%0 Journal Article
%A Phelan, Marisa
%A Aldabbagh, Fawaz
%A Zetterlund, Per B.
%A Yamada, Bunichiro
%D 2005
%T Mechanism and Kinetics of the Free Radical Ring-Opening
Polymerization of Eight-Membered Cyclic Allylic Disulfide Monomers
%U https://acs.figshare.com/articles/journal_contribution/Mechanism_and_Kinetics_of_the_Free_Radical_Ring_Opening_Polymerization_of_Eight_Membered_Cyclic_Allylic_Disulfide_Monomers/3295243
%R 10.1021/ma047894i.s001
%2 https://ndownloader.figshare.com/files/5132980
%K Polymerization rates
%K monomer
%K polymerization rates
%K methyl substituents
%K 2 M
%K rate coefficients
%K Monomer 1 b polymerized
%K Arrhenius parameters
%K fragmentation step
%K k p
%K k t
%K propagation rate
%K ceiling temperature
%K High concentrations
%X Remote methyl substituents were found to have a significant effect on the free radical ring-opening polymerization of cyclic allylic eight-membered disulfide monomers. High concentrations of
initiator were required to achieve reasonable polymerization rates for the monomer with a greater number
of methyl substituents, 2,2,4-trimethyl-7-methylene-1,5-dithiacyclooctane (1b). Monomer 1b polymerized
significantly slower than the analogous monomer containing only one 2-methyl substituent, 2-methyl-7-methylene-1,5-dithiacyclooctane (1a). Values of kp/kt0.5 (kp and kt are the rate coefficients for propagation
and termination, respectively) for both monomers were obtained at 30−120 °C. Examination of the
Arrhenius parameters for propagation revealed that the fragmentation step appeared to exert a greater
influence on the overall propagation rate for 1a. Polymerization rates were influenced by depropagation
at the relatively low temperatures of 50−60 °C (1a) and 70−85 °C (1b), and both monomers exhibited
the same ceiling temperature of approximately 125 °C at [M]0 = 2 M in benzene.
%I ACS Publications