Kimmo Hakala

Metallocene/methylaluminoxane-catalyzed copolymerizations of oxygen-functionalized long-chain olefins with ethylene

Copolymerizations of ethylene with 10-undecen-1-ol, 10-undecenyl methyl ether, 10-undecenyl trimethyl silyl ether, and 1-undecene were performed with rac-ethylene-bis(1-indenyl)zirconium dichloride as a catalyst and methylaluminoxane as a cocatalyst. All three oxygen-functional comonomers copolymerized with ethylene, although the activity of the catalyst decreased considerably compared with the homopolymerization of ethylene. The conversions of the comonomers varied from 17 to 40%, depending on the amount of comonomer in the feed. Under the same conditions, the conversion of 1-undecene was 50–75%. The incorporation (0.7–3.6 mol %, depending on the feed) and the effect on the activity of the catalyst were on the same level for all the functional comonomers, which indicates that trimethylsilyl or methyl groups do not act as effective protecting groups for oxygen atoms. According to NMR and Fourier transform infrared analyses, the final functional group in the copolymers of the trimethylsilyl ether comonomer was hydroxyl. In contrast, the methyl ether group remained untouched in the copolymer, which suggests that the formation of aluminum alkoxides via a reaction with a cocatalyst is not a prerequisite for comonomer incorporation.

Molecular modeling of metallocene catalyzed copolymerization of ethylene with functional comonomers

Abstract Metallocene catalyzed copolymerization of ethylene with comonomers having polar functional groups (alcohols, carboxylic acids and esters) has been studied experimentally and by molecular modeling. The polar functional groups strongly reduce the activity of the catalyst. The deactivation of the catalyst is investigated with DFT calculations on some model systems. The effect of the spacer length between the double bond and the functional group is analyzed using molecular dynamics and molecular mechanics methods, and compared with experiments.

Metallocene dichlorides bearing acenaphthyl substituted cyclopentadienyl rings: preparation and polymerization behavior

Abstract The unbridged complex [bis(η5-7,9-diphenylcyclopenta[a]acenaphthadienyl)] zirconium dichloride (8) and two asymmetric ethylene bridged metallocenes {bis[1,2-(η5-7,9-diphenylcyclopenta[a]acenaphthadienyl)-1-phenyl] ethane} zirconium dichloride (9) and {[1-(η5-7,9-diphenylcyclopenta[a]acenaphthadienyl)-2-phenyl-2-(η5-9-fluorenyl)] ethane} zirconium dichloride (10) were prepared and used as catalysts for ethene and propene homopolymerization after activation with MAO. Whereas zirconocenes 8 and 9, that bear two acenaphthyl substituted Cp-rings, have only moderate activity, 10 produces polyethene with high activity and high molecular weight. In propene polymerization only atactic polymer was formed and the chain termination occurred mainly via β-methyl elimination. The solid state structures of compounds 8, 9 and 10 were determined by means of X-ray diffraction analysis.

Compatibilization of polyethylene/polyamide 6 blends with functionalized polyethylenes prepared with metallocene catalyst

Metallocene catalyst technology was utilized to prepare functionalized polyethylenes, which were used as compatibilizers in polyethylene/polyamide 6 (40/60) blends. Polymerization of ethylene with 10-undecen-1-ol, 10-undecenoic acid, or N-methyl-10-undecenylamine resulted in ethylene copolymers with a small amount (0.2–1.2 mol %) of functionalized side chains. The blends were prepared in a twin-screw midiextruder, and injection molded with a mini-injection molding machine. The effect of the new compatibilizers on morphology and mechanical and thermal properties was studied. Toughness as well as stiffness and strength increased significantly with an addition of 10 wt % compatibilizer. Morphology became much more uniform, and crystallization and melting behavior changed. The Molau test with FTIR analysis was used to determine that the desired reactions between the compatibilizer and polyamide had actually taken place. The results showed functionalized polyethylenes prepared with metallocene catalysts to act as effective compatibilizers in polyethylene/polyamide 6 blends.

