This review presents current progress in the preparation methods of liquid crystalline nanocarbon materials and the liquid crystalline spinning method for producing nano-carbon fibers. In particular, we focus on the fabrication of liquid crystalline carbon nanotubes by spinning from superacids, and the continuous production of macroscopic fiber from liquid crystalline graphene oxide.

In this study, poly(amic acid) was prepared via a polycondensation reaction of 3,3'-dihydroxybenzidine and pyromellitic dianhydride in an N-methyl-2-pyrrolidone solution; reduced graphene oxide/polybenzoxazole (r-GO/PBO) composite films, which significantly increased the electrical conductivity, were successfully fabricated. GO was prepared from graphite using Brodie's method. The GO was used as nanofillers for the preparation of r-GO/PBO composites through an in situ polymerization. The addition of 50 wt% GO led to a significant increase in the electrical conductivity of the composite films by more than sixteen orders of magnitude compared with that of pure PBO films as a result of the electrical percolation networks in the r-GO during the thermal treatment at various temperatures within the films.

In this study, we present a facile method of fabricating graphene oxide (GO) filmson the surface of polyimide (PI) via layer-by-layer (LBL) assembly of charged GO. The positively charged amino-phenyl functionalized GO (APGO) is alternatively complexed with the nega-tively charged GO through an electrostatic LBL assembly process. Furthermore, we investi-gated the water vapor transmission rate and oxygen transmission rate of the prepared (reduced GO [rGO]/rAPGO)10 deposited PI film(rGO/rAPGO/PI) and pure PI film.The water vapor transmission rate of the GO and APGO-coated PI composite filmwas increased due to the intrinsically hydrophilic property of the charged composite films.However, the oxygen trans-mission rate was decreased from 220 to 78 cm3/m2·day·atm, due to the barrier effect of the graphene filmson the PI surface. Since the proposed method allows for large-scale production of graphene films, it is considered to have potential for utiliation in various applications.

Graphite oxide (GO) was produced using the modified Hummer's method. Poly(p-phenylene sulfide) (PPS)/reduced graphite oxide (RGO) composites were prepared by in situ polymerization method. The electrical conductivity of the PPS/RGO composites was no more than 82 S/m. It was found that as GO content increased in the PPS/RGO composites, the crystallization temperature and electrical conductivity of the composites increased and the percolation threshold value was at 5-8 wt% of GO content.

Carbon nanotubes (CNTs) have exceptional mechanical, electrical, and thermal properties compared with those of commercialized high-performance fibers. For use in the form of fabrics that can maintain such properties, individual CNTs should be held together in fibers or made into yarns twisted out of the fibers. Typical methods that are used for such purposes include (a) surfactant-based coagulation spinning, which injects a polymeric binder between CNTs to form fibers; (b) liquid-crystalline spinning, which uses the nature of CNTs to form liquid crystals under certain conditions; (c) direct spinning, which can produce CNT fibers or yarns at the same time as synthesis by introducing a carbon source into a vertical furnace; and (d) forest spinning, which draws and twists CNTs grown vertically on a substrate. However, it is difficult for those CNT fibers to express the excellent properties of individual CNTs as they are. As solutions to this problem, post-treatment processes are under development for improving the production process of CNT fibers or enhancing their properties. This paper discusses the recent methods of fabricating CNT fibers and examines some post-treatment processes for property enhancement and their applications.

For polyacrylonitrile (PAN) based carbon fiber (CF) process, we developed a lab scale wet spinning line and a continuous tailor-made stabilization system with ten columns for controlling temperature profile. PAN precursor was spun with a different spinning rate. PAN spun fibers were stabilized with a total duration of 45 to 110 min at a given temperature profile. Furthermore, a stabilization temperature profile was varied with the last column temperature from 230 to 275℃. Stabilized fibers were carbonized in nitrogen atmosphere at 1200℃ in a furnace. Morphologies of spun and CFs were observed using optical and scanning electron microscopy, respectively. Tensile properties of resulting CFs were measured. The results revealed that process conditions such as spinning rate, stabilization time, and temperature profile affect microstructure and tensile properties of CFs significantly.