Facile Strategy to Prepare Poly(ionic liquid)-Coated Solid Polymer Electrolytes through Layer-by-Layer Assembly.

The inability of solid polymer electrolytes to preserve strong mechanical strength with high ionic conductivity hinders the commercialization of lithium metal batteries (LMBs). The success of fabricating layer-by-layer (LbL)-assembled electrolytes has realized the application of flexible solid polymer electrolytes in electrochemical devices. Here, we demonstrate a rational strategy to construct solid electrolytes coated with multiple ultrathin layers of polyanions (poly(sodium 4-styrenesulfonate)) and polycations (linear poly(1-butyl-3-(4-vinylbenzyl)-1H-imidazolium chloride) (BVIC)/linear poly(PEG4-VIC)/SiO2-g-poly(PEG4-VIC)) using an LbL assembly method. Poly(ionic liquid) backbones and PEG side groups are employed to facilitate the transport of lithium ions via the segmental motion of the macromolecular matrix. The fabricated free-standing membranes exhibited good ionic conductivities of 9.03-10 × 10-4 S cm-1. Furthermore, a Li/LiFePO4 cell assembled with the LbL-membrane electrolytes exhibits an initial high discharge capacity of 143-158 mAhg-1 at 60 °C with high columbic efficiency. This approach, which combines polymer synthesis and LbL self-assembly, is an effective and facile route to fabricate solid polymer electrolyte membranes with superior ionic conductivity and mechanical robustness, which are useful for electrochemical devices and high-voltage battery applications.

Selective deconstruction of mixed plastics by a tailored organocatalyst.

Plastic represents an essential material in our society; however, a major imbalance between their high production and end-of-life management is leading to unrecovered energy, economic hardship, and a high carbon footprint. The adoption of plastic recycling has been limited, mainly due to the difficulty of recycling mixed plastics. Here, we report a versatile organocatalyst for selective glycolysis of diverse consumer plastics and their mixed waste streams into valuable chemicals. The developed organocatalyst selectively deconstructs condensation polymers at a specific temperature, and additives or other polymers such as polyolefin or cellulose can be readily separated from the mixed plastics, providing a chemical recycling path for many existing mixed plastics today. The Life Cycle Assessment indicates that the production of various condensation polymers from the deconstructed monomers will result in a significant reduction in greenhouse gas emissions and energy input, opening a new paradigm of plastic circularity toward a net-zero carbon society.

Covalent narlaprevir- and boceprevir-derived hybrid inhibitors of SARS-CoV-2 main protease.

Emerging SARS-CoV-2 variants continue to threaten the effectiveness of COVID-19 vaccines, and small-molecule antivirals can provide an important therapeutic treatment option. The viral main protease (Mpro) is critical for virus replication and thus is considered an attractive drug target. We performed the design and characterization of three covalent hybrid inhibitors BBH-1, BBH-2 and NBH-2 created by splicing components of hepatitis C protease inhibitors boceprevir and narlaprevir, and known SARS-CoV-1 protease inhibitors. A joint X-ray/neutron structure of the Mpro/BBH-1 complex demonstrates that a Cys145 thiolate reaction with the inhibitor's keto-warhead creates a negatively charged oxyanion. Protonation states of the ionizable residues in the Mpro active site adapt to the inhibitor, which appears to be an intrinsic property of Mpro. Structural comparisons of the hybrid inhibitors with PF-07321332 reveal unconventional F···O interactions of PF-07321332 with Mpro which may explain its more favorable enthalpy of binding. BBH-1, BBH-2 and NBH-2 exhibit comparable antiviral properties in vitro relative to PF-07321332, making them good candidates for further design of improved antivirals.

Controlling the elasticity of polyacrylonitrile fibers via ionic liquids containing cyano-based anions.

