FTIR study of gamma-irradiated cis-1,4-polyisoprene

The effect of gamma-irradiation on the structure and oxidation of cis-1,4-polyisoprene is investigated by ATR-FTIR technique. This method provides the valuable insight into the type of oxidation products produced and the extent and nature of intramolecular cyclization and chain scission reactions. The formation of ketones, alcohols and/or ethers, and hydroperoxides is apparent already at small doses of gamma-radiation and it increases with the exposure time significantly. At the highest dose of 309 kGy a decrease in the intensity of C=O stretching mode of ketones (1717 cm(-1)) was observed while the overall area of the band remained the same as in the case of 188 kGy dose. The shoulders observed at 1740 cm(-1) and 1772 cm(-1) could be assigned to C=O stretching frequency of esters and five-membered-ring lactones, respectively. Higher doses of gamma-radiation also cause the formation of two relatively strong bands in the region of conjugated double bonds. These could origin from the aromatic products or cycloenes with one double bond formed by cyclization and chain scission processes.