Alkyne metathesis with simple catalyst systems: Efficient synthesis of conjugated polymers containing vinyl groups in main or side chain

The synthesis of novel conjugated polymers by acyclic diyne metathesis (ADI MET) is reported. These polymers are hybrids between poly(p-phenylenevinyle ne) and poly(p-phenyleneneethynylene) (PPE). They contain phenylene, ethyny lene, and vinylene groups (-=-Ph-=-Ph-, PPVE). Simple in situ catalysts for med from Mo(CO)(6) and 4-chlorophenol were used to metathesize the dipropyn yl(tetraalkyl)stilbene monomers. The monomers are made by a combination of Horner reactions and Heck-type couplings. The PPVEs form in high yields and are structurally defined. They show degrees of polymerization (P-n) of 30- 220 repeating units (i.e. 60-450 benzene rings), demonstrating that the pre sence of the double bonds does not interfere with alkyne metathesis. The PP VEs were structurally characterized by XRD and electron microscopy. They sh ow fibrillar and network-type morphologies, which should make them interest ing for applications in molecular electronics. Solid samples of PPVEs displ ay powder XRD patterns almost identical to those of the PPEs. PPVEs thus as sume similar doubly lamellar structures as the PPEs. The aggregation behavi or of PPVEs was studied. In addition, ADIMET to a poly(2,7-fluorenyleneethy nylene) carrying unsaturated side chains is reported. In this case the pres ence of unsaturation does neither interfer with efficient alkyne metathesis .