Are Methylaluminoxane Activators Sheets?

Density functional theory calculations on neutral sheet models for methylaluminoxane (MAO) indicate that these structures, containing 5-coordinate and 4-coordinate Al, are likely precursors to ion-pairs seen during the hydrolysis of trimethylaluminum (Me3 Al) in the presence of donors such as octamethyltrisiloxane (OMTS). Ionization by both methide ([Me]- ) and [Me2 Al]+ abstraction, involving this donor, were studied by polarizable continuum model calculations in fluorobenzene (PhF) and o-difluorobenzene (DFB) media. These studies suggest that low MW, 5-coordinate sheets ionize by [Me2 Al]+ abstraction, while [Me]- abstraction from Me3 Al-OMTS is the likely process for higher MW 4-coordinate sheets. Further, comparison of anion stabilities per mole of aluminoxane repeat unit (MeAlO)n , suggest that anions such as [(MeAlO)7 (Me3 Al)4 Me]- =[7,4]- are especially stable compared to higher homologues, even though their neutral precursors are unstable.

Eco-Friendly Methods for Extraction and Modification of Cellulose: An Overview.

Cellulose is the most abundant renewable polymer on Earth and can be obtained from several different sources, such as trees, grass, or biomass residues. However, one of the issues is that not all the fractionation processes are eco-friendly and are essentially based on cooking the lignocellulose feedstock in a harsh chemical mixture, such as NaOH + Na2S, and water, to break loose fibers. In the last few years, new sustainable fractionation processes have been developed that enable the obtaining of cellulose fibers in a more eco-friendly way. As a raw material, cellulose's use is widely known and established in many areas. Additionally, its products/derivatives are recognized to have a far better environmental impact than fossil-based materials. Examples are textiles and packaging, where forest-based fibers may contribute to renewable and biodegradable substitutes for common synthetic materials and plastics. In this review, some of the main structural characteristics and properties of cellulose, recent green extraction methods/strategies, chemical modification, and applications of cellulose derivatives are discussed.

Superanionic Solvent-Free Liquid Enzymes Exhibit Enhanced Structures and Activities.

The surface of a carboxylate-enriched octuple mutant of Bacillus subtilis lipase A (8M) is chemically anionized to produce core (8M)-shell (cationic polymer surfactants) bionanoconjugates in protein liquid form, which are termed anion-type biofluids. The resultant lipase biofluids exhibit a 2.5-fold increase in hydrolytic activity when compared with analogous lipase biofluids based on anionic polymer surfactants. In addition, the applicability of the anion-type biofluid using Myoglobin (Mb) that is well studied in anion-type solvent-free liquid proteins is evaluated. Although anionization resulted in the complete unfolding of Mb, the active α-helix level is partially recovered in the anion-type biofluids, and the effect is accentuated in the cation-type Mb biofluids. These highly active anion-type solvent-free liquid enzymes exhibit increased thermal stability and provide a new direction in solvent-free liquid protein research.

Surface Anionization of Self-Assembled Iron Sulfide Hierarchitectures to Enhance Capacitive Storage for Alkaline-Metal-Ion Batteries.

Due to the ever-growing demand for cost-effective batteries toward greener and sustainable applications, continuous effort has been devoted to tailoring the interfacial kinetics of electrode materials. Herein, surface anionization has been introduced for the hierarchical assembly of iron sulfides on three-dimensional (3D) graphene foam (denoted FeS2@3DGF and FeS@3DGF). The surface-anchored sulfate species provide ideal electroactive sites, which is correlated with enhanced capacitive contribution and boosted energy storage. Consequently, remarkable rate capability and stable cyclability can be achieved in alkaline-metal-ion batteries. Specifically, FeS@3DGF displays superb cycling stability when evaluated as anodes for Li-ion batteries (a steady capacity of 1109 mAh g-1 after 200 cycles at 200 mA g-1). Moreover, superior rate capability can be achieved for Na-ion batteries (203 mAh g-1 at 10 000 mA g-1). These findings provide new insights into reinforcing interface kinetics during electrochemical processes and hold great promise for versatile applications in the future.