Research On The Structure And Properties Of Polyarylene Ether Nitrile Films Prepared Via Wet Phase Inversion Method

Phase inversion polymer membranes possess various advanced functions and significant advantages,such as light weight,easy functionalization,diverse preparation processes,and adjustable pore structure,and are expected to be used in sensors,low dielectric,electromagnetic shielding and other fields.Compared with other methods for preparing porous polymer films,the wet phase inversion method possesses the advantages of simplicity,controllability,easy operation,adjustable microporous structure,and suitability for large-scale preparation,which is considered to be one of the most effective ways to introduce pores into polymer matrices.As a new type of high-performance polymer with excellent performance,polyarylene ether nitrile has significant advantages such as high strength,remarkable thermostability,oxidation resistance,corrosion resistance,etc.and has widespread application prospects in the fields of aerospace,electronic appliances,capacitors,power batteries,high-voltage power transmission and transformation,transformer insulation parts,etc.At present,there is no report involving with the design,preparation and application of phase inversion polyarylene ether nitrile film.The introduction of pores into the polyarylene ether nitrile matrix by the wet phase inversion method is helpful to combine the inherent advantages of the polyarylene ether nitrile and the porous structure broadening the application field of the polymer phase inversion film to further extent.This dissertation is devoted to the structural design and performance research of phase inversion polyarylene ether nitrile films.Polyarylene ether nitrile is used as the polymer matrix,and the wet phase inversion method is adapted to introduce pores into the polymer matrix.The surface/interface functionalization method is used to design and prepare films with different structures and properties.Phase inversion polyarylene ether nitrile films with outstanding performance are developed via comprehensively adjusting various preparing parameters,and the application of the obtained films is explored in low dielectric,electromagnetic shielding and other electronic and electrical fields.1.Poly(arylene ether nitrile)films is fabricated via wet phase inversion using bisphenol A poly(arylene ether nitrile)as polymer matrix.The effects of four main factors,including solvent type,polymer concentration,solvent content and non-solvent content in coagulation bath,on the structure and properties of the films are investigated.The regulation of the structure and properties of the films is achieved by studying the formation mechanism and influencing factors of the films.The research results show that the films formation rate can be adjusted by changing the concentration of the casting liquid and the type of the coagulation bath.The films with porosity ranging from 86.2%to 58.5%,dielectric constant ranging from 1.30 to 1.91,tensile strength ranging from 5.5MPa to 12.1 MPa and elongation at break ranging from 21.9%to 63.4%are obtained.2.Bisphenol AF polyaryl ether nitrile with hydrophobic group-CF₃ is prepared by condensation polymerization.By changing the composition of the coagulation bath to change the mass transfer resistance during the phase inversion process and control the film formation rate of the wet phase inversion method,phase inversion bisphenol AF polyarylene ether nitrile films with micro-nano structure on the surface are prepared.The research results show that the hydrophobic film with micro-nano structure on the surface has stable ultralow dielectric constant and excellent mechanical properties.The surface roughness of the films increases from 8.5 nm to 509 nm,the water absorption decreases from 0.48%to 0.1%,the dielectric constant ranges from 1.16 to 1.43,and the tensile strength increases from 7.2 MPa to 13.5 MPa.The dielectric constant growth rate of the films decreases from 32.8%to 3.5%after static immersion in water for 7 days.3.Based on the interaction between Zn²⁺and electron-rich groups in polyarylene ether nitrile,2-methylimidazolium zinc salt(ZIF-8)is formed in situ on the pore wall of films during the phase inversion method,resulting ZIF-8 functionalized phase inversion polyarylene ether nitrile films.By controlling the content of ZIF-8 precursor in the film formation process,the honeycomb pore structure can be effectively adjusted,and various properties of the ZIF-8 functionalized films can be regulated.The formation of ZIF-8promotes the increase of the honeycomb pore size of the films from 1.6?m to 5.8?m,the decrease of the dielectric constant from 1.82 to 1.41,and the increase of the elongation at break from 58.9%to 112.4%.The ZIF-8 generated at the interface of the films improves the hydrophobicity of the obtained films,thereby enhancing the dielectric stability of the ZIF-8 functionalized films under humid environment.4.Phase inversion polyarylether nitrile films enriched with MWCNTs on the pore walls are prepared,obtaining a three-dimensional conductive network structure,via the dispersion of multi-walled carbon nanotubes(MWCNTs)by polyvinylpyrrolidone(PVP K30).By controlling the mass ratio of PVP K30 to MWCNTs during the film preparing process,the honeycomb pore morphology can be adjusted,and the agglomeration of high content of MWCNTs can be avoided,promoting the uniform accumulation of MWCNTs on the pore walls and reducing the content of MWCNTs required for the construction of a continuous conductive network pathway.Benefiting from the synergistic effect of uniform enrichment of MWCNTs on the pore walls and the honeycomb structure,incident electromagnetic waves are reflected and absorbed repeatedly in the film enriched with MWCNTs on the pore walls,achieving excellent electromagnetic shielding.The total electromagnetic shielding performance of the films enriched with MWCNTs on the pore walls exceeds 26.5 d B at 8.2 GHz,and the absorption efficiency reaches 23.6 d B,which is much greater than the reflection efficiency of 2.9 d B.The tensile strength of the films is up to 9.6 MPa,and the elongation at break is as high as 104%.5.The alternating multilayer films with stable electromagnetic shielding performance are constructed through the hydrogen bonding between Pluronic F127anchored on the surface of phase inversion polyarylether nitrile film and the cellulose nanofibers(CNF)in the MWCNTs/CNF conducting layer to increase the interaction force between the layers.The research results show that in the alternating multilayer films,the Pluronic F127 modified film layer plays the role of increasing the interlayer interaction force,supporting the substrate and isolating the conducting layer.The MWCNTs in the functional layer MWCNTs/CNF is regarded as the agent to enhance the electromagnetic interference shielding,and the CNF is regarded as the agent to enhance the interaction force between the MWCNTs/CNF conducting layer and the film layer and improve the mechanical properties.Compared with the single-layer structure,the construction of the alternating multi-layer structure increases the number of times the electromagnetic wave reflected inside the films,thereby enhancing the electromagnetic shielding performance of the alternating multilayer films.When the number of layers is 4,the electromagnetic shielding performance of the alternating multilayer film is as high as 27.4 d B at 8.2 GHz.