Preparation And Properties Of Low Dielectric Constant Transparent Polyarylate And Its Films

Polyarylates(PARs)are high-performance engineering plastics with benzene ring and ester bond in the main chain and have been widely used in military,electronic devices,health care,automotive,aerospace and other high-tech fields for their excellent comprehensive performance.And polyarylate films with lower dielectric constant,higher transparency and heat resistance have become the main direction of current research,especially applied in electronic communications,computers,LED and other fields.Therefore,high-performance polyarylate film products need to be explored and developed in line with market demand to meet the requirements of microelectronics and 5G communication technology.Based on the goal of preparing polyarylate films with high heat resistance,high transparency and low dielectric constant,a series of ternary polyarylates were prepared firstly by phase transfer interfacial polycondensation by adjusting the ratio of isophthaloyl chloride(IPC)to terephthaloyl chloride(TPC),and the ratio of acyl chloride monomers was determined based on the thermal performance and transparency of these polyarylates.On this basis,starting from molecular structure design,fluorine-containing groups,bulky side groups and twisted structures were introduced into the polymer molecular framework to explore the influence of bisphenol monomers on polymer properties,especially on dielectric properties.In consideration of the comprehensive properties of the material,environment and cost factors,the quaternary polyarylates were prepared by the copolymerization method and their properties have been studied.The above work is mainly divided into the following three parts:1.Bisphenol-A polyarylates with different meta-benzene and p-benzene contents were prepared by phase transfer interfacial polycondensation with 2,2-bis(4-hydroxyphenyl)propane(BPA),isophthaloyl chloride(IPC)and terephthaloyl chloride(TPC)as raw materials by adjusting the ratio of IPC to TPC,and the films were formed by solvent volatilization.They were named P1-P11,corresponding to the ratio of IPC to TPC from 0:10 to 10:0 respectively.The structure and properties of these polymers were systematically characterized by Fourier transform infrared spectrum(FT-IR),proton nuclear magnetic resonance(~1H-NMR),solubility test,viscosity test,X-ray diffraction(XRD),differential scanning calorimeter(DSC),thermogravimetric(TG),mechanical properties,ultraviolet-visible spectrum(UV-Vis)and dielectric properties test.It is shown that PARs with IPC to TPC ratios of 0:10,1:9 and 10:0 are crystalline polymers,which are difficult to dissolve in most organic solvents.PARs with a ratio of IPC to TPC between 2:8-9:1 are amorphous polymers.And the closer IPC and TPC feeding amount is,the better solubility,lower crystallinity,higher mechanical strength and transparency,and lower dielectric constant and dielectric loss of polymers.In particular,P5 with IPC to TPC ratio of 4:6 exhibits excellent solubility and outstanding heat resistance,and its glass transition temperature is 217.4?.Additionally,its film shows a good mechanical property,a light transmittance of 87.7%at 400 nm and a dielectric constant of 2.4(1 MHz),and the comprehensive performance of it is the best.2.A series of ternary PAR resins were synthesized with selecting 2,2-bis-(4-hydroxyphenyl)hexafluoropropane(Bis AF),4,4'-(1-phenylethyl)bisphenol(Bis AP),2,2-bis(4-hydroxyphenyl)butane(Bis B)and 4,4'-dihydroxydiphenylsulfone(Bis S)as bisphenol monomers to be copolymerized with IPC and TPC successively,and the ratio of IPC to TPC was 4:6.They were named PAR-F,PAR-P,PAR-B and PAR-S,respectively.The effects of bisphenol monomers on the structure and properties of PARs were systematically studied.It is shown that the solubility,non-crystallinity and heat resistance of PAR-S are all worse than P5,PAR-F,PAR-P and PAR-B.Compared with P5,the introduction of-CF₃,benzene ring and-CH₂CH₃ groups in the molecular structure leads to a certain degree of decrease in the mechanical strength of PAR-F,PAR-P and PAR-B,but it also contributes to some improvement in solubility,thermal properties,transparency and dielectric properties.In particular,PAR-F performs best among the four PARs.It can be dissolved in most organic solvents at room temperature.The visible light transmittance of its film at 400 nm is as high as 89.1%,and the dielectric constant is only 1.5(1 MHz),which is 37.5%lower than that of P5.3.Based on the above conclusions,the quaternary PARs and their films were further prepared in this work with selecting Bis AF and BPA as bisphenol monomers to be copolymerized with IPC and TPC,and the ratio of IPC to TPC was 4:6.The influence of Bis AF content in the bisphenol monomer on the structure and performance of PARs was studied.It is shown that compared with P5,the transparency and low dielectric properties of the polymers become better with the increase of Bis AF content.It is noteworthy that the solubility and heat resistance of PAR(F20)containing only 20%Bis AF in the bisphenol system are basically equivalent to PAR-F.Meanwhile,F20 also maintains high transparency and low dielectric constant.It has a visible light transmittance of 87.3%at 400 nm and a dielectric constant as low as 2.0(1 MHz).In addition,its tensile strength is 57.7MPa,17.3%higher than PAR-F and only 4.4%lower than P5.It can be seen that the introduction of 20%Bis AF into bisphenol system can not only effectively reduce the dielectric constant of PAR,but also reduce the cost and make it more environmentally friendly on the premise of maintaining good solubility,heat resistance,transparency and mechanical properties of the polymer.In general,F20 has broad prospects and far-reaching significance.