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We investigate self-assembly of nanocomposite films composed of lamellar-forming poly(styrene-b-methyl methacrylate) (PS-b-PMMA) and PMMA-grafted magnetite (Fe3O4) nanoparticles (NPs). The Fe3O4 NPs are grafted with PMMA brushes with molecular weights ranging from 2700 to 35 700 g/mol. For the NP with the lowest molecular weight brush, the morphology of the nanocomposite film depends on the NP concentration (ϕNP). At low ϕNP, the block copolymer self-assembles into mixed morphology of perpendicular lamellae (⊥Lam) and parallel lamellae (∥Lam), and the ⊥Lam are stabilized by individual NPs or small NP aggregates. The NPs can also retard the dynamics of self-assembly of block copolymer films. At high ϕNP, NPs form small aggregates which inhibit the formation of a lamellar structure. As the molecular weight of the PMMA brush increases to 13 300 or 35 700 g/mol, the Fe3O4 NPs form aggregates in the as-cast nanocomposite films, and this behavior is attributed to aggregation of NPs in the solution state. Since ...

0897-4756; We describe a novel purification process for single-wall carbon nanotube (SWNT) materials that removes non-nanotube carbon and reduces ferromagnetic impurities to levels at which native SWNT magnetic properties predominate. Ferromagnetism is reduced from 1.04 to less than 0.013 emu/g by magnetic gradient filtration. This procedure creates samples of sufficient quality for spectroscopies such as nuclear magnetic resonance (NMR). The overall cleanliness and purity of the material is confirmed through NIR absorption spectroscopy, X-ray diffraction, C-60 filling experiments with yields exceeding 90%, and high-resolution C-13 NMR.