A Sequence-Defined ABC Dendritic Macromolecule with Amino Acid Peripheral Functionality via Iterative Chemoselective Reactions.

Chemoselective reactions allow near-precision control over the polymer composition and topology to create sequence-controlled polymers with similar secondary and tertiary structures to those found in proteins. Dendrimers are recognized as well-defined macromolecules with the potential to mimic protein surface functionality due to the large number of functional groups available at its periphery with the internal structure acting as the support scaffold. Transitioning from using small-molecule dendrimers to dendritic macromolecules will not only allow retention of the high peripheral functionality but also provide an internal scaffold with a desired polymer composition within each generational layer. Here, we exemplify a systematic approach to creating a dendritic macromolecule with the placement of different polymer building blocks in precise locations within the internal structure and the placement of three different amino acid moieties clustered at the periphery. The synthesis of this ABC dendritic macromolecule was accomplished through iterative chemoselective reactions.

Electrochemical Synthesis of Gold-N-Heterocyclic Carbene Complexes.

An electrochemical synthesis of gold(I)-N-heterocyclic carbene (Au-NHC) complexes has been developed. The electrochemical methodology uses only imidazolium salts, gold metal electrodes, and electricity to produce these complexes with hydrogen gas as the only by-product. This high-yielding and operationally simple procedure has been used to produce eight mononuclear and three dinuclear Au-NHC complexes. The electrochemical procedure facilitates a clean reaction with no by-products. As such, Au-NHC complexes can be directly transferred to catalytic reactions without work-up or purification. The Au-NHC complexes were produced on-demand and tested as catalysts in a vinylcyclopropanation reaction. All mononuclear Au-NHC complexes performed similarly to or better than the isolated complexes.

Inactivation of human coronaviruses using an automated room disinfection device.

The emergence of more virulent and epidemic strains of viruses, especially in the context of COVID-19, makes it more important than ever to improve methods of decontamination. The objective of this study was to evaluate the potential of on-demand production of chlorine species to inactivate human coronaviruses. The commercial prototype disinfection unit was provided by Unipolar Water Technologies. The Unipolar device generates active chlorine species using an electrochemical reaction and dispenses the disinfectant vapour onto surfaces with an aspirator. The minimum effective concentration and exposure time of disinfectant were evaluated on human hepatoma (Huh7) cells using 50% tissue culture infectious dose (TCID50) assay and human coronavirus 229E (HCoV-229E), a surrogate for pathogenic human coronaviruses. We showed that chlorine species generated in the Unipolar device inactivate HCoV-229E on glass surfaces at ≥ 400 parts per million active chlorine concentration with a 5 min exposure time. Here, inactivation refers to the inability of the virus to infect the Huh7 cells. Importantly, no toxic effect was observed on Huh7 cells for any of the active chlorine concentrations and contact times tested.

Lewis Acid-Induced Reversible Disproportionation of TEMPO Enables Aqueous Aluminum Radical Batteries.

Nitroxide radicals, such as 2,2,6,6-tetramethylpiperidyl-1-oxy (TEMPO), are typical organic electrode materials featuring high redox potentials and fast electrochemical kinetics and have been widely used as cathode materials in multivalent metal-ion batteries. However, TEMPO and its derivatives have not been used in emerging rechargeable aluminum-ion batteries (AIBs) due to the known disproportionation and possible degradation of nitroxide radicals in acidic conditions. In this study, the (electro)chemical behavior of TEMPO is examined in organic and aqueous Lewis acid electrolytes. Through in situ (electro)chemical characterizations and theoretical computation, we reveal for the first time an irreversible disproportionation of TEMPO in organic Al(OTf)3 electrolytes that can be steered to a reversible process when switching to an aqueous media. In the latter case, a fast hydrolysis and ligand exchange between [Al(OTf)3TEMPO]- anion and water enable the overall reversible electrochemical redox reaction of TEMPO. These findings lead to the first design of radical polymer aqueous AIBs that are fire-retardant and air-stable, delivering a stable voltage output of 1.25 V and a capacity of 110 mAh g-1 over 800 cycles with 0.028% loss per cycle. This work demonstrates the promise of using nonconjugated organic electroactive materials for cost-effective and safe AIBs that currently rely on conjugated organic molecules.

Printable Hydrogel Arrays for Portable and High-Throughput Shear-Mediated Assays.

