The Synthesis Of Diamine Monomer Containing Fluorene Structure And Its Application In Polyimides

Polyimides(PI)is considered to be one of the best choice for flexible OLED(FOLED)substrate or packaging materials due to its outstanding properties,such as thermal stability,dimensional stability and so on.However,the barrier properties of PI materials can not reach the requirements of FOLED package,which limits its application as FOLED substrate and packaging materials.However,PI has a strong structure design,which provices the possibility for preparation of high barrier PI materials.In this paper,with characteristics of rigid plane of fluorene structural unit as the center,three diamine monomer containing rigid plane fluorene structure were designed through the rational sesign of molecule.The three diamine monomer(FDA,FPDA and FMPDA)were synthesized vis Suzuki coupling reaction and reduction reaction,and their structure and properties were characterized by low resolution mass spectrometry(MS),nuclear magnetic resonance(NMR),infrared spectroscopy(FT-IR),differential scanning calorimetry(DSC)and thermal gravimetric analysis(TGA).The homogeneous and viscous polyamide acid(PAA)glue was obtained by condensation reation of diamine monomers containing fluorene structure and pyromellitic dianhydride(PMDA).Then corresponding three PI films containing fluorene structure(FPI,FPPI and FMPPI)were prepered by thermal imidization.The structure and properties of PI films were characterized and the effect of rigid plane structure on the structure and properties of PI films was study systematically by FT-IR,wide angle X-ray diffraction(WAXS),density test,positron annihilation test(PALS),oxygen permeation rate determination instrument,DSC,synamic thermal mechanical analysis(DMA),thermal mechanical analysis(TMA),thermal gravimetric analysis(TGA),mechanical property test and atomic force microscope(AFM).The result showed that: three diamine monomer containing fluorene structure with rigid plane was successfully synthesized,and the polyimidefilm containing fluorene structure were obtained.The planer structure can give the polymer molecular chian to have a better close packing,and the and the molecular chain arrangement is more orderly,and the free volume of the polymer is reduced.The result of WAXS test showed that three PI films containing fluorene structure has good crystallization behavior,they are semi crystalline polymer materials.The result of density and positron lifetime indicated that three PI films have higher density and small free volume.The density of three PI films are 1.4743 g/cm3?1.3119 g/cm3?1.3366 g/cm3,respectively,While the density of ODA-PMDA(Kapton)is1.4246 g/cm3.Positron annohilation measurement result show that three PI films have smaller free volume,the ?~2 of three PI films are 0.36 ns,0.36 ns and 0.37 ns respectively,and ?~2 of Kapton is 0.47 ns.Because of the introduction of the planar structure makes the polymer melecular chain more closely,arrangement more orderly,so the polymer has a smaller free volume.Rigid structure can weaken the creep properties of polymer molecular chain and the gas molecules are difficult to in the polymer diffusion,so as to improve the barrier properties,and rigid structure can endow the thermal stability and mechanical properties of PI films had better.Barrier property test results showed that the three PI film has good barrier properties and better than Kapton film.The oxygen Transmission coefficient(OTR)of FPI,FPPI and FMPPI of 1.01cc/(m~2·day),8.30 cc/(m~2·day)and 86.50 cc/(m~2·day)respectively,and the OTR of the Kapton film of 111.98 cc/(m~2·day).The glass transition temperature(Tg)of three PI films were 370 ?,392 ? and 369 ?respectively and five percent of thermal weight loss temperature(Td5%)were 519 ?,582 ? and 474 ?,thermal expansion coefficient(CTE)between the 5.719 ?m/(m·?)to 47.67 ?m/(m·?)in range of 50~300 ?,the tensile strength and elastic modulus can reach 12.23 MPa and 2.29 GPa.The result of AFM show that three PI films hane godd flatness,and the surface roughness(Rq)in the range of 0.683~0.810 nm.