AbstractThe photodegradation of polyisobutylene (PIB) film in air at a temperature where volatile formation is negligible was studied by means of light scattering, chemical actiometry, and spectrophotometric techniques. The degradation is accelerated by addition of tris(α‐thiopicolinanilide)—cobalt(III) (TPAC). The sensitization and the course of the degradation were determined by weight‐average molecular weight, energy of activation, and quantum yield of the photolysis of the polymer film with 254‐nm light. The plots of molecular weight, weight‐average chain scission, and degree of degradation vs. irradiation time are linear and confirm the random nature of chain scission of the polymer. The unsaturation produced is proportional to the time of irradiation. Ultraviolet and infrared absorption spectra have been employed to substantiate a mechanism of the degradation process which does not involve hydrogen abstraction from the polymer, but direct cleage of the polymer backbone and addition of initiating radicals of TPAC at the sites o
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