Chain length distributions concentration

All computations so far have been performed with the full width of the chain length distributions, i.e. chains with aspect ratios Lld< 10 have also been included. However, the effects of stress transfer across chain ends and the stress concentrations may become important below this aspect ratio. In the theory by Yoon these effects are neglected. In particular, for the Flory distribution containing a relatively large proportion of very short chains, the effects may be considerable. Therefore, calculations are performed in which the negative effect of the very short rods is approximated by assuming that for an aspect ratio L/d<4 the contribution of these rods to the strength is set to zero. 

The first volume concentrates on separation techniques. H. Pasch summarizes the recent successes of multi-dimensional chromatography in the characterization of copolymers. Both, chain length distribution and the compositional heterogeneity of copolymers are accessible. Capillary electrophoresis is widely and successfully utilized for the characterization of biopolymers, particular of DNA. It is only recently that the technique has been applied to the characterization of water soluble synthetic macromolecules. This contribution of Grosche and Engelhardt focuses on the analysis of polyelectrolytes by capillary electophore-sis. The last contribution of the first volume by Coelfen and Antonietti summarizes the achievements and pitfalls of field flow fractionation techniques. The major drawbacks in the instrumentation have been overcome in recentyears and the triple F techniques are currently advancing to a powerful competitor to size exclusion chromatography. 

The process is based on the previous observation that in the absence of ethylene, olefins alkylate TEA in proportion to the concentration of each individual olefin present in the alkylation mixture. Thus, the distribution of alkyl groups of the alkylated TEA will be equal to the olefin chain length distribution fed to the alkylator. 

Figure 12 shows the beneficial effects of 5% excess persistent species on the control of the chain length distribution for a rather fast living polymerization that shows little control without the excess, because the parameters are close to point B in Figure 5. Of course, the much better control is obtained at the expense of a strong retardation of the monomer conversion that amounts to a factor of 150. For fast polymerizations and parameters close to point C in Figure 5, one expects control but little livingness for large conversions, and in this case the improvement requires quite large initial nitroxide concentrations.50...

The findings of Scholte and Derham et al. revealed that g for quasi-binary solutions ought to depend not only on T and (j>, but on at least one more variable. It is not evident whether, in the early 1970s, one had a clear recognition that this third variable should be the chain length distribution f P) or, to be equivalent, that g should depend on the concentrations of the individual polymer components ((/> ,, [Pg.307]

The influence of salt concentration on the reduced viscosity of different polyacrylamide -co -acrylates which have the same degree of polymerization and chain length distribution. 

The equations for the concentrations of polymer of chain length k can be transformed by a number of related methods, termed here transformation techniques, into a finite set whose solution yields both the moments of the polymer chain length distribution as well as the polymer chain length distribution (PCLD) itself. 

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