Non-isocyanate polyurethanes (NIPUs) exhibit significantly greater sustainability than conventional polyurethanes (PUs) by adhering to key principles of green chemistry, particularly the elimination of toxic chemicals. In this study, waterborne non-isocyanate polyurethane (WNIPU) latexes, exclusively stabilized by cellulose nanocrystals (CNCs) and partially derived from renewable resources, were synthesized for the first time via suspension polymerization. A polyaddition reaction between a siloxane diamine and 1,6-hexanediol bis(cyclic carbonate) occurred within the monomer-in-water Pickering emulsion droplets effectively stabilized with CNCs. The concentration of the CNCs was optimized for the Pickering emulsion. The CNCs acted as nanoparticle surfactants on the surface of the WNIPU latex particles, as confirmed using rhodamine B-labelled CNCs and confocal laser scanning microscopy. Spherical-shaped monomer droplets and WNIPU latex particles with a median size of 10 mu m were achieved. The effect of the cyclic carbonate-to-amine molar ratio on the amine monomer conversion, molecular weight, and thermal properties of the WNIPU was investigated. The obtained WNIPU suspensions exhibited fluorescence under UV irradiation at 365 nm owing to the clustering of carbamates. Combining the fluorescence properties with low glass transition temperatures, these latexes open various potential applications as functional coatings.

Polyurethanes are widely used in adhesive applications, but their conventional synthesis relies on hazardous isocyanates and often solvent-based formulations. In this work, waterborne polyhydroxyurethanes (PHUs) were synthesized from 1,6-hexanediol bis(cyclic carbonate) and bio-based Priamine 1075 via catalyst-free suspension polymerization in water. Pristine cellulose nanocrystals (CNCs) acted as the sole stabilizers, eliminating the need for petroleum-derived surfactants while simultaneously serving as reinforcing nanofillers. Stable monomer-in-water emulsions were obtained with CNC loadings up to 200 mg mL–1 per monomer, corresponding to ∼17 wt % CNCs in the final dried nanocomposites. In the latex state, CNCs were located at the particle surfaces, ensuring colloidal stability, while in the dried PHU/CNC nanocomposites they were uniformly distributed throughout the matrix, yielding adhesives with markedly enhanced performance. The nanocomposites exhibited up to 680% and 340% increases in probe tack adhesion strength and lap-shear strength, respectively, compared with surfactant Tween 80-stabilized waterborne PHUs, reaching performance levels comparable to commercial pressure-sensitive adhesives. These findings demonstrate that combining bio-based monomers with CNC stabilization offers a robust strategy for producing sustainable, high-performance PHU adhesives consistent with green chemistry principles. 

Utilizing the swelling behavior of the cellulose nanofiber network structure in water, we present a facile approach to prepare cellulose nanofibrils (CNFs)/regenerated silk fibroin (RSF) composites with improved mechanical properties and biocompatibility by rehydrating CNF films in RSF water solutions. Two rehydratable nanocellulose film structures were employed: one featuring random-in-plane distributed CNF (ROCNF) and the other containing nematic-ordered CNF (NOCNF). These films were rehydrated to facilitate the infiltration of RSF, resulting in composites where RSF interpenetrates the CNF network. The composites showed a higher density, enhanced optical transparency, and synergistically increased modulus, yield strength, and tensile strength, in contrast to the neat CNF films. Particularly, the NOCNF80/RSF20 composites exhibited a Young’s modulus of 20.1 GPa and a tensile strength of 429 ± 17 MPa in the dry state and a Young’s modulus of 78.6 MPa and a tensile strength of 1.66 MPa in phosphate-buffered saline (PBS). Biocompatibility assessed by an in vitro cell test confirmed the ability of the CNF/RSF composites to support the adhesion and growth of L929 fibroblasts, highlighting the potential for various applications as biomedical materials. This approach provides promising opportunities for producing strong and functional CNF-based composites with water-soluble polymers and latexes for diverse applications in different fields.

