Synthesis And Properties Of Polyimide Materials Containing Pyridine Ring And Trifluoromethyl Structure

With the continuous advancement of society,the development of high technology is getting faster and faster,and electronic products are also favored.This requires PI to have excellent performance and wide application range,although traditional aromatic polyimide materials have good mechanical and chemical properties,but they have some shortcomings such as processing difficulties and dark colors.This is one of the important reasons for researchers to continuously modify and extract polyimide materials.Studies have shown that the introduction of fluorine atoms or fluorine-containing groups in the PI skeleton,due to the strong pull-electron effect of the fluorinated structure itself,thus largely restricts the free-moving electrons,and the trifluoromethyl group itself,the large spatial effect increases the distance between the molecular chains,and the solvent is easily dispersed into the material to improve the solubility and processability of the material.The introduction of sulfur atoms in the PI chain can increase the mobility of the molecular chain.The flexible rotation of the molecular chain weakens the cross-linking of the molecular chain,so that the solubility and flexibility of the PI are improved,and the introduction of sulfur atoms can improve the transmittance of the material;In addition,the structures of both the heterocyclic pyridine and the benzene ring are similar(aromaticity and symmetry),and therefore,introduction of a pyridine ring in the PI skeleton can significantly increase the mechanical,mechanical and thermal properties of the film material,while at the same time,because of the large volume of the heterocyclic ring,the distance between the molecular chains can be increased,and the degree of close packing between the molecules can be reduced,thereby improving the solubility of the material.To this end,we have studied the design of the fluorinated structure,sulfur atom,pyridine heterocycle and naphthalene ring into the polyimide skeleton to improve its performance.This article mainly explores from two systems:First,we used 4-fluoro-2,2,2-trifluoroacetophenone(F3FAP)as a raw material to react with p-fluorothiophenol to obtain 4-((4-fluorophenyl)thio)phenyl three.Fluoromethyl ketone(FTP3FK),then FTP3FK is nucleophilically added with phenol to give 1,1-bis(4-hydroxyphenyl)-1-(4-(4-fluorophenyl)thio)phenyl-2,2,2-trifluoroethane(3FBPT),2-trifluoroethane(BAPFTPT)diamine monomer,then reacting diphenol 3FBPT with 4-chloronitrobenzene to obtain dinitro-1,1-bis[(4-nitrophenoxy)phenyl]-1-[4-(4-fluorophenyl)thio]phenyl-2,2,2-trifluoroethane(BNPFTPT),and finally,Reduction of dinitro BNPFTPT to give 1,1-bis[(4-aminophenoxy)phenyl]-1-[4-(4-fluorophenyl)thio]phenyl-2,2,2-Trifluoroethane(BAPFTPT)diamine monomer,and then BAPFTPT and commercial dianhydride(ODPA,PMDA,BPDA)were separately polymerized to obtain FPI series membrane materials,and then compared with NPI series membrane materials.For the solubility properties,the FPI series of polyimides can be better dissolved in high-boiling polar solvents,and also have good solubility in low-boiling solvents,but the solubility of the NPI series relative to the FPI series is poor.For optical performance,the transmission ratios of FPI and NPI are 74.1-82.7%and 69.7-82.7%at the cutoff wavelength of 500 nm,respectively.The film thickness is not uniform,and the FPI series is better than the NPI series.For thermal performance,the FPI and NPI series have a temperature range of 483-510? and 508-522? at 5%decomposition of the material;the glass transition temperature ranges are 222-253?and 237-263?,respectively,indicating FPI material Maintained good thermal performance.For mechanical properties,the tensile strength range of the FPI series is 36.55-78.69 MPa,the elongation at break ranges from 2.0-5.3%,the tensile modulus ranges from 2.62-3.48 Gpa,and the tensile strength range of the NPI series is 23.3-78.2 MPa,the elongation at break ranges from 1.5-4.9%,and the tensile modulus ranges from 1.86-3.00 Gpa,indicating that the FPI series has good mechanical properties.For hydrophobicity,the FPI series is better than the NPI series.From the above,it is known that the introduction of a fluorinated group and a sulfur atom improves the properties of the material.Secondly,we react with the relatively inexpensive 4-methoxy-l-naphthaldehyde and p-nitroacetophenone to give 4-(naphthalen-1-y1-4-methoxy)-2,6-bis(4-nitrophenyl)pyridine(NBNP),then NBNP is reduced under conditions of Pd/C hydrazine hydrate to give the monomeric diamine 4-(naphthalen-1-yl-4-methoxy)-2,6-Bis(4-aminophenyl)pyridine(NBAP)was blended with NBAP and ODA in combination with ODPA to obtain a PI film,which was named PI1-PI4,and then compared with PIo.As a result,it is known that for optical performance,the transmittance of PI1-PI4 at T500 ranges from 78.4-83.0%,and that of PIo is 83.2%,which indicates that optical performance is maintained;for solubility,it is improved compared with PIo;In terms of thermal performance,PI1-PI4 has a glass transition temperature range of 262-283?,while PIo is at 251?,which indicates that its thermal properties are further improved.In terms of mechanical properties,the tensile strength range of PI1-PI4 is 66.7-93.8 MPa,the elongation at break ranges from 1.5-6.9%,the tensile modulus ranges from 2.89-6.88 Gpa,and the PIo is 74.1 MPa,7.1%,and 2.74 Gpa,respectively,indicating that the mechanical properties are improved.In summary,the introduction of a pyridine ring and a naphthalene ring into the chain provides a more comprehensive improvement in performance.