multilayer core-shell structure. Angew Chem Int Ed 44 5083-5087 Zhu Y, Shah NH et al (2006) Controlled release of a poorly water-soluble drug from hot-melt extrudates containing acrylic polymers. Drug Dev Ind Pharm 32 569-583... 

Alexei R. Khokhlov s main research interests are polymer science, statistical physics of macromolecules, physical chemistry of polyelectrolytes and ionomers, microphase separation in polymer systems, polymer liquid crystals, polyelectrolyte responsive gels, topological restrictions in polymer systems, dynamics of concentrated polymer solutions and melts, coil-globule transitions, associating polymers, computer simulation of polymer systems, biomimetic polymers, and proton-conducting polymer membranes. 

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