The rubber-like cuticle of arthropods is a complex nanocomposite of chitin and resilin. High-quality chitin nanofibrils (ChNFs) were combined with recombinant resilin-like proteins (RLPs) to study the mechanical properties of hydrated nanocomposites and ChNF/resilin interactions. Constructs from the resilin gene CG15920 found in Drosophila melanogaster were cloned. These constructs contained exon I (comprising 18 N-terminal elastic repeats), either with or without exon II (a chitin-binding domain (ChBD)). The encoded proteins were then expressed as soluble products in Escherichia coli. The RLPs were purified using immobilized metal affinity chromatography. Their adsorption to chitin was studied in a water suspension of ChNFs by centrifugation and on the model surface of ChNFs by a quartz crystal microbalance. RLP with ChBD interacted strongly with the ChNF, which demonstrates the role of ChBD. ChNF suspensions were mixed with resilin solutions, followed by casting and ruthenium (II)-mediated photo-crosslinking. Tensile properties of hydrated ChNF/resilin nanocomposites were measured in water. The addition of 70 % ChNF resulted in nanocomposites with 30 times higher strength, of 9 MPa compared with the neat ResChBD RLP of 0.3 MPa, at 80 % hydration state, clarifying the reinforcement function of chitin in arthropod cuticles and demonstrating that resilin-like hydrogels showed a strength of 0.2–0.3 MPa and a strain to failure of 167–214 % at an 80 % water content.

Mildly delignified softwood holocellulose fibers featuring native tracheid fiber cell wall structure and high hemicellulose content are prominent building blocks for wood derived fiber-based materials. However, preserving the natural alignment of long softwood fiber is challenging since top-down structure-retaining delignified softwood is unstable as extensive removal of lignin from intercellular space induces cracking and disintegration of wood structure. Here we report the use of chemical crosslinking pretreatment to improve the intercellular bonding between softwood fibers, therefore preserving the integrity of the naturally aligned softwood fibers after delignification. The crosslinked softwood veneer was delignified with peracetic acid and further densified into transparent and high-density film by thermal compression. The obtained transparent film of naturally aligned softwood holocellulose fibers showed high optical transmittance of 71 %, high haze of 85 %, strong optical anisotropy, as well as high tensile strength of 449 ± 58 MPa and high Young's modulus of 49.9 ± 5.6 GPa. This study provides a facile approach to preserve the natural alignment of softwood fibers for the fabrication of high performance holocellulose fibers-based materials.

Incorporating biobased nanofillers including cellulose nanocrystals (CNCs) and chitin nanocrystals (ChNCs) into nonisocyanate polyurethane (NIPU) offers a multifunctional approach to improving mechanical and thermal properties while promoting sustainability and green chemistry. Nanocomposites of segmented thermoplastic polyhydroxyurethane (PHU) from vanillyl alcohol bis(cyclocarbonate) (VABC), poly(tetramethylene oxide) diamine (PTMODA), and bis(aminomethyl) norbornane (NORB) reinforced with a low amount of CNCs and partially deacetylated ChNCs were prepared and characterized. Fourier transform infrared spectroscopy, atomic force microscopy, and small-angle X-ray scattering revealed that partially deacetylated ChNCs were covalently grafted to the PHU through aminolysis of carbonate end groups in the hard segment, while CNCs were mixed with the PHU without interfacial covalent bonding. Consequently, the PHU/ChNC nanocomposites showed nanophase separation with smaller hard domains compared to neat PHU, while the PHU/CNC nanocomposites exhibited a phase-mixed system with broader interface regions. Dynamic mechanical analysis and tensile tests further revealed that the PHU/ChNC nanocomposites demonstrated a 49-fold increase in Young's modulus, a 20-fold increase in ultimate tensile strength, and a three-order-of-magnitude enhancement in storage modulus in the rubbery state compared to the PHU/CNC nanocomposites, highlighting the profound influence of interfacial covalent linkages in enhancing the thermal mechanical performance of segmented PHU.

Plastic pollution is an environmental emergency and finding sustainable alternatives to traditional plastics has become a pressing need. Seaweed-based bioplastic has emerged as a promising solution, as it is biodegradable and made from renewable biomass, while seaweed cultivation itself provides various environmental benefits. However, the feasibility of implementing a brown seaweed-based bioplastic supply chain in a realistic setting remains unclear, as previous research focused either on single processing steps or on virtual supply chains aggregating data from different studies. This study describes a case study for seaweed-based bioplastic within the PlastiSea research project: from seaweed cultivation to biomass processing and bioplastic and composite material development at the lab and pilot scale, thus providing insights into its feasibility. Adopting a multidisciplinary approach, the study employs multiple methods to characterize each stage in the supply chain and provides an overall life cycle assessment (LCA) as well as lessons learned throughout the process. The analysis showed potential for producing and utilizing multiple co-products from the same seaweed source, including biopolymer extracts with varying degrees of refinement for use in low-cost (bioplastic films) and high-cost (microfiber composites) applications. The use of residual biomass as a source of alginates for producing bioplastics offers a low-cost and sustainable biomass supply currently not competing with other markets. The LCA results indicate the potential for reducing the environmental impact of seaweed-based bioplastic production through upscaling and increasing process efficiency.

