Dilute poor solvent

Plot the size r of a labelled section of n consecutive Kuhn monomers of a chain for different regions of the diagram in Fig. 5.1. (i) Dilute -solvent (ii) semidilute -solvent (iii) dilute poor solvent (iv) two-phase region (v) concentrated poor solvent (vi) dilute good solvent (vii) semidilute good solvent (viii) concentrated good solvent. 

A single extrapolation of the ratio D/s measured at a series of very low concentrations would then suffice. The graphical method advocated above for handling osmotic and turbidity data could be applied here also for the purpose of obtaining (D/s)o = RT/M, Again, if a poor solvent is used, so that T2 is very small, D/s should be nearly independent of c over the dilute range. 

The slope of the lines in Figure 3.10, i.e., the virial constant B, is related to the CED. The value for B would be zero at the theta temperature. Since this slope increases with solvency, it is advantageous to use a dilute solution consisting of a polymer and a poor solvent to minimize extrapolation errors. 

If a diesel fuel is low in viscosity due to kerosene dilution or solvent dilution, its lubricity is probably poor. The possibility of wear of the high-pressure fuel injection pump parts will increase. The effect of kerosene dilution on the lubricity of a typical low sulfur diesel fuel is shown in FIGURE 5-2. 

Viscosity Measurements. Although in typical polymer-plasticizer systems, the polymer is the major component, it is possible to use the viscosity of dilute polymer solutions as a measure of the solvent power of the liquid for the polymer. Thus, liquids with high solvent power for the polymer cause a stretching out of the chain molecules, whereas a liquid of poor solvent power causes the chains to coil up. This is because, in the liquid with poor solvent power, the segments of the polymer chain (the monomer units) prefer to stay close to each other, while in a good solvent, interaction between polymer segments and solvent molecules is preferred. 

Tristearin and triglycerides of higher molecular weight have a very low solubility in the mobile phase used, and either precipitate at injection (in the valve loop or in the connecting tube between the injection valve and the column) when the sample solution is diluted in a rather poor solvent or are so strongly retained that they are eluted only after a prohibitively long time, giving broad peaks barely discernible from baseline oscillations. 

Experimentally, good solvent conditions have been observed [22,23,27,28, 34,35]. On the other hand, none has been reported for the prediction of the theta condition, y = 101, whereas the prediction of poor solvent conditions giving rise to y > 3 has been reported. These all have y < 20 except for two they are poly(methyl acrylate) at lower temperatures [34] and poly(dimethyl siloxane) [24]. Others have failed to reproduce them since. A caveat needs to be raised with these results. Since the semi-dilute regime is so narrow in r before the collapse state sets in whereby the power exponent is commonly deduced for a r range less than one full decade hence, the r scaling is at best qualitative in the static characterization. 

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