Isotactic polypropylene nanocomposites were obtained by the melt blending of polypropylene-graft-maleic anhydride and orgarrophilic layered silicate (OLS) consisting of synthetic fluorohectorite modified by cation exchange with protonated. octadecylamine. The composition of the inorganic clay was varied between 2.5 and 10 wt %, and films of the composites were obtained via hot-press molding. X-ray analysis showed that nanocomposites in which silicate layers were either delaminated or ordered as in an intercalated structure were obtained. The elastic modulus of the samples was higher than that of the pure polymer over a wide temperature range and increased with increasing inorganic content. The transport properties, sorption and diffusion, were measured for two organic vapors, dichloromethane and n-pentane. For both vapors, the sorption was not very different from that of the pure polymer, whereas the zero-concentration diffusion parameter strongly decreased with increasing OLS content. Therefore, the permeability, that is, the product of sorption and diffusion, decreased for both vapors as a result of the decreased value of the diffusion parameter. The decrease was higher for the less interacting n-pentane. (C) 2003 Wiley Periodicals, Inc.