Light scattering Zimm plot

A graphical method, proposed by Zimm (thus tenned the Zinnn plot), can be used to perfomi this double extrapolation to detemiine the molecular weight, the radius of gyration and the second virial coefficient. An example of a Zinnn plot is shown in figure Bl.9.6 where the light scattering data from a solution of poly... 

One of the most important fiinctions in the application of light scattering is the ability to estimate the object dimensions. As we have discussed earlier for dilute solutions containing large molecules, equation (B 1.9.38) can be used to calculate tire radius of gyration , R, which is defined as the mean square distance from the centre of gravity [12]. The combined use of equation (B 1.9.3 8) equation (B 1.9.39) and equation (B 1.9.40) (tlie Zimm plot) will yield infonnation on R, A2 and molecular weight. 

Zimm plot analychem A graphical determination of the root-square-mean end-to-end distances of coillike polymer molecules during scattered-light photometric analyses. zim,plat ... 

Zimm plot Type of double extrapolation used to determine the weight-average molecular weight in light-scattering photometry. 

Figure 16. Zimm plot of 514.5 nm light-scattering data characterizing associated kraft lignin sample in DMF following desalting after incubation at 170 gL 1 for 300 h in 1.0 M ionic strength aqueous 0.40 M NaOH.

For analysis by means of the most general graphical treatment of light scattering measurements (the Zimm plot), the scattering equation (5.23) is rewritten in the following easy-to-use form (Burchard. 1994 Evans, 1972 Tanford, 1961) ... 

Fig. 19. Zimm plot for light scattering data on PTHF in ethyl acetate at 30° C (69), [13] in ethyl acetate...

Kinetic Light-Scattering Method. Isochronous Interpolation. When high-activity samples of endocellulase are used, the reaction proceeds so quickly that, since the measurements of scattered intensity at different angles are not performed at the same extent of reaction, the extrapolations to zero angle and the subsequent calculations are erroneous. For this reason Kratochvil et al. (27) have proposed an isochronous interpolation method, whereby the Kc/Re values are plotted against sin21 (0/2) + kft. As in the double-extrapolation method of Zimm, the value of k may be chosen arbitrarily in order to space the experimental data. 

Figure 2.6 A Zimm plot, in which light-scattering data are simultaneously extrapolated to zeroscattering angle and zero concentration. Reprinted with permission from J. E. Mark, Physical Chemistry of Polymers, ACS Audio Course C-89, American Chemical Society, Washington, DC, 1986. Copyright 1986, American Chemical Society.

Dynamic light scattering, coupled with modern computer programs and auxiliary equipment, automatically graphs Zimm plots and computes Mw, Rg, , Cl, and flow rates. New techniques have expanded the method to the semidilute and concentrated regimes (Barth and Sun, 1991). 

FIG. 10.5 Example of a Zimm plot of light scattering data. 

Fig. Schematic illustration of Zimm plot for analysing light-scattering data. The solid points ( ) represent experimental measuements the open circles (O) are extrapolated points.

Zimm Plot A graph used in the determination of root-mean-square end-to-end distances of dispersed species based on light-scattering data. 

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