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A novel method is reported for the preparation of a hybrid gibbsite-cellulose nanofibril (CNF) nanocomposite film with improved wet and dry mechanical properties and barrier properties. A gibbsite and cationic CNF dispersion was dewatered at pH 7 to prepare well-ordered films. Thereafter, the charge on gibbsite was reversed by dipping the film in pH 12 water to induce an ionic interaction between CNFs and gibbsite, enhancing the film properties; modulus improved from 9 GPa to 12 GPa, with a maintained strain-at-break of 6 % and tensile strength of 190 MPa. Additionally, the charge-reversed film swelled a factor of 24 less than a film without any gibbsite. At 23 °C and 80 % RH, the oxygen barrier properties were improved by a factor of 28, to a value of 18 ml·μm·m−2·kPa−1·24 h−1 and the water vapour barrier properties were improved by a factor of 12, to a value of 105 g·μm·m−2·kPa−1·24 h−1. [Display omitted] [ABSTRACT FROM AUTHOR]

Abstract: Flexible battery solutions is an emerging field due to a demand for bendable electronic devices. In this study, a route to make flexible positive electrodes for Li-ion batteries by utilizing nano-fibrillated cellulose (NFC) as binder material has been examined. These LiFePO4-based electrodes are made by filtration of a water dispersion of NFC, LiFePO4 and Super-P carbon particles, resembling a paper-making process. The resulting electrodes show good mechanical properties both dry as well as when soaked with battery electrolyte with a stress at break of typically at 5.2 and 2.2MPa, respectively. The cycling performance was 151mAh/g at C/10 and 132mAh/g at 1C for samples dried at 170°C. The drying temperature, after the filtration step, was found to be important and to affect both the mechanical properties, rendering the electrodes more ductile at lower temperatures, as well as the electrochemical properties, causing a higher coulombic efficiency at higher temperatures. [Copyright &y& Elsevier]

Abstract: There is an increasing interest in the development of thin, flexible energy storage devices for new applications. For large scale and low cost devices, structures with the use of earth abundant materials are attractive. In this study, we fabricated flexible and conductive nanopaper aerogels with incorporated carbon nanotubes (CNT). Such conductive nanopaper is made from aqueous dispersions with dispersed CNT and cellulose nanofibers. Such aerogels are highly porous with open channels that allow the deposition of a thin-layer of silicon through a plasma-enhanced CVD (PECVD) method. Meanwhile, the open channels also allow for an excellent ion accessibility to the surface of silicon. We demonstrated that such lightweight and flexible Si-conductive nanopaper structure performs well as Li-ion battery anodes. A stable capacity of 1200mAh/g for 100 cycles in half-cells is achieved. Such flexible anodes based on earth abundant materials and aqueous dispersions could potentially open new opportunities for low-cost energy devices, and potentially can be applied for large-scale energy storage. [Copyright &y& Elsevier]

Abstract: The Young''s modulus of layer-by-layer (LbL) films containing starch was determined using the recently developed SIEBIMM (strain-induced elastic buckling instability for mechanical measurements) technique. By using cationic starch (CS) in combination with anionic starch (AS), silica nanoparticles (SNP), and nanofibrillated cellulose (NFC), the mechanical properties of these sub-micrometer starch-containing LbL films could be tailored. At 50% relative humidity (RH), the Young''s modulus of CS/AS, CS/SNP, and CS/NFC was 0.6GPa, 0.9GPa, and 1.8GPa, respectively, in the 25–85-nm thickness range. As expected for these hygroscopic starch-containing LbL films, the mechanical properties depended on RH. At 0% RH, the Young''s modulus was 2–4.5 times higher than at 50% RH. The LbL buildup on polydimethylsiloxane (PDMS) was studied in situ using quartz crystal microgravimetry with dissipation (QCM-D), and atomic force microscopy (AFM) was used to characterize the surface morphology and thickness of the films. [Copyright &y& Elsevier]