Hydrogels have been widely used to entrap biomolecules for various biocatalytic reactions. However, solute diffusion in these matrices to initiate such reactions can be a very slow process. Conventional mixing remains a challenge as it can cause irreversible distortion or fragmentation of the hydrogel itself. To overcome the diffusion-limit, a shear-stress-mediated platform named the portable vortex-fluidic device (P-VFD) is developed. P-VFD is a portable platform which consists of two main components, (i) a plasma oxazoline-coated polyvinyl chloride (POx-PVC) film with polyacrylamide and alginate (PAAm/Alg-Ca2+) tough hydrogel covalently bound to its surface and (ii) a reactor tube (L × D: 90 mm × 20 mm) where the aforementioned POx-PVC film could be readily inserted for reactions. Through a spotting machine, the PAAm/Alg-Ca2+ hydrogel can be readily printed on a POx-PVC film in an array pattern and up to 25.4 J/m2 adhesion energy can be achieved. The hydrogel arrays on the film not only offer a strong matrix for entrapping biomolecules such as streptavidin-horseradish peroxidase but are also shear stress-tolerant in the reactor tube, enabling a >6-fold increase in its reaction rate after adding tetramethylbenzidine, relative to incubation. Through using the tough hydrogel and its stably bonded substrate, this portable platform effectively overcomes the diffusion-limit and achieves fast assay detection without causing appreciable hydrogel array deformation or dislocation on the substrate film.

Electrochemical Synthesis of Poly(trisulfides).

With increasing interest in high sulfur content polymers, there is a need to develop new methods for their synthesis that feature improved safety and control of structure. In this report, electrochemically initiated ring-opening polymerization of norbornene-based cyclic trisulfide monomers delivered well-defined, linear poly(trisulfides), which were solution processable. Electrochemistry provided a controlled initiation step that obviates the need for hazardous chemical initiators. The high temperatures required for inverse vulcanization are also avoided resulting in an improved safety profile. Density functional theory calculations revealed a reversible "self-correcting" mechanism that ensures trisulfide linkages between monomer units. This control over sulfur rank is a new benchmark for high sulfur content polymers and creates opportunities to better understand the effects of sulfur rank on polymer properties. Thermogravimetric analysis coupled with mass spectrometry revealed the ability to recycle the polymer to the cyclic trisulfide monomer by thermal depolymerization. The featured poly(trisulfide) is an effective gold sorbent, with potential applications in mining and electronic waste recycling. A water-soluble poly(trisulfide) containing a carboxylic acid group was also produced and found to be effective in the binding and recovery of copper from aqueous media.

Ambient Preparation of Benzoxazine-based Phenolic Resins Enables Long-term Sustainable Photosynthesis of Hydrogen Peroxide.

Rational design of polymer structures at the molecular level promotes the iteration of high-performance photocatalyst for sustainable photocatalytic hydrogen peroxide (H2 O2 ) production from oxygen and water, which also lays the basis for revealing the reaction mechanism. Here we report a benzoxazine-based m-aminophenol-formaldehyde resin (APFac) polymerized at ambient conditions, exhibiting superior H2 O2 yield and long-term stability to most polymeric photocatalysts. Benzoxazine structure was identified as the crucial photocatalytic active segment in APFac. Favorable adsorption of oxygen/intermediates on benzoxazine structure and commendable product selectivity accelerated the reaction kinetically in stepwise single-electron oxygen reduction reaction. The proposed benzoxazine-based phenolic resin provides the possibility of production in batches and industrial application, and sheds light on the de novo design and analysis of metal-free polymeric photocatalysts.

Brush-like Polymer Prodrug with Aggregation-Induced Emission Features for Precise Intracellular Drug Tracking.

In this study, a brush-like polymer with aggregation-induced emission (AIE) features was synthesized for drug delivery and intracellular drug tracking. The polymer consisting of tetraphenylethene (TPE) chain-end as well as oligo-poly (ethylene glycol) (PEG) and hydrazine functionalities was successfully synthesized through copper (0)-mediated reversible-deactivation radical polymerization (Cu0-mediated RDRP). Anticancer drug doxorubicin (DOX) was conjugated to the polymer and formed a prodrug named TPE-PEGA-Hyd-DOX, which contains 11% DOX. The hydrazone between DOX and polymer backbone is a pH-sensitive linkage that can control the release of DOX in slightly acidic conditions, which can precisely control the DOX release rate. The drug release of 10% after 96 h in normal cell environments compared with about 40% after 24 h in cancer cell environments confirmed the influence of the hydrazone bond. The ratiometric design of fluorescent intensities with peaks at 410 nm (emission due to AIE feature of TPE) and 600 nm (emission due to ACQ feature of DOX) provides an excellent opportunity for this product as a precise intracellular drug tracker. Cancer cells confocal microscopy showed negligible DOX solution uptake, but an intense green emission originated from prodrug uptake. Moreover, a severe red emission in the DOX channel confirmed a promising level of drug release from the prodrug in the cytoplasm. The merged images of cancer cells confirmed the high performance of the TPE-PEGA-Hyd-DOX compound in the viewpoints of cellular uptake and drug release. This polymer prodrug successfully demonstrates low cytotoxicity in healthy cells and high performance in killing cancer cells.

