Faraday Discussions最新文献

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Plastics have enabled modern innovations through their unique attributes, which include a combination of light weight, durability, and cost-effectiveness. These characteristics, while central to their utility, have paradoxically contributed to the escalating plastic pollution crisis. No single approach can resolve this challenge; rather, it requires coordinated efforts with a diversity of strategies. Among them, compostable plastics have emerged as a particularly promising avenue. Under controlled conditions, such ephemeral plastics can degrade and transform into compost, offering environmental benefits that extend to soil, water, and agriculture. Nevertheless, substantial challenges remain before compostable plastics can achieve broad adoption and deliver their full promise. In this perspective, we (i) make the case for more widespread use of compostable plastics in the food packaging market, (ii) review labeling, infrastructure, and regulatory hurdles facing compostable-plastic adoption, and (iii) discuss the future of compostable-polymer research and development.

Lignin, a structurally complex biopolymer, represents a promising renewable feedstock for the production of platform chemicals, including functionalized aromatic molecules. However, efficient lignin valorization remains a major challenge due to its chemical stability, structural heterogeneity, and the propensity of reactive intermediates to undergo recondensation. To overcome these barriers and gain mechanistic insight into lignin oxidation pathways, we have developed a membrane-separated, two-compartment attenuated total reflectance infrared (ATR-IR) spectro-electrochemical cell for the in situ monitoring of the electrochemical oxidation of lignin model compounds. Using guaiacol as a representative model compound of the β-O-4 linkage monomer, we tracked real-time spectral changes during electrochemical oxidation. Characteristic vibrational signatures revealed the depletion of guaiacol and the formation of oxidized species, including quinones, catechols, and dimers and oligomers. In contrast, control experiments conducted without membrane separation exhibited additional spectral features, suggesting the occurrence of competing side reactions under conditions of unrestricted mass transport. These results highlight the importance of proper cell design for providing mechanistic insights and demonstrate the value of in situ ATR-IR spectroscopy in tracking the complex electrochemical transformation of lignin-derived molecules, to offer insights critical for advancing lignin valorization strategies under mild and tunable reaction conditions.

Lignin is a natural macromolecule with remarkable properties, such as UV-shielding and antioxidant capacity; however, its application is often limited by its intense, dark colour. In this paper, oxidation methods using hydrogen peroxide and peroxy-citric acid were employed to produce light-coloured lignins with tailored functional properties. The transition from the macroscale to the nanoscale enhanced both the UV-protective and antioxidant performance of bulk lignin, while further attenuating the visible coloration of the nanoparticle aqueous dispersions. Oxidized and unmodified lignin nanoparticles were incorporated into nanocellulosic films to develop protective coatings intended for the preservation of cellulosic cultural heritage artifacts, while safeguarding their aesthetic integrity. Nanoparticles derived from oxidized lignins imparted UV protection and antioxidant capacity to the films without significantly affecting their colorimetric properties. Therefore, the oxidized lignins presented herein offer a novel and environmentally friendly approach to lignin valorisation in colour-sensitive applications, including sophisticated uses such as the conservation of cultural heritage.

Recently, there has been an increased interest in developing functionalised carbohydrates, such as cellulose palmitate, as novel replacements for petroplastics. The functionalisation gives the materials excellent water barrier properties, as well as processability and mechanical properties akin to PET, while potentially having superior biodegradability to conventional first-generation biopolymers. However, the true biodegradability of these novel polymers is still unknown with some recent reports suggesting that it is limited. In this study, we investigated the potential of cellulose palmitate to biodegrade under controlled laboratory conditions, comparing the polymer to cellulose acetate. To this end, studies using specific enzymes, targeted whole cell fungal degradation and model edibility experiments were devised to study the biodegradability at end-of-life. On an enzymatic level, a combination of cellulase and lipase enzymes were found to hydrolyse the fatty acid linkages, allowing the cellulases to access the carbohydrate chain and release glucose. Under optimal conditions the biopolymer was completely hydrolysed within 6 hours. A soil fungi was then isolated from a compost heap that had been loaded with the functional material, to establish the most suitable species for whole cell degradation. This common soil fungi, Mucor sp., was then grown successfully under lab conditions on the functional material as a 95% carbon source. Finally, an edibility experiment was designed, using pepsin and pancreatic enzymes at precise pH concentrations found in the gastrointestinal tract to mimic real life conditions of ingestion by birds. While cellulose acetate broke down under just the acidic conditions, with no enzymes, the cellulose palmitate was found to be stable at the acidic conditions, but hydrolyse over 7 days when the enzymes were present. To the best of our knowledge this is the first study to confirm the biodegradability of functionalised cellulose highlighting the large promise of functionalised carbohydrates as a sustainable alternative to petrochemical plastics within the packaging industry.

