The radiation‐induced polymerization of dienes with sulfur dioxide

Abstract

Copolymers 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.

Soluble and Thermally Stable Polysulfones Prepared by the Regiospecific and Alternating Radical Copolymerization of 2,4-Hexadiene with Sulfur Dioxide

“…Our hypothesis for interpreting the solubility of the poly(diene sulfone)s is as follows: the symmetry of the repeating structure of the diene unit in the polymer chain is related to the solubility. Namely, poly(BD- alt -SO 2 ) has no asymmetric carbon center in the main chain because the diene units exclusively consist of the trans-1,4 repeating structure. − ,, Such a symmetric polymer chain structure is favored for partial crystallization, resulting in the poor solubility of poly(BD- alt -SO 2 ). Poly(HD- alt -SO 2 ) includes asymmetric centers in the main chain.…”

“…Namely, poly(BD-alt-SO 2 ) has no asymmetric carbon center in the main chain because the diene units exclusively consist of the trans-1,4 repeating structure. [18][19][20][21][22][23][24][25][26]31,32 Such a symmetric polymer chain structure is favored for partial crystallization, resulting in the poor solubility of poly(BD-alt-SO 2 ). Poly(HD-alt-SO 2 ) includes asymmetric centers in the main chain.…”

“…In contrast with the significant number of investigations for the synthesis and characterization of the poly(vinyl sulfone)s, only a few reports have been published regarding the poly(diene sulfone)s, which were prepared by the copolymerization of 1,3-diene monomers with SO 2 . For example, the alternating radical copolymerization of 1,3-butadiene (BD), − isoprene (IP), and 1,3-cycloalkadienes − as well as the random copolymerization of chloroprene with SO 2 were reported, but the details of the structure and properties of the copolymers have not been investigated. In 1970, Bauer et al reported the high crystallinity and the poor solubility of poly(butadiene sulfone) prepared by emulsion polymerization.…”

Thermally Stable Polysulfones Obtained by Regiospecific Radical Copolymerization of Various Acyclic and Cyclic 1,3-Diene Monomers with Sulfur Dioxide and Subsequent Hydrogenation

“…Especially, the regiospecific polymerization of diene monomers is required because the physical properties of diene polymers significantly depend on the repeating structure of the diene monomer units. − Highly regiospecific propagation has recently been reported for the alternating radical copolymerization of 1,3-diene monomers with O 2 and SO 2 . − It was demonstrated in our previous study that poly(diene sulfone) (PDS) could be synthesized by the regiospecific radical copolymerization of 2,4-hexadiene ( M5 in Chart ) with SO 2 and the transformation of the PDS into a thermally stable polymer by the hydrogenation of the carbon-to-carbon double bond of the main chain . Very few reports on the copolymerization of other diene monomers with SO 2 as well as the properties of the resulting PDSs have been published, − being in contrast to the high number of studies on the synthesis and characterization of the PDSs produced from olefins. − …”

Structure of the polysulfones of some conjugated dienes

“…Poly(2,3-dimethylbutadiene sulfone) Kearney et al (7) reported that when prepared by yirradiation this polymer is soluble in DMSO saturated with lithium chloride. However our polymers did not dissolve in this medium and we were therefore obliged to examine the spectrum of the terpolymer of sulfur dioxide, 2,3-dimethylbutadiene, and isoprene, which dissolved in TFA.…”