As the predominant precursor for high-performance carbon fiber manufacturing, the fabrication of polyacrylonitrile (PAN)-based composite fibers attracts great interest. Ionic liquids (ILs) have recently been investigated for melt-spinning of ultrafine PAN fibers. The plasticizing properties of ILs are significantly affected by the structure of ILs and can be influenced by electronegativity, steric effects, etc. Herein, we report a facile strategy to control the elasticity of the PAN/ILs fibers by tuning the anion structure of ILs. Particularly, the ILs containing nitrile-rich groups exhibited enhanced plasticizing effect and nucleating ability on dissolving PAN components, achieving highly stretchable PAN/ILs fibers.

Covalent narlaprevir- and boceprevir-derived hybrid inhibitors of SARS-CoV-2 main protease: room-temperature X-ray and neutron crystallography, binding thermodynamics, and antiviral activity.

The COVID-19 pandemic continues to disrupt everyday life, with constantly emerging SARS-CoV-2 variants threatening to render current vaccines ineffective. Small-molecule antivirals can provide an important therapeutic treatment option that is subject to challenges caused by the virus variants. The viral main protease (M pro ) is critical for the virus replication and thus is considered an attractive drug target for specific protease inhibitors. We performed the design and characterization of three reversible covalent hybrid inhibitors BBH-1, BBH-2 and NBH-2, whose structures were derived from those of hepatitis C protease inhibitors boceprevir and narlaprevir. A joint X-ray/neutron structure of the M pro /BBH-1 complex demonstrated that a Cys145 thiolate reaction with the inhibitor’s keto-warhead creates a negatively charged oxyanion, similar to that proposed for the M pro -catalyzed peptide bond hydrolysis. Protonation states of the ionizable residues in the M pro active site adapt to the inhibitor, which appears to be an intrinsic property of M pro . Structural comparisons of the hybrid inhibitors with PF-07321332 revealed unconventional interactions of PF-07321332 with M pro which may explain its more favorable enthalpy of binding and consequently higher potency. BBH-1, BBH-2 and NBH-2 demonstrated comparable antiviral properties in vitro relative to PF-07321332, making them good candidates for further design of improved antivirals.

Structural, Electronic, and Electrostatic Determinants for Inhibitor Binding to Subsites S1 and S2 in SARS-CoV-2 Main Protease.

Creating small-molecule antivirals specific for severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) proteins is crucial to battle coronavirus disease 2019 (COVID-19). SARS-CoV-2 main protease (Mpro) is an established drug target for the design of protease inhibitors. We performed a structure-activity relationship (SAR) study of noncovalent compounds that bind in the enzyme's substrate-binding subsites S1 and S2, revealing structural, electronic, and electrostatic determinants of these sites. The study was guided by the X-ray/neutron structure of Mpro complexed with Mcule-5948770040 (compound 1), in which protonation states were directly visualized. Virtual reality-assisted structure analysis and small-molecule building were employed to generate analogues of 1. In vitro enzyme inhibition assays and room-temperature X-ray structures demonstrated the effect of chemical modifications on Mpro inhibition, showing that (1) maintaining correct geometry of an inhibitor's P1 group is essential to preserve the hydrogen bond with the protonated His163; (2) a positively charged linker is preferred; and (3) subsite S2 prefers nonbulky modestly electronegative groups.

Synthesis of Poly(ionic Liquid)s-block-poly(methyl Methacrylate) Copolymer-Grafted Silica Particle Brushes with Enhanced CO2 Permeability and Mechanical Performance.

Poly(ionic liquid) (PIL)-based block copolymers are of particular interest as they combine the specific properties of PILs with the self-assembling behaviors of block copolymers, broadening the range of potential applications for PIL-based materials. In this work, three particle brushes: SiO2-g-poly(methyl methacrylate) (PMMA), SiO2-g-PIL, and SiO2-g-PMMA-b-PIL were prepared through surface-initiated atom transfer radical polymerization. Unlike the homogeneous homopolymer particle brushes, the block copolymer particle brush SiO2-g-PMMA-b-PIL exhibited a bimodal chain architecture and unique phase-separated morphology, which were confirmed by size-exclusion chromatography and transmission electron microscopy. In addition, the influence of the introduction of the PMMA segment on the gas separation and mechanical performance of the PIL-containing block copolymer particle brushes were investigated. A significant improvement of Young's modulus was observed in the SiO2-g-PMMA-b-PIL compared to the SiO2-g-PIL bulk films; meanwhile, their gas separation performances (CO2 permeability and CO2/N2 selectivity) were the same, which demonstrates the possibility of improving the mechanical properties of PIL-based particle brushes without compromising their gas separation performance.

