Polyaniline (PANI)/porous silica MCM-41 (MCM-41) composite was synthesized according to surface polymerization theory, and it was confirmed through comparing with PANI/solid silica (SiO2) by TGA and XPS techniques. The morphology and composition of the composite were also characterized by some techniques such as small-angle XRD, N-2-adsorption isotherm, SEM, FTIR, and UV-vis. The thermal stability for the PANI/MCM-41 composite was enhanced when compared with that of pure PANT. With the increase in the concentration of HCl, the doping degree increased and UV-absorption peak at about 700 nm showed a red shift. The conductivity of the composite was enhanced by increasing the concentration of HCl. The results of FTIR showed that there was a strong interaction between PANT and MCM-41. (c) 2006 Wiley Periodicals, Inc.