Study On The Role Of Amide-amide Hydrogen-Bonds And Electronic Effects In Performance Regulation Of Polyimides With Multifunctional Groups And Terphenylamine Moieties

With excellent thermal stability,mechanical strength and toughness,high electrical insulation properties,low dielectric constant and dissipation coefficient,high radiation,and wear resistance,aromatic polyimides（PI）can be processed into various forms of materials,including films,fibers,carbon fiber composites,engineering plastics,foams,porous films,coatings,etc.Due to their excellent combination of properties and variable processing performance,aromatic PIs have been widely used in various high-tech fields,including electrical insulation,microelectronics and optoelectronics,gas separation membranes,aerospace and aviation industries,etc.The traditional modifications mainly focus on reducing the CT effects and disrupting the conjugation system of PIs,thus improving the dielectric,and optical properties as well as the processability,in order to meet the requirements of sophisticated microelectronic,optoelectronic,and flexible display.However,there has always been a trade-off in modifications of PIs,in which the thermal and mechanical properties are sacrificed to a degree.Therefore,how to balance the general performances remains important for PIs’modifications.On the other hand,terphenyl-containing PIs play important roles in the memory storage field,where the electronic effects of pendent groups heavily influence the device’s efficiency.Aiming at the above-mentioned,two parts of research have been carried out in this thesis.In the first part,N,N′-(（4-（4-（tert-butyl）phenyl）pyridine-2,6-diyl）bis（4,1-phenylene）bis（4-aminobenzamide）（NTPA）containing a multifunctional structure of pyridine ring,amide bond,and tert-butyl was synthesized by the nucleophilic substitution reaction of 4-nitrobenzoyl chloride with 4-aminoacetophenone,followed by the Chichibabin pyridine synthesis reaction with 4-tert-butylbenzaldehyde,and finally reduced by the hydrazine hydrate catalyzed by Pd/C.The processability and transparency of PI have been improved by inhibiting the formation of charge transfer complexes（CTC）.At the same time,amide linkages were introduced into the diamine molecule with the aim of rebalancing the general properties of polyimide by reasonably increasing the stiffness of the polymer through amide-amide hydrogen bonding.The dianhydride BPADA was used for random copolymerization with NTPA and ODA in different ratios.The NPI_x films synthesized by a two-step imitation method showed good optical properties,with T₅₀₀ above 75%for all PIs and 83%for BPADA-NTPA.The incorporation of NTPA increased the solubility of the series in organic solvents,and the improved hydrophilicity was obtained with a maximum hydrostatic water contact angle of 91.1°.The mechanical properties of the NPI films were maintained through H-bonds,which contribute to the cohesion of the polymer chains,with a maximum tensile strength of 127 MPa.The amide-amide H-bond greatly counteracts the degrading effect of large pendent tert-butyl on the thermal properties of PI.The T_grange of the films containing NTPA molecules is 244-298℃,which is higher than the T_g of BPADA-ODA control NPI₀（218℃）.The design of this monomer aims to improve the solubility and processability of PI by introducing tert-butyl,and then the thermal properties of the material are maintained by an amide bond and pyridine ring.The multifunctionalized structural design better balances the general properties of the polymer and is expected to expand its application in the field of optoelectronics and microelectronics.In the second part,the nucleophilic reaction of 4-chloro-3-trifluoromethylaniline and 3,4-dimethoxy aniline with 4-fluoronitrobenzene,respectively,were used to obtain the corresponding nitro compound intermediates,in which cesium fluoride was used as the catalyst.Two diamine monomers,4-chloro-N,N-bis（4-aminophenyl）-3-（trifluoromethyl）aniline（CNTA）,3,4-dimethoxy-N,N-bis（4-aminophenyl）aniline（MNTA）,containing the electron-donating and electron-absorbing TPA units,respectively,were synthesized by hydrazine hydrate catalytic reduction under Pd/C.The two synthesized diamine monomers were homopolymerized with three commercial dianhydrides bisphenol A-type diether dianhydride（BPADA）,4,4’-oxydiphthalic anhydride（ODPA）,and 3,3’,4,4’-biphenyl tetracarboxylic dianhydride（BPDA）to obtain two series of FPI_x and MPI_x films,respectively.Both series of films showed good thermal and mechanical properties and the tensile strength of the FPI series was above 100 MPa,as high as 153 MPa.Meanwhile,FPI exhibited higher thermal weight loss temperature,with T_d5 above 495℃ and T_d10 above 512℃.MPI exhibited higher glass transition temperature,reaching 307℃.The hydrostatic water contact angle is above 74℃ except for MPI₃,especially reaching 94.8°for FPI₂,exhibiting good hydrophobic properties.The monomer is designed mainly to improve the thermal properties of PI so that it can withstand the high-temperature procedures in industrial production when used as a substrate material.TPA units are large electron donor units that can increase the CT effect and charge transfer channels and can be used as hole transfer materials and memory device materials.