Polyfluorene Derivatives with Hydroxyl and Carboxyl Substitution: Electrosynthesis and Characterization

Novel high-quality poly(9-hydroxyfluorene) (PHF), poly(9-fluorenecarboxylic acid) (PFCA), and poly(9-hydroxyl-9-fluorenecarboxylic acid) (PHFCA) films can be easily electrodeposited by low-potential anodic oxidation of fluorene derivatives, which contain either the electron-withdraw in g carboxyl group (-COOH) or the electron-donating hydroxyl group (-OH), using a midstrength Lewis acid boron trifluoride diethyl. etherate (BFEE) as the solvent and supporting electrolyte. The complexing reaction between the -COOH or -OH groups at the C(9) position of these fluorene derivatives and BFEE increased the ionic conductivity of the BFEE system as an electrolyte significantly. The C-13 NMR spectra clearly demonstrates that the chemical shift of carbons at the C(9) and C(14) positions has made a low-field shift. This change in the chemical shift of the carbon atoms confirms the formation of complexion cations when FCA or HFCA was mixed with BFEE. The as-formed polymer films showed good redox behavior and thermal stability. FTIR, H-1 NMR, and theoretical investigations indicated that the polymerization of HF, FCA, and HFCA monomers occurred mainly at the C(2) and C(7) positions. The fluorescence properties of the polymers were greatly improved in comparison with those of the monomers, implying that those polymers were good blue light emitters. SEM results indicated that PHF film is a nanomaterial.