Herein, we report a novel strategy for introducing a luminophore into generic polymers facilitated by mechanical stimulation. In this study, polymeric mechanoradicals were formed in situ under ball‐milling conditions to undergo radical–radical coupling with a prefluorescent nitroxide‐based reagent in order to incorporate a luminophore into the polymer main chains via a covalent bond. This method allowed the direct and conceptually simple preparation of luminescent polymeric materials from a wide range of generic polymers such as polystyrene, polymethyl methacrylate, and polyethylene. These results indicate that the present mechanoradical coupling strategy may help to transform existing commodity polymers into more valuable functional materials.

Visualization of mechanochemical damages, especially for those in the molecular-scale (e.g., bond scission in polymeric materials), is of great industrial and academic significance. Herein, we report a novel strategy for in situ and real-time visualization of mechanochemical damages in hydrogels by utilizing prefluorescent probes via oxygen-relayed free-radical trapping. Double-network (DN) hydrogels that generate numerous mechanoradicals by homolytic bond scission of the brittle first network at large deformation are used as model materials. Theoretical calculation suggests that mechanoradicals generated by the damage of the first network undergo an oxygen-relayed radical-transfer process which can be detected by the prefluorescent probe through the radical−radical coupling reaction. Such an oxygen-relayed radical-trapping process of the prefluorescent probe exhibits a dramatically enhanced emission, which enables the real-time sensing and visualization of mechanochemical damages in DN hydrogels made from brittle networks of varied chemical structures. To the best of authors' knowledge, this work is the first report utilizing oxygen as a radical-relaying molecule for visualizing mechanoradical damages in polymer materials. Moreover, this new method based on the probe post-loading is simple and does not introduce any chemical structural changes in the materials, outperforming most previous methods that require chemical incorporation of mechanophores into polymer networks.

The catalytic enantioselective nucleophilic borylation of ketimines is reported. A series of acyclic dialkyl ketimines reacted efficiently with bis(pinacolato)diboron in the presence of a copper(I)/chiral N-heterocyclic carbene catalytic system to furnish optically active α-amino tertiary boronates with high enantioselectivity (up to 99% ee). The products can be converted into peptidylboronic acid derivatives that bear bulky aliphatic substituents, compounds that are difficult to synthesize by other methods. Density functional theory calculations indicated that the enantioselectivity-determining step involves noncovalent interactions that recognize the prochiral dialkyl ketimine, leading to highly efficient enantiodiscrimination.

Herein, we report a novel strategy for introducing a luminophore into generic polymers facilitated by mechanical stimulation. In this study, polymeric mechanoradicals were formed in situ under ball‐milling conditions to undergo radical–radical coupling with a prefluorescent nitroxide‐based reagent in order to incorporate a luminophore into the polymer main chains via a covalent bond. This method allowed the direct and conceptually simple preparation of luminescent polymeric materials from a wide range of generic polymers such as polystyrene, polymethyl methacrylate, and polyethylene. These results indicate that the present mechanoradical coupling strategy may help to transform existing commodity polymers into more valuable functional materials.

A nitroxide‐based prefluorescent radical undergoes radical—radical coupling with in situ formed polymeric mechanoradicals under ball‐milling conditions to incorporate the coumarin‐based luminophore into generic polymers, as represented in the picture. By using this method, Koji Kubota, Mingoo Jin, Hajime Ito et al. prepared luminescent polymeric materials from a wide range of generic polymers without sophisticated chemical synthesis in their Research Article on page 16003.