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Improving k p Data Originating From Higher Order PLP‐SEC Peaks
Author(s) -
Kornherr Andreas,
Olaj Oskar Friedrich,
SchnöllBitai Irene,
Zifferer Gerhard
Publication year - 2004
Publication title -
macromolecular theory and simulations
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.37
H-Index - 56
eISSN - 1521-3919
pISSN - 1022-1344
DOI - 10.1002/mats.200400025
Subject(s) - maxima , inflection point , range (aeronautics) , disproportionation , order (exchange) , yield (engineering) , distribution (mathematics) , dispersion (optics) , chain (unit) , chemistry , maxima and minima , molecular physics , mathematics , thermodynamics , physics , materials science , optics , mathematical analysis , geometry , quantum mechanics , art , biochemistry , performance art , economics , composite material , finance , art history , catalysis
Summary: Based on certain features, especially the width of the so‐called extra peaks in the simulated chain length distribution (CLD) of polymers prepared by pulsed laser polymerization (PLP), it is calculated by which factor the positions of the higher order points of inflections and maxima deviate from the theoretical L 0 data that are to be used for the evaluation of k p . These corrections, which can be put into the form of master equations, are for slightly chain length dependent termination by disproportionation or combination and cover a wide range of chain lengths and primary radical production and a reasonable range of axial dispersion σ ad, k , caused by the chromatographic device used in the evaluation of the chain length distribution. They can be applied either to the point of inflection on the low molecular weight side of the extra peaks as well as to the peak maximum. For usual extents of column broadening ( σ ad, k ≈ 0.05) the mean error that is about 7% for uncorrected data from second order points of inflection is reduced to the order of 1.5% even if no assumption concerning the mode of termination is made. The situation is a little less satisfactory for the correction of the positions of the second order peak maxima. Third order peak data are a priori less falsified and yield still better results after correction. Thus the proper treatment of higher order peaks helps to extend the range of chain lengths for which highly reliable k p data can be gained from PLP experiments followed by chromatographic analysis.Plots of l LPI ( n ) /( nL 0 ) versus lg( L 0 ) obtained from first order (circles), second order (triangles) and third order (squares) peaks showing uncorrected values in the left diagram and corrected values using correction functions X in the right one, both calculated for σ ad, k = 0.05. (+) and (×) represent ill‐defined peaks.