Preparation And Properties Of Low Dielectric Constant Fluorinated Polyarylene Ether Nitrile Containing Propylene Groups/POSS Composites

As the microelectronics industry continues to grow in various of technical fields,especially in high-speed and high-frequency communication applications,signal loss greatly affects the performance of devices,resulting in degradation of signal transition rates and quality.Low-k dielectric can effectively reduce interference between conductors,improve signal integrity and ensure the reliability of electronic devices.Therefore,there is an urgent need for materials with low dielectric constant and low dielectric loss in the field of electronic applications.Polyarylene ether nitrile（PEN）is an emerging class of special functional polymers with its special structure,such as polar nitrile groups,rigid benzene ring and flexible oxyether bond,which exhibits advantages such as outstanding heat-resistance,mechanical and electrical properties.However,the dielectric constant of conventional PEN is between 3 and 5,which cannot meet the low dielectric requirement.Hence,this thesis focuses on both molecular design and filler filling to obtain PEN and its composites with ultra-low dielectric constants and excellent overall performance.Firstly,the thesis is based on the preparation of intrinsically low dielectric PEN from the perspective of molecular design.Four PEN copolymers with different double bond contents were synthesized from bisphenol AF,allyl bisphenol A and 2,6-difluorobenzonitrile,with a focus on studying the effect of different heat treatment temperatures on the cross-linking.The results showed that the double cross-linked networks,that is,the cross-linked network of double bonds and cyano,were constructed by heat treatment could effectively enhance the composite films performance.The dielectric constant and dielectric loss of the films were reduced,where the dielectric constant（k）of D20AF-PEN-280 film was 2.26 at 1 MHz and the dielectric loss was 0.004.Furthermore,it is worth mentioning that the presence of double bonds synergistically promoted the cross-linking of cyano groups.These provide a reference for subsequent studies of the composites.Secondly,the PEN matrix containing 10%propylene groups was preferably selected in the study,and octaphenyl POSS（BPOSS）was immobilized in the cross-linked network of PEN by physical blending.The effect of different contents of BPOSS on the properties of cross-linked PEN materials was studied.The results show that the cage structure of the POSS drastically reduces the dielectric constant of the material,with CPEN-8BPOSS shows dielectric constant of 2.19（1 MHz）.Finally,to further obtain the high-performance ultra-low dielectric constant PEN materials,this chapter designs and synthesizes vinyl crosslinkable POSS（VPOSS）containing chemical reactivity and explores the most suitable cross-linking mode for vinyl POSS/PEN composites,namely UV and thermal co-crosslinking.There are several cross-linked structures in composite systems,including propylene-based self-crosslinking of polymer matrix,cyano self-crosslinking,VPOSS self-cross-linking of fillers,and crosslinking between VPOSS and PEN.The cage structure of POSS and the multiple crosslinking networks effectively enhance the overall performance of the materials,in which CPEN-5VPOSS and CPEN-8VPOSS films have ultra-low dielectric constant of 1.88 and 1.79,respectively.Besides,due to the existence of multiple cross-linked structures in the system,CPEN-5VPOSS composite film exhibits excellent comprehensive properties such as low dielectric loss（less than 0.004 at high frequency）,high heat resistance(T_g=209°C,T_5%=508°C),excellent mechanical properties（tensile strength=91 MPa,tensile modulus=2.2 GPa）,ultra-low water absorption（0.20%）,and good bonding performance with metals（peel strength=7.4 N/cm）.