Restricted Molecular Rotation and Enhanced Emission in Polymer Blends of Poly(fluorene-alt-naphthol) and Poly(vinyl pyrrolidone) with Mutual Hydrogen-Bond Interactions

Abstract

In this study, fluorescent alternative copolymer poly(fluorene-alt-1,6-naphthol) (PFN) with inherent hydroxyl (OH) groups was blended with poly(vinyl pyrrolidone) (PVR) through facile hydrogen-bond (H-bond) interactions. The emission intensities of the resultant PFN/PVR mixtures of different compositions were shown to increase with increasing PVR content in both the chloroform solution and in the solid film states. The H-bond interactions between PFN and PVR resulted in the restricted molecular rotations of the fluorophores, which lead to the blockage of nonradiative energy decay channels and the accompanied emission enhancement. With the efficient H-bond interactions, the PFN/PVR blend with the low content (2.33 wt %) of fluorescent PFN component actually has a high quantum efficiency of 0.93, comparatively higher than other blends containing higher fluorescent PFN. The role of the H-bonding on the restricted molecular rotations of the PFN/PVR blends was therefore evaluated by the infrared, the 1H NMR sp...