Tunable Fluorescent Emission of Copolymers with Effects of Electron-Withdrawing Groups

To development of long-wavelength emissive nonconventional luminescent polymers remains a significant challenge. Herein, nonconjugated luminescent poly[(maleic anhydride)-alt-(vinyl acetate)] (PMV) derivatives with tunable emission wavelengths are achieved through a facile anhydride ring-opening reaction by introducing electron-withdrawing monomers. As the electron-withdrawing capacity of the amine-linked groups in the monomers increases, the strong donor-acceptor (D-A) interactions form between these groups and maleic anhydride (MAh) / vinyl acetate (VAc) enhance the quantity and intensity of n-π^* and/or π-π^* interactions, which narrow the HOMO-LUMO energy gap between excited and ground states and thus result in a red fluorescent emission. PMV-CPL (CPL: caprolactam) and PMV-MAM (MAM: methacrylamide) exhibit long-wavelength emission in solid and solution states, with emission maximum at 615 and 630 nm, respectively. Especially, the micro-crosslinking effect of the double bond in PMV-NVF (NVF: N-vinylformamide) promotes the compact stacking between subunits, resulting in effective electron delocalization and sufficient conformational rigidity, achieving a quantum yield (QY) of 10.86% at 650 nm for red emission. This study also reveals the potential applications of PMV derivatives in white light-emitting diodes and light conversion films.