Synthesis and characterization of fluorescent graft fluorene-co-polyphenol derivatives: The effect of substituent on solubility, thermal stability, conductivity, optical and electrochemical properties

A series of fluorene Schiff bases and their oligophenol derivatives were successfully synthesized using the condensation and graft copolymerization reactions, respectively. The synthesized compounds were good soluble in common organic solvents. Photoluminescence (PL) properties of the synthesized materials were determined in solution forms. As to the fluorene copolymers (FPs), higher PL intensities were obtained when compared with the monomeric models. Solvent effects on the fluorescence spectra and possible usages in spectrofluorometric ion sensors of the FPs were discussed. Optical and electrochemical band gaps of the polymers were lower than those of the Schiff bases indicating the more conjugated structures of the FPs. The oxidized states of the novel fluorene compounds were also examined by cyclic voltammetry (CV) technique. The solid state conductivity measurements showed that the synthesized FPs were semiconductors and when exposed to the iodine vapour their conductivities could be increased up to four orders of magnitude. The polymer having the lower band gap (FP-3) had also the highest undoped conductivity. Thermal characterizations of the synthesized compounds were carried out by TG-DTA and DSC methods. The initial degradation temperatures of the FPs were found quite high in the range of 220-300 °C.