Azo‐bis nitriles. II. Use of 2,2′‐azo‐bis‐isobutyronitrile as a catalyst for the polymerization of styrene

Abstract (1) The rate of polymerization catalyzed by 2,2′‐azo‐bis‐isobutyronitrile was found to be proportional to the square root of the catalyst concentration at 47.8° and 67.8° at a monomer concentration of 4 moles/liter. A square root dependence was also observed at 80.3° with 1‐azo‐bis‐cyclohexanecarbonitrile in pure monomer. At these temperatures, the number average degree of polymerization, assuming combination for the termination step, was inversely proportional to the square root of the catalyst concentration. These facts are additional evidence to support the unimolecular first‐order decomposition of the azo‐bis compound into radicals. (2) The monomer dependence on the over‐all rate was found to be 1.2, again at 68.2° this result is consistent with first‐order initiation and bimolecular termination. (3) The decomposition of 2,2′‐azo‐bis‐isobutyronitrile in pure styrene or in toluene and styrene is a unimolecular first‐order decomposition with a rate constant similar to that observed in pure toluene.