Synthesis Of Macromolecules Containing Phosphor Structural Units And Their Recognition Mechanisms For Heavy Metal Ions

Heavy metal ions pollute the ecological environment and pose a significant risk to human life and health.The establishment of a rapid and convenient,accurate and sensitive heavy metal ion detection technology has important scientific research and practical application significance.Fluorescent sensors have the advantages of higher sensitivity,better selectivity,lower cost,easy operation and wide applicability,and gradually play an important role in the field of heavy metal ion detection.Boron-dipyrromethene（BODIPY）fluorescent dyes have easily modified structures,high molar extinction coefficients,high fluorescence quantum yields,narrow fluorescence spectral peak widths,and good photothermal stability as well as chemical stability.It is an excellent phosphor.The preparation of fluorescent sensors with low detection limits to identify specific heavy metal ions has become one of the research hotpots in the field of scientific research.The presence of a"molecular wire effect"mechanism in the conjugated polymer structure allows for amplification of the fluorescent signal and higher sensitivity compared to small molecules.However,the poor water solubility of common polymeric fluorescent sensors greatly limits their application in aqueous environments or biological systems,and it is of great significance to develop water-soluble macromolecular fluorescent sensors to meet the needs of reality.During the polymerization reaction of synthetic macromolecules,the anionic polymerization is the best choice to obtain polymers with well-defined structure and controlled molecular weight.However,the anionic polymerization conditions are difficult,Reversible Addition-Fragmentation Chain Transfer（RAFT）as a new type of controlled reactive radical polymerization,its applicable monomers are widely used,the experimental conditions are mild,and have a variety of polymerization methods,which can be replace an anionic polymerization method and can be used in a wide range of applications such as molecular design.Based on the advantages of RAFT polymerization,this paper introduces small molecule BODIPY fluorescence sensors into macromolecular chain by RAFT polymerization method,and prepared a series of macromolecular fluorescent sensors,and detects the identification of heavy metal ions.The main research contents and results are as follows:（1）Small fluorescent molecule boron-dipyrromethene（BODIPY）bearing C=C bond was synthesized first.And then,via Suzuki reaction,recognition groups were introduced into the 2,6 positions of BODIPY.Thus,a small molecule fluorescent sensor which can be used as functional monomers was prepared.Finally,methacrylic acid（MAA）was copolymerized with the as-prepared small molecular fluorescent monomers via reversible addition-fragmentation chain transfer（RAFT）polymerization methodology.Four fully-water-soluble polymer sensors with BODIPY moieties in the end of the polymer chain were obtained eventually.In the presence of long PMAA chain,and by the assistance of it,BODIPY could be dissolved totally in water.These polymer sensors exhibited sensitive and selective recognition ability to Fe³⁺.Even the content rate of BODIPY was as low as 0.5%of the polymer（calculated from element analysis）,the detection limit could reach 1.2×10^-6M.（2）We first synthesized two BODIPY fluorescent small molecules containing C=N double-bond recognition sites,one of the small molecular structures contains a thioester bond which can be used as a chain transfer agent to participate in the polymerization process,and the other contains an unsaturated C=C double bond at the Meso position.Subsequently,methacrylic acid（MAA）and methacrylamide（MAM）were used as the main monomers,respectively,and small molecules of fluorescent monomers were introduced at the end of the main chain of the polymer,and finally four large molecules of fluorescent sensors were obtained by the RAFT polymerization method.The structures of the macromolecules were determined by FTIR,¹H NMR,GPC and elemental analysis,and the morphology of the macromolecules in aqueous solution was observed by TEM,and the four macromolecular fluorescent sensors could be dissolved in pure aqueous solution.（3）The four macromolecular fluorescent sensors from Chapter 3 were tested for their metal ion recognition ability,and we found that these fluorescent sensors exhibited high sensitivity to Fe²⁺/Fe³⁺,as well as good selectivity and anti-interference.The detection limits could be as low as 2.3×10^-7 M for Fe²⁺and 4.5×10^-7 M for Fe³⁺.In conclusion,in this paper,the synthesized small molecule fluorescent sensors were polymerized with MAA or MAM as functional monomers or chain transfer agents by RAFT polymerization.Due to the existence of hydrophilic carboxyl groups and long amide bonds,these macromolecular fluorescent probes achieve the purpose of water solubility,and they can be sensitive to Fe³⁺or Fe²⁺.This study provides a new ideas and methods for the preparation of water-soluble macromolecular fluorescent sensors.