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Free‐Radical Propagation Rate Coefficients via n ‐Pulse Periodic Polymerization
Author(s) -
Nikitin Anatoly N.,
Evseev Alexander V.,
Buback Michael,
Feldermann Achim,
Jürgens Michael,
Nelke Dorit
Publication year - 2002
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 - 10.1002/1521-3919(200211)11:9<961::aid-mats961>3.0.co;2-h
Subject(s) - polymerization , pulse (music) , methyl methacrylate , radical polymerization , laser , chemistry , yield (engineering) , analytical chemistry (journal) , molecular physics , pulse width modulation , materials science , polymer chemistry , thermodynamics , optics , physics , polymer , chromatography , organic chemistry , composite material , power (physics) , detector
Aspects of applying n ‐pulse periodic initiation in pulsed laser polymerization/size‐exclusion chromatography (PLP/SEC) experiments are studied via simulation of molecular weight distributions (MWDs). In n ‐pulse periodic PLP/SEC, sequences of n laser pulses at successive time intervals Δ t 1 up to Δ t n are periodically applied. With the dark time intervals being suitably chosen, n ‐modal MWDs with n well separated peaks occur. The n ‐pulse periodic PLP/SEC method has the potential for providing accurate propagation rate coefficients, k p . Among several measures for k p , the differences in molecular weights at the MWD peak positions yield the best estimate of k p under conditions of medium and high pulse laser‐induced free‐radical concentration. Deducing k p from n dark time intervals (corresponding to n regions of free‐radical chain length) within one experiment at otherwise identical PLP/SEC conditions allows addressing in more detail a potential chain‐length dependence of k p . Simulations are compared with experimental data for 2‐pulse periodic polymerization of methyl methacrylate.Measured MWD (solid line) and associated first derivative curve (dotted line) for a 2‐pulse periodic bulk polymerization experiment of MMA at 20 °C.