PolyTEMPO and polyviologen on carbon nanotubes: syntheses, structures and organic battery applications

Abstract

Scanning tunneling microscopy of semiconducting carbon nanotubes (sc-CNTs) treated with four redox active linear polymers shows throughout complex formation by helical wrapping. The compounds used are polyTEMPO I (poly-acetylene backbone and TEMPO side chain, new compound), polyTEMPO II (polymethacrylate backbone and TEMPO side chain), polyviologen I (main chain polyamide of diaminopropyl viologen and isophthalic acid), polyviologen II (main chain bipyridine dibromoxylene polymer)). Monomer subunit resolution was achieved in case of polyTEMPO I and II. Redox activity, such as in the TEMPO and viologen polymers is claimed crucial for electrostatically driven wrapping. Complex formation was modeled with the MM+ force field. No evidence of polymer complex formation was experimentally found with metallic CNTs and with vapor grown carbon fibers (VGCFs), possibly because of ``charge trapping'' exclusively on the semiconducting nanotubes. Composite electrodes (cathods) were prepared according to polyTEMPO I or II/VGCF and or sc-CNTs/poly-vinylidene fluoride (PVDF) and studied vs. a lithium electrode. polyTEMPO I has a higher theoretical capacity than the standard polyTEMPO II (127 and 111 mA h/g, respectively), but other specifications of polyTEMPO I, such as stability during cycling and potential vs. Li are inferior. The ratio of CNTs and VGCF used in the composite electrode does not influence the battery performance. (C) 2013 Elsevier Ltd. All rights reserved.