Phenoxyl mediators improve enzymatic degradation of organic pollutants: Effect and mechanism.

A mediation strategy can effectively overcome the low reaction activity of enzymes with nonspecific substrates. In this study, we demonstrated how phenol compounds can mitigate the substrate limitation of HRP in catalytic degradation of various organic pollutants. In a classical HRP/H2O2 system, phenol and natural phenolic compounds (4-HBA & pHBA), exhibited up to over 100-fold enhancement in eliminating organic dyes and persistent antibiotics while the loading is only 2-5 wt%. A combination of molecular modelling, docking and frontier orbital energy analysis was employed to elucidate the catalytic performance and mechanism. We revealed that (1) generating phenoxyl radicals required the proximity of mediators to the HRP active centre, and (2) the subsequent efficient radical transfer to pollutants was determined by the large energy gap between the SOMO energy of phenoxyl radicals and the HOMO energy of phenols. When considering phenols as pollutants, we showed a synergistic effect on catalytic degradation of phenols, dyes, and tetracycline with a removal efficiency of 71-92 %. Overall, this work not only demonstrates that phenoxyl mediators can overcome the lower efficiency and substrate-specificity limitations of the HRP/H2O2 system but also revealed their structure-mediation relationship, implying great potential in the biodegradation of diverse pollutants and their mixtures.

Modelling mercury sorption of a polysulfide coating made from sulfur and limonene.

A polymer made from sulfur and limonene was used to coat silica gel and then evaluated as a mercury sorbent. A kinetic model of mercury uptake was established for a range of pH values and concentrations of sodium chloride. Mercury uptake was generally rapid from pH = 3 to pH = 11. At neutral pH, the sorbent (500 mg with a 10 : 1 ratio of silica to polymer) could remove 90% of mercury within one minute from a 100 mL solution containing 5 ppm HgCl2 and 99% over 5 minutes. It was found that sodium chloride, at concentrations comparable to seawater, dramatically reduced mercury uptake rates and capacity. It was also found that the spent sorbent was stable in acidic and neutral media, but degraded at pH 11 which led to mercury leaching. These results help define the conditions under which the sorbent could be used, which is an important advance for using this material in remediation processes.

Heterocyclic Conjugated Polymer Nanoarchitectonics with Synergistic Redox-Active Sites for High-Performance Aluminium Organic Batteries.

The development of cost-effective and long-life rechargeable aluminium ion batteries (AIBs) shows promising prospects for sustainable energy storage applications. Here, we report a heteroatom π-conjugated polymer featuring synergistic C=O and C=N active centres as a new cathode material in AIBs using a low-cost AlCl3 /urea electrolyte. Density functional theory (DFT) calculations reveal the fused C=N sites in the polymer not only benefit good π-conjugation but also enhance the redox reactivity of C=O sites, which enables the polymer to accommodate four AlCl2 (urea)2 + per repeating unit. By integrating the polymer with carbon nanotubes, the hybrid cathode exhibits a high discharge capacity and a long cycle life (295 mAh g-1 at 0.1 A g-1 and 85 mAh g-1 at 1 A g-1 over 4000 cycles). The achieved specific energy density of 413 Wh kg-1 outperforms most Al-organic batteries reported to date. The synergistic redox-active sites strategy sheds light on the rational design of organic electrode materials.

Temperature-Directed Formation of Anisotropic Kettlebell and Tadpole Nanostructures in the Absence of a Swelling-Induced Solvent.

Anisotropic Janus ("snowman") nanoparticles with a single protrusion are currently made via the solvent swelling-induced method. Here, we demonstrate without the aid of toxic solvents a generally applicable method for the formation of anisotropic polymer nanoparticles directly in water by controlling polymer mobility through tuning its glass transition temperature (Tg ). Spherical structures, formed immediately after the emulsion polymerization, transformed into uniform tadpoles (with head diameter ≈60 nm and tail length ≈130 nm) through the protrusion of a single cylindrical tail when cooled to a temperature above the Tg of the polymer. Cooling the spheres to below the Tg produced kinetically trapped kettlebell structures that could be freeze-dried and rehydrated without any structural change. These unique kettlebells could transform into uniform tadpoles by heating above the Tg , representing a triggered and on-demand structural reorganization.

