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June 17, 2002
Volume 80, Number 24
CENEAR 80 24 p. 5
ISSN 0009-2347


MATERIAL SCIENCE

ALIGNING POLYMER NANOTUBES, EASILY
New method yields nanoscale structures from polymers and blends

MITCH JACOBY

A new chemical procedure can be used to prepare neatly aligned nanotubes from a wide range of polymers, polymer blends, and multicomponent solutions, according to researchers in Germany. The work provides a general technique for preparing functionalized structures for applications in nanotechnology.

By wetting ordered porous templates with droplets of polymer melts or polymer solutions, Martin Steinhart and Joachim H. Wendorff of Philipps University in Marburg, Ralf B. Wehrspohn and Ulrich M. Gösele of Max Planck Institute of Microstructure Physics in Halle, and coworkers coat template surfaces with polymer films that retain the shape of the template's pore array after the template is removed by chemical means [Science, 296, 1997 (2002)].

Using lithographically prepared alumina and oxidized silicon templates, the team prepared nanotubes with walls 20 to 50 nm thick and lengths of up to 100 mm. The group demonstrated the technique's versatility by fabricating nanotubes from polytetrafluoroethylene, polymethylmethacrylate, poly-L-lactide/palladium acetate, and other materials.

The products are hollow, the researchers explain, because the adhesive forces between the polymer melts or solutions and the template walls are greater than the cohesive forces needed to turn the polymers into solid plugs inside the template channels. Wetting template surfaces with thin films takes place on a faster timescale than completely filling the pores, the group says. The unwanted pore-filling process is shut down because, in the case of polymer melts, the material cools and hardens as it coats the surface. And with polymer solutions, the solvent evaporates as the solution wets the surface.

PACKED An electron micrograph shows that a simple and fast procedure can be used to prepare nicely ordered polymer nanotubes (polystyrene shown here).
COURTESY OF MARTIN STEINHART



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