Preparation And Dielectric Properties Of Functionalized Ionic Liquids Modified Carbon Nanotubes And Their Composites

Carbon nanotubes(CNTs)have been one of the most widely used percolation-type fillers in the preparation of polymer-based dielectric composites.Ionic liquids(ILs)have become a research hotspot of modified CNTs in recent years because of their excellent properties.The abundant anionic and grafting groups of ILs also bring new ideas to the application of CNTs in dielectric composites.The following research was done on this:(1)The structure and properties of ILs depend to a large extent on the choice of cations and anions.In our work,we obtained ionic liquids with different anions by anion exchange of vinyl imidazole-type ionic liquids.Three ILs with different anions were coated on the surface of the carbon nanotubes used divinylbenzene as the crosslinking agent.Several dielectric composites were prepared by using thermoplastic polyurethane(TPU)as the matrix polymer material and modified CNTs as the filler.Comparing the properties of the composites,it was found that the different anions carried by the ILs have a significant effect on the dielectric properties of the composites.(2)TheILswith a strong polar cyano group was synthesized,and copolymerized with divinylbenzene on the surface of carbon nanotubes(CNTs)to form a core-shell structured hybrid.Then the fillers compounded with epoxy to prepare a filler-well-dispersed composite.The ILs played a significant role in increasing the dielectric constant owing to interfacial polarization.Moreover,the crosslinked polymer shells decreased the dielectric loss,which are desirable properties for electronic devices.(3)The two vinylimidazole-type ILs were prepared,which were grafted with an amine group and an epoxy group,respectively.Then,the two ILs were introduced onto the surface of CNTs to form a stable crosslinked copolymer coating.Thereby the surface of the CNTs successfully carries the amino group and the epoxy group.Epoxy resin composites were prepared using the CNTs as fillers.Because of the amino groups and epoxy groups carried by ILs,the modified CNTs have good dispersion in the epoxy resin matrix.In addition,due to the presence of ionic bonds and imidazole rings in the ILs,the interfacial polarization of the filler and the matrix is enhanced.Both composites exhibit excellent dielectric properties.