Preparation And Properties Of Ultra-low Dielectric Constant Polyarylate And Its Films

To meet the market demand of 5G communication technology and semiconductor industry,polymer materials with lower dielectric constant and higher heat resistance have become a current research hotspot.Polyarylate（PAR）is an engineering plastic with excellent performance.Its main chain contains benzene rings and ester bonds,which endowing it with low dielectric constant and loss,high temperature resistance,low moisture absorption,and dimensional stability.Therefore,it is widely used in fields such as aerospace,military,electronics,medical,and automotive.This article aims to prepare amorphous polyaryate films with high heat resistance and ultra-low dielectric constant by introducing fluorinated groups and large volume groups.Their thermal and dielectric properties were mainly investigated.In the subsequent film preparation process,microporous structure was introduced through phase separation method to prepare polyarylate films with ultra-low dielectric constants.The structure and properties of polymers and their films were studied through IR,¹H-NMR,DSC,TG,DMA and SEM etc.The research results mainly include as follows.1.Interfacial polycondensation of 2,2-bis-（4-hydroxyphenyl）hexafluoropropane（Bis AF）,bisphenol A（BPA）,isophthaloyl chloride（IPC）,and terephthaloyl chloride（TPC）（molar ratio1:4:2:3）was carried out to prepare low dielectric constant fluorinated polyarylate PAR-F resin.N-methylpyrrolidone（NMP）was selected as the solvent,and a mixture of solvent NMP and non-solvent water was used as the coagulation bath to prepare ultra-low dielectric constant porous polyarylate thin films by introducing micropores through phase separation method.While the water content in the coagulation bath increases,the porosity in the ployarylate film increases,and the pores show a gradual development from sponge shape to finger shape,resulting in a linear decrease of the dielectric constant with porosity.The minimum dielectric constant of the porous film at 1MHz can reach 1.38.However,its mechanical properties have significantly decreased compared to polyarylate films without pores.When the water content in the coagulation bath is 20%（F1）,the tensile strength of the film is 12.8 MPa,the elastic modulus is0.29 GPa,the glass transition temperature is 223.4℃,and the dielectric constant is 1.61.Its comprehensive performance is optimum.However,it has not yet met the requirements for the use of interlayer dielectric materials at 250 ^OC.2.To improve the heat resistance of polyarylate films,9,9-bis（4-hydroxyphenyl）fluorene（BHPF）,isophthaloyl chloride（IPC）,and terephthaloyl chloride（TPC）（molar ratio 5:2:3）were subjected to interfacial condensation to prepare bisphenol fluorene type polyarylate PAR-B.And porous polyarylate films with high temperature resistance and low dielectric constant were prepared using phase separation method.It is indicated that the modified film has good mechanical properties,as well as excellent dielectric properties（dielectric constant in the range of 1.52-1.71）and thermal properties（glass transition temperature Tg is 301 ^OC）.Compared with the F-series microporous polyarylates in the previous chapter,the reduction effect of their dielectric constant is slightly inferior.3.Futhermore,Bis AF,BHPF,IPC,and TPC were subjected to interfacial polycondensation to prepare low dielectric constant polyarylate with high tempreture resistance.The effects of molar ratios of Bis AF and BHPF on the structure and properties of polymers and their films were studied.It is indicated that the higher the content of Bis AF,the lower the dielectric constant of the polymer;The higher the content of BHPF,the better the heat resistance of the polymer.The dielectric constant of the polyarylate（P3）with a ratio of Bis AF to BHPF of 60:40 is only 2.03with a dielectric loss of 0.027,which is smaller than the fluorinated polyarylate PAR-F in Chapter2.Its glass transition temperature is as high as 259.8 ^OC,which is significantly improved compared to PAR-F.It maintains good mechanical properties with a tensile strength of 56.7 MPa.Therefore,P3 was chosen for further sudy of the porous films.4.Polyarylate with molar ratio of Bis AF,BHPF,IPC,and TPC is 3:2:2:3 was selected to prepare porous films with heat-resistance and ultra-low dielectric constant P3-1 to P3-5.It was found that the Tg of all P3 prous films is above 250 ^OC.As the water content in the coagulation bath increases,the dielectric constant gradually decreases from 1.65 to 1.42,and the dielectric loss ranges from 0.49×10^-2 to 1.08×10^-2.In summary,the simultaneous introduction of fluorine atoms and large volume functional groups of fluorene,combined with the introduction of pores in the film through phase separation method,can achieve a significant reduction in the dielectric constant of the polyarylate film and improve its thermal performance.Polyarylate film with ultra-low dielectric constant and high heat resistance was successfully prepared.This polyarylate film is a candidate 5G material with excellent dielectric and thermal properties in high-frequency signal transmission.It will have broad application prospects in the field of 5G materials.