Redox Potential as a Predictor of Polyethylene Branching Using Nickel α-Diimine Catalysts

Abstract

The ability to control polyethylene branching density is of great interest as a means by which a polymer’s thermomechanical properties may be tailored. One particularly interesting way in which this can be achieved is by altering the electronic characteristics of Pd- and Ni-based α-diimine catalysts through the inclusion of electron-withdrawing or electron-donating substituents onto the ligand scaffold; however, a few critical fundamental studies are absent from the literature. These include a systematic examination of electronic perturbations of Ni-based α-diimine catalysts, as well as how placement of donating or withdrawing substituents on the backbone versus N-aryl moieties of the α-diimine ligand framework impact polymer topology. In addition, no method currently exists by which the polymer topology may be predicted based on an intrinsic characteristic of the (pre)­catalyst or ligand without requiring extensive polymerization studies. Herein, we use both experimental and computational methods to understand how the placement of electron-donating or electron-withdrawing substituents on Ni α-diimine catalysts affects PE branching density, and compare those results to the analogous unsubstituted catalyst. We will show that inclusion of electron-withdrawing substituents decreases resultant PE branching density, whereas electron-donating substituents exhibit little to no change in PE branching density. Finally, we will show that as the placement and identity of donating or withdrawing substituents are varied, so too is the redox half-wave potential (E1/2) of the precatalysts, which can be used to generate a predictive curve by which PE branching density may be estimated for other substituted Ni-based α-diimine catalysts without the need for extensive polymerization studies.

A Co-Anchoring Strategy for the Synthesis of Polar Bimodal Polyethylene

“…Many factors such as molecular weight, molecular weight distribution, and branching content strongly in uence the miscibility of polyole n blends, which is crucial to realizing desired properties for multimodal polyole ns. [30][31][32][33][34][35] As expected, good miscibility is di cult to achieve for mixtures of linear and branched polyole ns. 36,37 This poor miscibility is exponentially ampli ed for the above-mentioned bimodal polar functionalized polyole ns, since the low-molecular-weight fraction is both more branched and more polar than the high-molecular-weight fraction.…”

Identifying the Real Chemistry of the Synthesis and Reversible Transformation of AuCd Bimetallic Clusters

“…Apart from the steric hindrance effect, is there any other property of ligand that can tune the final structure of the AuCd cluster? As is well known, the electronic properties of substituents play very important roles in organic reactions. , Does it also work in the preparation of metal clusters, particularly, cluster transformation or doping? To eliminate the influence of the steric hindrance effect, three para-substituted thiophenols, e.g., 4- tert -butyl-benzenethiol (TBBT), 4-methoxybenzenethiol (4MOBT), and 4-(trifluoromethyl)­thiophenol (4TMBT), are selected in this study to investigate their function in Cd doping.…”

Significantly Tunable Foaming Behavior of Blowing Agent for the Polyethylene Foam Resin with a Unique Designed Blowing Agent System

“…Polyethylene (PE) is a commonly used plastic material with a wide range of applications. − The research studies of PE have also received extensive attention for its synthesis, modification, − application, − degradation, , etc. Foaming technology has been widely applied in PE products, such as injection foaming and rotational foaming. − The foaming behavior directly affects the performance of the PE foaming products.…”