The specific conductivities of molten N-methyl-, N-ethyl-, N-(n-propyl)-, and N-(n-butyl)pyridinium chlorides and N-ethylpyridinium bromide were measured from near the melting points to the thermal decomposition temperatures. Conductivities also were measured from 25 ~ to 125~ for mixtures of
2339rate of increase of Pn is accelerated while that of pw becomes relatively constant.From the figures representing Pn, P,, and H.I., it is evident that a small amount of chain transfer to monomer has an important effect on P , and Pvl but that the H.I. remains relatively unaffected. Although the general shapes of the Pn and isw us. per cent conversion curves are not altered by chain transfer, its inclusion lowers them considerably. This effect is most apparent, a t low catalyst concentrations.To observe the effect of tempera,ture on the variation of 2", and P,, a few calculations were made for polymerization of styrene a t 100'. While larger rates of increase in both Pn and P , were indicated, a limiting value for H.I. of 5.0 was found. These considerations are merely qualitative, however, since styrene undergoes appreciable thermal polymerization a t this temperaturels the effect of which was assumed to be negligible in these calculations.Polymerization of Isoprene.-The kinetic constants for the bulk polymerization of isoprene at various temperatures have been determined recently using the dead-end polymerization t h e~r y .~ Using these kinetic constants (Table 11) and applying the expressions developed in this paper, the cumulative number and weight average degrees of polymerization were computed for isoprene a t 80' assuming no chgin iransfer to monomer. The calculated values for Pn, P,, and H.I. are listed in Table 111.
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