Pyrolysis–molecular weight chromatography–vapor-phase infrared spectrophotometry: An on-line system for analysis of polymers. IV. Influence of cis/trans ratio on the thermal degradation of 1,4-polybutadienes

The influence of the cis/trans ratio of 1,4-polybutadienes on the volatile products formed during temperature programmed thermal degradation to 15 percent weight loss has been investigated using a mass chromatograph (a chromatograph which directly provides mass numbers of resolved components of a mixture) and an 'on the fly' vapor phase infrared spectrophotometer. In order of amounts, major volatile products were 4-vinyl-1-cyclohexene (dimer), 1,3-butadiene (monomer), cyclopentene and 1,3-cyclohexadiene. With increasing trans content the relative quantities of 4-vinyl-1-cyclohexene decreased strongly, cyclopentene increased strongly, 1,3-butadiene decreased moderately and 1,3-cyclohexadiene increased moderately. For a high trans polybutadiene, increasing the heating rate produced relatively more monomer and dimer but less cyclopentene. Mass chromatograms from 1,4-polybutadienes which had been heated to 15 percent weight loss in their prehistory were similar to those obtained from 1,2-poly-butadiene indicating that 1,4-polybutadiene undergoes isomerization prior to degradation. Mechanisms for the fromation of the main volatile products of decomposition are discussed. (Author)