Design And Synthesis Of Low Dielectric Constant Cyanate Ester Resins And Investigation Of Their Composite Properties

With the continuous development of defense and communication technologies,the demand for polymer materials with low dielectric constant and low loss has become increasingly urgent.These materials exhibit desirable characteristics,such as lightweight,heat resistance,and impact resistance,and are important components of polymer-based transmissive composite materials.They can reduce the external environment’s impact on radar antenna systems and ensure high-fidelity transmission of electromagnetic waves.In the 5G era,polymers with low dielectric constant and loss are also crucial for reducing signal delay and transmission loss in high-frequency signal transmission in areas such as integrated circuits,printed circuit boards,and communication materials.Cyanate ester resins are a type of polymer material with excellent comprehensive performance of low dielectric constant and loss due to their unique molecular structure,exhibiting good heat resistance,mechanical properties,and dielectric properties.Improving the dielectric properties while maintaining the mechanical properties has become a research focus of cyanate ester resins.In addition,fluorinated polyimide porous hollow polymer microspheres synthesized using fluorine-containing monomers are a type of high-heat-resistant polymer material that is expected to be used in the field of low dielectric constant fillers to further optimize the properties of cyanate ester.This thesis employs three different strategies to copolymerize and modify cyanate ester resin,and evaluates the dielectric properties,mechanical properties,thermal properties,and water absorption of each modified resin.A formula with excellent comprehensive performance is selected from many modified resins,and the influence of intermolecular hydrogen bonding in thermosetting polymers on dielectric properties is further explored.Furthermore,polyimide and fluorinated polyimide porous hollow microspheres were synthesized using a multiple emulsion method,and were characterized in detail.The factors affecting the morphology of polyimide porous hollow microspheres were also studied.The results show that the precursor molecular weight has a significant influence on the morphology of polyimide porous hollow microspheres,and the corresponding mechanism is discussed.Finally,the synthesized polyimide and fluorinated polyimide porous hollow microspheres were used to prepare microsphere/modified cyanate ester resin low dielectric composite materials,which were compared with commercial hollow glass microsphere/modified cyanate ester resin composite materials.The results showed that at 12.4 GHz,the dielectric constant of the microsphere/modified cyanate ester resin composite material was reduced to 2.57,and the dielectric loss was 0.0503;the initial thermal decomposition temperature was increased to 440℃.In addition,its bending strength was 98 MPa,higher than that of commercial cyanate ester,and the water absorption rate within 120 hours was 0.79%,lower than that of commercial cyanate ester.