Poly(ethylene terephthalate) (PET)/ clay nanocomposites are prepared by intercalation of a catalyst precursor and an organic modifier, followed by the polymerization of monomers between the adjacent clay layers. The mechanical properties, thermal deformation temperature, anti-UV-radiation properties, CO2 gas-barrier properties, and clarity of bottles blown from the PET/clay nanocomposites (see Figure) are improved.