MOLECULAR-DYNAMICS OF INITIAL EVENTS IN THE THERMAL-DEGRADATION OF POLYMERS

Computer simulations, based on molecular dynamics, were used to investigate the kinetic stability of model polymers as a function of temperature, secondary structure, and molecular weight. The rate constants for random scission of the carbon-carbon bonds were obtained from simulations starting from both planar zigzag and coiled conformations. The coiled polymers were found to be more stable than planar zigzag polymers with the same primary structure. The computer-generated rates correlated reasonably well with the functional predictions of the Rice, Ramsperger, and Kassel theory of unimolecular reactivity; however, deviations were observed for some of the short-chained polymers. Computer movies revealed pronounced coiling in the vicinity of dissociating bonds. This behavior was examined in light of proposed mechanisms for intramolecular hydrogen transfer.