Faraday Discussions最新文献

The chemical recycling of post-consumer polylactic acid by microwave-assisted alcoholysis promoted by a phenoxy-imine pyridine zinc is investigated. Different alcohols and diols are used to achieve, in all cases, outstanding activity and selectivity toward the targeted products. Thanks to the robustness of the catalyst the reactions can be performed in the air, with technical grade reagents and without the use of additional solvents, thus ensuring the full sustainability of the procedure.

The pressing need to replace petroleum-based plastics with renewable and biodegradable alternatives has sparked growing interest in biopolymers derived from lignocellulosic biomass as sustainable solutions. Among these, nanocellulose stands out as a versatile product capable of forming strong, transparent, and flexible films. However, these films lack active properties like antioxidant, antibacterial and UV-shielding capacity, essential for applications such as food packaging. To address this, incorporating lignin, a byproduct of lignocellulosic biorefineries, offers a promising route to enhance the functionality of nanocellulose films. In line with this idea, this work studies the incorporation of kraft lignin into nanocellulose films by two different protocols: the first protocol involves directly mixing a cellulose nanofiber (CNF) suspension with an aqueous lignin suspension; the second protocol uses lignin dissolved in acetone : water (9 : 1) which is transformed into lignin nanoparticles (LNPs) via solvent shifting when mixed with the aqueous CNF suspension. The resulting suspensions of CNFs and lignin were subsequently used to produce casting films. It was found that incorporating lignin into the CNF film not only conferred UV-shielding capacity, but also enhanced barrier properties without compromising the mechanical properties, particularly when lignin was introduced as LNPs (even at 10–20% LNP content). However, adding bulk lignin at a high concentration (20%) negatively affected water vapor permeability and mechanical properties. Antioxidant and antibacterial capacities correlated with lignin content, showing greater enhancement when lignin was present as nanoparticles compared to bulk lignin. These results indicate that forming LNPs in situ within the CNF suspension is a more effective approach to optimize the properties of nanocellulose films. Thus, the obtained films presented good active properties with mechanical properties comparable to those of traditional plastics, but significantly lower barrier properties.

The production of functional (nano)materials based on lignin as a renewable starting material depends on the thorough understanding of lignin’s physico-chemical properties, among which self-assembly and agglomeration/aggregation are the most important. Nevertheless, the knowledge about the structure–property relations for lignin is still in its infancy and needs further in-depth investigations. In this context, this works focuses on the study of the size and the colloidal stability of lignin nanoparticles (LNPs) prepared from softwood kraft lignin (SKL) using the solvent–antisolvent method. Conformational rearrangements of lignin chains were found to contribute significantly to the formation of the first lignin nuclei. The slow addition of ethylene glycol and THF into water caused the formation of nuclei with low aggregation numbers, minimizing the hydrodynamic volume of the final LNPs. On the other hand, a quick addition of these organic solvents created spatially and temporally higher lignin concentrations, yielding nuclei with high aggregation numbers and larger hydrodynamic volumes. Molecular dynamics simulations revealed the major role of intramolecular and intermolecular hydrogen bonds in this process, together with the contribution from π–π stacking interactions. The superficial concentration of phenolic and condensed guaiacyl units was found to strongly influence the corresponding LNPs’ zeta-potential values. Altogether, these results shed further light on the properties of colloidal lignin with a view to enabling its full potential as a key material for technological applications.

This paper summarizes a series of ideas and/or concepts, most of which were the object of the Faraday Discussion on ‘Structural and functional asymmetry of plasma membranes’. A historical review is provided of the early symmetrical and asymmetrical models for membrane structure. Membrane asymmetry in the framework of evolution is suggested as a possible field of study. Functional membrane asymmetry in experimental models is briefly discussed, and the hypothesis that functional asymmetry preceded structural asymmetry in evolution is proposed. Lipid asymmetry and lipid scrambling in bilayers are presented as two complementary aspects of the same process. The use of sphingomyelinases in experimental studies of asymmetry is criticized, due to the lipid scrambling properties of the sphingomyelinase end-product ceramide. The paper ends with a note on the (apparently?) cyclical nature of scientific research.

