51 32 p 8665 8701 kodama y k nishihata m nishio and n nakagawa attractive interaction between aliphatic and aromatic systems tetrahedron letters 1977 18 24 p 2105 2108 the strength of the ch u03c0 is one tenth of hydrogen bonding but multiple ch u03c0 interactions along the polymer chain length between the ch2 and the u03c0 bonds can add up to make the helical wrapping energetically favorable if the swnt structure does not change significantly after removing the pmma as a first order approximate the diffraction pattern of the pmma in the swnt pmma buckypaper can be obtained by subtracting the diffraction pattern of swnt from swnt pmma as shown in fig9 a the diffraction pattern of the energy minimized helical model was obtained using debyer and is shown in fig9 b which is similar to the diffraction pattern of the ordered pmma the suspendability of cnts is generally low even in good solvents in order to get a good swnt suspension during sonication a concentration of at most 14 mg l is required if the concentration of the swnts is too high the nanotubes will not disperse regardless of the sonication time sonicated swnt dmf and swnt pmma dmf suspensions have similar appearance initially fig1 a b however the swnt dmf suspension precipitates within 2 hours of centrifugation at 2 000 g fig1 c while the swnt pmma dmf dispersion is quite stable and exhibits very little sedimentation under comparable centrifugation conditions fig1 d this swnt pmma.