Nitroxide radical polymers for emerging plastic energy storage and organic electronics: fundamentals, materials, and applications.

Increasing demand for portable and flexible electronic devices requires seamless integration of the energy storage system with other electronic components. This ever-growing area has urged on the rapid development of new electroactive materials that not only possess excellent electrochemical properties but hold capabilities to be fabricated to desired shapes. Ideally, these new materials should have minimal impact on the environment at the end of their life. Nitroxide radical polymers (NRPs) with their remarkable electrochemical and physical properties stand out from diverse organic redox systems and have attracted tremendous attention for their identified applications in plastic energy storage and organic devices. In this review, we present a comprehensive summary of NRPs with respect to the fundamental electrochemical properties, design principles and fabrication methods for different types of energy storage systems and organic electronic devices. While highlighting some exciting progress on charge transfer theory and emerging applications, we end up with a discussion on the challenges and opportunities regarding the future directions of this field.

Water-Borne Nanocoating for Rapid Inactivation of SARS-CoV-2 and Other Viruses.

The rise in coronavirus variants has resulted in surges of the disease across the globe. The mutations in the spike protein on the surface of the virion membrane not only allow for greater transmission but also raise concerns about vaccine effectiveness. Preventing the spread of SARS-CoV-2, its variants, and other viruses from person to person via airborne or surface transmission requires effective inactivation of the virus. Here, we report a water-borne spray-on coating for the complete inactivation of viral particles and degradation of their RNA. Our nanoworms efficiently bind and, through subsequent large nanoscale conformational changes, rupture the viral membrane and subsequently bind and degrade its RNA. Our coating completely inactivated SARS-CoV-2 (VIC01) and an evolved SARS-CoV-2 variant of concern (B.1.1.7 (alpha)), influenza A, and a surrogate capsid pseudovirus expressing the influenza A virus attachment glycoprotein, hemagglutinin. The polygalactose functionality on the nanoworms targets the conserved S2 subunit on the SARS-CoV-2 virion surface spike glycoprotein for stronger binding, and the additional attachment of guanidine groups catalyze the degradation of its RNA genome. Coating surgical masks with our nanoworms resulted in complete inactivation of VIC01 and B.1.1.7, providing a powerful control measure for SARS-CoV-2 and its variants. Inactivation was further observed for the influenza A and an AAV-HA capsid pseudovirus, providing broad viral inactivation when using the nanoworm system. The technology described here represents an environmentally friendly coating with a proposed nanomechanical mechanism for inactivation of both enveloped and capsid viruses. The functional nanoworms can be easily modified to target viruses in future pandemics, and is compatible with large scale manufacturing processes.

The controlled growth of conjugated polymer-quantum dot nanocomposites via a unimolecular templating strategy.

Size and surface functionality are critically important for organic-inorganic hybrid semiconductive nanocomposites in terms of stable photoelectrochemical properties and superior device performance. The ability of reversible deactivation radical polymerization to control the chain length and dispersity of polymers is herein extended to the tailor-made synthesis of nanocomposites with tunable size, distribution, and surface coating. This is exemplified by the fabrication of cadmium selenide (CdSe) quantum dots (QDs) with uniform sizes from 2 to 10 nm that are intimately coated with poly(3-hexylthiophene) (i.e., CdSe@P3HT).

Temperature-Induced Formation of Uniform Polymer Nanocubes Directly in Water.

Conventional self-assembly methods of block copolymers in cosolvents (i.e., usually water and organic solvents) has yet to produce a pure and monodisperse population of nanocubes. The requirement to assemble a nanocube is for the second block to have a high molecular weight. However, such high molecular weight block copolymers usually result in the formation of kinetically trapped nanostructures even with the addition of organic cosolvents. Here, we demonstrate the rapid production of well-defined polymer nanocubes directly in water by utilizing the thermoresponsive nature of the second block (with 263 monomer units), in which the block copolymer was fully water-soluble below its lower critical solution temperature (LCST) and would produce a pure population of nanocubes when heated above this temperature. Incorporating a pH-responsive monomer in the second block allowed us to control the size of the nanocubes in water with pH and the LCST of the block copolymer. We then used the temperature and pH responsiveness to create an adaptive system that changes morphology when using a unique fuel. This fuel (H2O2 + MnO2) is highly exothermic, and the solution pH increases with the consumption of H2O2. Initially, a nonequilibrium spherical nanostructure formed, which transformed over time into nanocubes, and by controlling the exotherm of the reaction, we controlled the time for this transformation. This block copolymer and the water-only method of self-assembly have provided some insights into designing biomimetic systems that can readily adapt to the environmental conditions.

