Preparation Of Carbon Nanotube/Graphene Sheets Three-dimensional Network And Study Of Their Poly(Arylene Ether Nitrile) Composites

Polyarylene ether nitrile（PEN）is a new type of engineering resin.Its molecular structure containing nitrile and benzene-based rigid groups successfully endows PEN with excellent mechanical properties,electrical properties,chemical resistance,non-toxic and many other advantages,which is expected to play an important role in the military,aerospace,electronics and other fields.In this paper,we use phthalonitrile end-capped polyarylene ether nitrile,which exhibits excellent properties of thermoplastic polymer before high-temperature heating treatment,and is transformed to thermosetting polymer,showing more excellent thermal stability after high-temperature heating treatment.As a typical one-and two-dimensional carbon nanomaterial,both of Graphene and carbon nanotubes（CNT）exhibit ultra-high mechanical properties and excellent electrical conductivity in the in-plane direction,which are widely applied in preparation of nanocomposites.However,due to the strong p-p stacking tendency and high cohesive energy,the pure graphene or CNT tend to agglomerate or restack easily,which will decrease the surficial interaction with the polymer molecules,thereby hindering the carbon-based materials to express the excellent performance.In this paper,graphene oxide（GO）is employed as precursor for graphene.The existence of strong-polar oxygenic groups such as epoxy,hydroxyl,carboxyl,and carbonyl groups on the basal plane and edge of the sheets endows GO with high hydrophilic nature successfully,which makes it possible to be homogeneously dispersed in a variety of organic solvents.Meanwhile,those oxygen functional groups on the GO surface provide abundant reaction sites for further chemical modification,thereby realizing the effective preparation of the functional graphene-based materials.In this study,the phthalonitrile end-capped polyarylene ether nitrile will be used as the polymer matrix,whereas GO and CNT are also utilized to fabricate three-dimensional（3D）structural graphene-CNT hybrids through a physical or chemical methods.As a result,the 3D architecture will be combined with PEN to prepare the nanocompoistes.Meantime,the chemical modified graphene sheets and CNT can effectively enhance the interaction between the carbon materials and the polymer molecules,improving the the dispersion of graphene and CNT in polymer matrix,which will significantly promote the increase in the mechanical,dielectric and thermal stability of the nanocomposites.The main contents of this paper are as follows:（1）Firstly,a 3D structural CNTs-rGO hybrid is successfully fabricated by the self-assembly of GO sheets and acidulated CNT in the present of reducing agent.And then the hybrid is dipped in the dilute NMP solution of PEN.Finally,cross-linking PEN nanocompoistes containing 3D network structure（CNTs-rGO/CPEN）can be obtained by the following hot pressing.The SEM images of the smaples indicate that the carbon materials have good dispersibility in the polymer matrix and the electrical conductivity of the composites can be improved effectively.（2）In this part,3-aminophenoxyphthalonitrile（3-APN）is employed to realize the chemical modification on the surface of GO sheets and CNT with phthalonitrile moieties（GO-CN and CNT-CN）.And then the obtained GO-CN and CNT-CN combined with FeCl₃?6H₂O are utilized to fabricate the 3D structural Fe₃O₄-CNT/GS hybrids under the solvothermal reaction,which will be compounded with PEN to get（Fe₃O₄-CNT/GS）/PEN nanocomposites.XPS,XRD,FT-IR,and SEM are used to characterize GO-CN,CNT-CN and Fe₃O₄-CNT/GS,and the dispersibility of Fe₃O₄-CNT/GS in PEN.Moreover,the effect of cross-linking reation occurred in the polymer molecule on properties of the composites is also investigated before/after heat treatment.As a result,the final obtained nanocomposites exhibit a dramatic enhancement in the dielectric properties,thermal stability and mechanical properties.（3）In the self-assembly process,Zn²⁺is employed to realize the cross-linking between graphene sheet and CNT to form the GO-Zn-CNT hybrids by complexing with carboxyl and epoxy groups in the GO sheets and CNT,which is confirmed by the results of UV-vis spectra,TGA and SEM.Meanwhile,the optimal loading content of Zn²⁺is successfully filtrated in a value of Zn²⁺/C=0.01 mmoL/mg,thereby in-situ cross-linking the GO sheets and CNT to prepare the 3D structural GO-Zn-CNT hybrids in the PEN solution,which will be compounded with PEN to get（GO-Zn-CNT）/PEN nanocomposites.The obtained nanocomposites will be continuously thermal annealed at230 ^oC and 320 ^oC to gain the final PEN/GS-Zn-CNT and CPEN/GS-Zn-CNT,respectively.In comparsion with pure PEN,the glass transition temperature（T_g）,dielectric constant and tensile strength of CPEN/GS-Zn-CNT nanocomposites exhibts a substantial increase by 18%,181%and 27%when the loading content of GO-Zn-CNT is controlled at 2 wt%.