Studies On The Polyimides Material Prepared By A New Aliphatic-aromatic Asymmetry Diamine And Pyridine Alicyclic Structure Diamine

With the development of microelectronics,flexible display and photovoltaic industry,the development of polyimide also ushered in another spring.Traditional aromatic polyimides(PIs)are widely used for their excellent thermal and mechanical properties,but in some emerging industries their requirements are not limited to good thermal and mechanical properties.In microelectronics industry,polyimide need to have a lower dielectric constant(?'),while in the flexible display(OLED)industry,there are higher requirements for the optical transparency of polyimide.Therefore,it is necessary to carry out a variety of modification for traditional aromatic polyimide so that it can be applied to different areas.According to previous studies,the introduction of asymmetric structure in the polyimide backbone can decrease the close intermolecular accumulation,destroy the regularity of the molecule;aliphatic chain,ether bond can improve the flexibility of the molecular chain,the aliphatic chain can destroy the conjugation between molecules,effectively abate CT effect;Intermolecular crosslinking can restrict the movement of molecular chain,improve the thermal properties of materials;pyridine heterocyclic ring and benzene ring have similar structures and properties.However,because the pyridine heterocyclic ring-C=N-bond(4.10)has a higher molar refractive index than the-C = C-bond(1.76)in the benzene ring,which can effectively increase the optical transmittance of the material,at the same time the introduction of pyridine heterocyclic ring can also increase the thermal stability of PIs again,pyridine heterocyclic structure can hinder the interaction between molecules and increase the molecular chain spacing.Firstly,the 4-(5-nitropyridyloxy)benzaldehyde(NPyOBH)was synthesized by p-Hydroxybenzaldehyde and 2-Chloro-5-nitropyridine,and then used NPyOBH as the starting material to take Henry reaction with nitromethane to make ?-[4-(5-nitropyridyloxy)phenyl]nitroethanol(NPyOPhNE).The NPyOPhNE after going reduction get 2-amino-1-[4-(5-aminopyridyloxy)phenyl]-1-ethanol(AAPyPhE).Putting AAPyPh E as dopant into ODA in different ratio,and polymerized with ODPA,6FDA,BPDA,BTDA respectively by traditional two steps to get PIs films.To characterize the PIs films,the result is that,with the AAPyPhE added,the solution of PIs get improved.As for OPI-x series,the UV cutoff wavelength between 365 and 381 nm,transmittance in 500 nm(T500)between 74.1 and 83.3%.The d-spacing at 4.7~5.1 ? and tested by XRD.Owing to AAPyPh E can form a cross-linked structure between the molecular chains,when the AAPyPhE content reaches to a certain value,PIs material can still remain the original good thermodynamic and mechanical properties.Strain relief test suggested that the tensile strengths of PIs material range from 89.35 to 170.73 MPa,elongations at break ranging in 8.43~10.82%,and modulus of elasticity were 1.29~2.28 GPa.With the contains of AAPyPhE increasing,the Tg decreasing in turn and ranging from 185.5 to 253.3 oC,5% decomposition temperature at 338.7~498.3 oC,10% decomposition temperature at 391.6~545.5 oC and char yield between 49.1 and 56.6%.But because of the influence of structure,with the addition of AAPyPhE,there are some changes of dielectric properties.Dielectric tests showed that 5% mol amount of AAPyPhE can make dielectric constant ?' decrease,but as AAPyPh E continues to add,the ?' value will present a complex fluctuation.Secondly,using 1,1-bis[4-(4-pyridyloxy)phenyl]cyclopentane(BAPBP),which contains cardo alicyclic structure and pyridine heterocyclic ring groups and synthesized by our group.BAPBP polymerized with ODPA,6FDA,BPDA,BTDA respectively by traditional two steps to get PIs films.To characterize the PIs films,the result is that,due to the introduction of pyridine heterocyclic,the thermal performance of materials is excellent,optical performance is better too.And alicyclic structure destroyed the close packing of molecular chain,reduced the crystallinity of molecular improve the processing performance of materials.The dielectric constant of PIs is relatively low.Thirdly,based on our previous experiments result,we used 4-(5-nitropyridyloxy)benzaldehyde(NPyOBH)as start material to react with TMSCF3 or KBH4 obtained corresponding alcohols: 1-trifluoromethyl-1-[4-(5-nitropyridyloxy)phenyl] methanol(FNPyOPhMA)and 4-(5-nitropyridyloxy)phenylcarbinol(NPyOPh CA),and then react with paranitrobenzoyl chloride synthesized by asymmetric structure binitro compounds: 1-trifluoromethyl-1-[4-(5-nitropyridyloxy)phenyl] methyl-4-nitrobenzoate(FNPyOPh MNBZ)and 4-(5-nitropyridyloxy)benzyl-4-nitrobenzoate(NPyOBNBZ).FNPyOPhMNBZ and NPyOBNBZ reduced by palladium carbon and hydrazine hydrate obtained corresponding diamine: 1-trifluoromethyl-1-[4-(5-aminopyridyloxy)phenyl] methyl-4-aminobenzoate(FAPyOPhMABZ)and 4-(5-aminopyridyloxy)benzyl-4-aminobenzoate(APyOBABZ).The structure was determined by IR and NMR characterization.