Anodic aluminum oxide (AAO) membrane can be used as template for the synthesized nanostructures. In this article, we have prepared the AAO membrane by using electrooxidation of aluminum substrate in phosphoric acid, and fabricated poly(2,5-di-n-butoxyphenylene) (BuO-PPP) nanofibril arrays by oxidative coupling polymerization of 1,4-di-n-butoxybenzene (DBB) within the pores of the AAO template membrane. The detailed molecular structure of the pole. mer nanofibrils was characterized by using infrared and H nuclear magnetic resonance spectra, and estimated to consist of almost equal fractions of 1,4- and 1,3-linkages. We have used transmission electron microscopy, scanning electron microscopy, and atom force microscopy to confirm the morphologies and images of the AAO template membrane and the fabricated nanometer scale of BuO-PPP nanofibril arrays. The experimental results demonstrated that the pores of the AAO membrane were regular and uniform, and parallel each other, and the BuO-PPP chains in the narrowest template-synthesized nanofibrils were oriented parallel to the porous axes of the AAO membrane and perpendicular to the surface of the aluminum substrate. The polymer chain orientation was partially responsible for the enhanced conductivity. The ultraviolet absorption spectrum of the BuO-PPP nanofibril arrays shown that the polymer contains a better extended pi-conjugation system along poly(p-phenylene) backbone, which resulted in longer wavelength shift of the absorption band, the absorption maxima were located at 258 nm (E-1 absorption band) and 332 nm (E-2 absorption band), respectively. Photoluminescence spectrum of the BuO-PPP nanofibril arrays exhibited a blue emission. (C) 2003 Wiley Periodicals, Inc. J Appl Polym Sci 91: 425-430,2004.