Enhancement,Degradation And Recycling Mechanism Of Carbon Nanotube Thin Films By Hexahydrotriazine Compounds

CNTs have the advantages of light weight,high mechanical strength,good electrical,thermal and optical properties,and have been widely used in energy storage,artificial muscles,sensors,catalytic materials,separation and purification,electromagnetic interference shielding,aerospace and other fields.As one of the macromolecules of CNTs,CNT thin films not only have good mechanical and electrical properties,but also have large specific surface area,light weight and stable structure.It has important application value in the fields of high durability energy storage equipment,high-performance composite materials,transparent conductive films,portable wearable devices,sensors and health monitoring.However,problems and challenges such as hydrophobicity,difficulty in recycling,mechanical strength and electrical conductivity far inferior to those of single carbon nanotubes,which seriously hinder their extensive application.Therefore,the preparation of hydrophilic,high-strength,high-conductivity and recyclable carbon nanotube films is still an important research direction.Based on nitrogen doped in situ synthesis and thiol-ene click reaction surface modification technology,the introduction of hexahydrotriazine rings,hyperbranched polymer elastic network,the structure of the hydrogen bonding interaction were used to prepare CNT films with controllable wettability,high strength,high conductivity,recycability,self-healing of surface polymer.The mechanisms of wettability,mechanical strength and electrical conductivity,recycling and self-healing were explored.The specific research contents are showed as follows:(1)Enhancement of carbon nanotube films by trimercaptohexahydrotriazine and mechanism of degradation and recycling.Pristime CNT film was modified by in-situ nitrogen doping and thiol-ene click reaction to obtain six kinds of CNT thin films.The synergistic enhancement effect of nitrogen doping and thiol-ene click reaction was studied,and the mechanism of phosphoric acid degradation to compound in enhanced carbon nanotube thin film was analyzed.The influence factors and laws of tensile strength,electrical conductivity and recycling of carbon nanotube films were studied.Contact Angle measuring instrument,X-ray photoelectron spectroscopy(XPS),X-ray diffraction,Raman spectroscopy spectra,High resolution transmission electron microscopy,scanning electron microscopy,infrared spectroscopy,nuclear magnetic resonance,gas chromatography-mass spectrometry,thermogravimetric analyzer and universal tension machine were used to systematically characterize the wettability,morphology,structure and wall of functionated carbon nanotube films Number,lattice change,diameter distribution,light transmittance,chip resistance,mechanical properties and degradation cycle properties.Finally,carbon nanotube films with high wettability,high strength and high conductivity were obtained,and the recycling of carbon nanotube films and monomers was realized,revealing the strengthening mechanism and degradation recycling mechanism of carbon nanotube films.(2)Enhancement of carbon nanotube films by hexahydrohomotriazine thiol-ended hyperbranched polymer and mechanism of degradation and recycling.The thiol-ended hyperbranched polymers(BTHP-n,n=6,12,24)with different amount of end-thiol groups were prepared by thiol-isocyanate click reaction.Then,the enhancement effect of BTHP-n on carbon nanotube films and the mechanism of degradation and recycling were studied.The effects of the amount of photoinitiator,sulfhydryl polymer,click time,roller pressure and humidity on the mechanical properties of functionalized carbon nanotube films were studied systematically,and the preparation conditions with high strength were obtained: The mass ratio of CNT film to polymer was 1:300,the amount of photoinitiator was 2 wt% of polymer mass,the temperature was 60 ℃ and the humidity was 60%.Under these conditions,the tensile strength and electrical conductivity of carbon nanotube film are 537 MPa and750 S/cm,respectively,which are 1690% and 257% higher than the pristine carbon nanotube film.After 5 cycles,the mechanical properties and electrical conductivity remain above 90% and 87%,respectively,and the degradation and recycling of monomer and CNT films are realized.The enhancement mechanism and degradation cycle mechanism of hyperbranched polymer elastic network and hydrogen bond interaction on carbon nanotube thin films were revealed.(3)Enhancement of carbon nanotube films by hexahydrotriazine terminated UPy hyperbranched polymer and mechanism of degradation and recycling.UPy-NCO was prepared from 2-amino-4-hydroxy-6-methylpyridine(UPy)and hexamethylene diisocyanate,and then thiol-ended hyperbranched polymers(BTU)containing multiple hydrogen bonds was prepared by thiol-isocyanate click reaction.The structure of hyperbranched polymer(BTU)was characterized.The effect of the amount of photoinitiator,polymer,click time,rolling conditions,humidity on the strength of carbon nanotube films was studied.The tensile strength and electrical conductivity of the prepared CNT film can reach 617 MPa and 840 S/cm,which are1956% and 300% higher than those of the pristine CNTs film,respectively.The enhanced carbon nanotube films also have the function of degradation cycle and self-repair,and the mechanisms of degradation cycle and self-repair are explored.