Preparation And Properties Of Low Dielectric Constant Polyarylate And Its Films

Chip size is getting smaller and smaller in order to achieve higher integration with the rapid development of 5G communication technology.However,it will lead to the increase of resistance and capacitance in the line,resulting in the problem of signal transmission delay.In order to reduce the signal delay,a novel material with ultra-low dielectric constant and excellent thermal properties is urgently needed to adapt to the development of 5G materials.Amorphous polyarylate(PAR)is high-performance engineering plastic with aromatic ring and ester bond in the main chain,which has low dielectric constant and excellent thermodynamic properties.In this thesis,amorphous polyarylate film with ultra-low dielectric constant is explored to meet the application of microelectronics and 5G materials.In this thesis,polyarylate was prepared by interfacial polymerization.In the subsequent film preparation process,air is introduced into the polyarylate film through mechanical mixing of hollow glass bead and phase separation in order to prepare low dielectric polyarylate film.In terms of molecular structure,polyarylate films with higher thermal properties and lower dielectric properties were prepared by introducing large side monomer.The structure and properties of the polymers and their films were characterized by FT-IR,~1H-NMR,solubility,viscosity,thermogravimetry,scanning electron microscopy,mechanical and dielectric properties.The contents are mainly as follows:1.Bisphenol A(BPA),isophthaloyl chloride(IPC)and terephthaloyl chloride(TPC)were used as monomers to synthesize amorphous polyarylate of bisphenol A type by interfacial polymerization.Selecting N-methylpyrrolidone(NMP)as solvent,hollow glass bead with different mass ratios were added to prepare PAR pure film and hollow glass bead/polyarylate composite film by casting method.It was found that the dielectric properties of PAR pure film were good with the dielectric constant at 1 MHz was 2.50.With the increase of hollow glass bead,the dielectric constant of composite film decreases,but its dielectric constant also fluctuates greatly with the change of frequency.When the amount of hollow glass bead reached 25 wt%,the dielectric constant decreased to 2.01,and the mechanical properties of the film were reduced greatly.The performance of this film has not yet met the 5G requirements.2.Porous polyarylate film with low dielectric constant was prepared by introducing micropore in the coagulation bath composed of solvent NMP and nonsolvent water through phase separation.It is shown that the porosity of the polyarylate film increases with deionized water content in the coagulation bath,making the dielectric constant of the porous film decrease linearly.The lowest dielectric constant of the porous film at 1 MHz is 1.27.However,its thermodynamic performance is lower than that of the polyarylate film without micropore.When the water content in the coagulation bath is 20%,the tensile strength of the porous film is 13.0 MPa,the elastic modulus is0.29 GPa,the glass transition temperature is 198.1℃,and the dielectric constant is 1.51.The film has the best comprehensive properties among porous films.3.Three modified polyarylates,PAR-P,PAR-Z and PAR-F,were synthesized by interfacial polymerization with IPC,TPC and three large side group monomers 3,3-bis(4-hydroxyphenyl)-3H-isobenzofuranone(PP),1,1’-bis(4-hydroxyphenyl)cyclohexane(BPZ)and 9,9-bis(4-hydroxyphenyl)fluorene(BHPF),respectively.It is shown that the modified film has better dielectric properties(dielectric constant is in the range of 2.03-2.16)and thermal properties(Tg is in the range of 210.9-301.8℃).Among them,PAR-Z has the lowest dielectric constant(ε=2.03),and also has good solubility and thermodynamic properties.4.The PAR-Z resin with the lowest dielectric constant was selected to prepare porous PAR-Z film based on the best comprehensive performance conditions for preparing porous film in 2.Due to the introduction of micropore and large side group structure,the porous modified polyarylate film has ultra-low dielectric constant and certain mechanical properties.Its dielectric constant is 1.38(@1 MHz),tensile strength is 16.3 MPa,and elastic modulus is 0.42 GPa.This film has a broad application prospect in 5G material field due to its excellent dielectric properties,thermal properties and good mechanical properties.