In this work we study the water adsorption and adsorbed aniline interaction onto the mesoporous materials Na-AlMCM-41, compared with aniline adsorption onto Na-AISBA-15. The adsorption of aniline on Na-AlMCM-41 and Na-AlSBA-15 materials, synthesized by us, has been characterized by thermo-infrared spectroscopy analysis. The FTIR analysis of adsorbed aniline on Na-AISBA-15 shows the characteristic bands ascribed to N-H-2 bending and two C-C ring stretching at 1622-1625, 1604 and 1498.6 cm(-1), respectively; the results are similar to the adsorbed aniline on Na-AlMCM-41 host. Mainly, aniline molecules would be bounded through weak pi interactions onto the mesostructures. The organic molecules could be held stronger on Na-AlSBA-15 than on Na-AlMCM-41. Two possible modes of adsorption of water have been identified on Na-AlMCM-41 and Na-AlSBA-15, which are characteristic of water adsorbed on the material. Different associations between aniline and hydrated and non-hydrated mesostructures have been evaluated in order to favor the posterior in-situ polymerization of adsorbed aniline. Polyaniline/SBA-15 composite, obtained by an in-situ polymerization technique, has been characterized by infrared spectroscopy, UV-vis spectroscopy and surface area studies. (c) 2007 Elsevier B.V. All rights reserved.