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A chemical processing technology that allows the continuous spinning of single-walled carbon nanotubes (SWNTs)-nylon 6 (PA6) fibers by the in-situ polymerization of caprolactam in the presence of SWNTs, which simultaneously optimizes the morphology of the composite, is reported. The results suggested that caprolactam is an excellent solvent for carboxylic-acid-fictionalized SWNTs (SWNT-COOH) and that this allows the efficient dispersal of the SWNTs.

Carbon nanotubes are aligned by post-treatment techniques utilizing electrical, magnetic, mechanical forces and self-assembly and in situ during their growth. The in situ method, which is mainly carried out by the chemical vapor deposition (CVD) process, requires high temperatures (>800 degree Celsius) and a reactive environment because of which it is not applicable to devices with limited stability.

We report an approach to the chemical engineering of the single-walled carbon nanotube (SWNT)-polymer interfacial interaction in a nylon 6 graft copolymer composite which is based on the degree of SWNT functionality. Continuous fibers are drawn from composites fabricated from the in situ polymerization of caprolactam with SWNTs possessing a range of carboxylic acid (SWNT-COOH) and amide (SWNT-CONH(2)) functionalities. Mechanical performance evaluation of the composite fibers shows that a high concentration of the carboxylic acid functional groups leads to a stronger SWNT-nylon interfacial interaction, as reflected in greater values of the Young's modulus and mechanical strength. Replacement of the COOH group by CONH(2) in the SWNT starting material changes the grafting polymerization chemistry, thereby leading to the covalent attachment of longer graft copolymer chains to the SWNTs, and alters the composite morphology while increasing the composite flexibility and toughness.