STUDIES OF POLYMERS AND POLYMERIZATION: IV. OBSERVATIONS ON THE POLYMERIZATION OF ISOPRENE AND 2, 3-DIMETHYLBUTADIENE-1, 3

Abstract

The polymerization of isoprene and dimethylbutadiene at temperatures ranging from 10° to 145 °C. has been studied with reference to the nature of the dimeric products and the influence of the temperature and period of heating on the extent of polymerization, the ratio of oil to rubber and the molecular weight of the rubber and viscosity of its sols. There was no evidence of the formation from either diene of an open chain dimer, polymerizable to rubber, such as the "β-myrcene" of Ostromislenski. The ratio of oil:rubber from a given diene is approximately constant in different periods of polymerization at a given temperature. The ratio increases with rise of temperature. Isoprene gives far more oily by-product than dimethylbutadiene. As polymerization progresses, the molecular weight of the rubber and the viscosity of its sols rises. The higher the temperature of polymerization, the lower is the molecular weight ultimately attained. The polymerization is catalyzed by air. The viscosity of the sols of the synthetic rubbers is low and falls on keeping owing to oxidation.