Despite the different chemical approaches used earlier to increase the ductility of fibre-based materials, it has not been possible to link the chemical modification to their mechanical performance. In this study, cellulose fibres have been modified by periodate oxidation, alone or followed either by borohydride reduction, reductive amination or chlorite oxidation. In addition, TEMPO oxidation, and TEMPO oxidation in combination with periodate oxidation and further reduction with sodium borohydride have also been studied. The objective was to gain understanding of the influence of different functional groups on the mechanical and structural properties of handsheets made from the modified fibres. It was found that the modifications studied improved the tensile strength of the fibres to different extents, but that only periodate oxidation followed by borohydride reduction provided more ductile fibre materials. Changes in density, water-holding capacity and mechanical performance were also quantified and all are dependent on the functional group introduced. [ABSTRACT FROM AUTHOR]

The high structural anisotropy and colloidal stability of cellulose nanofibrils' enable the creation of self-standing fibrillar hydrogel networks at very low solid contents. Adding methacrylate moieties on the surface of TEMPO oxidized CNFs allows the formation of more robust covalently crosslinked networks by free radical polymerization of acrylic monomers, exploiting the mechanical properties of these networks more efficiently. This technique yields strong and elastic networks but with an undefined network structure. In this work, we use acrylate-capped telechelic polymers derived from the step-growth polymerization of PEG diacrylate and dithiothreitol to crosslink methacrylated TEMPO-oxidized cellulose nanofibrils (MATO CNF). This combination resulted in flexible and strong hydrogels, as observed through rheological studies, compression and tensile loading. The structure and mechanical properties of these hydrogel networks were found to depend on the dimensions of the CNFs and polymer crosslinkers. The structure of the networks and the role of individual components were evaluated with SAXS (Small-Angle X-ray Scattering) and photo-rheology. A thorough understanding of hybrid CNF/polymer networks and how to best exploit the capacity of these networks enable further advancement of cellulose-based materials for applications in packaging, soft robotics, and biomedical engineering. [Display omitted] [ABSTRACT FROM AUTHOR]

Interactions between dry cellulose were studied using model systems, cellulose beads, and cellulose films, using custom-built contact adhesion testing equipment. Depending on the configuration of the substrates in contact, Polydimethylsiloxane (PDMS) film, cellulose films spin-coated either on PDMS or glass, the interaction shows three distinct processes. Firstly, molecular interlocking is formed between cellulose and cellulose when there is a soft PDMS thin film backing the cellulose film. Secondly, without backing, no initial attraction force between the surfaces is observed. Thirdly, a significant force increase, ∆F, is observed during the retraction process for cellulose on glass, and there is a maximum in ∆F when the retraction rate is increased. This is due to the kinetics of a contacting process occurring in the interaction zone between the surfaces caused by an interdigitation of a fine fibrillar structure at the nano-scale, whereas, for the spin-coated cellulose surfaces on the PDMS backing, there is a more direct adhesive failure. The results have generated understanding of the interaction between cellulose-rich materials, which helps design new, advanced cellulose-based materials. The results also show the complexity of the interaction between these surfaces and that earlier mechanisms, based on macroscopic material testing, are simply not adequate for molecular tailoring. [Display omitted] [ABSTRACT FROM AUTHOR]

Abstract: Paper is a versatile material with obvious advantages in being both inexpensive and environment friendly. However, a major drawback compared with many other materials, such as plastics, is that it is sensitive to both liquid water and moist air. Traditionally paper is protected from liquid water by sizing. The present work presents a new way to make paper water resistant by combining the layer-by-layer (LbL) technique with the adsorption of a colloidal wax onto the multilayer structure. After the adsorption of five layers of poly(allylamine hydrochloride) and poly(acrylic acid) followed by the adsorption of 8mg paraffin wax per gram fibre, the contact angle measured 60s after a drop of water was applied to the sheet was about 138°. If the sheets were cured for 30min at 160°C after sheet making, the contact angle was ca. 150°. The heat treatment of sheets prepared from LbL-modified fibres without the addition of wax gave a contact angle of about 113°. To decouple structural effects from changes in surface energy upon heat treatment of PAH/PAA LbL films, model experiments were carried out where LbL assemblies were prepared on silicon oxide and cellulose model surfaces. The contact angle increased when these films were heat treated but it did not exceed 90°. The reason for this is due to the lack of structure of the model surfaces on a micrometre scale. The adsorption of wax impaired the mechanical properties of paper sheets made from modified fibres compared to sheets from the LbL-modified fibres. However, at an adsorption of 8mg paraffin wax per gram fibre there was still an increase by 37±1% in tensile strength index compared to the untreated reference pulp (33.8±0.7 and 24.7±0.6kNm/kg respectively). [Copyright &y& Elsevier]

