Synthesis Of Fluorinated Polyarylene Ether Sulfone And Study On Its Low Dielectric Functional Composites

Polyarylene ether sulfone is a kind of high-performance thermoplastic engineering plastics,which has been widely used in the fields of aerospace,national defense,military affairs,electronic appliances because of their high heat resistance,good thermal stability,good chemical resistance,excellent mechanical properties and outstanding dielectric properties.In order to meet the demand of high performance and low dielectric constant materials in the rapidly developing microelectronics field,the dielectric constant of materials can be effectively reduced by introducing fluorine-containing groups into polyarylene ether sulfone,and fluorine-containing polyarylene ether sulfone with good low dielectric properties can be prepared.Then,pore fillers is introduced into the polymer to further reduce its dielectric constant,so as to realize the development of fluorine-containing polyarylene ether sulfone-based low dielectric function composite materials with good comprehensive properties and apply them to microelectronic devices.In this thesis,a series of fluorinated polyarylene ether sulfones(PAES-6AF)were synthesized by introducing trifluoromethyl with low polarizability and large volume of rigid biphenyl groups into the molecular chain of polyarylene ether sulfone through chemical copolymerization.The relationship between the structure and properties of this series of PAES-6AF was emphatically studied.Then,the PAES-6AF with the best dielectric properties in the above research was selected as the polymer matrix,and cage silsesquioxane(POSS)was used as the pore filler.A series of composite materials with different POSS mass fraction were prepared by solution casting film method.The microstructure,thermal properties,mechanical properties and dielectric properties of this series of composites were studied in detail.Firstly,a series of PAES-6AF polymers with different composition contents were synthesized by adjusting the molar ratio of BP to 6AF with biphenyl diphenol(BP),hexafluorobisphenol A(6AF)and 4,4?-dichlorodiphenyl sulfone(BCPS)as main raw materials.The results showed that PAES-6AF polymers have high molecular weight(M_w>5.7×10⁴ g/mol),good solubility,high glass transition temperature(T_g=179?226?),excellent thermal stability(T_5%=527?561?)and high tensile strength(68?76).With the increase of 6AF mole fraction(0%to 100%),the dielectric constant of PAES-6AF polymer gradually decreases from 3.32 to 2.96 at 1 MHz,and the dielectric loss is lower than 0.01.Then,PAES-6AF homopolymer with 100%molar fraction of 6AF was selected as the polymer matrix.Octylphenyl silsesquioxane(OPS)with hollow structure was introduced into PAES-6AF matrix to prepare a series of fluorinated polyarylene ether sulfone/octaphenyl silsesquioxane composites with different OPS mass fractions.It was found that the dielectric constant of PAES-6AF/OPS composites decreases with the increase of OPS mass fraction(0 wt%to 40 wt%).When the OPS content is 40 wt%,the dielectric constant of the composite is as low as 2.40(1 MHz).Compared with pure PAES-6AF polymer,it is about 19%lower and the dielectric loss is 0.015.In addition,the T_g of this series of composite materials is higher than 175?,and T_5%is higher than 480?.Although the mechanical properties of PAES-6AF/OPS composites decrease obviously with the increase of OPS mass fraction,it still has relatively good tensile strength and flexibility.Finally,in order to improve the interfacial compatibility between OPS particles and PAES-6AF matrix.OPS particles were nitrated with fuming nitric acid to obtain polynitrophenyl silsesquioxane(NPS).A series of fluorinated polyarylene ether sulfone/polynitrophenyl silsesquioxane composites with different NPS mass fractions were prepared by introducing NPS into PAES-6AF matrix.It is found that the dielectric constant of PAES-6AF/NPS composites still shows a trend of greatly decreasing.With the increase of NPS mass fraction,its dielectric constant decreases from 2.96 to 2.41 at 1 MHz.All the composites showed higher glass transition temperature and good thermal stability,with T_gvarying from 175?to 197?and T_5%higher than 485?.Furthermore,compared with PAES-6AF/OPS composites,the mechanical properties of this series of composites have been significantly improved.When the mass fraction of NPS is 40 wt%,its tensile strength is 47 MPa and elongation at break is 3.3%.To sum up,PAES-6AF/NPS composites not only retain the excellent thermal and mechanical properties of the polymer matrix itself,but also incorporate the low dielectric properties of fillers,which has a good application prospect in the field of high-performance low dielectric constant materials.