First hydrogen-bonding-induced self-assembled aggregates of a polyfluorene derivative

A convenient approach to a novel polyfluorene derivative (PI) with hydrogen-bonding interactions and another derivative P2 without hydrogen-bonding interactions has been developed. The structure of polymers PI and P2 is verified by FT-IR, ¹H and ¹³C NMR, and elemental analysis. The investigation demonstrates that the intramolecular and intermolecular H-bonding interactions play an important role in the optical properties of PI in the dilute solution and in films. PI emits different light in dilute solutions (blue color) and in solid states (yellowish-orange) under the irradiation of UV light. The time-resolved PL decay dynamics also demonstrate the existence of such interactions in PI. However, this phenomenon is not observed in another polymer (P2) without hydrogen-bonding interactions. The scanning electron microscopic (SEM) results of PI at solid states reveal the formation of entangled nanostructures induced though the hydrogen-bonding interactions. Therefore, the investigation shows that the interaction between the nitrogen and the hydroxy group at the 9-position effectively affects the optical properties of PI, which might provide a new approach to control over molecular ordering through interchain interactions, especially the hydrogen bonding.