Polyaniline (Pani) and its blends with poly(vinyl alcohol) (PVA) and PVA + Cu(II) complex were synthesised by in situ chemical oxidative polymerisation technique with potassium perdisulphate (PDS) oxidant in aqueous sulphuric acid medium. The polymer samples were characterised by conductivity, XRD, TGA and spectral (IR and UV-visible) methods. Both conductivity and thermal stability of Pani decreased largely with PVA. XRD and spectral studies revealed that PVA-modified structural and chemical characteristics of Pani through intermolecular hydrogen bonding and thereby effected these changes. In PVA + Cu(II) complex,however, the hydroxyl groups of PVA were tied and as a result the complex as a whole interacted with Pani. Consequently, it redeemed the characteristics of Pani substantially with the additional advantage of imparting higher thermal stability to Pani. (C) 2002 Elsevier Science B.V. All rights reserved.