Abstract
AbstractThe instantaneous differential molecular weight distribution curves for a polymer prepared under the influence of periodic laser flashes of constant intensity were calculated as a function of conversion and accumulated up to final conversions in the range between 0 and 20%. If these cumulated distributions are subjected to the conventional analysis with respect to the position of the inflection points, which are an excellent measure of kp · [M]t0 (kp = rate constant of chain propagation, [M] = monomer amount concentration, t0 = pulse separation), it is seen that this relationship, the validity of which was originally established in the limit of vanishing conversion, becomes the more deficient the higher is the conversion. This is even so when the initial monomer concentration is replaced by the average monomer concentration over the conversion interval examined. In the latter case, however, the deviations are reasonably small and do not exceed the limits of experimental accuracy in determining the position of the inflection point. Thus the application of this method of calculating kp is justified also for conversions up to at least 20%. The determination of k/t from rate of polymerization and weight‐average degree of polymerization (kt representing the rate constant of mutual chain termination) on the other hand, is completely insensitive towards conversion.
Published Version
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