Biocompatible Aliphatic-Terpolymers via In Situ Fluorescent Monomers for Three-in-One Applications: Polymerization of Hydrophobic-Monomers in Water

: Biocompatible, nonconventional, multifunctional, purely-aliphatic, light-emitting terpolymers, i.e., acrylonitrile-co-3-(N-isopropylacrylamido)propanenitrile-co-N-isopropylacrylamide (AN-co-NIPAMPN-co-NIPA, 1) and acrylonitrile-co-3-(N-hydroxymethylacrylamido)propanenitrile-co-N-hydroxymethylacrylamide (AN-co-NHMAMPN-co-NHMA, 2), were designed and synthesized via N-H functionalized C-C + N-C coupled in situ protrusions/ grafting of fluorophore-monomers, i.e., NIPAMPN and NHMAMPN, in solution-polymerization of highly-hydrophobic two non-emissive monomers in water. These scalable-and-reusable 1 and 2 were suitable for high-performance three-in-one applications, such as Fe(III)-sensor, imaging in Madin-Darby canine kidney (MDCK) and human lung cancer (A549) cells, and security-ink. The structures of 1 and 2, N-C coupled in situ attachments/ grafting of third fluorophore-monomers, grafting events, and aggregation-enhanced emissions (AEEs) were understood via 1H and 13C NMR, X-ray photoelectron spectroscopy (XPS), Fourier transform infrared (FTIR) spectroscopy, ultraviolet-visible (UV-vis) spectroscopy, thermogravimetric (TG) analysis, high-resolution transmission electron microscopy (HRTEM), dynamic light scattering (DLS), fluorescence imaging, and fluorescence lifetime. The geometries, electronic structures, and absorption/ emission properties of 1 and 2 at optimized compositions were examined via density functional theory (DFT), time-dependent DFT (TDDFT), and natural transition orbital (NTO) analyses. The limits of detection were 3.20 x 10-7 and 1.37 x 10-7 M for 1 and 2, respectively. The excellent biocompatibility of 1 and 2 were understood from >95% retention of MDCK and A549 cell-morphologies.