Rigid chain polymers dilute solution

We will also deal with sohm features of the behaviour of rigid-chain polymer molecules in dilute solutions with emphasis on their dinamooptical and electroop-tical properties. 

Tables 1—3 give the values of molecular parameters characterizing the equilibrium rigidity and hydrodynamic properties of molecules of some rigid-chain polymers obtained from viscometric and diffusion-sedimentation measurements of their dilute solutions.

In compensation schemes the recording of FB can be conducted either by visual observation or by use of a photoelectric receiver. It has been found that the optical anisotropy of rigid-chain polymer molecules is fairly high. However, when very dilute solutions are studied, the measured excess birefringence can be very low. Hence, to obtain reliable information on the molecular characteristics of polymers, methods ensuring maximum sensitivity of the instrument should be used. 

Papkov, S. P. Estimation of Kuhn segment value of rigid-chain polymers by viscous properties of diluted solutions. High-Molecular Compounds, B, 1982, 24(11), 869-873. 

PROPERTIES OF RIGID-CHAIN POLYMERS IN DILUTE AND CONCENTRATED SOLUTIONS... 

In studying the viscous properties of dilute solutions of rigid-chain polymers [10-16], it was shown that the Martin equation [9] applies to them, as to solutions of flexible-chain polymers, for low concentrations c ... 

The manner in which individual molecules crystallize depends on the conformation of the chains. Flexible chain polymers, as shown schematically in Figure 5.18, fold to form microlamellar plates. Rigid chain polymers form bundles of rod-like structures. The bulk structure or macrostmc-ture of the polymer depends on whether crystallization occurs from dilute solution or from the melt state. When crystallization occurs under quiescent conditions in a dilute solution, then single crystals consisting of folded chains arise. When crystallization from the melt occurs under quiescent... 

It is now generally accepted that folding is universal for spontaneous, free crystallisation of flexible polymer chains. It was first of all found in crystallisation from very dilute solutions, but it is beyond doubt now, that also spherulites, the normal mode of crystallisation from the melt, are aggregates of platelike crystallites with folded chains, pervaded with amorphous material. "Extended chain crystallisation" only occurs under very special conditions in the case of flexible chains for rigid polymer chains it is the natural mode ("rigid rod-crystallisation" from the melt in case of thermotropic polymers, and from solution in case of the lyotropic liquid-crystalline polymers both of them show nematic ordering in the liquid state). 

The main part of the side group in these macromolecules consists of the alkoxy-benzoic acid moiety. This acid may form thermotropic liquid crystals. The investigation of the hydrodynamic properties of PPhEAA molecules in dilute solutions has revealed that the equilibrium rigidity of their main chains is relatively low (Table 12). Hence, since for all flexible-chain polymers, the shear optical coefficient An/Ar in PPhEAA solutions is independent of molecular weight the segmental anisotropy - tt2 and the anisotropy of the monomer unit Aa may be determined by use ofEq. (67). 

It can be shown that an isolated polymer, in solution in pure water is always completely ionized (Z = V) then the polyion has the shape of a nearly rigid rod. This entails that the solutions that are currently used are nearly always semi-dilute, i.e. in these solutions the chains overlap one another. 

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