High molecular weight tail and long-chain branching in SRM 1476 polyethylene

The composition of the high molecular weight tail in the branched polyethyl ene standard reference material SRM 1476 was studied in detail using size e xclusion chromatography coupled with a refractive index, a viscosity, and a light scattering on-line detector. The light scattering determinations of both molecular weight and radius of gyration point at a difference in kind between the molecular species below and above 10(6) Da. In particular, abov e 10(6) Da, increases in molecular weight resulted in a marked "densificati on" process. This is consistent with a greater concentration of long-chain branching and/or with a change in molecular architecture. Previous literatu re results for this polymer and a critical comparison of the performance of the different detectors are also discussed. (C) 1999 John Wiley & Sons, In c.