Multifunctional Poly(2,5-benzimidazole)/Carbon Nanotube Composite Films
AIR FORCE RESEARCH LAB WRIGHT-PATTERSON AFB OH MATERIALS AND MANUFACTURING DIRECTORATE
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The AB-monomer, 3,4-diaminobenzoic acid dihydrochloride was recrystallized from an aqueous hydrochloric acid solution and used to synthesize high-molecular-weight poly2,5- benzimidazole ABPBI. ABPBIcarbon nanotube CNT composites were prepared via in situ polymerization of the AB-monomer in the presence of single-walled carbon nanotube SWCNT or multiwalled carbon nanotube MWCNT in a mildly acidic polyphosphoric acid. The ABPBISWCNT and ABPBIMWCNT composites displayed good solubility in methanesulfonic acid and thus uniform films could be cast. The morphology of these composite films was studied by X-ray diffraction, scanning electron microscopy transmission electron microscopy, and atomic force microscopy. The results showed that both types of CNTs were uniformly dispersed into the ABPBI matrix. Tensile properties of the composite films were significantly improved when compared with ABPBI, and their toughness 200 MPa was close to the natures toughest spider silk 215 MPa. The electrical conductivities of ABPBISWCNT and ABPBIMWCNT composite films were 9.10 10 5 and 2.53 10 1 Scm, respectively, whereas that of ABPBI film was 4.81 10 6 Scm. These values are 19 and 52,700 times enhanced by the presence of SWCNT and MWCNT, respectively. Finally, without acid impregnation, the ABPBI film was nonconducting while the SWCNT- and MWCNT-based composites were proton conducting with maximum conductivities of 0.018 and 0.017 Scm, respectively.
- Organic Chemistry
- Refractory Fibers