Rapid In Situ Polymerization of Polyacrylonitrile/Graphene Oxide Nanocomposites as Precursors for High-Strength Carbon Nanofibers

Abstract

Graphene oxide (GO) has been widely used as an additive of polyacrylonitrile (PAN)-based carbon nanofibers (CNFs) to optimize its crystal structure and improve the mechanical performances of nanofibers. However, the homogeneous dispersion of GO nanosheets among entangled PAN molecular chains is always challenging, and the poor dispersion of GO severely limits its positive effects on both the structure and performances of CNFs. Considering this issue, this paper provides for the first time an effective solution to achieve rapid and uniform introduction of GO in PAN-based nanofibers via in situ polymerization, and the optimization of the nanofiber structure by GO is systematically studied in three consecutive stages (polymerization, electrospinning, and carbonization) of the production process. During in situ polymerization, PAN is tightly attached on GO nanosheets to form PAN/GO nanocomposites, and this interaction is maintained throughout the spinning process. Not only the arrangement of PAN molecular chains but also the crystal size of the final turbostratic structure of CNFs is considerably improved by the interaction between PAN and GO. Besides, the direct proof that GO nanosheets promote the crystallization and orientation of the nanofiber matrix is presented. As a result, the tensile strength of CNFs is remarkably increased by 2.45 times with 0.5 wt % addition of GO. In summary, this paper provides a method for efficiently introducing nanoscale additives into PAN-based nanofibers and gives insights into the production of high-performance CNFs with the addition of GO.

Polyacrylonitrile-Coated Onion-like Carbon Nanoparticles for Carbon Nanofibers with Enhanced Strength and Toughness

“…The FTIR spectra of polymer samples show the typical peaks of C�N bonds at 2240 cm −1 , C−H bonds at 2940, 1454, 1357, 1247, and 1070 cm −1 , and C�N bonds at 1620 cm −1 (Figure 3a). 7 In particular, the addition of OLC shifts the peak of C�N to lower wavenumbers (Figure 3b). It is inferred that the redshift of this peak is attributed to the interaction between C�N and OLC, which enlarges the conjugated electron system and results in the reduction of the vibration frequency of C�N bonds.…”

“…7 Moreover, the thickness of crystal domains (Lc) can also be evaluated from the XRD patterns, which is inversely proportional to the full width at half-maximum (fwhm) of the 17°p eak. 7 It is shown that the crystallinity of PAN keeps decreasing with the increasing addition of OLC, while the Lc of PAN increases as the addition of OLC rises from 0 to 1 wt %, and suddenly drops to a relatively low value with 5 wt % OLC (Figure 3f). It is deduced that the increased Lc mainly comes from the attraction of OLC to the PAN matrix (Figure 2e), which makes the polymer segments near the nanofillers stack up orderly to a larger thickness.…”

“…Initiate the polymerization of AN monomers among dispersed nanofillers, known as the in situ polymerization process, the uniform mixing of PAN and OLC is expected to be accomplished. 7 On this basis, this paper successfully develops OLC as a new carbon nanofiller to enhance the mechanical properties of CNFs. One of the primary issues of concern in the research is the actual mixing effect of OLC with the PAN precursor of CNFs via the in situ polymerization method, which is a prerequisite for the potential reinforcement roles of the nanofillers.…”

“…6 However, in practical production, the graphitic structure of CNFs is always defective with small size and poor orientation, and the whole fiber graphitization degree also needs to be improved. 7,8 As a result, the mechanical properties of CNFs are significantly compromised, which further limits the application of CNFs. 9 Aiming to optimize the structure of CNFs, one of the most popular methods is introducing carbon fillers, such as carbon nanotubes (CNTs) and graphene, into the nanofiber.…”

Polymer/Graphene Nanocomposite Membranes: Status and Emerging Prospects

“…Polyacrylonitrile nanofibers and derived membranes with graphene and GO have been exploited for technical applications [74,75]. Poly(lactic acid), GO-based nanofibers and the resulting membranes have been employed in tissue engineering scaffolds [76].…”