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Kinetics of Bulk Free‐Radical Polymerization of Butyl Methacrylate Isomers Studied by Reaction Calorimetry
Author(s) -
VictoriaValenzuela David,
HerreraOrdonez Jorge,
ArcosCasarrubias Antonio,
VazquezTorres Humberto
Publication year - 2018
Publication title -
macromolecular reaction engineering
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.37
H-Index - 32
eISSN - 1862-8338
pISSN - 1862-832X
DOI - 10.1002/mren.201700046
Subject(s) - monomer , methacrylate , differential scanning calorimetry , polymer chemistry , chemistry , steric effects , polymerization , radical polymerization , kinetics , polymer , thermodynamics , organic chemistry , physics , quantum mechanics
The kinetics of bulk free‐radical polymerizations of n ‐butyl methacrylate ( n ‐BMA), iso ‐butyl methacrylate ( i ‐BMA), and tert ‐butyl methacrylate ( t ‐BMA) are studied by differential scanning calorimetry and with the aid of a mathematical model previously reported by the authors. In all the cases, the rate of polymerization ( R p ) evolution curve exhibits a minimum at low conversions and the characteristic maximum of the autoacceleration effect. It is found that the monomer conversion x min at which the minimum is observed, follows the order n ‐BMA > i ‐BMA > t ‐BMA and that for monomer conversions ( x ) smaller than x min , the termination rate coefficient ( k t ) shows a plateau. According to the model results it is obtained that for x > x min , the termination reaction is chemically controlled whereas for x > x min , it is diffusion‐controlled and that the x min values are related to the value of the termination rate coefficient of the chemical step ( k t0 ) of every isomer, which is highly influenced by the steric hindrance of the alkyl substituent group.