Dispersibility Of Ionic Liquid And Polyimide On Single-walled Carbon Nanotubes

Compared with multi-walled carbon nanotubes,single-walled carbon nanotubes have a complete structure and fewer defects,and have a very wide range of applications in the fields of optics,electromagnetism,and thermals.According to the difference in electrical conductivity,SWNTs can be classified into metallic and semiconducting.Among them,monodisperse,single conductivity SWNTs are more widely used,but it is difficult to obtain high purity,single conductivity and monodisperse SWNTs products by traditional preparation methods.Therefore,in this paper,firstly,the crude SWNTs were prepared by the arc discharge method,and then the crude SWNTs were purified by means of ball milling,high temperature oxidation,concentrated hydrochloric acid immersion and K₂S₂O₈ oxidation.The experimental results show that impurities such as amorphous carbon,metal catalysts and metal oxides are removed after the purification treatment in the above steps.Four imidazolyl ionic liquid intermediates were synthesized by quaternization reaction,and four imidazolyl fluoroborate ionic liquids were synthesized by anion conversion method.The hydrophilic SWNTs oxidized by K₂S₂O₈ were then ultrasonically dispersed in four ionic liquid aqueous solutions.The results of Fourier Transform Infrared Spectroscopy characterization prove that we have successfully synthesized four imidazolium-based ionic liquids.The characterization results of UV-vis-NIR spectroscopy and Raman spectroscopy show that the aqueous solution of 1-n-hexyl-3-methylimidazolium fluoroborate ionic liquid have certain dispersibility for hydrophilic SWNTs,and certain enrichment for metallic SWNTs.There have been no reports on the selective dispersion of hydrophilic SWNTs directly using low-concentration ionic liquid aqueous solutions before.In addition,we synthesized five polyimide polymers with different aromatic backbones,and used their DMF solutions to ultrasonically disperse the above-mentioned concentrated hydrochloric acid-impregnated SWNTs samples respectively.The characterization results of UV-vis-NIR spectroscopy,Raman spectroscopy and TEM have together demonstrated that PIa has a monodisperse effect on SWNTs and has obvious selectivity for semiconducting SWNTs.Then,the transfer mechanism of charge from PI to SWNTs was discussed based on the results of UV-vis-NIR spectroscopy and Raman spectroscopy characterization.These conclusions provide a valuable reference for in-depth research on the selective enrichment of SWNTs by polymers and the application of carbon nanotube composite electronic devices.