Creating the "plumber's nightmare" Nedoma, Alisyn J
Science (American Association for the Advancement of Science),
2024-Jan-05, 2024-01-05, 20240105, Volume:
383, Issue:
6678
Journal Article
Peer reviewed
Chemically modifying polymer ends enables tailoring of nanostructured materials.
Recently, we have demonstrated the use of wood-derived nanocellulose papers, herein termed nanopapers, for organic solvent nanofiltration applications. In this study, we extend the use of these ...nanopapers to tight ultrafiltration (UF) membranes. The feasibility of such nanopaper-based UF membranes intended for use in water purification is shown. Four types of nanocelluloses, namely bacterial cellulose, wood-derived nanocellulose, TEMPO-oxidized cellulose nanofibrils and cellulose nanocrystals, were used as raw materials for the production of these nanopaper-based membranes. The resulting nanopapers exhibit a transmembrane permeance in the range of commercially available tight UF membranes with molecular weight cut-offs ranging from 6 to 25kDa, which depends on the type of nanocellulose used. These molecular weight cut-offs correspond to average pore sizes of a few nanometres. The rejection performance of the nanopapers is on the border of nanofiltration and UF. We demonstrate that the pore size of the nanopapers can be controlled by using different types of nanocellulose fibrils.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UL, UM, UPCLJ, UPUK
Layered transition metal oxide cathode materials can exhibit high energy densities in Li-ion batteries, in particular, those with high Ni contents such as LiNiO2. However, the stability of these ...Ni-rich materials often decreases with increased nickel content, leading to capacity fade and a decrease in the resulting electrochemical performance. Thin alumina coatings have the potential to improve the longevity of LiNiO2 cathodes by providing a protective interface to stabilize the cathode surface. The structures of alumina coatings and the chemistry of the coating–cathode interface are not fully understood and remain the subject of investigation. Greater structural understanding could help to minimize excess coating, maximize conductive pathways, and maintain high capacity and rate capability while improving capacity retention. Here, solid-state nuclear magnetic resonance (NMR) spectroscopy, paired with powder X-ray diffraction and electron microscopy, is used to provide insight into the structures of the Al2O3 coatings on LiNiO2. To do this, we performed a systematic study as a function of coating thickness and used LiCoO2, a diamagnetic model, and the material of interest, LiNiO2. 27Al magic-angle spinning (MAS) NMR spectra acquired for thick 10 wt % coatings on LiCoO2 and LiNiO2 suggest that in both cases, the coatings consist of disordered four- and six-coordinate Al–O environments. However, 27Al MAS NMR spectra acquired for thinner 0.2 wt % coatings on LiCoO2 identify additional phases believed to be LiCo1–x Al x O2 and LiAlO2 at the coating–cathode interface. 6,7Li MAS NMR and T 1 measurements suggest that similar mixing takes place near the interface for Al2O3 on LiNiO2. Furthermore, reproducibility studies have been undertaken to investigate the effect of the coating method on the local structure, as well as the role of the substrate.
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IJS, KILJ, NUK, PNG, UL, UM
We investigate the impact of fullerene C60 on the thermal properties and glass formation of polystyrene (PS) by differential scanning calorimetry (DSC) and dielectric spectroscopy (DS), for C60 ...concentrations up to 30% mass fraction. The miscibility and dispersibility thresholds of PS/C60 nanocomposites are first estimated by a combination of microscopy, small angle neutron scattering (SANS) and wide-angle X-ray scattering (WAXS) experiments, and these thresholds were found to be ≃1 mass% and ≃4 mass% C60, respectively. The addition of C60 increases the glass-transition temperature (Tg) of rapidly precipitated PS composites, up to a ‘threshold’ C60 concentration (≃4 wt%, in agreement with the dispersibility estimate). Beyond this concentration, the Tg reverts gradually towards the neat PS value. We present a comprehensive study for composites based on PS of molecular mass 270 kg/mol, and demonstrate the generality of the impact of C60 on Tg for PS matrices of 2 and 20 kg/mol. Thermal annealing or slowly evaporated composites largely reverse these effects, as the dispersion quality decreases. The dynamic fragility m of the composite is found to increase in the presence of C60, but the scaling of m with Tg for PS is retained. Similarly, physical ageing experiments show a reduction of relaxation enthalpy in the glass regime, which is largely accounted for by the increase of Tg with C60. The slowing down of the PS α-relaxation with C60 contrasts with the local ‘softening’ indicated by former Debye-Waller measurements and increase in fragility m. This effect is opposite to that of antiplasticizer additives, which both stiffen the material in the glassy state and reduce Tg, and simulations suggest this could be due to an increase in packing frustration. Finally, we review observations on the effect of nanoparticles on the Tg of PS and discuss the non-universal nature of Tg shifts by various types of nanoparticles.
