Polyphenylenes and poly(phenyleneethynylene)s with 9,10-anthrylene subunits

Abstract

Light-emitting conjugated polyphenylenes and poly(phenyleneethynylene)s have been synthesized, which comprise of 9,10-linked anthracene repeat units with branched alkyl side-chains (2-octyldecyl) at the 2,6-positions with p-terphenyl (P1), p-diethynylbenzene (P2), and diphenylacetylene (P3) units. Both Sonogashira-Hagihara and Suzuki-Miyaura-type cross-coupling reactions under palladium catalysis were used as polycondensation methods. The branched alkyl side chains not only improve the solubility of the resulting copolymers but also prevent stacking in the solid state as evident from the almost identical PL spectra in solution and film. The copolymers P1 and P3 display pure blue emission while P2 exhibits green emission due to the extended re-system along the polymer backbone. All polymers possess high thermal stability and P1 shows the best solubility and film-forming ability among the three copolymers investigated. Furthermore, the enhanced color stability of this material is demonstrated by the almost identical PL spectra obtained on annealing at 200°C.