Morpholine-modified polyacrylamides with Polymerization-Induced emission and its specific detection to Cu2+ ions

Abstract

In this work, three morpholine-modified polyacrylamide derivatives (MMPAm) were successfully prepared by free radical polymerization of monomers with morpholine moiety. The intramolecular aggregation of morpholine rings on macromolecular backbone gives MMPAm a significant polymerization-induced emission (PIE). Particularly, poly(N-morpholine acrylamide) (PNMPA) has the characteristics of strong fluorescence at 450 nm, and its fluorescence quantum yield reaches 2.87 %. The introduction of morpholine moiety, the length of CH2 spacer between morpholine ring and the backbone and the molecular weight play the important roles in PIE properties of PNMPA. Interestingly, PNMPA can recognize and detect Cu2+ specifically even in the presence of 12 other metal ions by thorough fluorescence quenching, and the detection limit of PNMPA is 17.3 μM. Furthermore, the dynamic quenching of PNMPA by Cu2+ ions and the complexation ratio of 1:2 according to JOB's working diagram were confirmed by fluorescence titration. Under the assistance of EDTA, a reversible detection system for Cu2+ is achieved, and a portable test paper from PNMPA for the detection of Cu2+ was also made. In conclusion, PNMPA is endowed with a significant PIE effect by the intramolecular aggregation of morpholine rings along the backbone in the polymerization of non-fluorescent monomer, and is expected to be a promising material for specific detection to Cu2+ ions.