In this work, residues from banana cultivation were upgraded by isolating the cellulose fibers, modifying them chemically, and integrating them into superabsorbent polymer (SAP) systems designed for enhanced water uptake. After extraction, the cellulose was oxidized in a controlled manner with sodium periodate to generate dialdehyde cellulose (DAC) with an modular aldehyde content. DAC was further modified through a Horner-Wadsworth-Emmons (HWE) olefination with triethyl phosphonoacetate, yielding cellulose containing sodium propenoate units forming dialdehyde cellulose acrylate (DACAcr). The modified cellulose served as both a grafting agent and a cross-link-enhancing copolymer for the synthesis of hybrid BioSAPs (DACAcr-g-poly(AA-co-IA)) via radical polymerization in water using acrylic acid (AA) and itaconic acid (IA) were copolymerized in aqueous medium in the presence of the modified cellulose, which acted as a graftable macromolecular component. N,N '-methylenebis(acrylamide) (MBA) served as the cross-linking reagent, while potassium persulfate (KPS) initiated the radical polymerization. The incorporation, after oxidation, of a double bond at C2 and C3 positions of the anhydroglucose units, improving their capacity to react with acrylic acid and increasing the number of hydrophilic carboxylate functionalities. This combination produced a flexible and robust polymer network exhibiting enhanced swelling and improved water retention properties which leads to a good compromise between the formation of pores in polymer networks and the mechanical stability of the hydrogel. A thorough analysis of the synthesized SAPs was performed using Fourier-transform infrared spectroscopy (FTIR), scanning electron microscopy (SEM), and rheological analysis. Kinetic studies revealed that the hybrid BioSAPs exhibited exceptional water absorption capacities, with the SAP-DACAcr0.5eq composite achieving up to 1441 +/- 59 gg-1 in distilled water. The results demonstrate the potential of DACAcr and its derivatives as sustainable, high-performance materials for water retention and management applications, providing an eco-friendly alternative to conventional SAPs. Overall, these results open promising prospects for creating low-cost and environmentally conscious solutions utilizing agricultural waste.

The development of high-performance bio-based superabsorbent polymers (BioSAPs) remains a major challenge in the transition toward sustainable materials. In this study, dialdehyde cellulose (DAC), obtained by periodate oxidation of cellulose extracted from banana fiber residues, was functionalized through a β-alanine-catalyzed Knoevenagel condensation with diethyl malonate. Unlike conventional Schiff-base modifications, this approach generates stable carbon‑carbon linkages that are resistant to hydrolysis under typical swelling conditions. Functionalization was supported by FTIR, XRD, and conductometric titration, which showed an increase in carboxylate content from 1.29 ± 0.19 to 3.32 ± 0.21 mmol g-1 with increasing malonate content. The resulting DACMal derivatives were incorporated into poly (acrylic acid-co-itaconic acid) networks via free-radical polymerization. SEM revealed a highly porous interconnected structure, while rheological measurements showed enhanced storage modulus and mechanical stability with increasing DACMal functionalization. The BioSAPs exhibited an exceptional equilibrium swelling capacity of 1556 ± 58 g g-1 in distilled water and 124 ± 11 g g-1 in 0.9 wt% NaCl at an optimal DACMal0.25 eq loading of 5 wt%. In addition, the modified BioSAPs retained 89% of their initial absorption capacity after four swelling-drying cycles, compared with 67% for unmodified DAC-based systems. These results demonstrate the potential of Knoevenagel-modified cellulose for durable and high-performance BioSAPs.

