All-trans oligomers of 2,5-dialkyl-1,4-phenylenevinylenes - metathesis preparation and characterization

Oligomers of 2,5-dialkyl-1,4-phenylenevinylenes (DR-OPV, R = C4H9, C7H15, C10H21 and C6H11 (CyH) were prepared via metathesis polycondensation of the respective 2,5-dialkyl-1,4-divinylbenzenes. The synthesis of the monomers is described. The highly active metal-alkylidene complex Mo(NArMe2) (CHCMe2Ph)[OCMe(CF3)(2)](2)(Ar-Me2 = 2,6-dimethylphenyl) serves as a catalyst. The degree of polymerization can be controlled by variation of the solvent and by the length of the side chains, since the reaction proceeds as a precipitation polycondensation. The DR-OPVs are bilious-green products and, depending on the molecular weight, soluble in various solvents like toluene, THF and CHCl3. The solutions are highly fluorescent and coloured. The DR-OPVs have vinylic end groups. The vinylene double bonds are of all-trans configuration. Due to their rigid-rod structure, the DR-OPVs synthesized have a distinct tendency to crystallize in a highly ordered state, forming a sanidic layer structure.