Preparation And Multifunctional Application Of Polyvinylidene Fluoride/MXene Layered Conductive Composite Films

With the widespread use of high frequency and high power electronic communication technology,the resulting electromagnetic interference（EMI）pollution has driven the rapid development of efficient electromagnetic shielding materials.Two-dimensional transition metal carbide or nitride Ti₃C₂T_x MXene exhibits excellent assemblability and electromagnetic shielding properties by virtue of its metal-level conductivity,tunable surface chemistry,and solution processability.However,the durability and large-scale production of Ti₃C₂T_x MXene-based composites remain major obstacles for industrial applications.In contrast,polymer-based shielding composites offer light weight,corrosion resistance,and easy processing.For this reason,this thesis selects Ti₃C₂T_x MXene as the conductive filler and polyvinylidene fluoride（PVDF）,which has the advantages of easy film formation,chemical resistance,thermal stability and aging resistance,as the polymer matrix,and uses a blade-coating process to prepare electromagnetic shielding polymer composites on a large scale.The specific work are as follows:（1）Flexible and durable PVDF/Ti₃C₂T_x MXene layered films with a dense layered“brick-mortar”structure were prepared based on a blade-coating process that can be produced in large areas.The highly aligned and oriented MXene results in PVDF/MXene films with high electrical conductivity ranging from 21.1 to 214.6 S/cm.Among them,the PVDF/MXene₉₀ composite film with a thickness of 17μm has excellent electromagnetic interference shielding effectiveness（EMI SE）and absolute shielding effectiveness（SSE/t）of up to 19504.8 d B cm²/g.Due to the protective effect of the polymer matrix,the PVDF/MXene film is able to maintain stable electromagnetic shielding performance after mechanical deformation,high and low temperature treatment and chemical corrosion.In addition,due to the MXene surface plasmon resonance effect and the high electrical conductivity of the composite film,the PVDF/MXene film is endowed with versatile photothermal/electrothermal heating capability with fast response,high stability and controllability,which ensures its reliable electromagnetic shielding performance under extremely cold conditions.（2）In response to the great challenge of high contact electrical/thermal interfacial resistance within the face of polymeric"brick-mortar"laminate films,a direct contact in-plane electrical/thermal conduction network is constructed in the composite film based on the synergistic effect between MXene and graphene nanosheets（GNP）.On the one hand,a large layer of GNP can construct an effective connected conduction network,and on the other hand,a small layer of MXene enhances the denseness and orientation of the laminate structure.As a result,the PVDF/MXene-GNP composite film reveals both synergistic enhancements in electrical conductivity,EMI SE and in-plane thermal conductivity,with the best conductivity obtained at a mass ratio of MXene to GNP of 3:7,7423 S/m,36.3 dB and 36.9 W/mK,respectively.In addition,based on the excellent electrical conductivity and photothermal conversion ability of MXene and GNP,the composite film exhibits highly efficient multifunctional heating capabilities,such as photothermal/electric heating.The synergistic effect proposed in this work provides a reference method and theory for the preparation of multifunctional high-performance conductive composite films.