<i>In Situ</i> Generation of <i>N</i> -Heteroaromatic Polymers: Metal-Free Multicomponent Polymerization for Photopatterning, Morphological Imaging, and Cr(VI) Sensing

The electron-deficient N-heteroaromatic polymers are crucial for the high-tech applications of organic materials, especially in the electronic and optoelectronic fields. Thus, the development of new polymerizations to afford adaptable electron donating-accepting scaffolds in N-heteroaromatic polymers is in high demand. Herein, metal-free multicomponent polymerizations of diynes, diamines and glyoxylates are successfully developed for in-situ generation of poly(quinoline)s with high molecular weights (Mw up to 16 900) in nearly quantitative yields. By tuning the electron distributions of the polymer backbones, the resulting poly(quinoline)s show various aggregation-induced behaviors and photo-responsive abilities. The thin films of poly(quinoline)s can be readily fabricated into well-resolved photopatterns by photolithography techniques. They can be utilized as fluorescent probes to directly visualize the morphologies of polymer materials including spherulites and microphase separation of polymer blends. Their nanoparticles demonstrate sensitive and highly selective fluorescence quenching to hexavalent chromium ion Cr(VI), which provides access for the biological imaging of Cr(VI) in unicellular algae.