Hierarchical biomaterials embody nature's intricate design principles and offer multiple functionalities through the multi-level organization of their molecular and nanosized building blocks. However, 3D structural characterization over length scales ranging from nanometers to centimeters of biopolymer-based materials remains a challenge. Current limitations hinder understanding how macroscopic properties originate in the multiscale arrangement of nanoscale structures that cannot be fully captured from small sample volumes. Here, we demonstrate how multi-directional neutron dark-field tomography (MD-NDFT) provides structural information on multiple length scales in large volumes of heterogeneous hierarchical soft matter materials. By implementing 3D single-grid directional neutron dark-field reconstructions, we quantified the degree of preferential alignment of cellulose nanostructures in centimeter-sized assemblies of several nanocomposite foams simultaneously, probing structural features down to 50 nm through anisotropic ultrasmall-angle scattering, within a field of view ≳ 40 cm2. The successful application of MD-NDFT to nanocellulose, which is inherently radiation-sensitive, prevalent in natural systems and widely used in nanotechnology, proves the relevance of MD-NDFT for multiscale characterization of hierarchical biobased and bioinspired materials.

The global rise in single-use face mask waste during the pandemic has created an urgent need for sustainable valorization pathways. Here, we report a solvent-based route transforming mask wastes into lightweight and robust foams that are water-resistant and flame-retardant. The entire disposable mask—including nonwoven layers, the ear-loop fibers, and the metal wire—is successfully recycled. The method uses n-octadecane as a recyclable solvent to dissolve nonwoven layers and enables solvent removal and full recovery through ethanol-based separation. Foams prepared by phase-separation of solutions of polypropylene (PP) are reinforced by the incorporation of mildly processed ear-loop fibers. The composite foams exhibit a tunable density and porous architecture, good mechanical performance, and significant hydrophobicity. In addition, the application of a tannic acid (TA)–Fe coating endows the foams with enhanced flame retardancy. This work achieves a high overall mass upcycling rate of 91%, and life cycle assessment (LCA) reveals a competitive carbon footprint and a material circularity indicator of 0.39 for the foams thanks to the carbon retained within the technosphere. The flexibility in material composition, coupled with solvent recyclability and simple processing, offers a scalable route for mask waste valorization and provides inspiration for transforming multi-component wastes into functional materials.

There has been a recent surge of interest in biobased foams for applications ranging from building sustainability (insulation) to biomedicine, pharmaceutics, and electronics (scaffolds), with nanocellulose-based foams being particularly promising due to their porous and low-density structure. This study compares the production energy, structure, and properties of foams made from TEMPO-oxidized lignocellulose nanofibers (FTOLCNF) derived from unbleached wood pulp, and TEMPO-oxidized cellulose nanofibers (FTOCNF) from bleached cellulose pulp. Additionally, the incorporation of tannic acid (TA) as a biobased additive is explored for its ability to enhance the mechanical strength of FTOLCNF, contributing to improved performance. This builds upon the inherent advantages of FTOLCNF, which not only demonstrate superior structural integrity and load-bearing capacity (specific Young’s modulus of 37.4 J g–1, compared to 16.4 J g–1 for TOCNF) but also exhibit a higher yield during production due to the minimal processing required for unbleached pulp. Furthermore, FTOLCNF production requires about 18% less cumulative energy than FTOCNF (27 vs 33 MJ kg–1), largely owing to the energy-efficient preparation of TOLCNF from unbleached wood pulp. FTOLCNF also have a significantly lower cumulative energy demand (CED) compared to fossil-based alternatives like expanded polystyrene (EPS) and polyurethane (PU), highlighting their reduced environmental impact. Despite their lightweight nature, FTOLCNF exhibit competitive compressive strength, making them viable candidates for eco-friendly applications across various industries. Overall, this study demonstrates that FTOLCNF are an attractive alternative to other bio- and fossil-based foams, offering a balance of energy efficiency, higher yield, mechanical performance, and sustainability.

Nanocellulose is a promising alternative to fossil-derived materials, but its development is hindered by a limited understanding of cellulose–water interactions. Herein, quasielastic neutron scattering (QENS) is used to investigate how hydration and temperature affect the localized rotations in cellulose nanocrystals (CNC) and the diffusion of mobile water. QENS reveals that the C6 hydrogens and the C6 OH in the surface regions of CNC exhibit an isotropic rotation. The extracted mean square displacement shows that hydration enhances the overall hydrogen mobility in the cellulose chains. The mobile water diffusion at 270 K is unaffected by cellulose and consistent with diffusion of supercooled bulk water. At 310 K, the diffusion slows compared to bulk water, consistent with water diffusing on the CNC surface. Decoupling of the translational and rotational motion provides insight into the local cellulose–water motions. The localized motions of the nondiffusing water are found to be coupled with cellulose at 310 K, indicating a more complex dynamics at higher temperature. These findings provide new insights into how hydration modulates hydrogen mobility in cellulose, highlighting the interplay between water diffusion and molecular motion.

