Copolymerization of Ethylene with Sterically Hindered 3,3‐Dimethyl‐1‐Butene Using a Chain‐Walking Pd‐Diimine Catalyst

Abstract

In this Communication, the copolymerization of ethylene with a sterically hindered α-olefin comonomer, γ-trisubstituted 3,3-dimethyl-1-butene (DMB), using a chain-walking Pd-diimine catalyst, [(ArNC(Me)(Me)CNAr)Pd(CH(3) )(NCMe)]SbF(6) (Ar2,6-(iPr)(2) C(6) H(3) ) (1) is reported. In spite of its high steric bulkiness in the close proximity of the double bond, appreciable DMB incorporations (up to 3 mol-%) are successfully achieved in the copolymers. The chain microstructure of the copolymers is elucidated, and the effect of DMB incorporation on polymer topology and thermal properties are examined. This work thus demonstrates the high capability of the Pd-diimine catalyst in incorporating sterically encumbered α-olefins.

Hyperbranched polyethylenes by chain walking polymerization: synthesis, properties, functionalization, and applications

“…Considering this, Ye et al first examined the potential of externally incorporated isolated tertiary carbons (not generated intrinsically through chain walking) as chain-walking blocking sites. 37 To incorporate external tertiary carbons onto polymer backbones, chain walking copolymerizations of ethylene with sterically hindered 3,3dimethyl-1-butene (DMB, 15) were designed with catalyst 5 at the ethylene pressure of 1 atm (Scheme 7). 37 15 was selected specifically as the comonomer given its possession of a quaternary carbon at the g position, which can prevent the occurrence of chain straightening and the resulting loss of the tertiary carbon.…”

“Living” Polymerization of Ethylene and 1-Hexene Using Novel Binuclear Pd–Diimine Catalysts

“…From 1 H NMR analyses, the polymers are all highly branched with ca. 100 branches/1000 carbons, which was resulted from the characteristic chain walking mechanism of Pd–diimine catalysts [13,31,32,33,34,37,38,39,40,41,42,43,44,45,46]. The end-capping ester group –C(O)OCH 3 were evidenced in the 1 H NMR spectra of all the samples.…”

“…Typically, Pd–diimine catalysts have been reported to successfully facilitate the “living” polymerization of both ethylene and α-olefins at temperatures of ~5 °C [14,15,16,17,18,19,20,21,22,23,24,25,26,27,28,29,30]. Owing to their characteristic chain walking mechanism, Pd–diimine catalysts allow the novel synthesis of branched polyethylenes with controlled chain topologies in ethylene polymerization [31,32,33,34,37,38,39,40,41,42,43,44,45,46,47,48] and chain straightened poly(α-olefin)s with reduced branching density in α-olefin polymerization [14,16,49]. By employing their combined features, our group has tailor designed a family of polyethylenes of complex chain architectures, including hyperbranched, hybrid hyperbranched-linear, block, gradient and block-gradient, star, and surface-tethered polymer brushes, by Pd–diimine-catalyzed ethylene “living” polymerization.…”

Defects and defect engineering in Soft Matter

“…193,195 The chain-walking polymerization method has been widely used to adjust the thermal, rheological, and mechanical properties of polymers, specifically for macromolecules formed from a-olefin monomers. [196][197][198][199] In addition, Alamo and coworkers showed that chain-walking polymerization can be utilized to synthesize isotactic polypropylene with regional defects caused by irregularity in distribution or density of methyl groups along polymer chains. 200 They illustrated that at comparable defect density, polypropylenes with such chain-walking defects have lower melting points and much lower degrees of crystallinity than isotactic polypropylenes with regional defects induced by copolymerization with other 1-alkene comonomers.…”