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•C60 fullerenes increase glass transition temperature and fragility of well-dispersed poly(styrene) nanocomposites.•Fullerenes increase local fast dynamics and slow down segmental glassy dynamics, interpreted as due to packing frustration.•Upon fullerene aggregation, all dynamic changes are reversed back to the neat polymer behaviour.•Polystyrene Tg shifts depend qualitatively on surface interactions and quantitatively on filler loading and dispersion.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UL, UM, UPCLJ, UPUK
Transitioning to electrified transport requires improvements in sustainability, energy density, power density, lifetime, and approved the cost of lithium-ion batteries, with significant opportunities ...remaining in the development of next-generation cathodes. This presents a highly complex, multiparameter optimization challenge, where developments in cathode chemical design and discovery, theoretical and experimental understanding, structural and morphological control, synthetic approaches, and cost reduction strategies can deliver performance enhancements required in the near- and longer-term. This multifaceted challenge requires an interdisciplinary approach to solve, which has seen the establishment of numerous academic and industrial consortia around the world to focus on cathode development. One such example is the Next Generation Lithium-ion Cathode Materials project, FutureCat, established by the UK’s Faraday Institution for electrochemical energy storage research in 2019, aimed at developing our understanding of existing and newly discovered cathode chemistries. Here, we present our perspective on persistent fundamental challenges, including protective coatings and additives to extend lifetime and improve interfacial ion transport, the design of existing and the discovery of new cathode materials where cation and cation-plus-anion redox-activity can be exploited to increase energy density, the application of earth-abundant elements that could ultimately reduce costs, and the delivery of new electrode topologies resistant to fracture which can extend battery lifetime.
The distribution of an ionic liquid within microphase-separated domains of a block copolymer in mixtures of the two components is studied using contrast-matched small-angle neutron scattering (SANS) ...and differential scanning calorimetry (DSC). In concentrated mixtures of a poly(styrene-block-2-vinyl pyridine) (S2VP) copolymer in an imidazolium bis(trifluoromethane)sulfonimide (ImTFSI) ionic liquid (block copolymer volume fraction ranging from 0.51 to 0.86), the ionic liquid preferentially pervades the poly(2-vinyl pyridine) (P2VP) blocks. Unexpected differences in the degree of partitioning into P2VP-rich and polystyrene-rich (PS) microphases are observed in mixtures with hydrogenated versus deuterated ImTFSI. In the case of mixtures with hydrogenated ImTFSI, the microphase partition coefficient, defined as the ratio of the ionic liquid volume fraction in the PS-rich microphase relative to that in the P2VP-rich microphase, ranges from 0.0 to 0.1. In contrast, the microphase partition coefficient in mixtures with deuterated ImTFSI range from 0.0 to 0.7.
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IJS, KILJ, NUK, PNG, UL, UM
We report the polymer conformation and fullerene aggregation in a ternary system containing polystyrene, C60, and toluene measured by small angle neutron, static, and dynamic light scattering. We ...investigate polymer concentrations across the dilute and semidilute regime for five polymer molecular weights (M w = 20 kg/mol to 1 Mg/mol), and fullerene concentrations below and above its miscibility threshold in toluene. We find that the polymer radius of gyration (R g poly), hydrodynamic radius (R h), and the mixture correlation length (ξ) remain unchanged upon addition of C60. The miscibility of C60 in toluene, however, decreases upon addition of polystyrene forming aggregates with a time-dependent radius on the order of 100 nm, and this effect is amplified with increasing polymer M w. Our findings are relevant to the solution processing of organic photovoltaics, which generally require the effective solubilization of fullerene derivatives and polymer pairs in this concentration range.
