Nonconventional\nFull-Color Luminescent Polyurethanes:\nLuminescence Mechanism at the Molecular Orbital Level

The study of structure–activity relationships\nis a top priority\nin the development of nontraditional luminescent materials. In this\nwork, nonconjugated polyurethanes (PUs) with full-color emission (red,\ngreen, and blue) are easily obtained by control of the diol monomer\nstructure and the polymerization conditions. Selected diol monomers\nintroduced single, double, or triple bond repeating units into the\nmain chain of the PUs, in order to understand how unsaturated bonds\nand H-bonds affect their luminescence from a molecular orbital viewpoint.\nDetailed experimental and theoretical results show that the PUs have\ndifferent temperature-dependent behaviors related to the interplay\nof H-bonding, through-space n−π interactions, and aggregation\nproperties. The potential applications of PUs in colorful displays,\ncovert information transmission, and multifunctional bioimaging have\nbeen verified. This work provides a new general protocol for the simple\npreparation of multifunctional nonconventional fluorescent polymers\nand deepens the understanding of their luminescence mechanisms.