Influence of Transverse π-π-Bridging on Formation Properties of High-Modulus Carbon Nanotube Fibers

A theoretical model that interprets the increase in the elastic modulus of carbon nanotube fibers upon the formation of pi-pi cross links between individual nanotubes in the fiber is proposed. It is shown that the following three factors affect the elastic modulus of a fiber: the elastic modulus of the initial nanotubes; the degree of interaction between individual nanotubes in the fiber; and its aspect ratio, i.e., the ratio of the fiber length to its diameter. At the point of transition of these interactions from repulsion to attraction, the elastic modulus of the fiber reaches the corresponding value for an individual carbon nanotube and exceeds it in the region of attractive interactions. The basic factor for the rigidity of carbon nanotube fibers is their structure, which is characterized by fractal dimension.