UV-Cross-Linked Polymer Nanostructures with Preserved Asymmetry and Surface Functionality.

Polymer nanostructures can be designed with tailored properties and functions by varying their shape, chemical compositions, and surface functionality. The poor stability of these soft materials in solvent other than water can be overcome by introducing cross-links. However, cross-linking complex morphologies remains a challenge. Here, by using the temperature-directed morphology transformation method, we show that the symmetric (nanoworm) and asymmetric (tadpole) nanostructure cores can be UV-cross-linked through the coupling of styrene and para-chlorostyrene units found in the core by irradiating at 254 nm for up to 5 h. Once cross-linked, these nanostructures maintain their structure in organic solvent, further allowing us to couple on a water-insoluble pro-fluorescent probe with high efficiency.

Fibronectin-conjugated thermoresponsive nanobridges generate three dimensional human pluripotent stem cell cultures for differentiation towards the neural lineages.

Production of 3-dimensional neural progenitor cultures from human pluripotent stem cells offers the potential to generate large numbers of cells. We utilised our nanobridge system to generate 3D hPSC aggregates for differentiation towards the neural lineage, and investigate the ability to passage aggregates while maintaining cells at a stem/progenitor stage. Over 38 days, aggregate cultures exhibited upregulation and maintenance of neural-associated markers and demonstrated up to 10 fold increase in cell number. Aggregates undergoing neural induction in the presence or absence of nanobridges demonstrated no differences in marker expression, proliferation or viability. However, aggregates formed without nanobridges were statistically significantly fewer and smaller by passage 3. Organoids, cultured from aggregates, and treated with retinoic acid or rock inhibitor demonstrated terminal differentiation as assessed by immunohistochemistry. These data demonstrate that nanobridge 3D hPSC can differentiate to neural stem/progenitor cells, and be maintained at this stage through serial passaging and expansion.

Polyethylenimine Expanded Graphite Oxide Enables High Sulfur Loading and Long-Term Stability of Lithium-Sulfur Batteries.

To realize practical lithium-sulfur batteries (LSBs) with long cycling life, designing cathode hosts with a high specific surface area (SSA) is recognized as an efficient way to trap the soluble polysulfides. However, it is also blamed for diminishing the volumetric energy density and being susceptible to side reactions. Herein, polyethylenimine intercalated graphite oxide (PEI-GO) with a low SSA of 4.6 m2 g-1 and enlarged interlayer spacing of 13 Å is proposed as a superior sulfur host, which enables homogeneous distribution of high sulfur content (73%) and facilitates Li+ transfer in thick sulfur electrode. LSBs with a moderate sulfur loading (3.4 mg S cm-2 ) achieve an initial capacity of 1157 and 668 mAh g-1 after 500 cycles at 0.5 C. Even when the sulfur loading is increased to 7.3 mg cm-2 , the electrode still delivers a high areal capacity of 4.7 mAh cm-2 (641 mAh g-1 ) after 200 cycles at 0.2 C. The excellent electrochemical properties of PEI-GO are mainly attributed to the homogeneous distribution of sulfur in PEI-GO and the strong chemical interactions between polysulfides and amine groups, which can mitigate the loss of active phases and contribute to the better cycling stability.

Conjugated Nitroxide Radical Polymers: Synthesis and Application in Flexible Energy Storage Devices.

The synthesis and electrochemical behavior of nitroxide radical conjugated polymers (NCPs) have long been an intriguing topic in redox polymer-based energy storage. However, common (electro)chemical oxidation polymerization methods have proved difficult in the synthesis of well-defined NCPs, and many of these polymers have been difficult to process into thin films. In addition to these drawbacks and coupled with the complex charge-transfer and storage mechanisms, the use of NCPs as electrodes has been significantly limited. The aim of this work is to provide mechanistic insights into this complex charge-transfer and storage process using a new and well-defined NCP synthesized using an ultrafast cyclopolymerization with the Grubbs 3rd generation catalyst. The monomer, consisting of a 1,6-heptadiyne group and a TEMPO (i.e. 2,2,6,6-tetramethylpiperidine-1-oxy) radical, through the cyclopolymerization produced a well-defined NCP with a five-membered ring-containing polyene backbone. This polymer demonstrated excellent film formation properties, allowing the study of their thin-film electrochemical behavior. We found that the electrochemical oxidation of the conjugated backbone and its internal charge transfer to the nitroxide radicals were strongly affected by the applied potential window, current densities, and cycle numbers. Using these new insights, we successfully utilized our NCPs in a flexible energy storage device by fabricating high-performance NCP-coated carbon cloth-based flexible electrodes.