%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