Increasing the semiconductor band gap of PPVs

wo distinct types of copolymers were synthesized that had a larger semiconductor band gap and a bluer absorption spectrum relative to their respective parent compounds. The first copolymer type had alternating segments of ;Type 1 copolymer: An insoluble copolymer consisting of alternating segments of stilbene and bibenzyl was synthesized from the ring-opening metathesis polymerization of (2.2) paracyclophane-1-ene. The UV-vis spectrum of a suspension of the material in o-dichlorobenzene (o-DCB) showed that the semiconductor band gap was approximately 3.3 eV. Comparison with PPV (poly(p-phenylenevinylene)) showed that the band gap had increased by 0.8 eV. It is thermally stable, showing an onset of decomposition at 500;Type 2 copolymer: Bromination followed by base induced dehydrobromination of BeCHAPPV (poly(2,5-bis(3-epi-cholestanoxy)-p-phenylenevinylene) provided a means into copolymers that contained random blocks of phenylenevinylene and phenyleneethynylene. The UV-vis showed that the semiconductor band gap could be increased up to 2.6 eV from the initial 2.2 eV of the parent polymer. A photoinduced luminescence experiment showed that the luminescence wavelength had decreased from an initial red-orange to yellow-green. All type 2 copolymers were soluble and could be solution cast on quartz, sapphire and KBr substrates. The structure of the polymers were characterized using...