Synthesis and Characterization of Hyperbranched Polyethylenes Made with Nickel‐α‐Diimine Catalysts

Abstract

The polymerization of ethylene in the presence of 1,4‐bis(2,6‐diisopropylphenyl)acenaphthenediiminenickel(II) dichloride (1) and methylaluminoxane (MAO) gives hyperbranched polyethylene (HBPE) in appropriate reaction conditions. The system 1/MAO is active in solvents like toluene or hexane at temperatures as high as 80 °C and ethylene pressures ranging from 1 to 15 atm. The polyethylenes obtained show high molecular weights (up to 467 kg · mol−1) and more than 218 branches per 1 000 backbone carbon atoms, qualifying these materials as hyperbranched. Dynamic‐mechanical thermal analysis (DMTA) of these materials shows high β‐transitions, directly related to the branch content of these polyethylenes. DMTA analysis of polyethylenes obtained with 1/MAO at 0, 30, and 50 °C (corresponding to entries 1, 2 and 3).magnified imageDMTA analysis of polyethylenes obtained with 1/MAO at 0, 30, and 50 °C (corresponding to entries 1, 2 and 3).

Uniform, Axial‐Orientation Alignment of One‐Dimensional Single‐Crystal Silicon Nanostructure Arrays

“…The matched activities of metallocene and DMN catalyst offer a valid method to make the amount of polymer obtained using isolated catalyst comparable. In addition, the activity of the hybrid catalyst is higher than that of the isolated catalysts suggesting that a synergistic effect between the nickel and the titanium catalyst precursors occurs 18…”

“…It is not possible to distinguish the presence of two polymer phases in the SEM micrograph of the blend sample which indicates good compatibility between the polyethylene phases (Fig. 7(c)) 18, 32. Fiber‐type chains obtained using hybrid supported catalyst can also be observed which shows good replication of the support morphology.…”

“…Therefore, it is desirable to produce polymer blends with linear and branched chains using a hybrid catalyst in a single reactor without adding comonomer. Recently, Souza and co‐workers used a homogeneous binary catalyst (nickel α‐diimine/metallocene) to prepare LPE/BPE polymer blends 16–19. They reported that the molar fraction of BPE in the blends strongly depended on the polymerization conditions.…”

Mesoporous Silica Supported Multiple Single‐Site Catalysts and Polyethylene Reactor Blends with Tailor‐Made Trimodal and Ultra‐Broad Molecular Weight Distributions

“…[9][10][11][12][13][14][15][16][17] Much less is known concerning multi-site catalysts based upon post-metallocene catalysts, which have been employed to achieve reactor blends and polyethylenes with controlled polyethylene branching. [10,[18][19][20][21][22] Also different support materials were blended together in order to generate different catalytically active sites producing polyethylenes with different chain length. [23] Numerous interactions between different catalytically sites and also between catalytically active sites, monomer, and hydrogen render MWD control rather difficult.…”

Stereochemistry of Polymerization

“…Previous initiators based on late transition metals had low activity and were useful only for producing dimers and oligomers because of extensive b-hydride transfer. The use of bulky a-diimine ligands favors monomer insertion over b-hydride transfer and gives access to polymers Gates et al, 2000;Gibson and Spitzmesser, 2003;Ittel et al, 2000;Kunrath et al, 2002;Mecking, 2001].…”