Colloidal TiO2 rod shaped nanocrystals with different surface ligands (oleic and phosphonic acid) are used for tailoring the optical properties and tuning the chemical adsorption of bare poly(methyl metacrylate) (PMMA) thin films. Refractive index and absorption edge of the hybrid TiO2/PMMA thin films have been determined, for both oleic and phosphonic acid capped nanocrystals, as a function of the nanorod concentration. The swelling of the nanocomposite samples in presence of acetone and ethanol vapours has been investigated. Our results show that nanocomposites with phosphonic acid as surface ligands are more transparent and have a higher refractive index with respect to the films with oleic acid ligands. Furthermore, the presence of inorganic nanorods (NRs) modifies the vapour adsorbing ability of the PMMA and this modification is strongly influenced by the nature of the surface ligands and by the TiO …