Synthesis And Properties Studies On Polyimides Containing Asymmetric Benzyl And Trifluoromethylated Tertiary Carbon Structures

Conventional aromatic polyimides have excellent heat resistance, corrosion resistance and other properties. It is widely used in aerospace, automotive electronics,petrochemical and other fields. With the development of science and technology, in the field of modern information technology, the application of polyimide material already experienced technology breakthroughs and material innovation promoting microelectronics products tend to be multi-functional, high performance, portable and flexible. In order to solve the high-density, high-precision environment leading to the signal delay and power loss in the formation of integrated circuits and other issues,further meet flexible wearable equipment application requirements, a new generation of high-performance, low dielectric, high transparent colorless and other functional materials was necessary. As an important application materials in the microelectronics industry, how to develop new low dielectric and highly transparent polyimide materials has been one of the most important subject in high performance polyimide researchs.Traditional polyimide materials generally have higher dielectric constant and darker color. Acorrding to structural analysis, because of the strong interaction between molecular chains, the electron transfer of intramolecule makes the electron donor and electron acceptor easy to form complexes (CTC). To achieve high colorless and low dielectric constant of the polyimide material, we should reduce the influence of CT effect. For this purpose, we introduceda benzyl group of asymmetric structure, and trifluoromethyl structure inserting the polyimide backbone to optimize its performance.The research is mainly in the following two aspects:Firstly, 4-aminophenly-p-(4-aminophenoxy)-benzyl ether (APABE) monomer of asymmetric structure was obtained by three-step reaction based on p-hydroxybenzaldehyde as the starting material. The novel diamine APABE and 1,4,4-triphenyl ether diamine (1,4,4-APB) were polymerized with 6FDA, ODPA, BTDA,BPDA to obtain asymmetric and symmetrical two series polyimides, were named API1-API4 and SPI1-SPI4 respectively. The two series were performed a comprehensive properties test. By contrast, it was found that solubility and optical performance of API series were significantly better than the SPI series. In thermal and mechanical properties, the glass transition temperature of API series and SPI series were 237-265?and 249-313 ?, respectively. The thermal weight loss of 50% of API series and SPI series were 453-486 ? and 511-517 ?in nitrogen environment. The tensile strength of API series and SPI series were 88.2-99.5 MPa and 84.4-99.7 MPa. It indicated that the introduction of benzyl-containing polyimide maintain better thermal and mechanical properties. In addition, in the dynamic dielectric analysis, the dielectric constant (?') 2.57 (1 MHz and 25 ?) and the dielectric loss (?") 0.0040 value of API3 were higher than the dielectric constant (?') 3.22 (1 MHz and 25 ?) and dielectric loss(?') 0.1376 value of SPI3, which suggested that the incorporation of asymmetric structure also made CPI3 obtain lower dielectric properties.Secondly, 2,2,2-trifluoroacetophenone and acetophenone as the starting materials,reacted with first phenol and then trimellitic anhydride chloride (TMAC). 1,1-bis (4-trimellitic anhydride monoester phenyl) -1-phenyl-2,2,2-trifluoroethane (TAMPPTE)and 1,1-bis (4-trimellitic anhydride monoester phenyl) -1-phenyl-ethane (TAMPPE)dianhydride of fluorinated and nonfluorinated were obtained by typical two-step method. New kind of fluorinated dianhydride TAMPPTE and the nonfluorinated dianhydride TAMPPE were respectively polymerized with four aromatic diamines ODA, 1,4,4-APB, 1,3,4-APB and DMB to form fluorinated and nonfluorinated polyimides named as FPI1-FPI4 and NPI1-NPI4 respectively. The same comprehensive properties test of the two series were performed. In the solubility, the FPI series were significantly better than the NPI series. In the optical performance and thermal performance, FPI series and NPI series in T500 the transmittance were in the range of 93.3-95.7 and 92.4-95.2%, the glass transition temperature were in the range of 230-285 ? and 228-284 ?. It indicated that the FPI series showed better optical performance and thermal performance. In dielectric analysis, the dielectric constant (?')of FPI1 and FPI3 were 2.56 and 2.31 (1 MHz and 25 ?), which was significantly decreased compared with the commercial Kapton(?) membrane. It meant that the FPI containing the trifluoromethyl structure improved the dielectric properties of the material.