Synthesis and chemosensing behavior of fluorene-based alternating copolymers containing ether side chains and Si-vinylene units in the main chain

Alternating copolymerization of 9,9-bis(3,6,9-trioxadecyl)-2,7- dibromofluorene (ODFl) or 9,9-bis(3,6-dioxaheptyl)-2,7-dibromofluorene with Si containing divinyl compounds, divinyldiphenylsilane (VPS), or divinyldimethylsilane (VMS) is investigated using the Mizoroki-Heck reaction with palladium(II) acetate. The corresponding alternating copolymer is obtained in the copolymerization of ODFl with VPS. The copolymerization of ODFl with VMS yields low molecular weight oligomers. Optical properties of the ODFl-VPS copolymer have been investigated with UV-vis absorption and photoluminescence (PL) spectroscopy. The ODFl-VPS copolymer shows absorption peaks due to π-π* transition and intramolecular charge transfer through ω-π moiety at around 330 and 360-400 nm, respectively. An emission peak is observed at 450 nm in the PL spectrum of the ODFl-VPS copolymer, and the PL quantum yield is 0.19. The PL spectroscopy of ODFl-VPS copolymer is investigated in the presence of Li⁺, Na⁺, and K⁺, and the intensity of emission peak is decreased by those metal cations, especially by Na⁺.