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A number of novel C1-symmetric metallocenes based on substituted fluorenyl and indenyl ligands, [dimethylsilyl(2,7-di-tert-butyl-9-η⁵-fluorenyl)(1-η⁵-indenyl)]zirconium dichloride (3), [dimethylsilyl(1,1,4,4,7,7,10,10-octamethyl-1,2,3,4,7,8,9,10-octahydrodibenzo[b,h]-9-η⁵-fluorenyl)(1-η⁵-indenyl)]zirconium dichloride (5), and [dimethylsilyl(1,1,4,4,7,7,10,10-octamethyl-1,2,3,4,7,8,9,10-octahydrodibenzo[b,h]-9-η⁵-fluorenyl)(2-methyl-1- η⁵-indenyl)]zirconium dichloride, and the analogue complexes with a Ph2Si bridge (4, 6, and 8) have been synthesized and used for alternating ethene/propene copolymerizations and compared to the unsubstituted complexes 1 and 2. With growing sterical demand of the substituents, the activities of the catalysts at moderate temperatures decrease strongly, but a very high-temperature stability is achieved. Usage of catalyst species with a Ph2Si instead of a Me2Si bridge leads to higher activities and molar masses. The percentages of alternating triads are high for all catalysts and are decreasing with growing polymerization temperature. Surprisingly, the catalysts with the bulky substitution at the fluorene ring (5−8) yield at 15 and 0 °C copolymers with a lower alternating part than at 30 °C.

Branch contents in sparsely short-chain branched polyethylenes (<C28) and end-group concentrations in linear polyethylenes were investigated by solid- and melt-state ¹³C NMR using model copolymers of 1-octene, 1-octadecene, 1-hexacosene, and linear PE standards. Benchmark measurements were established for single-pulse acquisition under MAS on these melts at 423 K, using 7 mm ceramic rotors and commercially available solid-state probes at 300 and 500 MHz ¹H Larmor frequency. Signal improvement by a factor of 3−4 was observed, corresponding to a factor 10 reduction in measurement time, when compared to a reference solution-state (400 MHz ¹H) measurement. Transient NOE effects due to proton decoupling during FID acquisition were found to affect significantly the accuracy of branch content determination and end-group analysis in the melt spectra, even at moderate pulse repetition rates. ¹³C T1 and NOE buildup rates and intensity variations were established at 423 K and correlated to the local packing of the branched chain architecture. CP/MAS spectra at and below room temperature on the solid-state polyethylenes showed good agreement with reference spectra, providing an alternative method for sensitivity improvement, with about a factor of 10 saving in measurement time as compared to the melt measurements. Using an optimized parameter set, molecular weight determination of a linear polyethylene standard with Mn>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 T1ρ, T1, and T1^NOE. It was found that T1^NOE seems to have the best sensitivity to determine the approximate length of the side chain branches for n > 6.

Three olefin polymerization catalysts are supported onto a flat silica wafer employing spin-coating impregnation. These model catalysts feature a defined surface direction of the silica support and thus facilitate the direct correlation between catalyst dispersion and morphology of the polymer product. Depending on the interaction of the catalysts with the silica surface, the catalysts disperse in very different fashions, which induces different constraints on the polymer growth upon gas-phase polymerization. Chemical anchoring of the active species as in the CrOx/SiO2 (Phillips) system results in homogeneous polymer film of up to several 10 μm . In contrast the physisorbed Cp[1,3-(2,6-Me2C6H3)2C2H4N2C&dbd;N]TiBz2B(C6F5)3 forms clusters on the flat silica that evolve into highly porous, ball-shaped polymer beads. rac-[Me2Si(2-Me-4-(1-Naph)Ind)2]ZrCl2(CH3AlO)x forms a film of metallocene catalyst dispersed inside the cocatalyst matrix. Homogeneous regions of this film give rather homogeneous polymer films while local concentrations of active species (hotspots) form crater- and ball-shaped structures.

1-Butene and 1-pentene were polymerized with three different metallocenes:  dimethylsilylbis(2-methyl-4,5-benzoindenyl)zirconium dichloride [Me2Si(2-Me-4,5-BzoInd)2ZrCl2] (1), dimethylsilylbis(2-methyl-4-phenylindenyl)zirconium dichloride [Me2Si(2-Me-4-PhInd)2ZrCl2] (2), and dimethylsilylbis(indenyl)zirconium dichloride [Me2Si(Ind)2ZrCl2] (3). The polymerizations were conducted with the rac-isomers of the metallocenes and mixtures of the rac- and meso-systems for 1 and 2 and with the meso-form of catalyst 3 combined with MAO. It was shown that the activities in the polymerization of the α-olefins of the meso-isomers of 1 and 2 were much higher than those of the rac-metallocenes, while a vice versa behavior is observed for catalyst 3. Additionally, reaction profiles of 1 and 2 were recorded which underline that the stability of their meso-compounds is much higher than that of the rac-systems for the polymerization of the investigated monomers.

When polymerization of propene was conducted using the C2-symmetrical zirconocenes rac-Et(2,4,7-Me3Ind)2ZrCl2 (I) and rac-Me2Si(2-Me-4-Ph-Ind)2ZrCl2 (II) combined with Ph3CB(C6F5)4, the isotacticity ([mmmm]) and the melting point (Tm) of the produced polymer markedly increased, along with a decrease of the polymerization temperature from 30 to −78 °C. Thus, isotactic polypropene (iPP) with Tm = 168.9 °C was obtained from the polymerization with catalyst I at −78 °C, whereas the [mmmm] and Tm of iPP were almost unchanged in the same temperature range when the C1-symmetrical zirconocene iPr(3-tBuCp)(3-tBuInd)ZrCl2 (III or III‘) was employed.