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Propagation Kinetics of Free‐Radical Methacrylic Acid Polymerization in Aqueous Solution. The Effect of Concentration and Degree of Ionization
Author(s) -
Beuermann Sabine,
Buback Michael,
Hesse Pascal,
Kukučková Silvia,
Lacık Igor
Publication year - 2007
Publication title -
macromolecular symposia
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.257
H-Index - 76
eISSN - 1521-3900
pISSN - 1022-1360
DOI - 10.1002/masy.200750203
Subject(s) - polymerization , chemistry , ionization , methacrylic acid , aqueous solution , degree of polymerization , ionic bonding , monomer , dissociation (chemistry) , arrhenius equation , ionic strength , poly(methacrylic acid) , radical polymerization , polymer chemistry , analytical chemistry (journal) , polymer , chromatography , organic chemistry , ion , activation energy
Abstract Propagation rate coefficients, k p , of free‐radical methacrylic acid (MAA) polymerization in aqueous solution are presented and discussed. The data has been obtained via the pulsed laser polymerization – size‐exclusion chromatography (PLP‐SEC) technique within extended ranges of both monomer concentration, from dilute solution up to bulk MAA polymerization, and of degree of ionic dissociation, from non‐ionized to fully ionized MAA. A significant decrease of k p , by about one order of magnitude, has been observed upon increasing monomer concentration in the polymerization of non‐ionized MAA. Approximately the same decrease of k p occurs upon varying the degree of MAA ionization, α , at low MAA concentration from α = 0 to α = 1. With partially ionized MAA, the decrease of k p upon increasing MAA concentration is distinctly weaker. For fully ionized MAA, the propagation rate coefficient even increases toward higher MAA concentration. The changes of k p measured as a function of monomer concentration and degree of ionization may be consistently interpreted via transition state theory. The effects on k p are essentially changes of the Arrhenius pre‐exponential factor, which reflects internal rotational mobility of the transition state (TS) structure for propagation. Friction of internal rotation of the TS structure is induced by ionic and/or hydrogen‐bonded intermolecular interaction of the activated state with the molecular environment.