Premium
Chain‐length dependent termination in pulsed‐laser polymerization, 6 . The evaluation of the rate coefficient of bimolecular termination k t for the reference system methyl methacrylate in bulk at 25°C
Author(s) -
Olaj Oskar Friedrich,
Vana Philipp
Publication year - 1998
Publication title -
macromolecular rapid communications
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.348
H-Index - 154
eISSN - 1521-3927
pISSN - 1022-1336
DOI - 10.1002/(sici)1521-3927(19981001)19:10<533::aid-marc533>3.0.co;2-m
Subject(s) - polymerization , chain termination , chain (unit) , degree of polymerization , methyl methacrylate , moment (physics) , polymer chemistry , materials science , power law , analytical chemistry (journal) , chemistry , thermodynamics , radical polymerization , physics , polymer , statistics , organic chemistry , mathematics , quantum mechanics
The values for the rate coefficient of chain termination k t in the bulk polymerization of methyl methacrylate at 25°C were formally calculated (i) from the second moment of the chain‐length distribution and (ii) from the rate equation for laser‐initiated pseudostationary polymerization (both expressions were originally derived for chain‐length independent termination) by inserting the appropriate experimental data including the rate constant of chain propagation k p . These values were treated as average values, k t mand k t *, respectively. They exhibited good mutual agreement, even the predicted gradation ( k t m< k t *by about 20%) was recovered. The log‐log plot of k t vs. the average degree of polymerization of the chains at the moment of their termination v ′ yielded exponents b of 0.16–0.17 in the power‐law k t = A · v ′ −b , A ranging from 1.1 × 10 8 to 1.3 × 10 8 (L · mol −1 · s −1 ). A 70% contribution of disproportionation to overall termination has been assumed in the calculations.