Preparation Of Janus Mxene And Its Application In Conductive Inks

Conductive inks not only have good conductivity and can be printed/coated on flexible substrates,but also have the advantage of fast,high volume and low-cost manufacturing,which has a broad application prospect in the field of flexible electronics.Nanomaterials two-dimensional transition metal carbide/nitride（MXene）,pristine graphene（PG）,carbon nanotubes（CNT）have great potential for application in conductive inks due to their high conductivity and good mechanical properties.However,the hydrophilic groups on the surface of MXene make it difficult to disperse in nonpolar solvents,which not only discourages its long-term storage/transportation but also limits the application of MXene in multifunctional conductive coatings.In addition,the addition of surfactants in nanoconductive inks usually leads to the degradation of the electrical properties of the material.Janus structures are special structures consisting of two regions possessing different physical or chemical properties with asymmetry.Constructing the Janus structure allows the combination of parts with different polarities,which facilitates the versatility of the material and the expansion of multiple applications.This work addresses the above problems by selectively modifying MXene to obtain Janus MXene（J-MXene）with single-sided grafted polystyrene（PS）molecular chains,achieving stable dispersion of MXene materials in various organic solvents ranging from polar to non-polar,effectively overcoming the difficult problem that nanosheets/nanotubes tend to agglomerate and sink in solvents and are difficult to process,while achieving multifunctional and The preparation of high performance J-MXene materials/J-MXene modified nanomaterial conductive coatings was also realized.The main results obtained in this thesis are as follows,（1）Preparation of multifunctional Janus MXene ink and its performance study of conductive coating:To address the problem that MXene is difficult to disperse in non-polar solvents,J-MXene,which has the properties of both MXene and PS,was obtained by electrostatic mutual attraction between positively charged PS and negatively charged MXene and asymmetric grafting of MXene nanosheets by in-situ one-step transfer method.The strong interaction between the non-polar PS chains/polar functional groups on the surface of J-MXene and the solvent based on the principle of similarity（same polarity and/or similar structure）was used to achieve stable dispersion of MXene from polar solvent（water）to non-polar solvent（toluene）,and it exhibited high dispersion content of 20 wt%and long-term chemical stability in non-polar solvent.J-MXene dispersions dispersed in toluene solvent were isolated from two major oxidizing factors,oxygen and water molecules,and the flake morphology remained intact,the edge structure remained clear,and the flake size was well maintained after 35 days of storage at room temperature.J-MXene conductive ink with low surface tension and low boiling point as dispersant can be directly on hydrophilic or hydrophobic substrates to form a uniform and solid large-area coating,and because of the structure of conductive MXene on one side,hydrophobic molecules on the other side of the PS and show good electromagnetic shielding（EMI SE）performance and environmental stability,after 24 h immersion in water can still maintain almost100%of the initial shielding value.Meanwhile,the J-MXene film,which is the main carrier of heat generation and light absorption after the introduction of PS with conjugated structure,exhibits enhanced photothermal conversion performance,reaching a high temperature of 148°C and long-term（60min）/cycle（5 times switching）stability after 300 s irradiation at 300 m W cm^-2.（2）Preparation of Janus MXene modified nanomaterial ink and its performance study:In response to the problem that the addition of surfactants in nano-conductive inks usually degrades the electrical properties of the materials,uniform dispersion of MXene,PG,and CNT in a nonpolar solvent such as toluene was achieved by using the adsorption of conductive amphiphilic J-MXene on the surfaces of MXene,PG,and CNT and the interaction between J-MXene and the solvent.The good dispersion property brings better solution processability,and the graphene（PG/J）films and CNT（CNT/J）films added with J-MXene have a more compact structure with a distinct lamellar stacking structure compared to the directly deposited PG and CNT films.The better structure gives the material a more continuous conductive network and achieves a high conductivity of～19 S cm^-1 compared to non-conductive PG and CNT films.The high dispersion of J-MXene assisted MXene in a low boiling point,low surface tension solvent results in MXene/J inks that can be scraped directly onto a wide range of hydrophilic and hydrophobic substrates,resulting in coatings with good EMI SE performance over a wide frequency range from 8.2to 40.0 GHz,and at 16.8μm thickness in the Ka band up to 41.8 d B.