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Ultra-high-molecular-weight polyethylene (PE) with viscosity-average molecular weight (M v ) of 3.1 Â 10 6 to 5.2 Â 10 6 was prepared with a heterogeneous Ziegler-Natta MgCl 2 (ethoxide type)/TiCl 4 /triethylaluminum catalyst system under controlled conditions. The optimum activity of the catalyst was obtained at a [Al]/[Ti] molar ratio of 61 : 1 and a polymerization temperature of 60 C, whereas the activity of the catalyst increased with monomer pressure and decreased with hydrogen concentration. The titanium content of the catalyst was 2.4 wt %. The rate/time profile of the catalyst was a decay type with a short acceleration period. M v of the PE obtained decreased with increasing hydrogen concentration and polymerization temperature. The effect of stirrer speeds from 100 to 400 rpm did not so much affect the catalyst activity; however, dramatic effects were observed on the morphology of the polymer particles obtained. A stirrer speed of 200 rpm produced PE with a uniform globulelike morphological growth on the polymer particles. The particle size distributions of the polymer samples were determined and were between 14 and 67 lm.

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2015): The first mixed-ligand coordination compound involving 8-aminoquinoline and pyridine-2,6-dicarboxylic ligands: Synthesis, X-ray crystal structure and DFT studies, Journal of Coordination Chemistry, Self-assembly of pyridine-2,6-dicarboxylic acid (H 2 py-2,6-dc) and CrCl 3 ·6H 2 O in the presence of 8-aminoquinoline as a N-donor co-ligand leads to formation of a supramolecular coordination compound in which the cationic and anionic complexes differ in composition, namely, [Cr(py-2,6-dc)(8-aq)(H 2 O)][Cr(py-2,6-dc) 2 ]·2H 2 O (1). Single-crystal X-ray analysis reveals that the coordination sphere around Cr in the cationic complex consists of one (py-2,6-dc) 2-, one 8-aq and one H 2 O while the anionic complex is more symmetrical and has two (py-2,6-dc) 2-ligands in its coordination environment. Both Cr centres are six-coordinate with distorted octahedral geometries. The ionic coordination motifs in 1 are held together by intermolecular O−H···O, N−H···O and C−H···O hydrogen bonding as well as C−O···π, C−H···π and π−π stacking interactions to produce extended 2D architectures. We have analyzed the π−π stacking interactions by DFT calculations focusing our attention to the influence of the anionic/cationic nature of the complex.