THE INTERACTION BETWEEN POLYVINYLPYRROLIDONE AND I2 AS PROBED BY RAMAN SPECTROSCOPY

Abstract Polyvinylpyrrolidone (PVP) is known since long to interact with iodine producing a stable compound which has been largely employed as antiseptic owing to its iodophor property. Despite of the extensive number of studies involving such system, no attempts were made to investigate the low frequency region of the vibrational spectrum of PVP-I 2 . The characteristic vibrations of I 2 and its polyiodide derivatives (I 3 − and I 5 − ) give rise to strong peaks in the Raman spectrum which are observed in the region below 300 cm −1 . In this work the interaction of PVP and iodine is investigated from 80 to 1800 cm −1 using Raman spectroscopy. The spectra clearly shows the presence of I 3 − and I 5 − in a ratio that depends on the method used in the sample preparation. The PVP spectrum is not sensitive to the interaction, except by small shifts in the carbonyl band position towards higher wavenumbers, which seems to be a consequence of conformational changes caused by the halogen.