Polar Isotactic and Syndiotactic Polypropylenes by Organozirconium‐Catalyzed Masking‐Reagent‐Free Propylene and Amino–Olefin Copolymerization

Abstract

Polar functionalizedi sotactic and syndiotactic polypropylenes (PPs) are synthesized by direct, maskingreagent-free propylene and amino-olefin (AO, CH 2 = CH-(CH 2) x N n Pr 2 ,x= 2, 3, 6) copolymerizations using the activated precatalysts rac-[Me 2 Si(indenyl) 2 ]ZrMe 2 and [Me 2 C-(Cp)(fluorenyl)]ZrMe 2 ,r espectively.P olymerization activities at 25 8 8Ca re as high as 4208 and 535 kg/(mol hatm) with AO incorporation up to 4.0 mol %a nd 1.6 mol %, respectively. Remarkably,i ntroducing the amino-olefin comonomers significantly enhances stereoselection for both isotactic (mmmm: 59.5 %!91.0 %) and syndiotactic (rrrr:6 6.3 %!81.3 %) products.

Thermal and Dielectric Stability of Functional Photo-cross-linkable Carbazole-Modified Polypropylene

“…A similar stereochemical improvement has been also described for the copolymerization of propylene with amino-olefins. In that case, the polar group/active site interaction has been proposed to account for such stereoselectivity enhancement of the propylene insertion but, in our case, it is not clear that this factor may be argued given the predominance of the above-commented positive comonomer effect on the kinetics.…”

“…Such behavior seems to contradict the well-known fact that, polar groups strongly depress kinetics of transition-metal catalyzed olefin polymerization. , Indeed, the presence of heteroatoms with electron pairs, available to interact with the active metal site, allows the possibility of coordinating the olefin to be partially or completely disabled. In fact, direct copolymerization of olefins with nitrogen-bearing functionalities, like amines, has been possible by using alkyl or silyl protected groups, , whose interaction with the catalyst must, however, play a role in promoting effective insertion of the polar comonomer, as it has also been found for Sc metallocenes. , …”

“…In fact, direct copolymerization of olefins with nitrogen-bearing functionalities, like amines, has been possible by using alkyl or silyl protected groups, 35,36 whose interaction with the catalyst must, however, play a role in promoting effective insertion of the polar comonomer, 36 as it has also been found for Sc metallocenes. 37,38 In our case, there are some disabling interactions between UDK molecules and metal sites 26 that, seemingly, are not strong enough to counteract insertion enhancement, promoted by the activating interaction of a long-chain α-olefin.…”

Horizontally and Vertically Concerted Steric Strategy in α‐Diimine Nickel Promoted Ethylene (Co)Polymerization†

“…Polyolefins mainly including polyethylene and polypropylene with a vast scale of around 200 million tons annually all over the world are one of the largest commercial synthetic polymers and are ubiquitous in modern society. [ 1‐4 ] Late transition metal catalysts play a crucial role in the olefin polymerization and especially in the copolymerization of olefin and polar monomers for the preparation of (functionalized) polyolefins. [ 5‐13 ] As the most studied catalysts, seminal Brookhart's α‐diimine nickel and palladium catalysts have attracted much more attentions over the past two decades, due to a variety of polyolefin architectures produced by the unique chain walking pathway.…”