Determination of propagation rate on free ions and ion-pairs in living polymerizations

1 DETERMINATION OF PROPAGATION RATE ON FREE IONS AND ION-PAIRS IN LIVING POLYMERIZATIONS 

In studies of styrene polymerization in tetrahydrofuran, Geacintov et al. observed significant deviations from the simple circumstances described above. The effective rate constant decreased with increasing concentration of living centres [LC] [368]. This was explained by ion-pair dissociation to free ions and proved by the linear dependence of kpef on [LC]1/2 [369, 370]. 

The value of Kd can be obtained from conductivity or kinetic measurements (see Table 7). The calculation of and lc+ from experimental data is easy. The correctness of the assumptions and calculations can be verified by the 

Counter-ion From conductivity measurements From kinetic measurements Reference 

The value of k is independent of the type of solvent and of the counter-ion [374-376] k+ is generally much smaller and depend on these factors. 

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