  The elastic properties of nanotubes fabricated by layer-by-layer (LbL)
assembly of polyelectrolytes in the nanopores of polycarbonate track-etched
membranes have been investigated by resonant contact Atomic Force Microscopy
(AFM), for nanotube diameters in the range of 100 to 200 nm. The elastic
modulus of the nanotubes was computed from the resonance frequencies of a
cantilever resting on freely suspended LbL nanotubes. An average value of
115MPa was found in air for Young's modulus of these nanostructures, well below
the values reported for dry, flat multilayers, but in the range of values
reported for water-swollen flat multilayers. These low values are most probably
due to the lower degree of ionic cross-linking of LbL nanotubes and their
consequently higher water content in air, resulting from the peculiar mode of
growth of nanoconfined polyelectrolyte multilayers.
