Degradation of polyisoprene induced by chloranil

The aim of this work was to study the degradation of polyisoprene and polybutadiene in the presence of chloranil (tetrachloro-1,4-benzoquinone). The influences of polymer concentration, chloranil concentration and temperature were evaluated using a 2(3) factorial design. The efflux times of toluene solutions containing different polymer and chloranil contents at 25. 45 and 65 degrees C were measured, using a Ubbelohde viscometer. When high concentrations of polymer and chloranil were used, at 65 degrees C, the efflux time decreased to approximately 10% of its initial value after 7 min, and, after 250 min, the efflux time reduced to approximately 50% of its initial value. The efflux time of polybutadiene solutions containing chloranil did not decrease with the reaction time. H-1 NMR of polyisoprene and polybutadiene, dissolved in CDCl3 containing chloranil, were used to evaluate the changes in polymer unsaturation. H-1 NMR measurements showed an exponential decrease in the area for peaks due to the hydrogen bound to the unsaturated carbon in polyisoprene solutions. These results suggest the occurrence of degradation of polyisoprene. Using the same conditions, it was observed that polybutadiene degradation did not occur. Thus, it was concluded that the methyl group in polyisoprene is very important in the degradation in the presence of chloranil. (C) 1998 Elsevier Science Limited. All rights reserved.