The mechanical performance of plant fibres is linked to the presence of crystalline elements dispersed within an amorphous cohesive matrix. The more the crystalline reinforcement is aligned with the fibre axis, the better the mechanical properties of the fibre. With the aim of developing entirely biobased biomimetic fibres as alternatives to synthetic or resource-consuming fibres, we have studied the fabrication of hydrogel filaments made from mixtures of nanocelluloses, biobased crystalline nanoparticles acting as reinforcement, and xyloglucans, a plant wall hemicellulose with a strong affinity for cellulose surfaces. These will ensure cohesion between the nanocelluloses. To optimize the orientation of the nanocelluloses within the filaments, and thus potentially improve the mechanical properties of the fibres, we present a study on the development of a millifluidic method of flow-focusing. The developed setup uses external sheath flows to focus and align a nanocellulose suspension central flow. Different configurations in terms of concentrations, circuit designs and flow velocities are tested. 3D printed circuits are explored to produce versatile geometries and optimize the process design. To qualify the orientations during the process, observations with a polarized microscope (POM) are made, as the alignment of the nanocellulose crystalline structures creates birefringence in suspensions. Significant optical phase shifts related to the nanocellulose particles' orientations are visible by color gradients, varying with the suspensions' concentrations and flow velocities. Results demonstrate successful tuning of nanocellulose orientation into anisotropic hydrogels using different millifluidic circuit geometries, with the introduction of xyloglucans to produce new types of biosourced fibres.

In the context of global water shortages, there is an urgent need to implement effective strategies for the management of water resources. The objective of our research is to synthesize superabsorbent polymers to efficiently utilize water resources in agriculture, with a particular focus on the impact of cellulose sources and properties on absorption capacity. A hybrid superabsorbant polymer (SAP) hydrogel was prepared by combining 5

Nowadays, the increasing demand for sustainable energy has brought piezoelectric materials to the forefront due to their capability to convert mechanical energy into electrical energy. In response to increasing environmental concerns, cellulose has emerged as a promising piezoelectric material, owing to its availability, biocompatibility, sustainability, biodegradability and cost-effectiveness. Despite significant research on the use of various forms of cellulose for piezoelectric energy harvesting, a systematic review focusing on the factors that can affect the piezoelectric property in cellulose remains notably absent. The main goal of this review is to fill this gap by understanding the piezoelectric behaviour of cellulose at different hierarchical levels, from macro-scale natural materials to nano-scale structures. This review presents an overview of the general aspects of the piezoelectric effect, followed by a detailed examination of the piezoelectric properties of cellulose. It further explores the piezoelectric behaviour of cellulose-based natural materials. The review then addresses the piezoelectric characteristics of nanocellulose and regenerated cellulose in turn. Furthermore, the review examines cellulose-based hybrid materials and their piezoelectric properties. In conclusion, the review highlights the current challenges and outlines promising directions for future research in this emerging area.

The development of fully biobased hydrogels obtained by simple routes and in the absence of toxic or environmentally harmful reagents is a major challenge in meeting new societal demands. In this work, we discuss the development of hydrogels made from cellulose nanocrystals (CNCs) and xyloglucan (XG), two non-toxic, renewable, and biobased components. We present three strategies to fine-tune the functional properties. The first one consists in varying the XG/CNC ratio that leads to the modulation of the mechanical properties of hydrogels as well as a better comprehension of the gel mechanism formation. The second relies on tuning the XG chains’ interaction by enzymatic modification to achieve thermoresponsive systems. Finally, the third one is based on the increase in the hydrogel solid content by osmotic concentration. The high-solid-content gels were found to have very high mechanical properties and self-healing properties that can be used for molding materials. Overall, these approaches are a case study of potential modifications and properties offered by biobased nanocolloidal hydrogels.