Polymer-Grafted Porous Silica Nanoparticles with Enhanced CO2 Permeability and Mechanical Performance.

Three different types of polymer ligands, poly(methyl methacrylate) (PMMA), poly(methyl methacrylate-random-poly(ethylene glycol)methyl ether methacrylate) (PMMA-r-PEGMEMA), and poly(ionic liquid)s (PIL), were grafted onto the surface of 15 nm solid and large hollow porous silica nanoparticles (average particle size ∼60 nm) by surface-initiated atom transfer radical polymerization (SI-ATRP) to demonstrate the enhanced carbon dioxide (CO2) permeability as well as mechanical properties. After characterizing the purified products, free-standing bulk films were fabricated by the solvent-casting method. The poly(ionic liquid) nanocomposite films exhibited a much higher carbon dioxide permeance than PMMA and PMMA-r-PEGMEMA systems with a similar silica content. Also, the hollow silica-mixed matrix membranes showed a significant enhancement in CO2 permeability compared to the 15 nm solid silica films because of the pore structure. Despite the transparency loss due to the scattering of larger particle sizes, the hollow silica particle brush films exhibited the same mechanical properties as the 15 nm solid silica-derived ones.

Is a polymer semiconductor having a "perfect" regular structure desirable for organic thin film transistors?

This study utilized high temperature NMR and matrix-assisted laser desorption/ionization time-of-flight (MALDI-ToF) mass spectrometry to reveal that appreciable amounts of structural defects are present in the diketopyrrolopyrrole (DPP)-quaterthiophene copolymers (PDQT) synthesized by the Stille coupling polymerization with Pd(PPh3)2Cl2, Pd2(dba)3/P(o-tol)3, and Pd(PPh3)4 catalyst systems. It was proposed that these structural defects were produced via homocoupling side reactions of the C-Br bonds and the organostannane species. Model Stille coupling reactions further substantiated that the amount of structural defects are catalyst-dependent following the order of Pd(PPh3)2Cl2 > Pd2(dba)3/P(o-tol)3 > Pd(PPh3)4. To verify the structural assignments, "perfect" structurally regular PDQT polymers were prepared using Yamamoto coupling polymerization. When compared to the structurally regular polymers, the polymers containing defects exhibited notable redshifts in their absorption spectra. Surprisingly, the "perfect" structurally regular polymers showed poor molecular ordering in thin films and very low charge transport performance as channel semiconductors in organic thin film transistors (OTFTs). On the contrary, all the "defected" polymers exhibited much improved molecular ordering and significantly higher charge carrier mobility.

Tandem mass spectrometry characteristics of polyester anions and cations formed by electrospray ionization.

Electrospray ionization of polyesters composed of isophthalic acid and neopentyl glycol produces carboxylate anions in negative mode and mainly sodium ion adducts in positive mode. A tandem mass spectrometry (MS/MS) study of these ions in a quadrupole ion trap shows that the collisionally activated dissociation pathways of the anions are simpler than those of the corresponding cations. Charge-remote fragmentations predominate in both cases, but the spectra obtained in negative mode are devoid of the complicating cation exchange observed in positive mode. MS/MS of the Na(+) adducts gives rise to a greater number of fragments but not necessarily more structural information. In either positive or negative mode, polyester oligomers with different end groups fragment by similar mechanisms. The observed fragments are consistent with rearrangements initiated by the end groups. Single-stage ESI mass spectra also are more complex in positive mode because of extensive H/Na substitutions; this is also true for matrix-assisted laser desorption ionization (MALDI) mass spectra. Hence, formation and analysis of anions might be the method of choice for determining block length, end group structure and copolymer sequence, provided the polyester contains at least one carboxylic acid end group that is ionizable to anions.