Study On The Functionalization Of Cnts And Its Polybenzimidazole Nanocomposites

Functionalization of carbon nanotubes (CNTs) has aroused increasing interest due to the demand to improve CNTs'solubility and the fascinating capacity to fabricate novel namomaterials and nanodevices. Here we have proposed a novel method, which has combined the purification, functionalization of MWNTs and the polymerization of Poly[2,2'-(p-oxydiphenylene)-5,5'-bibenzimidazole](OPBI), to prepare high performance nanocomposites. It is called"one pot synthesis".Firstly, multiwalled carbon nanotubes grafted OPBI and OPBI (MWNT-g-OPBI/OPBI) composite was successfully synthesized by condensation polymerization of 3,3'-Diaminobenzidine (DAB) and 4,4'-Dicarboxydiphenyl ether (DCDPE) in the presence of MWNTs in PMMA (phosphorus pentoxidel/methanesulfonic acid in a ratio of 1:10 by weight). Such method has the advantage of reducing the conventional complex fabrication procedures and is particularly suitable for the bulk production of advanced polymer nanocomposites. Raman spectroscopy, SEM, TEM, XPS and 1H NMR measurements show that the covalent bonding between MWNTs and OPBI is formed, leading to the good dispersion of MWNTs in OPBI matrix. The composites obtained by this method exhibit obvious reinforcing effect in mechanical properties, including higher yield strength, tensile strength and enhanced young's modulus, as well as an improvement in the thermal stability and electrical conductivity.Secondly, MWNTs grafted hyperbranched polybenzimidazoles (HBPBIs) were successfully synthesized by condensation polymerization of 1,3,5-benzenetricarboxylic acid (BTA) and DAB in the presence of MWNTs in polyphosphoric acid (PPA). Different monomer addition manners and molar ratios resulted in different polymers, based on this point, we prepared carboxyl-terminated MWNT-g-HBPBI-1/HBPBI-1 and benzoic acid functionalized amine-terminated MWNT-g-HBPBI-3/HBPBI-3. Furthermore, single walled carbon nanotubes (SWNT) wrapped with HBPBI-3 displayed good solubility in DMSO. Besides, HBPBI-3 can act as stabilizer as well as reducer for silver ion converted to silver nanoparticles. Therefore, SWNT/HBPBI-3/Ag was prepared at room temperature without the reducer. Due to the antimicrobial property of NPAg, SWNT/HBPBI-3/Ag could be added to PBI fibers to make high performance materials.