Synthesis Of Amphiphilic Fluorescent Polymer Based On Polyethyleneimine And Its Application In Ion Detection

Environmental problem have always been the focus of social attention,because they are closely related to human health.Water pollution caused by excessive metal ions is particularly concerned.In this paper,an amphiphilic fluorescent polymer PEI-BP and fluorescent hydrogel PEI-BP@PEGMA are synthesized for the detection of metal ions.The specific work is as follows:1.The amphiphilic fluorescent polymer PEI-BP was synthesized by Schiff base reaction using PEI（polyethyleneimine）and BP（benzophenone）as raw materials.Its structure and properties were characterized by infrared spectroscopy（IR）,nuclear magnetic resonance（NMR）,ultraviolet spectroscopy（UV）and fluorescence spectroscopy（FL）,and the result demonstrated that the PEI-BP amphiphilic polymer was successfully synthesized.At the same time,basing on the amphiphilic characteristics of PEI-BP,the self-assembly process was explored by FL,scanning electron microscope（SEM）,dynamic lighting scanning（DLS）,Zeta potential and other technologies,and when the concentration of PEI-BP was higher than 0.01 mg/m L,PEI-BP would automatically form micelles.Under SEM,the micelles were round and regular with an average particle size of 70 nm.In addition,the changes in the Zeta potential of the PEI-BP solution under different pH conditions ranging from 1 to 14indicated that it was relatively stable under acidic conditions and unstable under strong alkaline conditions;2.The responsiveness of fluorescent polymer PEI-BP to metal ions was studied.The PEI-BP sloution had good environmental stability at different pH（2～8）and temperature（25～45℃）due to the large number of conjugated structures in the polymer.The introduction of imine bond further improved its binding ability with metal ions.Basing on this ability,we developed a metal ion sensor.The sensor had good stimulus responsiveness to Co²⁺,Cu²⁺and Fe³⁺.The detection limits for Co²⁺,Cu²⁺and Fe³⁺were 6.97μM,6.43μM and 4.93μM,respectively,and the response time was fast.Under the coexistence of other ions,PEI-BP had good anti-interference.In addition,through the experiments of fluorescence lifetime and UV absorption spectra,we believed that the principle was:metal ions interacted with the excited state of the fluorophore and collide,resulting in the steady-state fluorescence intensity and fluorescence lifetime changed.3.Using polyethylene glycol methyl acrylate（PEGA）,2-methoxyethyl acrylate（MEA）and acrylic acid（AA）as raw materials,combined with the amphiphilic fluorescent polymer,a fluorescent hydrogel called PEI-BP@PEGMA was successfully synthesized.PEI-BP@PEGMA had good stability under different pH（1～7）conditions.The hydrogel has good selectivity for Fe³⁺,and the detection limit for Fe³⁺was 8.22μM.In addition,it had good anti-interference ability under the coexistence of other ions.The swelling ratio,adsorption performance and adsorption kinetics of the PEI-BP@PEGMA was also studied.However,due to the pore structure of the original hydrogel being occupied by fluorescent molecules,it was impossible to enter the gel through diffusion and only interacted with the surface.The combination of the gel and fluorescent molecules leaded to decrease in adsorption capacity.