Crystallization behavior and structure of metallocene polyethylene with long-chain branch.

The investigations of the branching chain have influence on the crystallization behaviors and structures in metallocene polyethylene (mPE) as compared to the Ziegler–Natta polyethylenes that have grown significantly since the introduction of metallocene catalytic polymerization in industrial applications. A zirconium dichloride complex, three intermediates, and methylaluminoxane were used as metallocene catalysts for the polymerization of ethylene to obtain the mPEs. The structures of the mPEs were characterized by ¹³C nuclear magnetic resonance (¹³C-NMR), gel permeation chromatography (GPC), differential scanning calorimetry (DSC), wide-angle X-ray diffraction (WAXD), and dynamic rheology method. The results on the crystallization of the mPEs showed master curve features and indicated fractal topology of the long-chain branch. The conflicting result obtained from the ¹³C NMR and rheology is due to the long-chain fractal structure. The successive self-nucleation and annealing (SSA) was used to characterize the length of crystallizable methylene sequence length (MSL) methylene sequence. It was found that the lamellar thickness calculated via Thomson-Gibbs equation exhibits two scaling relationships with MSL related to the molecular weight of the polyethylene chain entanglements M e . [ABSTRACT FROM AUTHOR]