Research On Preparation And Properties Of Polyarylene Ether Nitriles Nanocomposites Based On Multi-Dimension And Multi-scale Nanofillers For Dielectrics

In recent years,with the rapid development of science and technology,the design and manufacture of new miniaturized,lightweight and portable electronic devices to meet the needs of modern capacitors has attracted great attention,among which high performance dielectric materials are the key factors affecting the performance of components.Traditional ceramic dielectric materials have high dielectric constant but their weight is large and their texture is brittle;polymer dielectrics have the characteristics of light weight and flexibility but their dielectric constant is relatively low.Therefore,in order to realize the complementary advantages of polymer matrix and inorganic nanoparticles,one of the most ideal ways is to develop lightweight polymer matrix composites with high dielectric constant and good toughness.Poly（arylene ether nitrile）（PEN）,as a new class of special engineering plastics,has excellent heat resistance and toughness.In addition,the dielectric constant of PEN is about 4.0 due to the presence of strong polar-CN groups.Firstly,a series of glass transition temperature gradients and poly（arylene ether nitrile）resins with different configurations were obtained by molecular structure design and modification of aromatic dicarboxylic phenol structure;Secondly,the new multi-dimensional and multi-scale nanoparticles were constructed through the corresponding physical or chemical means based on the 0D BaTiO₃ nanoparticles,1D CNTs nanowires and 2D GO nano-sheets.Then,the prepared novel nanofillers were introduced into the PEN matrix by continuous ultrasonic technique and solution blending to obtain PEN-based nanocomposite dielectric films.The effects of different configurations,dimensions and sizes of nanoparticles on the PEN morphology,thermal,dielectric and other properties were investigated in detail.（1）Firstly,a series of glass transition temperature gradients and PEN resins with different configurations were obtained by molecular structure design and modification of aromatic dicarboxylic phenol structure.The effects of molecular structure on the thermal,mechanical,dielectric and breakdown strength of PEN films were investigated in detail.Meanwhile,BP-PEN films with high orientation were prepared by hot-stretching,and the effects of different stretched temperatures and ratios on the structure and properties of BP-PEN films were discussed.The results show that the glass transition temperature（T_g）is between 170℃-260℃,and the tensile strength is over 90 MPa,among which BP-PEN shows the best tensile strength,reaching 116 MPa.Meanwhile,the energy storage density of BP-PEN is over 0.8 J/cm³,exhibiting the best energy density;moreover,when the hot-stretched ratio of the BP-PEN film increases from 0%to 200%（under 280℃）,its melting enthalpy increases by 9 times,the tensile strength increases by 2.8 times,and the dielectric constant increases by 72%.These results show that the BP-PEN exhibited the optimal thermal stability,mechanical properties and dielectric properties,so BP-PEN was chosen as the matrix resin for the follow-up research system.（2）Secondly,PEN based composite dielectric materials were prepared based on the interfacial modification of 0D barium titanate（BT）.The inorganic amorphous carbon,organic polymers and organics were loaded on the surface of BT nanoparticles by hydrothermal method,in-situ polymerization method and chemical grafting method,respectively.Thus,novel BT@C,PANI-f-BT and BT-g-CuPc nanoparticles with core-shell structure were successfully prepared.Then,the effect of shell modified layer material and size on the properties of PEN based composites was studied in detail.At the same time,the secondary ordered dispersion of nanoparticles in PEN matrix is realized by hot-stretching method,and the effect of unidirectional hot-stretching on the properties of PEN based nanocomposites is systematically studied.For PEN/PANI-f-BT nanocomposites,the best interfacial modified layer size of nanoparticles is about 6 nm;and when the PEN based nanocomposite films are hot-stretched from 0%to 100%,the tensile strength increases by 92%and the dielectric constant increases by 34%.In addition,the results show that the PEN/BT-g-CuPc nanocomposites have the best dielectric constant and energy density,reaching 14.9 and 1.81 J/cm³（1 kHz）,respectively,indicating that the metal phthalocyanine modified layer can be used as the material type for interfacial functionalization of the subsequent systems.（3）The CNTs nanowires of different sizes were prepared by controlling ultrasonic and acid acidification oxidation time.Then,the multi-dimensional and multi-scale CNTs-g-BT nanoparticles with“rivet”like structure were prepared by in-situ chemical bonding with the ceramic nanofillers mentioned above.The effect of the filling content on the properties of PEN based nanocomposites was studied in detail.The results show that the CNTs-g-BT prepared by chemical bonding has good stability,and its“rivet”like structure can increase the contact area with PEN matrix and form molecular chain interlocking,which can effectively enhance the thermal,mechanical and dielectric properties of PEN matrix:the T_g of all PEN/CNTs-g-BT nanocomposites were above 215℃;the tensile strength is more than 90 MPa,and the tensile modulus is over 1900 MPa.When the filling content of nanoparticles is 20 wt%,the dielectric constant and energy density of the nanocomposites reaches 18.4 and 2.27 J/cm³ at 1 kHz,respectively.Even when the temperature is up to 180℃,the energy density of the nanocomposites remains about 1.6J/cm³.（4）Finally,based on the 2D GO nanosheet structure and its abundant oxygen-containing functional groups on the surface,the GO surface was cyanylated by chemical grafting.Then,combined with the above research results,GO was introduced into the CNTs-g-BT nanoparticles as a carrier template,and a new three-dimensional structured nano-filler（CNTs-BT-GO）was prepared by chemical bonding method.The effect of different filling contents on the structure and properties of PEN matrix was studied in detail.The results show that the 3D nanofillers have good compatibility with the PEN matrix.The design of 3D nano-structure avoids the defects such as local agglomeration of fillers in the matrix,etc,which improves the dispersion of nanofillers in the PEN matrix.In addition,the 3D structure of CNTs-BT-GO is stable and can form interpenetrating network with the PEN macromolecular chain,which increases the interaction of organic-inorganic chemical interface.All these results improve the thermal and mechanical properties of the PEN based nanocomposites to some extent:the T_g of all PEN/CNTs-BT-GO nanocomposites in this system is more than 215℃.The tensile strength is more than100 MPa,and the tensile modulus is above 2000 MPa.When the filling content of nanoparticles is 20 wt%,the dielectric constant and energy density of the nanocomposites reaches 20.3 and 2.6 J/cm³ at 1 kHz,respectively.Even when the temperature is up to 180^oC,the energy density of the nanocomposites remains at about 1.8 J/cm³.