Preparation And Aggregation Induced Emission Properties Of Polyamic Acid With Indolyl Sulfoxide As Matrix

Polyamide acid(PAA)is a kind of polymer material with amide/?-carboxyl structure.It has good flexibility and good chemical modifiability of molecular chain.By adjusting the structure of molecular chain,different luminescence properties can be realized.However,the emission intensity of traditional luminescent polymer molecules in dilute solution is rapidly weakened or even quenched under high concentration or in solid state.This phenomenon is called ACQ.This phenomenon greatly limits its application in the field of organic luminescent materials.Aggregation induced emission(AIE)is a phenomenon exactly opposite to ACQ.AIE materials have strong fluorescence emission in the state of aggregation or even in solid state,which has gradually become a research hotspot in the field of luminescent materials.Constructing polymers with AIE properties can not only give molecular systems unique AIE properties,but also retain the advantages of polymers.Therefore,the construction of AIE polyamidoic acid materials and the combination of AIE and polyamide acid,for solve the ACQ problem of traditional PAA luminescent materials have scientific and technical significance for its application in the field of organic luminescent materials.AIE polymer is usually constructed by introducing AIE small molecules into the polymer molecular chain to achieve AIE properties.In this paper,small molecules with AIE properties were synthesized by using 5-nitroindole and 4,4-difluorodiphenyl sulfone.Then,four binary copolymerized PAAs and three ternary copolymerized PAAs were obtained by condensation reaction with four dianhydride(6FDA,PMDA,HPMDA,BPDA)and mixed dianhydride respectively.Its structure and performance were characterized and analyzed,and the specific research contents and results were as follows:(1)Small molecule ID-DPS was synthesized by nucleophilic substitution reaction between 5-nitroindole and 4,4-difluorodiphenyl sulfone under alkaline conditions.In the water/DMF mixed solvent system,the luminescence intensity increased obviously when the undesirable solvent increased to form the aggregated state.It also has strong luminescence intensity in solid powder state.The small molecule,ID-DPS,has obvious AIE properties;(2)Four kinds of binary copolymerized PAA molecules were obtained by binary copolymerization reaction between diamine molecule AID-DPS and four kinds of dianhydride6FDA,PMDA,HPMDA and BPDA.The structure of PAA was characterized by Fourier exchange infrared spectroscopy.Combined with the characteristic absorption peak of PAA molecular structure,the successful synthesis of the product was confirmed.GPC test results showed that the molecular weight of the prepared PAA could reach 105 orders of magnitude,with high degree of polymerization and uniform molecular weight distribution.DSC spectra showed that the glass transition temperature of the four PAAs was higher,up to 253?,and the glass transition temperature was directly related to the flexibility of the molecular chain:the more flexible the molecular chain,the lower the glass transition temperature;The more rigid the molecular chain,the higher the glass transition temperature.The luminescence properties of the aggregated state formed in H₂O/DMF mixed solution were tested.With the increase of water content,the luminescence intensity gradually increased,showing AIE property.The four binary copolymerized PAA powder states also have strong fluorescence emission,and the fluorescence emission wavelength is related to the PAA dianhydride unit structure,the greater the degree of conjugation of molecular structure units,the more red shift of the emission wavelength.As can be seen from the luminous photos and CIE color plots,the luminous wavelength is between 465-552 nm,and the luminous color is in the range of cyan blue to yellow.(3)Three kinds of PAA molecules were obtained by terpolymer polymerization with diamine molecule AID-DPS and mixed dianhydride 6FDA-HPMDA,6FDA-PMDA and6FDA-BPDA.Ternary copolymer PAA also has a higher glass transition temperature,up to250?.Both PAA-6 and PAA-7 showed obvious AIE properties when forming aggregated state in H₂O/DMF mixed solution,but the AIE properties of PAA-5 were not obvious,which may be caused by the vibration of the six-member ring skeleton in the solution system.The three kinds of terpolymer PAA in solid state have strong emission intensity,and the emission wavelength is related to the conjugation of molecular structural units,the greater the degree of conjugation,the more red shift of emission wavelength.The luminescence wavelength ranges from 462-544 nm,which expands the overall luminescence color range of PAA materials.In summary,the obtained PAA polymer has higher molecular weight and glass transition temperature,and the PAA molecule in the aggregate state even in the solid state has a strong emission intensity,has a good AIE properties.The study of PAA material provides a new feasible scheme for its application in organic luminescent materials and flexible display.