Abstract: The primary goal with this work is to create electrically conductive cellulose fibres, this has been done to explore possible new applications for fibre based material. This research uses various methods to create polyelectrolyte multilayers (PEMs) on bleached softwood fibres and on SiO2 model surfaces, by sequentially treating these materials with poly(3,4-ethylenedioxythiophene):poly(styrene sulphonate) (PEDOT:PSS) and poly(allyl amine) (PAH). Paper sheets were then produced from the PEM-modified pulp and evaluated in terms of tensile strength, adsorbed amount of polymer, and electrical conductivity. To evaluate the influence of fibre charge on the measured paper properties, pulps of two different initial fibre charge densities were prepared via carboxymethylation. Because of the bluish colour of PEDOT:PSS, the build-up of PEM could be easily followed, since the fibres grew increasingly darker blue throughout the modification sequence. The conductivity of the fibre network increased by 2−3 orders of magnitude when the pulp of a higher fibre charge density was used. This suggests that it is more important to create a fibrous network with a high fibre–fibre joint strength and a large total joined area in the sheet rather than to maximize the adsorbed amount of PEDOT:PSS. A difference in conductivity could also be noted depending on the polyelectrolyte adsorbed in the outer layer, PAH lowered the conductivity compared to PEDOT:PSS. Evaluating the mechanical properties revealed that the use of PEDOT:PSS reduces the tensile strength of the paper. When five double layers had been adsorbed onto the carboxymethylated sample in which PEDOT:PSS formed the outer layer, calculations indicated a 25% decrease in tensile strength compared to that of reference material without PEMs. ESEM studies indicate that PEM treatment produces a significantly changed and somewhat smoother fibre surface. [Copyright &y& Elsevier]

[Display omitted] Multifunctional, light-weight, responsive materials show promise in a range of applications including soft robotics, therapeutic delivery, advanced diagnostics and charge storage. This paper presents a novel, scalable, efficient and sustainable approach for the preparation of cellulose nanofibril-based aerogels via a facile ice-templating, solvent exchange and air-drying procedure, which could replace existing inefficient drying processes. These ambient-dried aerogels (∼99% porosity) exhibit a high specific compressive modulus (26.8 ± 6.1 kPa m3 kg−1, approaching equivalence of carbon-nanotube-reinforced aerogels), wet stability and shape recovery (80–90%), favorable specific surface area (90 m2 g−1) and tunable densities (2–20 kg m−3). The aerogels provide an ideal nanofibrillar substrate for in-situ growth of metal–organic frameworks (MOFs), via co-assembly of MOF precursors with proteins in aqueous solutions. The resulting hybrid aerogels show a nine-fold increase in surface area (810 m2g−1), with preserved wet stability and additional protein biofunctionality. The hybrid aerogels facilitate a pH-controlled release of immobilized proteins, following a concomitant disassembly of the surface grown MOFs, demonstrating their use in controlled delivery systems. The colorimetric protein binding assay of the biofunctionalized hybrid aerogel also demonstrates the potential of the material as a novel 3D bioassay platform, which could potentially be an alternative to plate-based enzyme-linked immunosorbent assay. [ABSTRACT FROM AUTHOR]

