Template synthesis of highly oriented polyfluorene nanotube arrays

摘要

Polyfluorene nanotubes are synthesized by solution assisted wetting of porous anodic alumina membranes. Well aligned arrays of close packed (similar to 10(9) tubes/cm(-2)) discrete nanotubes are obtained. Individual tubes have diameters of similar to 260 nm and wall thicknesses of similar to 50 nm. X-ray diffraction measurements carried out on nanotube arrays embedded in host templates indicate a polymer chain alignment along the long axes of the template pores and, as a result, along the long axes of the nanotubes themselves. Optical spectroscopic studies of mats of nanotubes on glass substrates yield well resolved emission spectra reflecting a narrowed distribution of emitting chain segments with increased effective conjugation lengths. The data indicate intrachain reorientation of the amorphous random poly(9,9-dioctylfluorene-2,7-diyl) molecular conformation to the more planar (low energy) extended 2(1) helical beta-phase conformation within the tubes. Raman spectra acquired for template embedded tubes are also consistent with beta-phase formation. Finally, polarization resolved photoluminescence data demonstrate a pronounced axial orientation of the emissive beta-phase chains within the tubes.