Heterogenization of racemic ethylenebis 1-indenyl zirconium dichloride on trimethylaluminum vapor modified silica surface

Abstract Heterogeneous metallocene catalysts were prepared by adsorbing rac -Et(Ind) 2 ZrCl 2 on a modified silica surface in solution. The modification of silica was conducted in gas phase with atomic layer chemical vapor deposition (ALCVD) technique, where the silica, preheated at either 350 or 600°C, was allowed to react with vaporized trimethylaluminum (TMA) at 250°C. Modified carriers and heterogeneous catalysts were characterized with FTIR, 1 H MAS (magic-angle spinning) NMR, 13 C , and 29 Si CP (cross-polarization) MAS NMR spectroscopies and elemental analyses. In the reaction of TMA with silica, a saturated surface was formed consisting of different (O) 4− n Si(CH 3 ) n ( n =1, 2 or 3) and AlCH 3 groups. The ratio of SiMe to AlMe groups was approximately 1.5 in the TMA/SiO 2 carriers. When the metallocene was adsorbed onto the carrier it seemed to react with the surface AlCH 3 groups and possibly ZrCH 3 groups were formed. Heterogeneous catalysts were tested in the polymerization of ethylene and propylene in the presence of methylalumoxane (MAO). And they produced similar polymer as the homogeneous rac -Et(Ind) 2 ZrCl 2 catalyst, but with lower activity. A catalyst with the best activity was achieved from silica that was preheated at 600°C. Moreover, leaching of catalyst was examined whereupon a part of zirconium was observed to desorb from the carrier.

Interaction of oxygen functionalized alkenes with a methylaluminoxane-zirconocene catalyst studied by NMR

Abstract Reactions of hydroxyl, ether and carbonyl functionalized alkenes with methylaluminoxane prepared in toluene- d 8 (MAO) and zirconocenedichloride (Cp 2 ZrCl 2 ) were investigated by 1 H- and 13 C-NMR spectroscopy at 27°C. The 11 alkenes studied bear a terminal CC bond separated by 7–9 (–CH 2 –) units from the heteroatom moiety. Intramolecular connectivities in mono (alkene), bi (alkene and MAO) and tri (alkene, MAO and Cp 2 ZrCl 2 ) component mixtures were determined by 2D HSQC, HMBC, ROESY and NOESY NMR techniques. The five studied alkenols formed aluminium alkoxides with MAO even in the case of a substantial steric hindrance around the OH group. Zirconocene enhanced the formation of aluminium alkoxides. Decomposition to free alkenol was observed only for the straight chain alkenol (10-undecen-1-ol). The OTMS derivatives formed dimers of the type CH 2 CR 1 R 2 along with methyl derivatives, CH 2 C(Me)(R) and (Me)CHCH(R), in the presence of MAO and Cp 2 ZrCl 2 . 10-Undecenyl methyl ether and methyl decenoate remained mainly as a free comonomer in the presence of MAO or MAO/Cp 2 ZrCl 2 , though a transient coordination of the former to MAO was deduced. Unsaturated species Me 2 CCH–Al–X and CH 2 CH(CH 2 ) 5 CH 2 CHC( t -Bu)O–Al–X (X=MAO oligomer) were formed in the reaction of t -butyl undecenoate or 2,2-dimethyl-11-dodecen-3-one with MAO or MAO/Cp 2 ZrCl 2 . Interaction of the CH 2 CH part of the functionalized alkenes with zirconocene was not observed. A possible coordination of the CC bond to MAO was observed only for the sec alkenols.

Functional Polyolefins Through Polymerizations by Using Bis(indenyl) Zirconium Catalysts

The discovery of metallocene catalysts has enabled synthesis of new polyolefin structures through the ability to incorporate comonomers that are not applicable using Ziegler–Natta or other conventional olefin polymerization catalysts. Extensive research has been carried out on the copolymerization behavior of different bis(indenyl) zirconium catalysts in order to understand their comonomer response, chain termination mechanisms, and chain-end isomerization. Metallocene-catalyzed copolymerization enables unforeseen material structures, leading to functional polyolefins with strongly or weakly interacting comonomers or long-chain branches. These copolymers show interesting technical properties like reactive functionality, compatibility, adhesion properties, and modified rheology.

Dynamic NMR study of tri-tert-butylcarbinol and of a carbinol–methylaluminoxane mixture

The reaction of tri‐tert‐butylcarbinol and oligomeric methylaluminoxane (MAO) prepared in toluene‐d8 was studied by analysing the reaction mixture utilizing ROESY, HSQC and HMBC 2D NMR experiments. The formation of one main alkoxide was observed in the reaction. Dynamic 13C NMR and semiempirical PM3 molecular modelling were used in concert to study the tert‐butyl group rotation barriers of this alkoxide. From several modelled acyclic and cyclic MAO fragments, an open chain—Al(Me)OAl(Me)—fragment was observed to be consistent with the NMR results. Copyright