Differential Impact of the COVID-19 Pandemic on Female Graduate Students and Postdocs in the Chemical Sciences.

Over the past two and a half years, the COVID-19 pandemic severely disrupted almost all aspects of life as people throughout the world were instructed to work-from-home. Scientific researchers, whose work is reliant on access to laboratory equipment, have been acutely impacted by these global changes. In this study, we surveyed graduate students and postdocs in the chemical sciences at a selected number of academic institutions in the United States.

Poly(2,3-Dihydrofuran): A Strong, Biorenewable, and Degradable Thermoplastic Synthesized via Room Temperature Cationic Polymerization.

Creation of strong and tough plastics from sustainable and biorenewable resources is a significant challenge in polymer science. This challenge is further complicated when attempting to make these materials using an economically viable process, which is often hindered by the production and availability of chemical feedstocks and the efficiency of the monomer synthesis. Herein, we report the synthesis and characterization of a strong thermoplastic made from 2,3-dihydrofuran (DHF), a monomer made in one step from 1,4-butanediol, a bioalcohol already produced on the plant scale.

Photoredox Catalysis in Photocontrolled Cationic Polymerizations of Vinyl Ethers.

Advances in photocontrolled polymerizations have expanded the scope of polymer architectures and structures that can be synthesized for various applications. The majority of these polymerizations have been developed for radical processes, which limits the diversity of monomers that can be used in macromolecular design. More recent developments of photocontrolled cationic polymerizations have taken a step toward addressing this limitation and have expanded the palette of monomers that can be used in stimuli-regulated polymerizations, enabling the synthesis of previously inaccessible polymeric structures.

Air-Tolerant Nickel-Catalyzed Cyanation of (Hetero)aryl Halides Enabled by Polymethylhydrosiloxane, a Green Reductant.

An air-tolerant nickel-catalyzed cyanation of aryl bromides is reported. The reaction uses a NiCl/Xantphos catalyst in combination with substoichiometric quantities of zinc cyanide and polymethylhydrosiloxane. This silane is a green, homogeneous alternative to the traditional, insoluble solid reductant zinc and renders the reaction tolerant to air.

Reversible C-C Bond Formation, Halide Abstraction, and Electromers in Complexes of Iron Containing Redox-Noninnocent Pyridine-imine Ligands.

The exploration of pyridine-imine (PI) iron complexes that exhibit redox noninnocence (RNI) led to several interesting discoveries. The reduction of (PI)FeX species afforded disproportionation products such as (dmpPI)FeX (dmp = 2,6-Me-CH, X = Cl, Br; -X) and (dippPI)FeX (dipp = 2,6-Pr-CH, X = Cl, Br; -X), which were independently prepared by reductions of (PI)FeX in the presence of PI. The crystal structure of -Br possessed an asymmetric unit with two distinct electromers, species with different electronic GSs: a low-spin ( = 1/2) configuration derived from an intermediate-spin = 1 core antiferromagnetically (AF) coupled to an = 1/2 PI ligand, and an = 3/2 center resulting from a high-spin = 2 core AF-coupled to an = 1/2 PI ligand.

Controlling the Shape of Molecular Weight Distributions in Coordination Polymerization and Its Impact on Physical Properties.

High-density polyethylene (HDPE) is utilized in a multitude of commercial products worldwide due to its broad spectrum of physical properties and low production costs. Molecular weight and dispersity () are known to affect the tensile and rheological properties of HDPE, but little is known about the influence of the molecular weight distribution (MWD) shape on these properties. In this work, we investigate this matter through the temporal regulation of initiation in a living coordination-insertion polymerization of ethylene.