Conjugated ethynylene-fluorenepolymers with electro-donating TTF as pendant groups: Synthesis, electrochemical and spectroscopic properties

A series of conjugated ethynylene-fluorene polymers with electro-donating TTF as pendant groups (P2–P4) were synthesized by using Sonogashira coupling reaction, and two functionalization methods, i.e. prepolymerization and postpolymerization, were developed. The composition and purity of the corresponding products were analyzed by 1H NMR. The results proved the functionalization of P2 (pre) and P2 (post) were 40% and 100%, respectively. The results also indicated that the postpolymerization method would be a better approach to prepare TTF-pendant conjugated ethynylene-fluorene polymers. The postpolymerization methodology could be extended to synthesize other conjugated fluorene-based polymers bearing TTF units (P3 and P4). The polymers mentioned above exhibited good solubility in normal organic solvents and higher conductivity (neutral conductivity ∼2–4 × 10−6 S cm−1; doped conductivity ∼1–3 × 10−3 S cm−1). Moreover, the fluorescence intensity of P2 (post) could be modulated by the oxidation of TTF units, which makes it an attractive candidate for the fluorescence switch.