Relaxation solution viscosity

Figure 13 Aqueous glucose solutions. Dependence of the relaxation times upon solution viscosity. O, T3I , 2tj <> 4ti (R roduced by permission from J. Solution Chem., in press)...

Fig. 7.8.1. Reorientational relaxation time t versus solution viscosity for benzene solutions O and neat benzene. (From Alms et al., 1973b.)...

From Fig. 12.3.1 we see that the CHCla single-particle relaxation time is constant at constant solution viscosity. The light-scattering reorientation time extrapolated to infinite dilution is in excellent agreement with this single-particle time. Thus the concentration dependence of xt at higher concentrations is due to the increasing importance... 

Figure 7. The coil-stretch relaxation time (t) as a function of solution viscosity.

Furthermore, as discussed in Subsection 5.1.3, direct proportionality between ionic relaxation rates and solution viscosity is not observed experimentally. Two other weak points in Deverell s treatments are ... 

The quantity RllM Y is Rg in A, a measure of chain stiffness. For example, polycarbonate, with (RpM y = 0.457, is stiffer than polystyrene, which has a value of 0.275. The importance of these quantities lies in their relation to physical and mechanical behavior. Both melt and solution viscosities depend directly on the radius of gyration of the polymer and on the chain s capability of being deformed. The theory of the random coU (Section 5.3), strongly supported by these measurements, is used in rubber elasticity theory (Chapter 9) and many mechanical and relaxation calculations. 

As apparent in these measurements of the relaxation times for QH6 and CeHe in CO2 over similar pressures and temperatures, there is no experimental manifestation of a specific intermolecular interaction between CO2 and fluorine. These interactions, if prevalent, would be expected to be seen in a change in relaxation rate or mechanism at high densities where the intermolecular distance between the CO2 molecule and the fluorine group would be the smallest and their potential specific interaction the greatest. It appears that at high densities, solution viscosity dominates the relaxation process, and the relaxation mechanism for both F and are similar. Therefore, there is no experimental evidence for a specific CO2-F interaction that impacts on the relaxation of these two molecules, which supports the calculations of Diep et al. (34) and the experimental efforts of Yee et al. (35). 

In a probe diffusion experiment, one examines the motions of dilute mesoscopic particles dispersed in a polymer solution. In some systems, a single relaxation is found. In others, probe motions involve multiple relaxation processes. Probe diffusion is sensitive to the probe radius R, matrix polymer molecular weight M and concentration c, solution viscosity r], solvent viscosity t]s, and other variables. 

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