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Preparation of Surface-functionalized Graphene and Its Influence on the Mechanical Properties of Nanocomposite Materials

Author: DaiJing
Tutor: LangMeiDong
School: East China University of Science and Technology
Course: Materials Science and Engineering
Keywords: graphene surface functionalization sheet resistances composite materials mechanical properties
CLC: TB332
Type: Master's thesis
Year: 2012
Downloads: 142
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Abstract


Graphene, a new 2D one-atomically thick carbon nanostructure with sp2-hybirdized carbon atoms arranged in a honeycomb lattice, has attracted enormous attentions because of its fascinating electronic and mechanical properties. Substantial efforts have been paid to harness these properties for macroscopic applications such as a conductor of electricity and heat. However, its wider application depends on how to get high-quality single- or few-layered graphene sheets and how well the sheets can be stabilized under various conditions. Recently, the success of covalent chemical modification of the graphene sheets paves a new way to achieve functionalized graphene sheets with permanent stabilization compared to that stabilized via non-covalent interaction.In this dissertation, we presented a new strategy to prepare functionalized graphene sheets, in which graphite or graphene (number of layers>7) was modified with proper substances firstly to produce chemically functionalized graphite or graphene, and then sonicated in an organic solvent and exfoliated the graphite into mono- or few-layered functionalized graphene sheets. And then, the content of the attached groups and structural features of functionalized graphene were characterized. Finally, we investigated the effect of graphene on the mechanic properties of composite materials.The main contents of this dissertation are summarized below:(1) pyrrolidine-functionalized graphene was prepared by used 1,3-dipolar cycloaddition of azomethine ylide generated by in situ condensation of N-methyl-glycine and pentafluorobenzaldehyde. The content of the attached groups on the sheets was determined by thermogravimetric analysis (TGA) and X-ray photoelectron spectroscopy (XPS), the disturbedπ-electron structure was investigated by Raman spectrum. The structural features were characterized by microscopic technologies such as atomic force microscope (AFM), transmission electron microscope (TEM), and scanning electron microscope (SEM). Moreover, the dispersion of functionalized graphene was investigated. Since the surface-anchored organic groups can act as "molecular wedges", the intercalation of the solvent molecules into the layers of graphite was facilitated which made the graphite readily exfoliate to achieve well-dispersed single- or few-layered graphene sheets.(2) Pentafluorophenyl-functionalized graphene was synthesized via diazotization reaction of Pentafluoroaniline diazotized. The content of the attached groups, structural features, the number of layers on the graphene were researched by TGA XPS, TEM, SEM, AFM, and Raman. Then, pentafluorophenyl-functionalizationed graphite (PFP-f-graphite) for the production of uniform graphene films by simply filtering EFG dispersions in DMF on aluminum oxide membrane amd transferring to PET film, followed by annealing. The sheet resistances of the graphene films was 0.047~1.48 kΩ/sq at 13~65% optical transmittance. Another, the nnucleophilic substitution reaction can be performed between the para-F and-NH2. Thus, NH2-end-polymer can be attached on the graphene to regulate the interreaction of solvent and graphene.(3) Graphene oxide(GO)/PMMA and PFP-f-graphene/PMMA composites were prepared by blending with GO or PFP-f-graphene and PMMA, and the performance of these composites were characterized. The results showed that graphene as fillers can effectively improve the mechanic properties of PMMA.

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