Isolated Ethylene Units in Isotactic Polystyrene Chain: Stereocontrol of an Isospecific Post‐Metallocene Titanium Catalyst

Abstract

Summary: Copolymerization of styrene with small amounts of ethylene using the catalyst system dichloro{1,4‐dithiabutanediyl‐2,2′‐bis(4,6‐di‐tert‐butyl‐phenoxy)}titanium/methylaluminoxane results in the unprecedented formation of isotactic polystyrene containing isolated ethylene units. 13C NMR spectroscopic analysis of the copolymer indicates that an “enantiomorphic site” control mechanism for isospecific propagation is operating. DSC measurements also indicate the presence of isolated ethylene units which modify the crystallization behavior of the isotactic polystyrene.Schematic representation of the copolymerization of styrene with small amounts of ethylene using dichloro{1,4‐dithiabutanediyl‐2,2′‐bis(4,6‐di‐tert‐butyl‐phenoxy)}titanium/methylaluminoxane as catalyst system.imageSchematic representation of the copolymerization of styrene with small amounts of ethylene using dichloro{1,4‐dithiabutanediyl‐2,2′‐bis(4,6‐di‐tert‐butyl‐phenoxy)}titanium/methylaluminoxane as catalyst system.

Groups 3 and 4 single-site catalysts for styrene–ethylene and styrene–α-olefin copolymerization

“…Styrene-rich copolymers (up to 99 mol% styrene content) with only few isolated ethylene units could also be achieved with this catalytic system when adding very small amounts of ethylene [78]. The 13 C NMR analyses of the styrenic units configuration in the vicinity of isolated ethylene unit allowed to determine that an enantiomorphic site control mechanism takes place rather than a chain-end controlled one.…”

Stereoregular Polymers

“…Copolymerization of ethylene with styrene by methylene-bridged C 2 -symmetric zirconocene (72)/MAO affords the corresponding block copolymer having the isotactic polystyrene block (276). The ethylenestyrene copolymer, having an isotactic styrene-styrene linkage and isolated ethylene units, can be obtained by copolymerization of styrene with a small amount of ethylene by dithiobisphenolate Ti catalyst (69) (277).…”

Binary copolymerization of 4-methyl-1,3-pentadiene with styrene, butadiene and isoprene catalysed by a titanium [OSSO]-type catalyst

“…In contrast, the solely homogeneous systems able to produce isotactic 1,2‐poly‐4MPD are based on titanium complexes incorporating [OSSO]‐type bis(phenolato) ligands . Notably, while in the case of syndioselective catalysts the polymerization with other olefinic monomers such as styrene or ethylene results in a mixture of homopolymers, the [OSSO]‐type titanium catalysts have been shown to be a very active and versatile class of catalysts for the synthesis of various copolymers with unprecedented molecular architectures having stereoregular styrene and diene segments . In order to further expand the scope of these catalytic systems, here we report the binary copolymerization of 4MPD with styrene, butadiene and isoprene using the catalyst dichloro{1,4‐dithiabutanediyl‐2,2′‐bis[4,6‐bis(2‐phenyl‐2‐propyl)phenoxy]}titanium ( 1 ) (Scheme ), activated by MAO, and the complete characterization of the resulting copolymers.…”