Random copolymerization of acetylenic monomers and 1,3-dienes

Copolymerization of acetylenic monomers and 1,3-dienes was carried out by use of nickel naphthenate–diethylaluminum chloride catalyst. The molecular weight of the copolymers is rather low, and the copolymers are suitable as prepared for direct use as coating vehicles. In the system of acetylene and 1,3-dienes, the order of the copolymerization rate decreases in the following order: butadiene > isoprene > 2,3-dimethylbutadiene > chloroprene. 1,3-Dienes substituted at 1-and/or 4-position were scarcely copolymerized with acetylene. Methylacetylene and dienes tend to form cyclized copolymers. In the system of phenylacetylene and dienes, polyphenylacetylene was the main product; the copolymer was not obtained. The copolymer composition and the sequence distribution of linear copolymers were evaluated by ¹H-NMR spectra. Comparison of dyad fractions of copolymers evaluated from NMR spectra and those calculated by assuming random polymerization indicated that the copolymers of acetylene and dienes were random, and that the copolymers of methylacetylene and dienes were somewhat blocky. The coordination of monomers on the catalyst may play an important role in controlling the copolymerizability.