Kevlar Functionalized Carbon Nanotubes for Next-Generation Composites

We report a sequential functionalization methodology for the covalent modification of multiwalled carbon nanotubes (MWNTs) with one and a half repeat units of the polymer poly-p-phenyleneterephthalamide (PPTA), Kevlar. Covalent attachment of PPTA monomer units, p-phenylenediamine (PDA) and terephthaloyl chloride (TPC), to the surface of MWNTs results in PPTA oligomer units forming an organic sheath around the nanotubes, PPTA-functionalized-MWNTs (PPTA-MWNTs). PPTA-MWNTs possess chemical functionality identical to that of PPTA, and thus provide nanoscale scaffolds which may be readily dispersed within a monomer solution and participate in the polymerization reaction to form a PPTA-MWNT/PPTA composite. We show that formation of PPTA in the presence of PPTA-MWNTs leads to a uniform dispersion of MWNTs within the polymer matrix, in contrast to aggregated masses of MWNTs in the case of pristine-MWNTs. The covalent attachment of oligomeric PPTA units to the surface of MWNTs represents the formation of a functional nanoscale building block which can be readily dispersed and integrated within the polymer PPTA to form a novel composite material. The implications of tuning the surface chemistries of carbon nanotubes (CNTs) to the chemistry of host polymer matrices are considered.