Nontraditional Redox Active Aliphatic Luminescent Polymer for Ratiometric pH Sensing and Sensing‐Removal‐Reduction of Cu(II): Strategic Optimization of Composition

Abstract

Abstract Here, redox active aliphatic luminescent polymers ( ALP s) are synthesized via polymerization of N , N ‐dimethyl‐2‐propenamide (DMPA) and 2‐methyl‐2‐propenoic acid (MPA). The structures and properties of the optimum ALP3 , ALP3 ‐aggregate and Cu(I)‐ ALP3 , ratiometric pH sensing, redox activity, aggregation enhanced emission (AEE), Stokes shift, and oxygen‐donor selective coordination‐reduction of Cu(II) to Cu(I) are explored via spectroscopic, microscopic, density functional theory‐reduced density gradient (DFT‐RDG), fluorescence quenching, adsorption isotherm‐thermodynamics, and electrochemical methods. The intense blue and green fluorescence of ALP3 emerges at pH = 7.0 and 9.0, respectively, due to alteration of fluorophores from –C(═O)N(CH 3 ) 2 / –C(═O)OH to –C(O − )═N + (CH 3 ) 2 / –C(═O)O − , inferred from binding energies at 401.32 eV (–C(O − ) ═N + (CH 3 ) 2 ) and 533.08 eV (–C(═O) O – ), significant red shifting in absorption and emission spectra, and peak at 2154 cm −1 . The n − π * communications in ALP3 ‐aggregate, hydrogen bondings within 2.34–2.93 Å (intramolecular) in ALP3 and within 1.66–2.89 Å (intermolecular) in ALP3 ‐aggregate, respectively, contribute significantly in fluorescence, confirmed from NMR titration, ratiometric pH sensing, AEE, excitation dependent emission, and Stokes shift and DFT‐RDG analyses. For ALP3 , Stokes shift, excellent limit of detection, adsorption capacity, and redox potentials are 13561 cm −1 /1.68 eV, 0.137 ppb, 122.93 mg g −1 , and 0.33/−1.04 V at pH 7.0, respectively.