High molecular weight tail and long-chain branching in low-density polyethylenes

The composition of the high molecular weight tail in branched low-density p olyethylenes made by both tubular and autoclave reactors was studied in det ail using size-exclusion chromatography (SEC) coupled with a viscosity dete ctor (VD) and a two-angle light-scattering detector (LSD). The detection of a second peak at very small elution volumes in the light-scattering chroma togram but not in the refractive index chromatogram and viscosity chromatog ram is due to high molecular weight species. It is also indicative of a cha nge in the long-chain branching distribution. It was found that the intrins ic viscosity contraction factor g' scales with the radius of the gyration c ontraction factor, g, with the exponent, epsilon, having a value in the ran ge 0.4-1.4. Furthermore, epsilon shows significant molar mass dependence. ( C) 2001 John Wiley & Sons, Inc.