Grafting of Vapor-Grown Carbon Nanofibers via in-Situ Polycondensation of 3-Phenoxybenzoic Acid in Poly(phosphoric acid)

Abstract

In-situ polymerization of 3-phenoxybenzoic acid in the presence of various amounts (1-30 wt %) of vapor-grown carbon nanofibers (VGCNF) was carried out in poly(phosphoric acid)/phosphorus pentoxide (PPA/P 2O5; 1:4 w/w) medium. 3-Phenoxybenzoic acid polymerizes via Friedel-Crafts acylation in PPA to form poly(oxy-1,3-phenylenecarbonyl-1,4-phenylene) or mPEK. The resulting mPEK-g-VGCNF products that contained less than 10 wt % of VGCNF were soluble in N-methyl-2-pyrrolidinone and had intrinsic viscosity values ranging from 1 to 1.73 dL/g in methanesulfonic acid (MSA) at 30 ( 0.1 °C. The overall evidence based on the data from elemental analysis (EA), thermogravimetric analysis (TGA), and Fourier transform infrared spectroscopy (FT-IR) as well as scanning electron and transmission electron microscopies of the resulting materials implicates that VGCNF remained more or less structurally intact under the mildly acidic, relatively high-shearing and hot polymerization conditions. It is also evident that under these reaction conditions mPEK was grafted onto the surface of VGCNF, resulting in the formation of "hairy tubes". The wide-angle X-ray diffraction result showed the growth of the 3.35 Å peak characteristic of VGCNF that increased in intensity proportionately to the presence of VGCNF in the sample and correlated well with the EA and TGA results. The conductivity of the cast film (10 wt % VGCNF) is 0.25 S/cm (bottom of film) and 0.30 S/cm (top of film).

Mild and Nondestructive Chemical Modification of Carbon Nanotubes (CNTs): Direct Friedel-Crafts Acylation Reaction

“…In addition to CNTs, the covalent modification method of direct Freidel-Crafts acylation reaction in a mild PPA/P 2 O 5 medium can be expanded to other carbon-based nanomaterials such as fullerene (C 60 ) [14], carbon nanofiber [7,[15][16][17] and graphene [19][20][21][22]. Buckminster fullerene, C 60 , which is of the most abundant carbon sphere, is generally considered as a stable electron deficient material.…”

“…ferrocene, Fe(CO) 5 , etc.) and have an outer diameter of 60-200 nm, a hollow core of 30-90 nm, and length in the order of 50-100 μm [15][16]. Furthermore, VGCNFs have been widely used for tailoring properties in their polymer composites via cost-effective way, because of their inherent electrical and mechanical properties.…”

“…However, these approaches generally require multi-step synthetic procedures and limited species of materials can be utilized. To overcome these problems, Baek et al, developed efficient functionalization and grafting methods onto the surface of VGCNF in a mild PPA/P 2 O 5 medium, called as a direct FriedelCrafts acylation reaction ( Figure 13) [15][16][17]. As a result, the dispersion, interfacial adhesion and solution processabiliy of VGCNF have been greatly improved, which is quite beneficial for the development of high performance polymer-based nanocomposites.…”

“…As a result, the dispersion, interfacial adhesion and solution processabiliy of VGCNF have been greatly improved, which is quite beneficial for the development of high performance polymer-based nanocomposites. Similarly to CNTs, the functionalization of VGCNF via direct Friedel-Crafts acylation reaction in PPA/P 2 O 5 with various materials such as small molecules [7,32], linear [15] and hyperbranched poly(ether-ketone) [16][17] have been successfully demonstrated. Specifically, the covalent attachment of hyperbranchedhyperbranched poly(ether-ketone) onto the surface of VGCNF has been clearly verified by TEM analysis.…”

“…Furthermore, it can be expanded to all types of carbon-based nanomaterials such as fullerenes [14], carbon nanosfibers [7,[15][16][17], nanodiamonds [18] and graphene [19][20][21][22]. Therefore, direct FriedelCrafts acylation reactions could be one of ideal chemical modifications for carbon based materials, specifically CNTs.…”