Amorphous Aggregation Enhanced Room Temperature Phosphorescence Emission From Naphthalimide Derivative

In recent years, organic room temperature phosphorescence (RTP) materials have been well developed. Especially, when the the organic compounds are doped into a rigid polymeric matrix, their RTP performances can be greatly enhanced. However, the dispersibility and stability of the organic compounds are difficult to be controlled. Herein, an amorphous homo-polymer (P1) containing naphthalimide units is synthesized and further dispersed into a polyvinyl alcohol (PVA) matrix via a solution mixing procedure. The resultant composites (P1@PVA) exhibit a yellow afterglow under room temperature. In P1@PVA, the naphthalimide chromophores are constrained in an amorphous aggregation state. Unlike in a crystalline state, intermolecular interactions between the amorphous aggregated chromophores are enhanced, while the π–π interaction is weakened. In the presence of PVA, the non-radiative decay can be synergistically suppressed by the external hydrogen bonds and the internal intermolecular interactions. As a results, the RTP performances of P1@PVA are much enhanced. Comparing with the PVA composites containing naphthalimide compounds, the RTP lifetime of P1@PVA is prolonged as 1.5 folds.