Polystyrenes broad

Figure 20 shows an example of its use. As expected, the GPC 2 chromatogram of a fraction of a monodisperse standard (obtained by sampling it with GPC 2 at its peak) is narrower than the whole standard which in turn is narrower than chromatograms of slices of broad polystyrene distributions. In Figure 20, two examples of the latter show the difference obtained by improving resolution in GPC 1. 

There is so-me scatter in the computed Mar k-Houw i nk constants from the broad polystyrene standards of Table lib. However, the average of the four samples is very close to that found from the set of narrow standards. 

FIG. 15.37 Extrudate swell ratio vs. shear stress at the wall, for melts of polystyrenes of broad and narrow molecular-weight distributions. Filled symbols the broad polystyrene mentioned in Fig. 15.34-15.36 Mw = 2.2 x 105 and Mw/Mn = 3.1. Open symbols narrow polystyrene Mw = 1.6 x 105 and M /Mn < 1.1. From Greassley et al. (1970). Courtesy Society of Rheology. 

Figure 6. Log M versus local root-mean-square radius for a broad polystyrene standard (-----) and narrow polystyrene standards (m).

Figure 7. Particle-scatteringfunction at 15° measured for broad polystyrene...

Using the K constant determined by using the broad polystyrene DOW 1683, it is then possible to measure the dn/dc of each branch because they are very pure and their concentrations are perfectly known. Finally, assuming the dn/dc of the star copolymer is extremely close to the one of the branches (there are only very few amounts of coupling agent), it is just necessary to set the software in the concentration correction position to determine the correct slice concentration using the DRI signal, K, and dn/... 

Figure 3 shows the MAES-derived molar mass and rms radius as a function of elution volume for a broad polystyrene sample. Measurements were made in toluene at 690 nm. The value of dnidc chosen was 0.11. From Fig. 3, it should be noted that the radius data be-... 

Fig. 3 shows the MALS-derived molar mass and RMS radius as a function of elution volume for a broad polystyrene sample. Measurements were made in toluene at 690 nm.The value of dn/dc chosen was 0.11. From Fig. 3, it should be noted that the radius data begins to deteriorate around 10 nm, whereas the mass data extends to its detection limits. From the mass and radius data of Fig. 3, a conformation plot is easily generated with a slope of about 0.57 (i.e., corresponding to a random coil). These same data can also be used immediately to calculate the mass and size moments of the sample as well as its poly-dispersity as shown in the next section. 

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