Synthesis Of Benzimidazole Polymers And Their Application In Modification Of Carbon Nanotube And Graphene

Due to their high mechanical properties, excellent thermal, electrical conductivities and ultrahigh specific areas, carbon nanotubes(CNTs) and graphene, which are one and two dimension carbon nano-materials, respectively are the ideal components to composite with polymers or metal nano-particles for making high performance and functional nano-composites. However, poor dispersion and weak interfacial force with metal nano-particles or polymer matrixes are two obstacles for CNTs and graphene, which limit their applications. So, it is essential to modify the surface of CNTs and graphene to increase the dispersion in solvents and enhance the interfacial force with metal nano-particles or polymer matrixes without destroying the conjugated structures of CNTs and graphene, which are still the challenges for academic and industry.Polybenzimidazole polymer(PBI) has been widely applied to the aerospace, chemistry, protected fileds and so on, because of its high mechanical property and perfect thermostability. Meanwhile, PBI can be acted as functional polymer in fuel cell and metal nano-particles composites with its inner imidazole group. Besides, PBI is a candidate to modify the surface and enhance the dispersions of the nano-carbon materials due to the special properties and the strong π-π conjugation, which is important to prepare high performance and multi-functionalities composites.Based on the above considerations, this dissertation focused on the modification and dispersion of carbon nano-materials through the PBI and derivatised PBIs, as well as preparations of high performance and functional nano-pariticles composites. Firstly, the dispersions of the carbon nano-materials with the assist of PBI were optimized, and the different derivatised PBI to enhance the interfacial forces with nano-carbon materials were synthesized. After that, the surfaces of CNTs and graphene were modified by non-covalent and covalent modification with these polymers towards physical blending and chemical grafting. Then, several high performance composites or functional nano-composites were prepared, which can be applied to the fields of catalyst, direct ethanol fuel cell, aerospace and so on. The details of research are as follows:(1) Highly concentrated dispersions of homogenously dispersed MWNTs were obtained by optimizing the dispersion conditions of organic solvent with PBI as a non-covalent modifier, which were used to produce buckypapers by filtration method. TEM, Element Analysis and other measurements indicated that the centrifugal force had a great effect on the properties of the buckypapers during the preparing process. After that, the Ag/MWNTs-PBI hybrid was obtained by the composite of the buckypaper and Ag NPs. This hybrid was found to be a highly active and reusable catalyst for reduction of 4-nitrophenol.(2) The Poly(dimethylbenzimidazolium) iodide(P(DMBI)-I-) with excellent solubility was synthesized by alkylation reaction and non-covalent modified CNTs. Several measurements demonstrated that compared with PBI, the dispersions of CNTs prominently increased with the assist of the P(DMBI)-I-. Taking advantages of the coordination effect of imidazole groups and the electrostatic attraction to Pd NPs, Pd/MWNTs-P(DMBI)-I- hybrid was prepared. Electrochemical results indicated that this hybrid was of well electro-catalytic activity to the ethanol.(3) Hyperbranched-linear polybenzimidazoles with well solubility and formability were synthesized by in-situ polymerization. And, this method was suitable to other aromatic polymers. Then CNTs were modified by this new polybenzimidazoles through non-covalent method and the mechanism of the dispersion of modified CNTs was discussed based on the results of the dispersion. Several measurements demonstrated that the CNTs dispersion was totally increased with the help of hyperbranched-linear polybenzimidazole(15PH). Finally, MWNTs-15PH/15 PH composites were prepared by solution blending and casting coating. The mechanical property results of the composites revealed high reinforcement effect of the MWNTs-15 PH with better dispersion and compatibility.(4) The hyperbranched-linear co-polybenzimidazole with the ratio of 15:1 between linear PBI and HBPBI(15PH) which had the best dispersion to CNTs among the hyperbranched-linear polybenzimidazoles was chosen to modify the Graphene by non-covalent modification. The exfoliation conditions of graphene in DMAc solvent with PBI and 15 PH as non-covalent modifier were optimized. Finally, GP-15PH/15 PH composites were prepared by solution blending and casting coating. The mechanical property measurements revealed high reinforcement efficient of the GP-15 PH to the polymer matrix.(5) Under the ER(MSA : P2O5 with the mass ratio was 10:1) condition, OPBI was grafted to the surface of the GP by one-pot polymerization to achieve the covalent modification. Several measurements demonstrated that the well-exfoliated state and dispersion of the graphenes prepared by this method were obtained. GP-OPBI/Epoxy composites were prepared by solution blending and casting molding. And the mechanical properties of the composites revealed that GP-OPBI has high reinforcement effect on the Epoxy resin.