The effect of 1,3-diphenylisobenzofuran on the photo-oxidative degradation of cis-1,4-polybutadiene

Abstract 1,3-Diphenylisobenzofuran (DPBF) is easily photo-oxidized by two mechanisms viz free radical oxidation and singlet oxygen oxidation. The final products of DPBF oxidation by these two mechanisms are the same. Using light in the range 280–480 nm, DPBF is an effective sensitizer of photooxidative degradation of polybutadiene in the solid and in solution. In a system with methylene blue (MB) in methanol-benzene solution (0.5:9.5) where free radicals from MB and 1O2 are formed during irradiation with visible light, DPBF is oxidized by both 1O2 and free radical mechanisms. DPBF cannot stop free radical degradation of PB initiated by MB radicals in MB-methanol-benzene solution. These results show that the DPBF is an ineffective stabilizer for polydienes against 1O2 and free radical oxidation. It rather acts as a sensitizer for photo-oxidation of polydienes.