Distribution of short‐chain branching in low‐density polyethylene

The distributions of short‐chain branching in some commercial low‐density polyethylenes have been investigated by measuring the degree of short‐chain branching of their fractionated samples. The results obtained on the fractions which were fractionated with respect to molecular weight showed that some polyethylenes have broad distributions and others have narrow distributions, and these results have been considered to depend mainly on the polymerization conditions. These fractions of which the molecular weight is considered to be approximately uniform were further refractionated with respect to degree of short‐chain branching, and thus cross‐fractionations were accomplished. The distributions of short‐chain branching in those parent fractions were also examined, and it was found out that the parent fractions have fairly broad distributions, and the distribution is broader when the molecular weight is lower, but the difference of distribution is not so great in the different samples. The distributions in those parent fractions showed close agreement with the theoretical distributions which were calculated on the basis of statistical branch formation.