Polymerization of cis‐ and trans‐8‐oxabicyclo[4.3.0]nonane

The polymerization of cis‐ and trans‐8‐oxabicyclo[4.3.0]nonane in bulk was investigated with PF5 as initiator. The trans‐isomer polymerizes very readily to high polymers (M̄w up to 200 000), whereas the cis‐isomer under identical conditions fails to polymerize. This difference in behavior is attributed mainly to the fact that the strain in the trans‐isomer is much higher than in the cis‐isomer. The polymerization results with the trans‐isomer for the temperature interval of −25 to 75°CC are interpreted in terms of propagation/depropagation reactions via an oxonium ion mechanism and a concurrent chain breaking reaction which is noticeable by the decrease in molecular weight with time. The polymerization systems are not reversible with changing temperature and the data indicate that at the upper end of the temperature interval there is a deactivation, which was investigated. Copolymerization of the cis‐ and trans‐isomers shows that the cis‐isomer is reactive in the presence of the trans‐isomer. The molecular weight of the polymers decreases with increasing cis‐isomer content in the feed.