Study of molecular weight and configurational stability of substituted polyacetylenes

Complexes [Rh(cycloolefin)(acac)] (cycloolefin = norborna-2,5-diene, cycloocta- 1,5-diene and cyclooctatetraene) were investigated as catalysts of polymerization of monosubstituted acetylenes into stereoregular cis-transoid polyacetylenes. All complexes were highly active in arylacetylenes polymerizations in both coordinating and non-coordinating solvents. Selection of solvent and cycloolefin ligand of the catalyst allowed the control over polymer MW. The onset of initiation in the [Rh(cycloolefin)(acac)]/monomer systems proceeded as the proton transfer from the monomer molecule to the acac ligand under the release of acetylacetone and coordination of -C≡CR ligand to Rh(cycloolefin) moiety. Cis-transoid poly(phenylacetylene) and poly[(2,4-difluorophenyl)acetylene]s with required initial MW were prepared with these catalysts and submitted to the long-term ageing in which the polymers were exposed to the atmosphere and diffuse daylight either dissolved in tetrahydrofuran or in the solid state. Tightly connected processes of cis-to-trans isomerization of the polymer main-chains double bonds and oxidative degradation were found to proceed during polymers ageing in the solution. Besides, the formation of corresponding cyclotrimers accompanied the polymers ageing. However, the cyclotrimers amount was too..