In this study, epoxidized lignins were prepared by reacting softwood (SW) and hardwood (HW) technical (kraft) lignins with a biobased epichlorohydrin. The chemical structures, rheological behaviors, and thermomechanical properties of the epoxidized lignins were measured and compared with those of petroleum-based (DGEBA) epoxy resin. First, the chemical and physical properties of the lignin samples were assessed using Fourier-transform infrared spectroscopy (FTIR), gel permeation chromatography (GPC), quantitative phosphorus nuclear magnetic resonance spectroscopy (³¹P NMR), and 2D-heteronuclear single quantum coherence (HSQC) NMR analyses. Subsequently, the unmodified lignins were epoxidized over a short period (3 hours), using ethyl lactate as a biobased co-solvent. The ³¹P NMR and HSQC analysis of the epoxidized lignins confirmed that phenolic hydroxyl and carboxylic acid groups in lignin were selectively epoxidized without any other significant changes to the chemical structure of lignin. Rheological multi-wave curing studies of both lignin-based and bisphenol A-based (DGEBA) resins cured with a biobased curing agent revealed that the lignin-based systems exhibited significantly shorter gelation times and lower activation energies. Further analyses, including gel fraction, swelling ratio, thermal gravimetric analysis (TGA), and dynamic mechanical analysis (DMA) results, demonstrated that lignin-based thermosets had comparable properties to the petroleum-based epoxy system when both were prepared with solvent (40 wt%) inclusion. Notably, the thermoset resin made with kraft hardwood lignin exhibited superior thermomechanical properties compared to the softwood system.

Two technical lignins, a softwood kraft lignin (SKL) and a wheat straw organosolv lignin (WSOSL) were fractionated using a Soxhlet extractor that was connected to a piston pump for solvent movement such that Soxhlet extraction using non-azeotropic solvent mixtures was feasible. Fractionation of the lignins using such solvent mixtures that could be tuned in terms of hydrogen-bond acceptor and donor characteristics and polarities yielded novel fractions not accessible in standard Soxhlet-based fractionations. Two SKL fractions could be obtained applying aqueous acetone that displayed homogeneous structural characteristics while differing significantly in molecular weights. WSOSL could be gradually purified, allowing for the generation of a rather pure lignin carbohydrate complex (LCC) fraction and a purified high molecular weight lignin fraction.

The development of artificial intelligence and machine learning in chemistry is opening new avenues for data-driven discoveries. However, the application of such methodologies in polymer chemistry has been hampered due to the complex structure–properties relationship of polymers and the lack of (meta)data available. Recent efforts have been made to experimentally determine or computationally evaluate thermodynamic parameters associated with (de)polymerisation reactions, such as enthalpy and entropy of polymerisation, as well as ceiling temperature, to design polymers primed for chemical recycling. Here, we report TROPIC (Thermodynamics of Ring-Opening Polymerisation Informatics Collection), an open-source database harnessing experimental and computational thermodynamic parameters for ring-opening polymerisation (ROP) from the academic literature. TROPIC links thermodynamic parameters with the experimental conditions or the computation methodologies used to determine them, to allow further analysis. TROPIC can be accessed via an interactive website or application programming interface (API) and presents a first step towards facilitating the data-driven discovery of novel functional polymers.

Future materials should be made from renewable resources and be sustainable without compromising the mechanical properties compared to conventional products. Kraft lignin is an available renewable raw material, sourced globally as a by-product from paper pulp production, and currently burnt at a low value. Kraft lignin has been converted into thermoplastics, however the mechanical properties worsen by degree of blending. Thermosets containing kraft lignin give materials with high strength, where the lignin matrix contributes to the mechanical properties. However, pre-fractionation or multistep chemistries have been applied to give high performance materials. Herein, we have combined kraft lignin with bio-based glycerol 1,3-diglycidyl ether to give a resin with enhanced mechanical properties. This resin – LigniSet® – is odorless, which is a unique property for kraft lignin-based products. The resin is, due to its hydrophilicity, compatible with natural fibers to give strong composite materials. The material can be recycled to give new materials without reduction in performance. Life cycle assessment shows that transformation of lignin to materials instead of burning shows significant benefits with respect to environmental sustainability.

The thermodynamics of ring-opening polymerization (ROP) are central when predicting the chemical recyclability of aliphatic polyesters and polycarbonates. Conceptually, the enthalpy of polymerization, , is widely understood as a measure of ring-strain for a given monomer. However, the ring-strain is commonly larger than , generating the question of how the release of ring-strain energy during ring-opening transforms. In this work, we propose that is the sum of the energy released by the ring-strain and the energy absorbed by the polymer conformations . Owing to the similar ring-strain, but vastly different values, δ-valerolactone, δ-caprolactone, δ-octalactone, and δ-decalactone were used as model compounds to evaluate the energy cost of polymer conformational freedom. Polymer conformation, measured by ¹³C NMR, DSC, and molecular dynamics, results are in good agreement with the hypothesis and can explain previous literature observations i.e. positive for systems with ring-strain, substituent effects, and solvent effects, that are difficult to understand when only using the analogy of ring-strain and . We believe that our results provide a deeper understanding of the underlying thermodynamics and their interpretation in ROP.