The radiation‐induced polymerization of dienes with sulfur dioxide

Abstract

AbstractCopolymers of sulfur dioxide and butadiene, isoprene, 2,3‐dimethylbutadiene, and chloroprene were prepared by irradiation at low temperatures with remarkably high efficiency. The polymers were all insoluble in the monomer mixtures and therefore only limited kinetic data could be obtained. However, the following conclusions could be reached from the data. Isoprene, butadiene, and 2,3‐dimethylbutadiene all produced 1:1 copolymers with sulfur dioxide across a wide range of temperature and composition. At high sulfur dioxide contents the cyclic sulfones began to form. Chloroprene behaved differently in that copolymers containing considerably more than 50 mole‐% of chloroprene were obtained. Also, the infrared spectra revealed a considerable proportion of pendant vinyl groups as compared with the predominately 1,4 addition in the case of the other dienes studied. The isoprene and 2,3‐dimethylbutadiene polymers were found to be soluble in highly polar solvents containing dissolved salts. At lower temperatures the radiation caused concurrent degradation of the polymer. The compositions of isoprene, 2,3‐dimethylbutadiene and sulfur dioxide terpolymers were found to be unusually sensitive to the polymerization temperature. Thermal gravimetric analysis of the various polymers showed thermal stabilities in the order, 2,3‐dimethylbutadiene > isoprene and butadiene > chloroprene. A sample of tetramethylene polysulfone prepared chemically showed greatly enhanced thermal stability, catastrophic degradation beginning about 100°C. higher than the corresponding butadiene copolymer. Attempts to hydrogenate the diene copolymers were unsuccessful although the corresponding cyclic sulfones were hydrogenated successfully. The highly efficient radiation polymerizations are believed to be free radical in nature and to proceed via monomer complex function. The difficulty of chain termination between sulfonyl radicals is suggested as a reason for the very high yields and molecular weights obtained at low temperatures.