Poly(lactide-co-valerolactone) copolymers were prepared via the one-pot copolymerisation of rac-lactide or S,S-lactide with δ-valerolactone at ambient temperature, mediated by bis(dimethylsilyl)amido lanthanum complexes supported by ligands derived from a salan framework (salan = N,N′-bis(o-hydroxy, m-di-tert-butylbenzyl)-1,2-diaminoethane), which incorporate either benzyl or 2-pyridyl groups at the tertiary amine moieties. Poly(δ-valerolactone)s were also prepared by the ring-opening polymerisation of δ-valerolactone and high molecular weight polymers (up to 83.6 kg mol⁻¹) with narrow dispersities were obtained. The poly(lactide-co-valerolactone) copolymers were fully characterized using ¹H and ¹³C NMR spectroscopy, gel-permeation chromatography and differential scanning calorimetry. Both the reaction solvent (toluene or THF) and the number of 2-pyridyl groups the complex possesses affect the complex activity and copolymer microstructure. The use of a non-coordinating solvent and presence of at least one 2-pyridyl group is required for high conversion of both monomers. Variation of the monomer feed ratio allowed copolymers across the full compositional range to be prepared. The copolymers are formed via a transesterification mechanism whereby all of the lactide undergoes rapid polymerisation in the early stages of the reaction and the δ-valerolactone is subsequently incorporated into the polymer. The rate and extent of δ-valerolactone polymerisation increases with the number of 2-pyridyl groups in the catalyst in toluene and is more rapid in non-coordinating solvent (toluene) than coordinating solvent (THF). Only low levels of the T_II mode of transesterification occur, with the T_I transesterification mode dominating, leading to the formation of copolymers with intact lactidyl units.

The gas reactivity of high-entropy nanoalloys (HENAs) is an emerging area of research with significant potential for applications in catalysis, gas sensing, hydrogen storage, and corrosion resistance. Insights into the structure–reactivity relationships that dictate the behavior of HENAs in reactive gas environments are critical for optimizing their performance across these applications. However, understanding the complex structural attributes of HENAs, such as size, shape and structure in response to a gas stimulus, remains challenging because of the limited accessibility to methods capable of probing these attributes under in situ or operando conditions. Here, we performed aberration-corrected environmental gas scanning transmission electron microscopy (STEM) observations to investigate the atomic and chemical structures of quinary CoNiCuPtAu HENAs in response to pure oxygen exposure at atmospheric pressure and elevated temperatures. The nanoparticles were fabricated by pulsed laser deposition with a high degree of control over both size and composition. Atomic-scale STEM imaging combined with energy dispersive X-ray (EDX) spectroscopy at the single particle level revealed a complex structural and chemical evolution pathway for CoNiCuPtAu HENAs under oxygen at atmospheric pressure during progressive heating up to 700 °C. Notably, we have identified substantial mass transfers between nanoparticles accompanied by oxygen-induced demixing of components, nanovoid formation and the stabilization of platelet-like nanostructures crystallizing as a Co–Ni oxide solid solution.

