POLYMER REACTIONS .10. THERMAL PYROLYSIS OF POLY(ISOPRENE)

Poly(isoprene) (97% cis-1,4 and 3% 3,4) has been pyrolysed in a carrier stream of helium from 315 to 384°. The products were online identified and quantitatively analysed by an interfaced pyrolysis GC peak identification system. The first order rate constant for pyrolysis is 1.1 × 10-2 sec-1 at 384° with an overall activation energy of 41 kcal mol-1. The main products are isoprene and 1-methyl-4-isopropenyl cyclohexene. The dominant initiation process has been shown to be β chain scission leading to two allylic radicals. The former product is derived from an unzipping reaction, the latter together with 1.5-dimethyl-5-vinylcyclohexene are the main C10 products from the allylic radicals. All the other minor products can be account for by simple chain propagation reactions with or without intramolecular hydrogen transfers. © 1979.