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IJS, KILJ, NUK, PNG, UL, UM
Perovskite solar cells are one of the most active areas of renewable energy research at present. The primary research objectives are to improve their optoelectronic properties and long-term stability ...in different environments. In this paper, we discuss the working principles of hybrid perovskite photovoltaics and compare them to the competing photovoltaic technologies of inorganic and organic photovoltaics. The current challenges that hinder the commercialisation of perovskite solar cells are then discussed. This is followed by a description of perovskite material properties and some characterisation techniques commonly used to assess perovskite properties, fabrication processes including the use of antisolvents, and degradation mechanisms. We intend that this work should serve as a beginner’s guide to the study of perovskite solar cells.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UILJ, UL, UM, UPCLJ, UPUK, ZAGLJ, ZRSKP
Functional ring‐opening polymerization (ROP) initiators can instill a wide array of chemical, physical, and biological effects into a polymeric chain. Highlighting the versatility of this “active” ...initiator approach, a broad range of characteristics can be achieved through the use of initiators with chemistries spanning from drugs and dyes (key in the case of drug delivery or nanoparticle applications) through to radically active monomers, polymerization transfer agents, and catalysts. The selection of a suitable “active” initiator (monomers for tandem reactions, dyes, drugs, stereo‐catalysts, etc.) can not only provide the final polymers with interesting application potential but also facilitate the implementation of ROP reactions in tandem with other polymerization techniques. Overall, this review will highlight that functionalities and properties can be effectively tuned by exploiting simple chemistry approaches, allowing readers to identify how these approaches could be of benefit to their own work in a range of applications including drug/gene delivery, amphiphilic bio/degradable carriers, drug/scent controlled release, and stereo‐controlled polymers.
In this review, the versatility of “active” initiators for ring‐opening polymerization (ROP) strategy is summarized, reporting the use of initiators with various chemistries and intrinsic properties that range from drugs and dyes to radically active monomers, polymerization transfer agents, and catalysts. The selection of the most suitable initiators can not only produce the final polymers with interesting applications, but also provide the potential to perform ROP reactions in tandem with other polymerization techniques.
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BFBNIB, FZAB, GIS, IJS, KILJ, NLZOH, NUK, OILJ, SBCE, SBMB, UL, UM, UPUK
2‐methyltetrahydrofuran (2‐MeTHF) is a readily available, inexpensive, neoteric, bio‐based solvent. It has been adopted across a wide range of chemical processes including the batch manufacture of ...fine chemicals, enzymatic polycondensations and ring opening polymerizations. To reduce the environmental burden related to the synthesis of pharmaceutical‐grade polymers based on lactide and caprolactone, we envisaged the use of 2‐MeTHF. For the first time, we combined a series of metal‐free and enzymatic ROPs with free radical and controlled RAFT polymerizations (carried out separately and in tandem) in 2‐MeTHF, in order to easily tune the chemistry and the architecture of the final polymers. After a simple purification, the amphiphilic polymers were formulated into nanoparticles and tested for their cytocompatibility in three model cell lines, to assess their application as potential polymeric excipients for nanomedicines.
In this article, the suitability of 2‐MeTHF was tested as a green solvent for organo‐and enzymatically catalyzed ROP of simple diblocks and in the production of more interesting A–B–C block copolymers using a single or double catalyst system. Labileester ROP initiators HEMA and PEGMA were also used to initiate LA macromonomers. To further demonstrate the versatility of 2‐MeTHF as “multipolymerization” green solvent, the produced macromonomers were tested in FRP and RAFT tandem polymerization.
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BFBNIB, FZAB, GIS, IJS, KILJ, NLZOH, NUK, OILJ, SBCE, SBMB, UL, UM, UPUK
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