Synthesis and properties of fluorene or carbazole-based alternating copolymers containing Si and vinylene units in the main chain

Abstract

Alternating copolymerization of 9,9-dihexyl-2,7-dibromofluorene (HF1), N-hexyl-2,7-dibromocarbazole (2,7-HCz) or N-hexyl-3,6-dibromocarbazole (3,6-HCz) with Si-containing divinyl or diallyl compounds, divinyldimethylsilane, divinyldiphenylsilane, 1,3-divinyltetramethyldisiloxane, 1,4-bis(dimethylvinylsilyl)benznene, diallyldimethylsilane, or diallyldiphenylsilane has been investigated using Mizoroki-Heck reaction with a Pd catalyst. The corresponding alternating copolymers were obtained in good yield. The alternating copolymers from HF1 or 2,7-HCz showed good solubility in typical organic solvents. On the other hand, the copolymer with 3,6-HCz became insoluble due to the crosslinking. Photophysical properties of the resulting copolymers were investigated with UV-vis absorption and photoluminescence spectroscopy. All the copolymers showed absorption peak derived from π-π* transition at around 340 nm, which was blue shifted in comparison with that of the corresponding homopolymer. Whereas emission peaks of the copolymers of the cast film were red shifted in comparison with that of the homopolymers. Multiple broad absorption peaks, which would be derived from intramolecular charge transfer through σ-π moiety, were also detected in the range from 390 to 450 nm in the spectra of the copolymers containing Si-vinylene unit.