In this study, cyclic olefin copolymer (COC)/layered silicate nanocomposites (CLSNs) were prepared by the intercalation of COC polymer into organically-modified layered silicate through the solution mixing process. Both X-ray diffraction data and transmission electron microscopy images of CLSNs indicate most of the swellable silicate layers were disorderedly intercalated into the COC matrix. The effect of layered silicate on the mechanical and barrier properties of the fabricated nanocomposites shows significant improvements in the storage modulus and water permeability when compared with that of neat COC matrix. Surfaces of COC and CLSN films were modified by a mixture of oxygen (O-2) and nitrogen (N-2) plasmas with various treated times, system pressures, and radio frequency (RF) powers. The surfaces of plasma-modified COC and CLSN were investigated using scanning probe microscopy and contact-angle measurements. The exposure of the COC and CLSN film to the plasmas led to the combination of etching reactions of polymer surface initiated by plasma and the following addition reactions of new functional groups onto polymer surfaces to change the topology of COC film surfaces. The surface roughness was closely related to how high and how long the RF power was input into the system. The plasmas also led to changes in the surface properties of the CLSN surfaces from hydrophobic to hydrophilic; and the contact angle of water on the surface decreases. (c) 2005 Wiley Periodicals, Inc.