Improving kp Data Originating from PLP Number Distributions

Abstract

Summary: Based on certain features, especially the width of the so-called extra peaks in the simulated number-chain-length distribution (CLD) of polymers prepared by pulsed laser polymerization (PLP), it is calculated by which factor the positions of the points of inflections and maxima deviate from the theoretical L₀ data that are to be used for the evaluation of k_p. These corrections are for slightly chain-length-dependent termination by disproportionation or combination and cover a wide range of chain-lengths and primary radical production. They can be applied either to the point of inflection on the low-molecular weight side of the extra peaks or to the peak maximum. On average, the mean error that is about −2.5% for uncorrected data from first-order points of inflection is reduced to the order of less than 1% even if no assumption concerning the mode of termination is made. The situation is similar for the positions of the first-order peak maxima where the mean error of about +7% likewise can be cut down to less than 1% if the proper correction function is chosen. Second- and third-order peaks data, which are a priori less falsified, yield still better results after correction. Mass sensitivity of the detection process has comparatively little effect: it is only for unrealistically high extents of chain-length dependence in detection that considerable falsifications are to be expected. As an additional result it turned out that correction functions obtained for number distributions are also applicable to mass spectrometry raw distributions and even for mass distributions x(l) · l provided Poissonian broadening is the only broadening process.