No abstract

Metallocene/methylaluminoxane catalysts are able to design copolymers with tailored architectures. It is possible to copolymerize ethene with higher α‐olefins and cyclic olefins. The terpolymer of ethene/1‐hexene/norbornene shows a better flexibility than the ethene/norbornene copolymer by a similar high transparency. The influence of the comonomer concentration on activity, molecular weight, and glass transition temperature is given as well as the comparison to 1‐hexene/norbornene and propene/norbornene copolymers. Hexene/norbornene copolymers were found to have a predominant alternating microstructure.

Homogeneous catalysts in addition with MAO were used to synthesize copolymers of 3-methyl-1-butene (3MB1) with ethylene and propylene. Three series of ethylene/3MB1 copolymerizations were catalyzed by the organometallic compounds [Me 2 Si(Me 4 Cp)(N t Bu)]TiCl 2 (1), [Ph 2 Si(OctHFlu)(Ind)]ZrCl 2 (2), and rac-[Me 2 C(Ind) 2 ]ZrCl 2 (3). For the copolymerization of 3MB1 with propylene, the metallocenes rac-[Me 2 C(Ind) 2 ]-ZrCl 2 (3) and [Me 2 C(Cp)(Flu)]ZrCl 2 (4) were used. For each metallocene, the influence of the molar fraction of 3MB1 in the feed as well as the influence of the polymerization temperature on the copolymerization behavior was investigated. In this regard copolymerization parameters were calculated. All copolymers were characterized by 13 C NMR spectroscopy, differential scanning calorimetry, and gel permeation chromatography techniques. Very small amounts of incorporated 3MB1 have a remarkable effect on the melting temperatures of the obtained polymers. Already by incorporation of 1 mol % of 3MB1 in the polymer, the melting temperature of the obtained LLDPE is lowered to 120 °C, whereas twice as much 1-butene is necessary to achieve the same effect, which should facilitate the processing.

Six half-sandwich chromium complexes, in which the carbocyle is substituted by a nitrogen containing heterocycle as additional ligand were investigated regarding their polymerization behavior toward propylene. For each catalyst precursor, polymerization series in which the influence of the monomer concentration and of the polymerization temperature were analyzed, were conducted, using methylaluminoxane (MAO) as cocatalyst. Besides, several polymerizations with 1-butene were made, which brought further aspects into the interpretation of the for the polymerization of propylene complex NMR spectra. Because of the chain-walking tendency of all investigated systems, by sole polymerization of propylene, polymers are obtained, which have a structure which resembles those of ethylene/propylene copolymers with regioinverted propylene units. The ethylene share of the polymers with a value up to 30 mol % is astonishingly high. The different tendencies toward 2,1insertions with succeeding chain-straightening of the chromium complexes and of each single catalyst by variation of the polymerization conditions is expressed in a broad range of the glass transition temperatures of the synthesized polymers, which vary between -14 and -38 °C.