THE EFFECT OF CARBON NANOTUBES DOPE CONCENTRATION ON THE WET-SPUN FIBER MACROSCOPIC PROPERTIES
On the molecular level, carbon nanotubes (CNTs) exhibit excellent mechanical strength, thermal and electrical conductivity properties, combined with low density. This unique-feature combination makes CNTs ideal candidates for processing multifunctional macroscopic fibers. However, translating the unique characteristics of a single molecule into macroscopic material is challenging.
The large-scale use of CNTs in applications was significantly promoted with the discovery of spontaneous molecular dissolution of CNTs in chlorosulfonic acid (CSA). The phase behavior of the CNT/Superacid system show different stages as function of CNTs concentration. At low concentrations the CNTs are individually dissolved, forming an isotropic solution. Starting at a critical concentration, the CNTs phase-separate into liquid crystalline nematic phase, coexisting with an isotropic solution. Further increase in concentration leads to the formation of a fully liquid crystalline phase. The properties of the CNT-based macroscopic structures are affected by the degree of alignment of the CNTs.
Here, we study with cryogenic scanning electron microscopy (cryo-SEM) and wide-angle x-ray scattering, how the CNTs nanostructure in the solution affect the macroscopic properties of the fiber. The fibers were tested for their degree of alignment, conductivity, diameter, and tensile strength. Cryo-SEM results demonstrate that liquid crystalline domains become wider with increasing CNT concentration, and at the same time, the volume fraction of the isotropic solution decreases. Furthermore, while other parameters do not appear to depend on CNT concentration, the tensile strength results show a decrease with increasing CNT concentration.