Lytic polysaccharide monooxygenase (LPMO)-catalyzed oxidative processes play a major role in natural biomass conversion. Despite their oxidative cleavage at the surface of polysaccharides, understanding of their mode of action, and the impact of structural patterns of the cellulose fiber on LPMO activity is still not fully understood. In this work, we investigated the action of two different LPMOs from Podospora anserina on celluloses showing different structural patterns. For this purpose, we prepared cellulose II and cellulose III allomorphs from cellulose I cotton linters, as well as amorphous cellulose. LPMO action was monitored in terms of surface morphology, molar mass changes and monosaccharide profile. Both PaLPMO9E and PaLPMO9H were active on the different cellulose allomorphs (I, II and III), and on amorphous cellulose (PASC) whereas they displayed a different behavior, with a higher molar mass decrease observed for cellulose I. Overall, the pretreatment with LPMO enzymes clearly increased the accessibility of all types of cellulose, which was quantified by the higher carboxylate content after carboxymethylation reaction on LPMO-pretreated celluloses. This work gives more insight into the action of LPMOs as a tool for deconstructing lignocellulosic biomass to obtain new bio-based building blocks.

Cellulose-based actuators hold great promise for diverse applications, including soft robotics, biomedicine, and electronics. Achieving reversible motion is crucial to design high performance bio-based actuators. In this study, we explore the impact of carboxymethylation and 2,2,6,6-tetramethylpiperidine-1-oxyl radical (TEMPO) oxidation on the reversible performance of cellulose-based pH-responsive actuators. Both methods introduce negatively charged groups onto the surface of cellulose fibers, enabling increased water uptake at high pH. However, comparative analyses revealed structural differences, guiding the design of reversible actuators. Carboxymethylated CNFs (CMCNFs) displayed enhanced water uptake and pH sensitivity, attributed to their less cohesive structure. Actuation and reversibility tests on bilayer films validated these findings. This research advances the understanding of cellulose functionalization for tailored actuation, contributing to the development of programmable materials for multiple applications.

The development of porous, water-resistant cellulose-based materials with shape-recovery performance requires control of the swelling behaviour of these materials. In this context, TEMPO-oxidized CNF (CNFt) cryogels, were prepared by non-directional (ND) and unidirectional (UD) freezing step followed by freeze-drying to obtain lightweight porous materials (22.6 kg m -3 and 98% air content), CNFt-ND ou CNFt-UD, with different pore morphologies. Indeed, honeycomb-like or lamellar structures were obtained as evidenced by microscopy and X-ray tomography analysis. Determination of cryogels absorption capacities in water (pH 6) or HCl (pH 2) solution showed different swelling behaviours depending on the charge state of carboxyl groups, but also on pore morphology NFCt cryogels. Measurements of 1 H T 2 relaxation times using Low-Field (LF) NMR demonstrated the appearance of different population of water molecules characterized by different mobilities due to the structuration of NFCt gel during the freeze-casting procedure. Finally, tests of compression cycles on H 2 O- or HCl-swollen NFCt-ND and NFCt-UD cryogels demonstrated the higher compressive resistance of swollen-cryogels after protonation and a recovery shape performance of about 87% was obtained after 50 compression cycles.

Pressurized cells with strong walls make up the hydrostatic skeleton of plants. Assembly and expansion of such stressed walls depend on a family of secreted RAPID ALKALINIZATION FACTOR (RALF) peptides, which bind both a membrane receptor complex and wall-localized LEUCINE-RICH REPEAT EXTENSIN (LRXs) in a mutually exclusive way. Here we show that, in root hairs, the RALF22 peptide has a dual structural and signalling role in cell expansion. Together with LRX1, it directs the compaction of charged pectin polymers at the root hair tip into periodic circumferential rings. Free RALF22 induces the formation of a complex with LORELEI-LIKE-GPI-ANCHORED PROTEIN 1 and FERONIA, triggering adaptive cellular responses. These findings show how a peptide simultaneously functions as a structural component organizing cell wall architecture and as a feedback signalling molecule that regulates this process depending on its interaction partners. This mechanism may also underlie wall assembly and expansion in other plant cell types. The authors show that RALF22 has a dual role in cell wall assembly in root hairs: as a structural component organizing cell wall architecture and as a feedback signalling molecule that regulates this process depending on its interaction partners.

