Ma. Tlenkopatchev et al., Computional study of metathesis degradation of rubber, 2 - Distribution ofcyclic oligomers via intramolecular metathesis degradation of natural rubber, MACROMOL TH, 10(5), 2001, pp. 441-446
The results of molecular modeling of the ring distributions for the intramo
lecular metathesis degradation of natural rubber (NR) at HF/6-31G(d) level
of theory showed that in the ring-ring equilibrium participate cyclic oligo
mers containing from two to four isoprene units with all-trans cyclic isopr
ene trimer being the main product. The formation of trans,trans,trans- 1,5,
9-trimethyl-1,5,9-cyclododecatriene from larger rings is thermodynamically
favored, According to the calculations, the ring-ring equilibrium for the i
ntramolecular metathesis degradation of cis-polybutadiene (cis-PB) is compl
etely shifted towards the all-trans cyclic butadiene trimer. These results
are in reasonable agreement with recent experimental data.