Non-sustainable single-use plastics used for food packaging needs to be phased out. Films made from cellulose nanofibrils (CNFs) are suitable candidates for biodegradable and recyclable packaging materials as they exhibit good mechanical properties, excellent oxygen barrier properties and high transparency. Yet, their poor water vapour barrier properties have been a major hindrance in their commercialisation. Here, we describe the preparation of 25 μm thick CNF films with significantly improved water vapour barrier properties after deposition of ultrathin polymeric and metallic coatings, parylene C and aluminium, respectively. When first adding a 40 nm aluminium layer followed by an 80 nm parylene layer, i.e. with a combined thickness of less than one percent of the CNF film, a water vapour transmission rate of 2.8 g m−2 d−1 was achieved at 38 °C and 90 % RH, surpassing a 25 μm polypropylene film (4–12 g m−2 d−1). This is an improvement of more than 700 times compared to uncoated CNF films, under some of the harshest possible conditions a packaging material will need to endure in commercial use. The layers showed a good and even coverage, as assessed by atomic force microscopy, and the parylene-coated surfaces were hydrophobic with a contact angle of 110°, providing good water repellency. [Display omitted] [ABSTRACT FROM AUTHOR]

The fundamental understanding concerning cellulose-cellulose interactions under wet and dry conditions remains unclear. This is especially true regarding the drying-induced association of cellulose, commonly described as an irreversible phenomenon called hornification. A fundamental understanding of the mechanisms behind hornification would contribute to new drying techniques for cellulose-based materials in the pulp and paper industry while at the same time enhancing material properties and facilitating the recyclability of cellulose-rich materials. In the present work, the irreversible joining of cellulose-rich surfaces has been studied by subjecting cellulose nanofibril (CNF) films to different heat treatments to establish a link between reswelling properties, structural characteristics as well as chemical and mechanical analyses. A heating time/temperature dependence was observed for the reswelling of the CNF films, which is related to the extent of hornification and is different for different chemical compositions of the fibrils. Further, the results indicate that hornification is related to a diffusion process and that the reswellability increases very slowly over long time, indicating that equilibrium is not reached. Hence, hornification is suggested to be a kinetically limited phenomenon governed by non-covalent reversible interactions and a time/temperature dependence on their forming and breaking. [Display omitted] [ABSTRACT FROM AUTHOR]

Development of strong cellulose nanofibril (CNF) networks for advanced applications, such as in the biomedical field, is of high importance owing to the biocompatible nature and plant-based origin of cellulose nanofibrils. Nevertheless, lack of mechanical strength and complex synthesis methods hinder the application of these materials in areas where both toughness and manufacturing simplicity are required. In this work, we introduce a facile method for the synthesis of a low solid content (< 2 wt%), covalently crosslinked CNF hydrogel where Poly (N-isopropylacrylamide) (NIPAM) chains are utilized as crosslinks between the nanofibrils. The resulting networks have the capability to fully recover the shape in which they were formed after various drying and rewetting cycles. Characterization of the hydrogel and its constitutive components was performed using X-ray scattering, rheological investigations and uniaxial testing in compression. Influence of covalent crosslinks was compared with networks crosslinked by the addition of CaCl 2. Among other things the results show that the mechanical properties of the hydrogels can be tuned by controlling the ionic strength of the surrounding medium. Finally, a mathematical model was developed based on the experimental results, which describes and predicts to a decent degree the large-deformation, elastoplastic behavior, and fracture of these networks. [Display omitted] [ABSTRACT FROM AUTHOR]

EDC-mediated coupling has frequently been utilized to poly(ethylene glycol) functionalize (PEGylate) cellulose-based materials, but no work has previously been reported on the direct N -(3-dimethylaminopropyl)- N -ethylcarbodiimide (EDC)-mediated PEGylation of cellulose nanofibrils (CNF). Herein, we report the first study where CNF has been directly sterically stabilized with amine-terminated PEG employing N -hydroxysuccinimide (NHS)-assisted EDC-coupling. This work has shown that this coupling reaction is highly sensitive to the reaction conditions and purification procedures, and hence an optimized coupling protocol was developed in order to achieve a reaction yield. Elemental analysis of the nitrogen content also showed the successful PEGylation. It was also shown that a surprisingly low PEGylation (1%) is sufficient to significantly improve the colloidal stability of the PEGylated samples, which reached dispersion-arrested-state-transitions at higher concentrations than neat CNF. The colloidal stability was preserved with increasing ionic strength, when comparably long polymer chains were grafted, targeting only 1% PEGylation. [ABSTRACT FROM AUTHOR]

