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Difference in propagation rate constants between photo‐and thermal‐initiated polymerization of styrene – effects of light irradiation
Author(s) -
Kamachi Mikiharu,
Kajiwara Atsushi
Publication year - 1997
Publication title -
macromolecular chemistry and physics
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.57
H-Index - 112
eISSN - 1521-3935
pISSN - 1022-1352
DOI - 10.1002/macp.1997.021980310
Subject(s) - polymerization , photochemistry , styrene , photopolymer , radical polymerization , irradiation , chemistry , reaction rate constant , thermal , polymer chemistry , electron paramagnetic resonance , wavelength , radical , materials science , copolymer , kinetics , polymer , nuclear magnetic resonance , thermodynamics , organic chemistry , physics , optoelectronics , quantum mechanics , nuclear physics
Propagation rate constants ( k p ) for photo‐ and thermal‐initiated radical polymerizations of styrene were determined by electron spin resonance (ESR) spectroscopy. The k p value for the former at 70°C ((420 ± 30) M −1 · S −1 ) was more than twice as large as that for the latter ((190 ± 10) M −1 · s −1 ) although the former value was almost the same as that obtained with the pulsed‐laser polymerization method. To evaluate the origin of the difference in the k p values between photo‐ and thermal‐initiated polymerization the absorption spectrum of a model of the propagating radical was measured and both the influence of the wavelength of the irradiation light on k p values and the activation energy of the photo‐initiated radical polymerization of styrene were determined. k p decreases for wave‐lengths shorter than 370 nm and is in agreement with the k p value for thermal‐initiated polymerization. No wavelength dependence of k p was obtained for dienes whose propagating radical does not absorb above 300 nm. The difference in k p values for photo‐ and thermal‐initiated polymerizations is considered to be due to the photoactivation (photoinduced excitation) of the propagating radical of styrene.