One polyethylene and nine ethene/α-olefin copolymers differing in amount (0.4−2.9 mol %) and molar mass of the comonomer were characterized by NMR, SEC-MALLS, and rheology. Samples were polymerized using a [Ph2C(2,7-di-t-BuFlu)(Cp)]ZrCl2/MAO catalyst, with octene, octadecene, and hexacosene as comonomers, resulting in polymers of M w ≈ 190 kg/mol. The comonomer content was determined by melt-state NMR. For the homopolymer 0.37 and 0.30 LCB/molecule were found by NMR and SEC-MALLS, respectively. Rheological quantities, such as the zero shear rate viscosity (η0), increased with LCB as compared to linear samples of the same M w. The shape of the viscosity function and the linear steady-state elastic compliance ( ) showed a dependence on comonomer content and length. These findings are used to elucidate the various long-chain branching architectures. The highest comonomer content samples behaved like typical linear polymers in rheological experiments, while those with less comonomer contents were found to be long-chain branched. Besides the comonomer content, the type of comonomer has an influence on the branching structure.

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Summary: Linear and long‐chain branched high‐density polyethylenes with a molar mass $\overline M _{\rm w}$ between 1 700 and 1 150 000 g · mol−1 were synthesized using metallocene catalyst systems. Depending on the polymerization parameters the molar mass distribution reached values ranging from 2 to 12. The resins were characterized with various analytical methods. The branch detection took place via two independent methods, melt rheology and SEC‐MALLS. New relationships between catalyst structure, polymerization conditions, and the branching content of polyethylenes were established. Besides the branched materials strictly linear polymers are presented; for those no long‐chain branches were detected either by light scattering or by rheology. The viscosity function was observed to be strongly influenced by the molar mass distribution and the degree of long‐chain branching. The molar mass distribution was affected by the catalyst type and the polymerization conditions. A dependence of the melting point and the melting enthalpy on the molar mass was observed.

Branch contents in sparsely short-chain branched polyethylenes (100 000 g/mol was shown to be feasible in both solid-state and melt measurements in less than a one-day measurement, obtained on a 500 MHz spectrometer and 4 mm rotor. Using this enhanced signal intensity, NMR relaxation times were investigated in the melt with respect to their inherent sensitivity to the branching architecture. These measurements included T 1 ρ, T 1, and T 1 NOE. It was found that T 1 NOE seems to have the best sensitivity to determine the approximate length of the side chain branches for n > 6.

Copolymers of ethene and 1-octene, 1-dodecene, 1-octadecene, and 1-hexacosene were carried out with [Ph 2 C(2,7-ditert BuFlu)(Cp)]ZrCl 2 /methylalumoxane as a catalyst to obtain short-chain branched polyethylenes with branch lengths of 6-26 carbon atoms. This catalyst provided high activity and a very good comonomer and hydrogen response. In this study, the influence of the length and number of the side chains on the mechanical properties of the materials was investigated. The crystalline methylene sequence lengths of the copolymers and lamellar thicknesses were calculated after the application of a differential scanning calorimetry/successive self-annealing separation technique. By dynamic mechanical analysis, the storage modulus as an indicator of the stiffness and the loss modulus as a measure of the effect of branching on the a and b relaxations were studied. The results were related to the measurements of the polymer density and tensile strength to determine the effect of longer side chains on the material properties. The hexacosene copolymers had side chains of 24 carbons and remarkable material properties very different from those of conventional linear low-density polyethylenes. The side chains of these copolymers crystallized with one another and not only parallel to the backbone lamellar layer, depending on the hexacosene concentration in the copolymer. The side chains crystallized even at low hexacosene concentrations in the copolymer. A transfer of these results to 16 carbons