Natural biological systems feature hierarchical nanostructured architectures achieving high strength and toughness. In this work, the spontaneous adsorption of xyloglucan (XG) and cellulose nanocrystals (CNC) onto flax fabrics is considered to develop hierarchical interphases with improved interfacial adhesion in epoxy-based biocomposites. A multi-scale analysis is carried out, from the nano & micrometric scale with the characterization of fibre surface topography, work of adhesion and interfacial shear strength (IFSS) between flax fibres and epoxy resin, to the macroscopic scale with the transverse mechanical properties of biocomposites. At the fibre scale, XG and CNC increase the surface roughness of flax fibres, as well as their adhesion to epoxy resin with IFSS improved by 60 %, up to 22.3 MPa. At the composite scale, the treatments have a major influence on the cohesion of flax cell walls and microstructure of the biocomposites. Transverse tensile tests reveal both cohesive and adhesive interfacial failure.

The study focus is the valorization of banana agriculture by products by the extraction and derivatization of cellulose and its incorporation in formulations to produce superabsorbent materials endowed with high water absorption performances. The extracted cellulose (BP) was subjected to a controlled oxidation by sodium periodate to convert it to cellulose dialdehyde (DAC) with controlled aldehyde content. The cellulosic materials were incorporated into a suspension containing acrylic acid (AA) and itaconic acid (IA) to produce composite hybrid hydrogels (SA-BP/SA-DAC) by radical chain polymerization in water, using N,N-methylene-bis-acrylamide (MBA) as a cross-linking agent and potassium persulfate (KPS) as an initiator. The prepared materials were characterized using techniques such as Fourier-transform infrared spectroscopy (FTIR), scanning electron microscopy (SEM), and rheological analysis. Additionally, the absorption and re-swelling capacities of the superabsorbent composites (SAPs) were assessed through kinetic studies in water and NaCl solution. Notably, dialdehyde cellulose (DAC), due to its low crystallinity index, hydrophilicity (attributed to aldehyde and hemiacetal functions), and high polarity, holds promise for enhancing the swelling and water retention capacity of the hydrogel. A water absorption capacity as high as 1240 +/- 60 g.g-1 was obtained for SA-DAC with a DAC content of 5 %wt. Additionally, the reusability of the SAPs was evidenced.

In this study, glucose units within the polymeric structure of cellulose were transformed into 2,4-dihydroxy-3-(1-hydroxy-2-oxoethoxy) butanal, denoted as cellulose containing dialdehyde units, through oxidation with sodium periodate. Subsequently, a Horner–Wadsworth–Emmons reaction with triethyl phosphonoacetate was employed to convert dialdehyde cellulose (DACs) into cellulose containing sodium 2,3-dipropenoate units (DACAcr). The modified cellulose underwent thorough characterization using various methods and was utilized as both a copolymer of acrylic acid and itaconic acid and a grafting agent to synthesize an environmentally friendly super-absorbent material, designated as DACAcr-g-poly(AA-IA). The introduction of double bonds at the C2 and C3 positions of β-d-glucose units is supposed to enhance linkages between cellulose and acrylic acid by copolymerization and increased the overall number of hydrophilic carboxylate groups, resulting in the development of a more robust, flexible and expanded network for the swelling process in water. This network exhibited the capacity to efficiently absorb and store significant amounts of water, attributed to increased Bio-Superabsorbents (BioSAP) flexibility. The study delved into investigating the modification and synthesis conditions of the super-absorbent, determining the oxidation state of glucose units and evaluating the impact on water absorbency.

