Chain conformation dependent fluorescence of blue-emitting poly(arylene ether nitrile)

Poly(arylene ether nitrile) (PEN) containing phenolphthalin moiety is an intrinsically blue-emitting fluorescent polymer with outstanding mechanical and thermal properties. Herein, the fluorescent properties of the fluorescent PEN (FPEN) have been, for the first time, correlated with the conformation manipulation of polymer chain that is enabled by the variation of concentration, molecular weight, polydispersity and aggregation states in solvent-nonsolvent system. The experimental results indicate that the fluorescent emission of FPEN is highly dependent on concentration, with the strongest fluorescence detected at a critical concentration in N,N-dimethylformamide (DMF). In the lower concentration range, where the polymer intermolecular interaction is minimized, the PEN fluorescence is mainly dependent on the molecular weight and local chain organization. On the contrary, the polydispersity index of FPEN plays a dominate role in the fluorescent emission when the concentration is higher than 50 mg mL⁻¹.