Cellulose nanocrystals (CNCs) are widely used in advanced materials due to their unique mechanical and physicochemical properties. However, their interactions with water, particularly in the context of drying, remain poorly understood. The presence of bound water in CNC poses challenges for processing, storage, and applications sensitive to moisture. In this study, we combine molecular simulations and experimental drying investigations to assess the extent of water retention in both native and TEMPO-CNC under different thermodynamic conditions. Our results demonstrate that while native CNCs can be fully dried under low pressure (≤1 mbar) and elevated temperature (110 °C), TEMPO-CNC retain a significant amount of water (1–7 wt%) due to electrostatic interactions between water molecules and the charged surface carboxylic groups and the sodium counter-ions. These findings provide fundamental insights into the drying behavior of functionalized nanocellulose and highlight the importance of considering residual bound water in applications requiring moisture-sensitive performance.

Superinsulating nanofibrillar cellulose foams have the potential to replace fossil-based insulating materials, but the development is hampered by the moisture-dependent heat transport and the lack of direct measurements of phonon transport. Here, inelastic neutron scattering is used together with wide angle X-ray scattering (WAXS) and small angle neutron scattering to relate the moisture-dependent structural modifications to the vibrational dynamics and phonon transport and scattering of cellulose nanofibrils from wood and tunicate, and wood cellulose nanocrystals (W-CNC). The moisture interacted primarily with the disordered regions in nanocellulose, and WAXS showed that the crystallinity and coherence length increased as the moisture content increased. The phonon population derived from directional-dependent phonon density of states (GDOS) increased along the cellulose chains in W-CNC between 5 and 8 wt% D₂O, while the phonon population perpendicular to the chains remained relatively unaffected, suggesting that the effect of increased crystallinity and coherence length on phonon transport is compensated by the moisture-induced swelling of the foam walls. Frequency scaling in the low-energy GDOS showed that materials based on hygroscopic and semicrystalline nanocellulose falls in between the predicted behavior for solids and liquids. Phonon-engineering of hygroscopic biopolymer-based insulation materials is promoted by the insights on the moisture-dependent phonon transport.

We have produced foams from cellulose nanofibrils from upcycled cotton (upCNF) and wood (wCNF) through unidirectional (UIT) and multidirectional ice-templating (MIT) and investigated the structural humidity response through in-situ WAXS, SAXS, and micro tomography (μCT) between 10 and 95 % relative humidity (RH). The upCNF and wCNF WAXS patterns displayed a shape- and position shift as the RH was increased, with a compression in the (200) direction and an elongation in the (004) direction. The average separation distance extracted from the 1D SAXS patterns revealed no significant change for the upCNF foams regardless of RH and processing route, while a significant increase was observed for the wCNF foams. The μCT measurements of the upCNF foams showed a slight shift in macropore distribution towards larger pores between 50 and 80 % RH which can be attributed to the weakening and partial disintegration of the pore wall as more moisture is introduced. The humidity-induced structural alterations of the upCNF foam were significantly lower compared to the wCNF foams, confirming our claim of upCNF being more moisture resistant than wCNF foams.

Actuators based on electrically conductive and hydrophilic two-dimensional (2D) Ti₃C₂T_X MXene are of interest for fast and specific responses in demanding environments, such as chemical production. Herein, Ti₃C₂T_X-based solvent-responsive bilayer actuators were developed, featuring a gradient polymer-intercalation structure in the active layer. These actuators were assembled using negatively charged pristine Ti₃C₂T_X nanosheets as the passive layer and positively charged polymer-tethered Ti₃C₂T_X as the active layer. 2D wide-angle X-ray scattering and simulations related the gradient polymer intercalated microstructure in the polymer/MXene composite active layer to the counterintuitive actuation behavior. The bending of the bilayer films in solvent vapor is triggered by the gradient polymer-intercalation and the differing diffusion rate of solvent molecules through the MX and MX-polymer layers of the bilayer actuator. With their ease of fabrication, remote light-control capabilities, and excellent actuation performance, the Ti₃C₂T_X-based bilayer actuators reported here may find applications in areas such as sensors for monitoring chemical production, infrared camouflage, smart switches, and excavators in toxic solvent environments.

The demands on chemical industry to transform towards safety and sustainability will require multi-disciplinary research and development where experts on chemistry and chemical engineering, toxicology, ecotoxicology, and life cycle assessment collaborate to develop novel production methods, chemicals and materials. Here we summarise the results of the Mistra SafeChem programme which has yielded considerable output in the areas of catalysis/bio-catalysis, hazard screening for humans and ecosystems and life cycle assessment with chemical footprints, both as individual scientific achievements and as part of an integrated approach to assess safety and sustainability of novel chemicals and chemical synthesis processes, in chemical value chains and across collaborations between industry- academia/ industry-industry. The outcomes from the programme are summarised and discussed and experiences from dialogues on the future of safe and sustainable chemistry are presented.