Functional modification of poly(vinyl alcohol) (PVA) with phosphorus containing nitrogen heterocyclic has been believed to have extensive thermal and biological applications in the area of polymers. Efforts have been taken for the synthesis of phosphorus-containing N-heterocyclic (5,6 member and fused ring) based PVA. The synthesized compounds were characterized using UV, FTIR, and NMR spectral studies. Thermal studies (DSC-TGA) scans display phosphorus-containing five membered and fused heterocyclic-based PVA has less thermal stability than six-membered compounds. Modified polymers infer to have excellent bacterial response against micro-organisms. (C) 2008 Wiley Periodicals, Inc. J Appl Polym Sci 110: 2549-2554, 2008