These concluding remarks summarise the Faraday Discussions that was held in Glasgow, Scotland, on Advances in supramolecular gels, between the 30th of April and the 2nd of May 2025. The meeting was organised by Prof. Dave Adams (University of Glasgow, UK) and Prof. Annela Seddon (University of Bristol, UK) who co-chaired the meeting, in collaboration with the Scientific Committee, Prof. Krishna K. Damodaran (University of Iceland, Iceland), Prof. Demetra Giuri (University of Bologna, Italy) and Prof. Xuehai Yan (Chinese Academy of Science, China). The meeting was organised in four main sections over the four day programme. These were broadly devoted to the characterising (Session 1), using (Session 2), designing (Session 3) of supramolecular gels, and multicomponent gel systems (in Session 4). A lively poster session with range of posters presented mainly by early career, students and postdoctoral fellows, as well as some more established researchers, ran throughout the meeting. The Faraday Discussions programme had contribution talks that highlighted the research area from the design and synthesis of (supramolecular) gels, formed from small organic gelators and bioinspired structures and conjugates, to the different types of characterisation techniques employed for such soft-material research, including the use of rheology, scattering techniques and a variety of imaging platforms, as well as computational studies. This was also completed by the contributions on the applications of functional soft materials with both established and emerging applications. Herein, I will provide a short introductory remark on this fast-growing research field, and a short summary of the work presented within the four sessions, along with the associated discussions that took place. I will then conclude with a brief personal focused discussion of what I consider the main points raised throughout the meeting associated with some of the challenges that this fast-growing research area is facing.

A set of new chiral monomeric (S)- and (R)-isomers of Al(III) compounds were synthesized using a proline-based ligand moiety. The reaction of AlMe₃ with one equivalent of pro-ligands (1a–d) in dry toluene yielded the corresponding dimethyl Al(III) compounds (2a–d) in high yields. The molecular structures of compounds 2a, 2c and 2d were confirmed using single-crystal X-ray diffraction analysis. These compounds exhibited a distorted tetrahedral geometry at the Al(III) center. These compounds were tested as catalysts for the ring-opening copolymerization (ROCOP) of cyclohexane oxide (CHO) with cyclic anhydrides to produce copolyesters with tetraphenyphosphonium chloride (TPPCl) as a cocatalyst. The (S)-isomer was found to be more reactive than the (R)-isomer towards the ROCOP. Alternating polyesters were obtained from the ROCOP of cyclohexene oxide (CHO) with phthalic anhydride (PA) and CHO with succinic anhydride (SA), producing copolyesters with moderate to high M_n (9589 g mol⁻¹) and with narrow dispersity (Đ) (1.23). The (S)-isomer substituted with fluorine atoms at the phenyl ring was most active for the polymerization reactions. The kinetics studies of ROCOP performed using 2a (S-isomer) as catalyst showed higher rate than 2d (R-isomer). 2a produced an isotactic-enriched semicrystalline polyester, whereas 2d formed an atactic amorphous polyester. The DSC traces revealed that the glass transition temperature (T_g) increases with increasing molecular weight (M_n) of these polyesters.

Additive manufacturing (AM) techniques, also named three-dimensional (3D)-printing, have been widely recognised as promising technologies for rapid production of novel, personalised drug-delivery systems and scaffolds for biofabrication, and in food applications and many more fields. Although there has been promising progress in identifying new materials for 3D-printing, the range of resins/polymers available is still limited, with big reliance on petroleum-derived materials and the advancement is not up to date with the fast-developing hardware. Therefore, new building blocks that are renewably sourced and biodegradable are desirable for expanding applicability and recyclability. Specifically, glycerol, a readily available waste product from biodiesel processing, is highly functionalisable since it bears three hydroxyl groups. We previously reported that an acrylated glycerol-based oligomer, polyglycerol-6-acrylate, fulfils all the necessary criteria for volumetric printing (transparency, photo-reactivity and viscosity) and was successfully used to print a variety of models with intricate geometries and good resolution. In the present work, we want to expand the use of (meth)acrylated-polyglycerols (4 and 6 units of glycerol) to stereolithography (SLA), as this technique presents numerous advantages, being also more commercially available. Printability parameters, different geometries, and biocompatibility are explored to confirm the amenability of SLA to these “greener” resins. In addition, as initial proof of concept, the replacement of (meth)acrylate moieties is explored by ring opening of maleic and norbornene anhydrides in order to achieve acrylic-free resins and preliminary curability tests on these bioderived resins were performed. By developing and testing these new acrylic/acrylic-free resins based on glycerol, we aim to accelerate the adoption of greener alternatives in AM, contributing to a more sustainable future in the 3D-printing world.

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