Preparation And Properties Of Poly(Arylene Ether Nitriles) Based Composites Wth High Dielectric Constant

Capacitor is one of the most fundamental and important electric devices among electrical industry.Recently,the demand for light-weight capacitors with high energy density in electrical fields is booming.The essential material of capacitors is dielectrics with high dielectric constant（high-k）.So,the key to fabricate capacitors with high energy density is to develop new materials with high-k.Compared to traditional ceramics in ceramic dielectrics,polymer based composites possess lighter weightness,however,the dielectric constant is much lower.The ideal way is to develop composites by adding high-k ceramics or conductive fillers into polymer matrix,in order to obtain composites with comlementary advantages,i.e.,high-k,light-weight,easy-to-process materials.The thermal stability and flexibility of polyarylene ether nitriles（PEN）is comparable to that of polyimide.The dielectric constant of PEN is between 3.5 and 4.5,the dielectric loss is about 0.01-0.02.In this paper,amorphous PEN（HQ-PP）and crystalline PEN（DP）were synthesized.Two-component PEN based composites were prepared by adding inorganic ceramics with different dielectric constant or adding conductive filler.Three-component PEN based composites were prepared by adding inorganic ceramics with different dielectric constant as well as conductive filler or by adding core-shell fillers.The morphology,thermal stability,mechanicalal properties and dielectric properties were studied in detail.First,amorphous PEN（HQ-PP）was synthesized via necleophilic reaction.Polymer based coposites was prepared by adding high-k titanate dioxide（TiO₂）,barium titanate（BaTiO₃）and calcium titanate（CCTO）.Before that,the surface of the TiO₂,BaTiO₃ and CCTO is functionalized,coated by a thin layer of PEN with carboxyl group（PEN-COOH）.It is found that inorganic fillers were was successfully coated by PEN-COOH,forming core-shell structured composites.Two-component PEN/TiO₂,PEN/BaTiO₃ and PEN/CCTO composite films were prepared by solution-casting method.The morphology,mechanical,thermal and dielectric properties of PEN/TiO₂,PEN/BaTiO₃ and PEN/CCTO composite films were studied in detail.It is found that PEN/BaTiO₃ posesses the highest dielectric constant.Hence,BaTiO₃ was choosed from them for further study,including prepare three-component composites and core-shell filler composites.Second,acidified multiwalled carbon nanotubes（MWCNT）was added into amorphous PEN（HQ-PP）matrix,PEN/MWCNT composite films were obtained.The content of MWCNT was 2 wt%,4 wt%,6 wt%,8 wt% and 10 wt%.It is found that the composite films with 6 wt% filler shows high dielectric constant,however,the electrical conductivity of the composites is too high.It is reported that the dielectric properties of polymer based composites can be tuned by hot stretch.Study shows that crystalline PEN（DP）is more appropriate for hot stretch treatment.So,crystalline PEN（DP）was synthesized via necleophilic reaction.Certain content of MWCNTs were added into PEN（DP）to prepare PEN/MWCNT composite films with 6 wt% filler content.Then,the composite films were cut into strips,and the strips were moved into high-temperature oven for hot stretch,the stretch ratios of the samples were 50%,100%,200% and 400%.It is found that hot stretch is an effective way to improve the mechanical properties and the energy density of the composites.When the stretch ratio is 50%,the energy density of the PEN/MWCNT composite films increased by 40%.Third,BaTiO₃ as well as MWCNT were added into PEN（HQ-PP）.The content of BaTiO₃ was fixed at 20 wt%,MWCNT as single variable.Three-component PEN/BaTiO₃/MWCNT composites containing inorganic BaTiO₃ and MWCNT were prepared via solution-casting method.The contents of MWCNT were 0.5 wt%,1.0 wt% 1.5 wt% and 2.0 wt%,respectively.The dielectric property of the composites was studied while changing the content of MWCNT.It is found that the three-component BaTiO₃/PEN/MWCNT composites maintained excellent mechanical property and possessed improved dielectric constant.Last,core-shell BaTiO₃@MWCNT was prepared in crystallization kettlethe via solution-thermal method.MWCNT is the core and BaTiO₃ acts as shell,the mass ratio is m BaTiO₃:mMWCNT=10:1.Then,BaTiO₃@MWCNT was added into PEN（HQ-PP）matrix to prepare PEN/BaTiO₃@MWCNT via solution-casting method.The relationship between dielectric constant and frequency,temperature and filler content were studied in detail.The mass fractions of the filler are 10 wt%,15 wt%,20 wt% and 25 wt%.It is found that the dielectric constant of the core-shell filled polymer composites differs from that of traditional three-component composites,which can be a guide to prepare high-k PEN based composites.