Substituent effects on Bergman cyclopolymerization kinetics of bis-ortho-diynylarene (BODA) monomers by dynamic scanning calorimetry

Bis-ortho-diynylarene (BODA) monomers polymerize thermally via the Bergman cyclization and diradical intermediates. The structure reactivity relationships of eight BODA monomers and their kinetics were studied by differential scanning calorimetry (DSC). The spacer (X=C(CF3)2, C(CH3)2, O, a bond) groups and alkyne terminal (R=Ph, Si(CH3)3, iso-propanol, pyridine, thiophene) groups were varied and the effect on polymerization rate was determined. Among the phenyl-terminated monomers, only the isopropylidene spacer group imparts a significant increase on the cure onset temperature and the activation energy. However, the terminal (R) groups play a significant role in polymerization rate of BODA monomers.