Nanoscale infrared (IR) spectroscopy and microscopy, enabling the acquisition of IR spectra and images with a lateral resolution of 20 nm, is employed to chemically characterize individual cellulose nanocrystals (CNCs) and cellulose nanofibrils (CNFs) to elucidate if the CNCs and CNFs consist of alternating crystalline and amorphous domains along the CNF/CNC. The high lateral resolution enables studies of the nanoscale morphology at different domains of the CNFs/CNCs: flat segments, kinks, twisted areas, and end points. The types of nanocellulose investigated are CNFs from tunicate, CNCs from cotton, and anionic and cationic wood-derived CNFs. All nano-FTIR spectra acquired from the different samples and different domains of the individual nanocellulose particles resemble a spectrum of crystalline cellulose, suggesting that the non-crystalline cellulose signal observed in macroscopic measurements of nanocellulose most likely originate from cellulose chains present at the surface of the nanocellulose particles. [Display omitted] [ABSTRACT FROM AUTHOR]

The structure and dynamics of networks formed by rod-shaped particles can be indirectly investigated by measuring the diffusion of spherical tracer particles. This method was used to characterize cellulose nanofibril (CNF) networks in both dispersed and arrested states, the results of which were compared with coarse-grained Brownian dynamics simulations. At a CNF concentration of 0.2 wt% a transition was observed where, below this concentration tracer diffusion is governed by the increasing macroscopic viscosity of the dispersion. Above 0.2 wt%, the diffusion of small particles (20–40 nm) remains viscosity controlled, while particles (100–500 nm) become trapped in the CNF network. Sedimentation of silica microparticles (1–5 μm) in CNF dispersions was also determined, showing that sedimentation of larger particles is significantly affected by the presence of CNF. At concentrations of 0.2 wt%, the sedimentation velocity of 5 μm particles was reduced by 99 % compared to pure water. [Display omitted] [ABSTRACT FROM AUTHOR]

Highlights: [•] A method to increase both strength and stretchability of paper is proposed. [•] The layer-by-layer technique is used to build up a multilayer onto pulp fibres. [•] The addition of salt in the system is a critical parameter. [•] Hyaluronic acid/polyallylamine is the most efficient system. [•] Strain at break and strength of treated paper sheets are increased by a factor 3. [ABSTRACT FROM AUTHOR]

Cellulose nanofibril-based aerogels have promising applicability in various fields; however, developing an efficient technique to functionalize and tune their surface properties is challenging. In this study, physically and covalently crosslinked cellulose nanofibril-based aerogel-like structures were prepared and modified by a molecular layer-by-layer (m-LBL) deposition method. Following three m-LBL depositions, an ultrathin polyamide layer was formed throughout the aerogel and its structure and chemical composition was studied in detail. Analysis of model cellulose surfaces showed that the thickness of the deposited layer after three m-LBLs was approximately 1 nm. Although the deposited layer was extremely thin, it led to a 2.6-fold increase in the wet specific modulus, improved the acid-base resistance, and changed the aerogels from hydrophilic to hydrophobic making them suitable materials for oil absorption with the absorption capacity of 16–36 g/g. Thus, demonstrating m-LBL assembly is a powerful technique for tailoring surface properties and functionality of cellulose substrates. Wet stable cellulose-based aerogels tailored through deposition of an ultrathin coating via a molecular layer-by-layer technique that facilitates efficient oil-water separation. [Display omitted] [ABSTRACT FROM AUTHOR]

