Poly(N-vinyl pyrrolidone) (PVP) and poly (vinyl alcohol) (PVA) homopolymers and their blended samples with different compositions were prepared using cast technique and subjected to X-ray diffraction (XRD) measurements, infrared (IR) spectroscopy, ultraviolet/visible spectroscopy, and thermogravimetric analysis (TGA). XRD patterns of homopolymers and their blended samples indicated that blending amorphous materials, such as PVP, with semicrystalline polymer, such as PVA, gives rise to an amorphous structure with two halo peaks at positions identical to those found in pure PVP. Identification of structure and assignments of the most evident IR-absorption bands of PVP and PVA as well as their blends in the range 400-2000 cm(-1) were studied. UV-vis spectra were used to study absorption spectra and estimate the values of absorption edge, E-g, and band tail, E-e, for all samples. Making use of Coats-Redfern relation, thermogravimetric (TG) data allowed the calculation of the values of some thermodynamic parameters, such as activation energy E, entropy Delta S-#, enthalpy Delta H, and free energy of activation Delta G(#) for different decomposition steps in the samples under investigation. (C) 2009 Wiley Periodicals, Inc. J Appl Polym Sci 114: 1202-1207, 2009