One-Step Synthesis of Low Molecular Weight Poly(p-phenyleneethynylenevinylene)s via Polyaddition of Aromatic Diynes by Catalysis of the [Ru(p-cymene)Cl2]2/AcOH System

Conjugated low molecular weight polymers characterized by regio- and stereoregular alternation of phenylene and (E)-1-en-3-yne moieties have been synthesized by polyaddition of 1,4-diethynylbenzene or of 2,5-diethynyl-1,4-alkoxybenzene monomers, employing the commercially available di-mu-chlorobis[(p-cymene)chlororuthenium(II)] complex as the metal catalyst source, under homogeneous, atom-economical, amine- and phosphine-free conditions. Bulk materials of poly(p-phenyleneethynylenevinylene) derivatives are obtained with yields larger than 80%, from which polymers readily soluble in chlorinated solvents and in tetrahydrofuran are extracted in 60-75% yields. The polymers with average degrees of polymerization in the range n(AV) = 4-8 display optical properties in solution similar to those of the higher molecular weights analogues.