L.-S. Tan, D.H. Wang, J.B. Baek
Air Force Research Laboratory, United States
pp. 412 - 415
Keywords: carbon nanotubes and nanofibere, graphite nanoplatelets, covalent functionaliztion, Friedel-Crafts acylation, defect chemistry
Inorganic acids such as HNO3, HCl, H2SO4 are commonly used to remove catalyst residues and carbonaceous impurities from carbon nanotubes and nanofibers. Under more forcing conditions, oxidizing nitric acid is known to “cut” the CNT into shorter tubes and introduces oxygen-containing organic functions to the defect sites. We have found that a much milder and non-oxidizing poly(phosphoric acid) or PPA, can be used not only for purifying CNT/CNF, but also for promoting electrophilic functionalization. PPA is quite effective in dispersing carbon nanomaterials such as VGCNF, MWNT, SWNT, detonation nanodiamonds, graphite nanoplatelets, etc. because of its acidic and viscous properties, the former promoting de-aggregation of these carbon nanoparticles while the latter impeding their rebundling. PPA is also known for its catalytic power to promote efficient Friedel-Crafts acylation, which we have successfully exploited based on the hypothesis that the defect sites in these nanomaterials contain C-H bonds that are susceptible to such acylation reaction. This presentation will provide an overview of our bottom-up approach in utilizing this versatile synthetic tool based on PPA to impart useful functional groups and generate polymer nanocomposites with the goal toward improving dispersion, interfacial adhesion and solution processability involving various types of condensation polymers.