Handbook of Size Exclusion Chromatography and Related ...

Figure 3 A light-scattering photometer. Polymer solution in cell is irradiated with an
incident beam, and scattered light intensity is measured at angle u.
utilizes a single angle measurement at ,108 (10) or 908 (11), two angles (12), or
multiangles (13,14).
The weight-average molecular weight, the radius of gyration, and the second
virial coefficient can be determined by measuring the scattered intensity as a
function of angle for a series of different dilute concentrations. These parameters
are determined from a Zimm plot of K*c=R(u) against sin 2 (u=2) þ kc for these
data (Fig. 4), where k is an arbitrary constant used to spread out the data. Avalue of
k ¼ 1=cmax, where cmax is the maximum concentration used, has been found to
work well (2). The data are extrapolated to zero angle and zero concentration, and
Figure 4 Zimm plot, which is a double-extrapolation procedure used in light-scattering
measurements for determining the second virial coefficient A2, mean square radius of
gyration kR2 gl and weight-average molecular weight Mw.
© 2004 by Marcel Dekker, Inc.