Diels‐Alder polymers. III. Polymers containing phenylated phenylene units

The Diels‐Alder reaction of biscyclopentadieneones with diacetylenes produces colorless, soluble, phenylated polyphenylenes of high molecular weight (M̄ n ≃ 40,000) in nearly quantitative conversions. The polymers are noncrystalline, form clear films, and are stable in air to 550°C. Under nitrogen, the polymers lost approximately half the phenyl groups attached to the phenylene main chain to give brown‐black insoluble polyphenylenes of very low crystallinity.