Polymer-rich/clay-rich phase-separated, polymer-layered silicate nanocomposites are prepared through a solution blending of poly(xylylidene tetrahydrothiophenium chloride) with two kinds of layered silicates. By spin-coating, thin films of each phase were obtained, followed by thermal elimination of tetrahydrothiophene and HCl to final poly(p-phenylenevinylene) (PPV)/layered silicate nanocomposite. At ambient conditions, the PPV films are easily photodegraded due to the oxygen diffused in. Poly(p-phenylenevinylene)/layered silicate nanocomposite showed improved environmental stability against photodegradation under an air ambient condition. Additionally, optical absorption and photoluminescence measurements demonstrate that the thin films of clay-rich phase are much less photodegraded than those of polymer-rich and PPV reference. (C) 2002 Elsevier Science B.V. All rights reserved.