Preparation And Application Of Photocured Ionic Liquids/Graphene Composite Conductive Coating

Graphene is a two-dimensional carbon material with excellent performance such as good mechanical,environmental responsiveness and electrical properties.In recent years,it has been widely used in composite materials,energy technology,electronic and biomedical fields.The carbon atom plane of graphene is composed of a large number of six-membered ring structures,which results in a strongπ-πinteraction between the graphene sheets in addition to van der Waals forces.Therefore,the agglomeration is highly prone to occur during preparation and the dispersion process in the medium for graphene,inhibiting the reinforcing effect of graphene on the mechanical and electrical properties.The dispersion and stability of graphene has always been an inherent problem in the preparation of graphene composites,and especially in polymer matrix with high content of graphene,the agglomeration problem of graphene is inevitable.Ionic liquids,especially ionic liquids with an aromatic ring structure of imidazoles,which have aπ-πconjugation effect and a cation-πinteraction with graphene,weaken the interaction between graphene sheets.Therefore,the dispersion stability of the graphene in the composite system is improved to some extent.On this basis,the subject utilizes different kinds of ionic liquids to covalently and non-covalently modify graphene to achieve the purpose of improving the dispersion and stability of graphene.At the same time,different functional methacrylic double bonds are introduced into the ionic liquids to prepare photocurable ionic liquids,and the graphene is non-covalently modified by the ionic liquid,so that it can be used in a photocuring system.Meanwhile,grafting modification of graphene oxide with the ionic liquid with an amino group weakens the interaction between the graphene sheets and promotes the dispersion of graphene in the polymer matrix.In addition,the temperature sensing performance of the prepared graphene/ionic liquid composite coating was studied.And the detailed experiments contents are as follows:1.The monofunctional photocurable ionic liquid was synthesized with1-methylimidazole,6-chloro-1-hexanol and methacryloyl chloride,and characterized to determine the structure by ¹H NMR and FT-IR.The functionalized ionic liquid（IL-NH₂）with amino group was synthesized from 1-methylimidazole and 3-chloropropylamine hydrochloride,and then used to modify the graphene oxide by amidation reaction.The structure,grafting rate and morphology of the modified graphene oxide（MGO）were characterized by FT-IR,XRD,Raman,TGA and XPS,and SEM.The non-covalent modification of the modified graphene oxide by the photocurable ionic liquid is used to further improve the dispersibility of the graphene.Then,it was dispersed in commercial modified epoxy acrylic resin to prepare graphene/ionic liquid composite photocurable coating after UV curing.Real-time infrared,TGA and Raman were carried out to characterize the photopolymerization kinetics,thermal properties and MGO thermal reduction of the coatings.The effects of the content for modified graphene oxide to dispersibility were investigated by XRD,XPS,DMA.In addition,the electrical properties of the coating were characterized using an electrochemical workstation and a digital multimeter.In order to visualize the dispersibility of graphene in the coating,PEDOT:rGO-PEI/Au was characterized by FTIR and Raman.The structure of nanoparticles was characterized by SEM and TEM.The results showed that the photocurable ionic liquid and the ionic liquid with amino group were successfully synthesized,and the double bond conversion rate of photocurable ionic liquid was about 70%,which can be used in the UV-curing system.Grafting reaction successfully occurred on the surface of GO and the presence of ionic liquid on the surface of graphene weakens the interaction between graphene sheets,resulting in an increase in the spacing between GO sheets.It is beneficial to improvement of the dispersion and stability of the modified graphene oxide.At the same time,the photocuring formulation system has good photocuring properties due to the photothermal effect of the modified graphene oxide,which can promote the double bond conversion in the system to some extent.The thermal stability of the obtained coating conforms to the basic requirements of the coating.It is required that the modified graphene oxide is well dispersed in the coating,and the addition of the modified graphene oxide makes the coating have good electrical properties,which can be used for sensing coating research.In addition,PEDOT:rGO-PEI/Au NPs was successfully synthesized,and the dispersion effect of ionic liquids and EDOT was similar.2.In view of the good environmental responsiveness of both ionic liquids and graphene,theoretically prepared composite materials can be used for sensing research.The temperature of the external environment was changed and the resistance change of the coating at different temperatures was recorded in real time,and the obtained data was fitted by the function relationship between the VFT equation and the parallel resistance.The results show that the coating with low contents of MGO is consistent with the constructed function.The coating with high contents of MGO will exhibit a more complicated functional relationship due to the linear relationship of data.Under the condition of higher contents of MGO,the response speed of the coating is effectively improved.The addition of modified graphene oxide can increase the thermal conductivity of the coating.Within the range of suitable contents of MGO,the response stability of the coating is significantly improved with the increase of contents of MGO.3.In order to ensure the stability of coating performance and reduce the influence of ionic liquid on the performance of the coating,multifunctional photocurable ionic liquids are synthesized.Difunctional photocurable ionic liquid（DPIL）was synthesized from monofunctional photocurable ionic liquid and synthetic sodium methacrylate and both its anion and cation can be polymerized.The structure of DPIL was confirmed by ¹H NMR and FT-IR,and the photocuring performance of DPIL was detected by real-time infrared.Commercialized graphene is dispersed by a synthetic difunctional photocurable ionic liquid,which is blended with a commercial modified epoxy acrylate resin to form a photocurable formulation,and the graphene/ionic liquid composite photocurable coating is prepared after UV curing.Real-time infrared,TGA,XPS,pendulum hardness testers and other test instruments were used to investigate the effect on the photocuring properties,basic film properties and thermal properties under different contents of graphene,DPIL and reactive diluent.The results showed that DPIL was successfully synthesized,and its double bond conversion rate was 87.8%,which was greatly improved compared with monofunctional photocurable ionic liquid.The photocurable formulation has a high double bond conversion rate,and especially in the low content of graphene due to the photothermal effect of graphene,the double bond conversion rate will gradually increase.The TGA and pendulum hardness test results show that the coating has good basic film properties and can meet the most requirements.The XPS spectrum and its statistical results indicate that there is indeed a cation-πinteraction between the ionic liquid and the graphene,which can be used to improve the dispersion stability of graphene.The characterization results of DMA,gloss meter and 3D ultra-depth-of-field microscope indirectly and directly reflect the good dispersion of graphene in the coatings.The strategy that DPIL dispersed graphene is universal and can be used to disperse commercial graphene and ensure the basic properties of the coating.