Direct laser writing of poly(phenylene vinylene) on poly(barrelene)

The ring-opening metathesis polymerization of barrelene (bicyclo[2.2.2]octa-2,5,7-triene) is described. The monomer was synthesized using an optimized route and characterized, for the first time, using X-ray diffraction analysis of a coordination complex. The solubility of poly(barrelene) was found to correlate with the ratio of cis to trans exocyclic vinylenes in the polymer backbone. Copolymers of barrelene and norbornene were also prepared and used to obtain robust films. The barrelene-containing polymers underwent spontaneous dehydrogenation under air or upon being subjected to laser pulses to afford poly(phenylene vinylene). A series of well-defined patterns with micrometer dimensions were created by direct laser writing on films of poly(barrelene-co-norbornene) and visualized by the fluorescence of the conjugated polymer that formed upon irradiation.