Communication
ChemComm
While PE produced in solution-phase polymerisations was Busico for the use of HTExplore (University of Naples); and Mr
clearly highly entangled, slurry-phase polymerisations using Alessio Mingione and Prof. Roberta Cipullo (HTExplore) for
sMAO led to the production of substantially disentangled running high-throughput polymerisation experiments and
UHMWPE (disUHMWPE) as evidenced by the rapid formation polymer analysis.
of two melting peaks (at approximately 135 and 142 1C), with
the low temperature peak increasing at the expense of the high
Conflicts of interest
temperature peak as annealing time is increased. The high
melting peak results from remaining nascent crystals while the
low melting peak arises from the melt-crystallised portion
There are no conflicts to declare.
formed from sequential chain detachment during annealing.
For a given Mw a more rapid increase in the normalised area of the
Notes and references
low melting peak is indicative of a more disentangled polymer.22
This is in contrast to the behaviour observed for commercial
entangled UHMWPE synthesised using Ziegler–Natta catalysts,
which has been shown by Rastogi et al. to have a significantly
different response to annealing, with the low melting peak increas-
ing in area at a dramatically slower rate.18,23
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i
Several alkylaluminium species, R3Al (R = Me, Et, Bu) and
MAO, were investigated as co-catalytic scavengers with 2sMAO
(Fig. 5). It was found that activity increased in the order TEA o
TMA o MAO o TIBA, with 2sMAO/TIBA having more than twice
the activity as 2sMAO/MAO. However, while polymer molecular
weight was high in all cases, there was a significant low
molecular weight fraction observed with both TEA and TMA,
resulting in larger PDIs and lower Mw values. This is presumed
to be due to the one-electron reduction of some titanium
centres in addition to increased chain transfer to aluminium
in these cases.
In conclusion, new ansa-permethylindenyl-phenoxide (PHENI*)
complexes have been synthesised and fully characterised. Hetero-
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utilising a range of inorganic supports for the slurry-phase poly-
merisation of ethylene. The PHENI* complexes have been found to
be significantly more active than the indenyl-PHENICS analogues,
as well as producing polyethylene with narrower molecular
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tBu2
weight distributions. sMAO-Me SB( ArO,I*)TiCl2 (2sMAO
) had
2
the highest slurry-phase activity of the complexes studied (3.7 Â
106 gPE molTi
hÀ1 barÀ1). Additionally, these PHENI*-based
À1
systems have been demonstrated to produce substantially disen-
tangled UHMWPE when supported on solid MAO, with molecular
weights up to 4.2 MDa when supported on an MAO-modified LDH.
C. G. C. R., J.-C. B., Z. R. T. would like to thank SCG
Chemicals Co., Ltd (Thailand) for financial support. We also
thank Ms Liv Thobru, Ms Sara Rund Herum, and Ms Rita
Jenssen (Norner AS) for running GPC analysis; Prof. Vincenzo
22 A. Pandey, A. Toda and S. Rastogi, Macromolecules, 2011, 44,
8042–8055.
23 S. Rastogi, D. R. Lippits, G. W. M. Peters, R. Graf, Y. Yao and
H. W. Spiess, Nat. Mater., 2005, 4, 635–641.
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Chem. Commun., 2021, 57, 8600–8603 | 8603