Interfibrillar phases and bonding in cellulose nanofibril (CNF)-based composites are crucial for materials performances. In this study, we investigated the influence of CNF surface characteristics, the guluronic acid/mannuronic acid ratio, and the molecular weight of alginates on the structure, mechanical, and barrier properties of CNF/alginate composite films. Three types of CNFs with varying surface charges and nanofibril dimensions were prepared from wood pulp fibers. The interfacial bonding through calcium ion cross-linking between alginate and carboxylated CNFs (TCNFs) led to significantly enhanced stiffness and strength due to the formation of an interpenetrating double network, compared to composites from alginates and CNFs with native negative or cationic surface charges. Various alginates extracted from Alaria esculenta (AE) and Laminaria hyperborea (LH) were also examined. The TCNF/AE composite, prepared from alginate with a high mannuronic acid proportion and high molecular weight, exhibited a Young’s modulus of 20.3 GPa and a tensile strength of 331 MPa under dry conditions and a Young’s modulus of 430 MPa and a tensile strength of 9.3 MPa at the wet state. Additionally, the TCNF/AE composite demonstrated protective properties as a barrier coating for fruit, significantly reducing browning of banana peels and weight loss of bananas stored under ambient conditions.

The 3D micro- and nanostructure of wood has extensively been employed as a template for cost-effective and renewable electronic technologies. However, other electroactive components, in particular native lignin, have been overlooked due to the absence of an approach that allows access of the lignin through the cell wall. In this study, we introduce an approach that focuses on establishing conjugated-polymer-based electrical connections at various length scales within the wood structure, aiming to leverage the charge storage capacity of native lignin in wood-based energy storage electrodes. We demonstrate that poly(3,4-ethylenedioxythiophene)-poly(styrenesulfonate) PEDOT/PSS, integrated within the cell wall lumen, can be interfaced with native lignin through the wood cell wall through in situ polymerization of a water-soluble S-EDOT monomer. This approach increases the capacitance of the conductive wood to 315 mF cm^-2 at a scan rate of 5 mV s^-1, which is seven and, respectively, two times higher compared to the capacitance of conductive wood made with the single components PEDOT/PSS or S-PEDOT. Moreover, we show that the capacitance is contributed by both the electroactive polymers and native lignin, with native lignin accounting for over 70% of the total charge storage capacity. We show that accessing native lignin through in situ creation of electrical interconnections within the wood structure offers a pathway toward sustainable, wood-based electrodes with improved charge-storage capacity for applications in electronics and energy storage.

The evaluation of plant-based feedstocks is an important aspect of biorefining. Nicotiana glauca is a solanaceous, non-food crop that produces large amounts of biomass and is well adapted to grow in suboptimal conditions. In the present article, compatible sequential solvent extractions were applied to N. glauca leaves to enable the generation of enriched extracts containing higher metabolite content comparing to direct leaf extracts. Typically, between 60 to 100 metabolite components were identified within the fractions. The occurrence of plant fatty acids, fatty acid alcohols, alkanes, sterols and terpenoids was detected by gas liquid chromatography-mass spectrometry (GC-MS) and metabolite identification was confirmed by comparison of physico-chemical properties displayed by available authentic standards. Collectively, co-products such waxes, oils, fermentable sugars, and terpenoids were all identified and quantified. The enriched fractions of N. glauca revealed a high level of readily extractable hydrocarbons, oils and high value co-products. In addition, the saccharification yield and cell wall composition analyses in the stems revealed the potential of the residue material as a promising lignocellulosic substrate for the production of fermentable sugars. In conclusion a multifractional cascade for valuable compounds/commodities has been development, that uses N. glauca biomass. These data have enabled the evaluation of N. glauca material as a potential feedstock for biorefining.