Copolymer of Single-Walled Carbon Nanotubes and Poly(p-phenylene benzobisoxazole)

The use of single-walled carbon nanotube (SWNT) copolymers in polymeric formulations may lead to better alignment of fibers, thereby producing higher performance materials. Although poly(p-phenylene benzobisoxazole) (PBO) fibers are some of the strongest organic polymer fibers known, the introduction of SWNTs into the PBO backbone might lead to improvements in their physical properties. Therefore, copolymerization of short (average length 60 nm) carboxylic acid functionalized SWNTs with PBO oligomers was successfully carried out in a mixed solvent of polyphosphoric acid and methanesulfonic acid (MSA) in the presence of P₂O₅ at 3.3 wt % concentration and 150 °C. The SWNTs were homogeneously distributed throughout the films of copolymerized products, as determined by Raman spectroscopy using the diagnostic radial breathing mode and D and G band emissions. Morphological differences between the copolymerized product and a physical mixture were readily seen using atomic force microscopy. The precipitated copolymerized nanotubes were separated by centrifugation from the MSA suspension of the products of short SWNTs and PBO oligomers. That benzoxazole moieties could be formed between the carboxylic acids of ultra-short (US) SWNTs and o-aminophenol derivatives was established by the condensation of US-SWNTs with o-aminophenols, and subsequent analysis of the products.