| Abstract: | A sample of a commercial low-density polyethylene was fractionated and values of number ? Mn and weight-average Mw, molecular weights obtained together with intrinsic viscosities η], measured in decalin at 135° and in a theta-solvent, diphenyl at 118°. Results are compared with those obtained using samples of high-density polyethylene, of narrow molecular weight distribution, in decalin at 135° and in diphenyl at 125°. Values of the z-average mean square radius of gyration (S?2)z, are converted to the weight-average unperturbed state. The branching parameters g and g1 thus obtained, indicate that long-chain branching increases with increasing molecular weight. Intrinsic ivscosities under theta-conditions for the low-density polyethylene fractions lead to a relationship η]θ = K w0·20, agreeing with the treatment of Zimm and Kilb. Some of the approximations involved in the estimation of long-chain branching are discussed. |
