Randomly branched polystyrene

Like SEC/LALLS, the viscosity detector is sensitive to high molecular weight fractions as shown in Fig, 7. A shoulder at 3,000,000 molecular weight detected by the DRI becomes a peak when detected by the viscometer detector. The usefulness of the SEC/Viscometer method is exemplified by the study of branched polymers. Fig. 8 shows a log [ ] vs. log M plot for a randomly branched polystyrene obtained from the SEC/ iscometer technique. 

The randomly branched polystyrene and two star-shaped polystyrenes were obtained from the Polymer Science Department at the University of Akron, Akron, OH. 

Randomly Branched Polystyrene. Branched molecules in solution are more compact than linear molecules and therefore the overall size of a branched polymer molecule in solution is smaller than the... 

Figure 15. Plot of Branching Index as a Function of Molecular Weight for a Randomly Branched Polystyrene.

The zero shear viscosities of these randomly branched polystyrenes were measured and compared with those of linear polystyrenes and it was found that t]0 for all of the branched polymers were far lower than that of linear homologues of the same overall molecular weight. In addition, a scaling of fJo was observed for the first two generations of each branched series of... 

Masuda, T. Nakagawa, Y. Ohta, Y. Onogi, S. Viscoelastic properties of concentrated solutions of randomly branched polystyrenes. Polym. J. 1972, 5 (1), 92-99. 

A) Mark-Houwink plot of log [u ] versus log M for a linear and a branched polystyrene. (B) Plot of branching index g as a function of molecular weight for the randomly branched polystyrene. (Adapted from Reference 36 and used with permission from the American Chemical Society.)... 

Table 2 Average branching ratio calculations for two randomly branched polystyrenes ...

Ferri, D., LomoUini, P. Melt rheology of randomly branched polystyrenes. /. Rheol. (1999) 43, pp. 1355-1372... 

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