Carbon Nanotubes Embedded in Oriented Polymer Nanofibers by Electrospinning

Abstract

The electrospinning process was used successfully to fabricate nanofibers of poly(ethylene oxide) (PEO) in which multiwalled carbon nanotubes (MWCNT) are embedded. Initial dispersion of MWCNTs in water was achieved using amphiphiles, either as small molecules (sodium dodecyl sulfate, SDS) or as a high molecular weight, highly branched polymer (Gum Arabic). These dispersions provided separation of the MWCNTs and their individual incorporation into the PEO nanofibers by subsequent electrospinning. The focus of this work is on the development of axial orientations in these multicomponent nanofibers. A theoretical model is presented for the behavior of rodlike particles representing CNTs in electrospinning. Initially the rods are randomly oriented, but due to the sinklike flow in a wedge they are gradually oriented mainly along the stream lines, so that straight CNTs are almost oriented upon entering the electrospun jet. The degrees of orientation of polymer, surfactant, and MWCNT were studied using X-ray diffraction and transmission electron microscopy. Oriented ropes of the nanofibers were fabricated in a converging electric field by a rotating disk with a tapered edge. A high degree of alignment of PEO crystals was found in electrospun nanofibers containing only PEO, as well as PEO/SDS. The latter also exhibited a high degree of alignment of the SDS layers. The axial orientation of PEO and SDS is significantly reduced in MWCNT-containing nanofibers. Transmission electron microscopy (TEM) images indicated that the MWCNTs were embedded in the nanofibers as individual elements, mostly aligned along the fiber axis. Nevertheless, there are also many cases in which the nanotubes appear twisted, bent, or with other irregularities. Comparison of cryo-TEM images of vitrified MWCNT dispersions with TEM images of the raw nanotubes indicated that sonication during the dispersion process may be responsible for the irregularities observed in some of the nanotubes.

Mechanical properties of individual electrospun polymer-nanotube composite nanofibers

“…While the topological properties of the network have a significant influence on its mechanical properties (7), the strength of the membrane is ultimately limited by the strength of the individual fibers. As such, significant work has gone into reinforcing the individual fibers through the incorporation of carbon nanotubes (7)(8)(9)(10)(11)(12)(13)(14)(15).…”

Nanocomposite toughness, strength and stiffness: role of filler geometry

“…25,26 Within the same category of structures are bundles that contain a smaller amount of CNTs, which sometimes form spontaneously as a result of aligned agglomeration of CNTs in a polymer solution, for example under extensional flow. 3,4 The latter phenomenon is usually perceived as undesirable from a mechanical viewpoint, but this is not always the case as will be shown further on. The cross-sectional geometry of an aligned bundle is an example of a filler with arbitrarily shaped outline and multiple cavities, as presented in Fig.…”

“…Nanofillers could potentially be used in standard composite applications, as well as in confined spaces, thin polymer nanofilms 1,2 and electrospun polymer nanofibers. [3][4][5] Nanofillers such as carbon nanotubes possess strength and stiffness an order of magnitude higher than traditional microfillers like carbon microfibers. 6,7 Furthermore, the ratio of the filler's interfacial area to volume (R/R 2 yR…”

Effect of Multi-wall Carbon Nanotubes(MWNTs) on Structural and Mechanical Properties of Poly(3-hydroxybutirate) Electrospun Scaffolds for Tissue Engineering Applications

“…By addition of 20 wt% to three di erent ceramic nanoparticles, namely Calcium Titanate (CT), Strontium Titanate (ST), and Barium Titanate (BT), Bagchi et al signi cantly increased the moduli and strength of poly(" caprolactone) [38]. In this context, a large number of other studies have shown that MWNTs, with low percentages, can signi cantly improve the mechanical properties of di erent polymers [39][40][41][42][43][44][45][46]. Li et al prepared the MWNT/ poly(3-hydroxybutyrate-co-3-hydroxyvalerate) sca olds by Melt Molding method, and reported that MWNTs can signi cantly improve the mechanical properties of the polymer [47].…”