Synthesis Of Acid-base Responsive Water-soluble Fluorescent Polymer And Detection Of Fe³⁺

In recent years,with its advantage of obtaining quickly and efficiently fluorescence detection technology in water,the research of fluorescent polymers with acid-base responsivenes will always be one of the hot topics in the study.In this thesis,two water-soluble fluorescent polymers with acid-base responsiveness are synthesized:one is P（B4-co-NIPAM）that is obtained by copolymerization of a naphthalene diimides derivative and N-isopropylacrylamide（NIPAM）;the other is PManEMA-b-TPE-NH₂（P2）.The tetraphenylethylene derivative（TPE-NH₂-BIBB）is used as an initiator,the mannose derivative is a monomer（M2）,and the polymer PAcManEMA-b-TPE-NH₂（P1）is prepared by atom transfer radical polymerization（ATRP）,and the acetyl group is removed to obtain the water-soluble polymer P2.The main contents and results of the thesis are as follows:1.Fluorescent compound（B4）is synthesized with 5-amino-1-pentanol and2,6-dibromonaphthalene-1,4,5,8-tetracarboxylic dianhydride by a series of reactions.And polymer P（B4-co-NIPAM）with acid-base responsivenes properties is prepared by radical copolymerization using B4 and NIPAM as monomers.The absorption peaks are located at446 nm and 473 nm of P（B4-co-NIPAM）in water（H₂O）,ethanol（EtOH）,dimethyl sulfoxide（DMSO）and N,N-dimethylformamide（DMF）,and the fluorescence intensity is weak.The absorption peaks are located at 397 nm,419 nm and 443 nm in tetrahydrofuran（THF）,while in dichloromethane（DCM）,the absorption peaks appeared at 400 nm,423 nm,449 nm and519 nm,and fluorescence emission peaks are showed at 457 nm and 487 nm when P（B4-co-NIPAM）is dissolved in THF or DCM.The effect of adding acid or base on fluorescence intensity is less obvious when P（B4-co-NIPAM）is dissolved in H₂O,EtOH and DMSO,however,adding acid or base greatly affects fluorescence properties when P（B4-co-NIPAM）is dissolved in DMF,THF and DCM.In THF,the fluorescent color of P（B4-co-NIPAM）is still blue-green after adding trifluoroacetic acid（TFA）,but fluorescent color turns red after adding triethylamine（TEA）into P（B4-co-NIPAM）.In DCM,the fluorescent color of P（B4-co-NIPAM）is blue-green and orange-yellow after adding TEA and TFA into P（B4-co-NIPAM）,respectively.2.The initiator of atom transfer radical polymerization（ATRP）reaction TPE-NH₂-BIBB is synthesized using the starting material of 4-aminobenzophenone by a series of reactions,polymer P1 is synthesized using TPE-NH₂-BIBB and M2 as initiator and monomer respectively,P2 is obstained by removing acetylation protection of P1.A series of characterizations of P2 show that the critical micelle concentration of P2 is about 7.08×10^-6mol/L.The fluorescence emission peak of P2 is blue-shifted with increasing of HCl concentration,and fluorescence intensity of P2 decreases with increasing of NaOH concentration,which shows that P2 has acid-base response performance.3.The fluorescence of the P2 aqueous solution can be quenched by Fe³⁺.The lower limit of detection of P2 to Fe³⁺is 2×10^-66 mol/L,when the concentration of P2 and Fe³⁺are 8×10^-6mol/L and less than 1×10^-5 mol/L,respectively.The fluorescence intensity of P2 decreases with the time increased of Fe³⁺,and balanced about 100 s.The interaction mechanism of P2and Fe³⁺is obtained by UV-vis,PL and dynamic light scattering analysis:When Fe³⁺is added into compound TPE-2NH₂ and P2 solution respectively,amino group of TPE-2NH₂ and P2complexed with Fe³⁺,and some coordination sites of Fe³⁺are occupied by water,which increased the water solubility of TPE-2NH₂ and P2 and reduced aggregation action leading to fluorescence quenching.NaOH solution and L-cysteine hydrochloride are added to the solution containing Fe³⁺respectively,the fluorescence intensity of P2 is enhanced.H₂O₂ is added to the solution containing Fe²⁺respectively,the fluorescence intensity of P2 is weakened.These results are proved that the selective response of P2 to Fe³⁺is reversible.In this thesis,two water-soluble fluorescent polymers P（B4-co-NIPAM）and P2 withacid-base responsiveness are successfully synthesized.P（B4-co-NIPAM）has a unique acid-base responsiveness and is expected to be applied to acid-base indicators.Because P2has good selectivity,high sensitivity and excellent reversibility to Fe³⁺,it can be used as a fluorescent probe to detect the fluorescence quenching of Fe³⁺.Therefor,P2 has potential application prospects in the fields of chemical sensors and ion detection.