Nonconventional Luminescence of Copolymer-Containing Ureido Moieties From Blue to Green

Nonconventional luminescent polymers with nonconjugated structures have attracted much attention due to their unique photophysical properties. However, it remains a significant challenge to develop nonconventional luminescent polymers with long-wavelength emission. Herein, four types of copolymer-containing ureido moieties, exhibiting fluorescence from the blue to the green region, were synthesized via free radical polymerization. Compared to other polymers, the fluorescence of poly[(N-allylurea)-co-(itaconic anhydride)] (PNI), which has ureido moieties in its main chain and a maleic anhydride ring as a pendant group, displayed a redshift to green region with the optimal excitation and emission wavelengths of 438 and 524 nm, respectively. The as-prepared copolymers show typical characteristics of excitation- and concentration-dependent emission. Copolymer PNI demonstrates a remarkable solvatochromic effect in electron-rich solvents such as DMF and DMSO, emitting red fluorescence upon exposure to 520 nm light. Moreover, the polymethyl methacrylate (PMMA)-copolymer films are highly emissive, and their maximum quantum yields reach up to 15.8%. This work not only proposes a strategy for design luminescent materials with long-wavelength emission but also provides a deeper understanding of their fluorescence mechanism.