Assembly of cell wall polysaccharides into specific patterns is required for plant growth. A complex of RAPID ALKALINIZATION FACTOR 4 (RALF4) and its cell wall-anchored LEUCINE-RICH REPEAT EXTENSIN 8 (LRX8)-interacting protein is crucial for cell wall integrity during pollen tube growth, but its molecular connection with the cell wall is unknown. Here, we show that LRX8-RALF4 complexes adopt a heterotetrametric configuration in vivo, displaying a dendritic distribution. The LRX8-RALF4 complex specifically interacts with demethylesterified pectins in a charge-dependent manner through RALF4's polycationic surface. The LRX8-RALF4-pectin interaction exerts a condensing effect, patterning the cell wall's polymers into a reticulated network essential for wall integrity and expansion. Our work uncovers a dual structural and signaling role for RALF4 in pollen tube growth and in the assembly of complex extracellular polymers.

Summary Pressurized cells with strong walls make up the hydrostatic skeleton of plants. Assembly and expansion of such stressed walls depend on a family of secreted RAPID ALKALINIZATION FACTOR (RALF) peptides which, curiously, bind both a membrane receptor complex and wall-localized LEUCINE-RICH REPEAT EXTENSINs (LRXs) in a mutually exclusive way. Here we show that, in root hairs, the RALF22 peptide has a dual structural and signaling role in cell expansion. Together with LRX1, it directs the compaction of charged pectin polymers at the root hair tip into periodic circumferential rings. Free RALF22 induces the formation of a complex with LORELEI-LIKE-GPI-ANCHORED PROTEIN 1 (LLG1) and FERONIA (FER), triggering adaptive cellular responses. These findings show how a peptide simultaneously functions as a structural component organizing cell wall architecture and as a signaling molecule that regulates this process. This mechanism may also underlie wall assembly and expansion in other plant cell types.

Lytic polysaccharide monooxygenase (LPMO) enzymes have recently shaken up our knowledge of the enzymatic degradation of biopolymers and cellulose in particular. This unique class of metalloenzymes cleaves cellulose and other recalcitrant polysaccharides using an oxidative mechanism. Despite their potential in biomass saccharification and cellulose fibrillation, the detailed mode of action of LPMOs at the surface of cellulose fibers still remains poorly understood and highly challenging to investigate. In this study, we first determined the optimal parameters (temperature, pH, enzyme concentration, and pulp consistency) of LPMO action on the cellulose fibers by analyzing the changes in molar mass distribution of solubilized fibers using high performance size exclusion chromatography (HPSEC). Using an experimental design approach with a fungal LPMO from the AA9 family (PaLPMO9H) and cotton fibers, we revealed a maximum decrease in molar mass at 26.6 °C and pH 5.5, with 1.6% w/w enzyme loading in dilute cellulose dispersions (100 mg of cellulose at 0.5% w/v). These optimal conditions were used to further investigate the effect of PaLPMO9H on the cellulosic fiber structure. Direct visualization of the fiber surface by scanning electron microscopy (SEM) revealed that PaLPMO9H created cracks on the cellulose surface while it attacked tension regions that triggered the rearrangement of cellulose chains. Solid-state NMR indicated that PaLPMO9H increased the lateral fibril dimension and created novel accessible surfaces. This study confirms the LPMO-driven disruption of cellulose fibers and extends our knowledge of the mechanism underlying such modifications. We hypothesize that the oxidative cleavage at the surface of the fibers releases the tension stress with loosening of the fiber structure and peeling of the surface, thereby increasing the accessibility and facilitating fibrillation.

In this work, we have prepared films based on cellulose nanofibers (CNFs) that mimic plant responsiveness to water by shape-changing. Film twisting was achieved by creating an asymmetrical expansion through a gradient of carboxylate groups within the CNF film thickness. We present the characterization of pristine and modified CNFs, and their swelling and mechanical performances when conditioned into films. The immersion in water and organic solvents (isopropanol, ethanol, DMSO, acetonitrile, and cyclohexane) allowed controlling the asymmetrical expansion. Hence, film twisting is triggered when immersed in water and their shape recoveries were accomplished by dipping them in organic solvents. We investigated the main physicochemical interactions between the different CNFs and solvents governing film expansion. This work leaves the door open for the design of biomimetic cellulose-based materials for soft robotics, building materials, and electronic applications.

