| Abstract: | The copolymerization of cyclohexene and sulfur dioxide to form an alternating copolymer was initiated by tert-butyl hydroperoxide. The enthalpies and entropies of formation of the cyclohexene-sulfur dioxide charge-transfer complex, which is present during the copolymerization, were determined in two solvents by means of ultraviolet spectroscopy. The reduction of ultraviolet absorption during copolymerization afforded a convenient means of investigating reaction kinetics. No evidence of the direct involvement of the complex in polymerization initiation was found. The observation that the use of unpurified cyclohexene led to spontaneous initiation appears to point to adventitiously formed hydroperoxide rather than the charge-transfer complex as providing initiating radicals which are produced by the redox reaction of the hydroperoxide with sulfur dioxide. A competing heterolytic scission reaction was found to result in the formation of tert-butyl peroxide and sulfuric acid. This reaction caused the polymerization reaction to stop after a short period of time due to a time-dependent decrease in initiator concentration. |