A strategy to functionalize cellulosic surfaces through physical adsorption of xyloglucan (XG) and carboxymethyl cellulose (CMC) derivatives bearing allyl or alkyne groups is reported. A set of functional polymer derivatives with degrees of substitution -DS- ranging from 0.10 up to 0.44 are first prepared through the opening of the epoxide ring of allyl glycidyl ether or propargyl glycidyl ether under mild basic aqueous medium. Contrary to alkyne-functionalized polymers, the radical copolymerization of allyl-XG and -CMC derivatives with acrylamide/acrylic acid leads to the formation of hydrogels, confirming their reactivity. The quantitative analysis of the deposition of these functionalized polysaccharides onto Whatman paper and wood pine fibers (spraying of aqueous solutions, drying and desorption step in water) shows that the physisorption of the polymer chains is not altered neither by the extent of the modification nor by the nature of the substituents. QCM-D experiments highlight a high affinity of allyl-XG for cellulosic substrates. The topochemical mapping by confocal Raman microscopy of cellulosic substrates on which alkyne polysaccharide derivatives have been deposited underpins that the surface coverage is rather uniform and that the diffusion of the polymer chains into the substrate reaches 40 μm. This aqueous functionalization/spraying procedure appears as a promising approach to confer novel adjustable surface properties to various cellulosic substrates, in a sustainable manner.

In this work, we have prepared cellulose-based actuators taking advantage of the pH-sensitive solubility of chitosan (CH) and the mechanical strength of CNFs. Bilayer films were prepared by vacuum filtration inspired by plant structures that exhibit reversible deformation under pH changes. The presence of CH in one of the layers led to asymmetric swelling at low pH, thanks to the electrostatic repulsion between charged amino groups of CH, and the subsequent twisting with the CH layer on the outside. Reversibility was achieved by substituting pristine CNFs with carboxymethylated CNFs (CMCNFs), that are charged at high pH and thus competed with the effects of amino groups. Swelling and mechanical properties of layers under pH changes were studied by gravimetry and dynamic mechanical analysis (DMA) to quantify the contribution of chitosan and the modified CNFs on the reversibility control. This work evidenced the key role of surface charge and layer stiffness to achieve reversibility. Bending was triggered by the different water uptake of each layer, and shape recovery was achieved when the shrunk layer shower higher rigidity than the swollen layer.

In this work, we evaluated the flexoelectric and piezoelectric contributions to the overall macroscopic polarization in cellulose films. To this end, the flexoelectric μ31 and transverse effective piezoelectric e31,f coefficients of cellulose films were determined using cantilever beam bending. The experiments were based on theoretical developments allowing to separate the flexoelectric from the piezoelectric contribution, represented by an effective flexoelectric coefficient, μeff, depending on both e31,f and μ31. Five free-standing and stainless steel/cellulose bilayer films were prepared from cellulose showing different morphologies and surface charge degrees: two almost neutral cellulose microfibers (CMF) and three (2,2,6,6-tetramethylpiperidin-1-yl)oxyl (TEMPO)-oxidized cellulose micro- (TCMF) and nanofibers (TCNF) bearing negative charged groups on the surface. The dielectric properties of the films indicated a low dielectric constant for unmodified CMF, and a huge increase for TEMPO-oxidized samples, which were up to 9 times higher than poly(vinylidene fluoride)-based polymers. TEMPO-oxidized cellulose films exhibited the largest flexoelectric coefficients (almost 7 times higher than those of synthetic polymer dielectrics), which evidenced that the presence of polar groups and surface charge boosted both flexoelectricity and piezoelectricity in unpoled cellulose films. These findings pave the way towards sustainable cellulose-based curvature sensors with large effective flexoelectric coefficients, without the need of preliminary energy consuming poling step.