Ion selective membranes are at the heart of energy conversion and harvesting, water treatment, and biotechnologies. The currently available membranes are mostly based on expensive and non-biodegradable polymers. Here, we report a cation-selective and low-cost membrane prepared from renewable nanocellulose and 1,2,3,4-butanetetracarboxylic acid which simultaneously serves as crosslinker and source of anionic surface groups. Charge density and structure of the membranes are studied. By using different degrees of crosslinking, simultaneous control over both the nanochannel structure and surface charge concentration is achieved, which in turn determines the resulting ion transport properties. Increasing negative charge concentration via higher crosslinker content, the obtained ion conductivity reaches up to 8 mS/cm (0.1 M KCl). Optimal ion selectivity, also influenced by the solution pH, is achieved at 20 wt% crosslinker addition (with ion conductivity of 1.6 mS/cm). As regular ~1.4 nm nanochannels were formed at this composition, nanofluidic contribution to ion transport is likely. • A renewable, low cost crosslinked nanocellulose membrane was reported. • The crosslinked membranes show excellent ion conductivity and selectivity. • A higher amount of crosslinker results in a greater ion conductivity. • An optimal ionic selectivity obtained at an addition of the crosslinker of 20 wt%. • This nanocellulose membrane is promising for ionic devices and upscaled applications. [ABSTRACT FROM AUTHOR]

Abstract: In this study, thermo-responsive nanofibrillated cellulose (NFC) has been produced by the adsorption of thermo-responsive polyelectrolytes to the NFC. Three block copolymers were synthesized in which the polyelectrolyte block was composed of quaternized poly(2-(dimethylamino)ethyl methacrylate) (qPDMAEMA) and the thermo-responsive block was composed of poly(di(ethylene glycol) methyl ether methacrylate) (PDEGMA). The block copolymers were synthesized employing atom transfer radical polymerization (ATRP) and the PDMAEMA block was utilized as a macroinitiator for the polymerizations of PDEGMA. The length and charge of the PDMAEMA block were kept constant in all three block copolymers, while three different molecular weights of the PDEGMA block was synthesized. The PDMAEMA block was quaternized to introduce positive charges and the block copolymers were subsequently adsorbed onto the negatively charged NFC that was dispersed in water. The lower critical solution temperatures (LCSTs) of the free block copolymers in solution were analyzed by dynamic light scattering (DLS). The composites were analyzed by QCM-D, FT-IR and TGA, which clearly showed an adsorption of the block copolymer onto the NFC. The grafted NFC showed a thermo-responsive behavior in solution upon heating and cooling, thus supporting that the properties of the polyelectrolyte can be transferred to the cellulose. By this methodology, thermo-responsive NFC materials can be produced in a straight-forward manner in water dispersions, without performing any chemical reactions on the NFC. [Copyright &y& Elsevier]

Abstract: Dry ultra-porous cellulose fibres were obtained using a liquid exchange procedure in which water was replaced in the following order: water, methanol, acetone, and finally pentane; thereafter, the fibres were dried with Ar(g). The dry samples (of TEMPO-oxidized dissolving pulp) had a specific surface area of 130m2 g−1 as measured using BET nitrogen gas adsorption. The open structure in the dry state was also revealed using field emission scanning electron microscopy. This dry open structure was used as a scaffold for in situ polymerization. Both poly(methyl methacrylate) and poly(butylacrylate) were successfully used as matrix polymers for the composite material (fibre/polymer), comprising approximately 20wt% fibres. Atomic force microscopy phase imaging indicated a nanoscale mixing of the matrix polymer and the cellulose fibril aggregates and this was also supported by mechanical testing of the prepared composite where the open fibre structure produced superior composites. The fibre/polymer composite had a significantly reduced water absorption capacity also indicating an efficient filling of the fibre structure with the matrix polymer. [Copyright &y& Elsevier]

Abstract: In this work, the objective was to synthesize a compatibilizer that can electrostatically adsorb onto cellulose fibers, in fiber-based composites, to enhance the interaction between the fibers and non-polar polymer matrices. This physical route to attach the compatibilizer onto and thereby modify a fiber surface is convenient since it can be performed in water under mild conditions. Polystyrene (PS) was used for the high molecular weight, non-polar, block and poly(dimethylamino)ethyl methacrylate (PDMAEMA) was used as the polar block, which was subsequently quaternized to obtain cationic charges. The block copolymer self-assembles in water into cationic micelles and the adsorption to both silicon oxide surfaces and cellulose model surfaces was studied. The micelles spread out on the surface after heat treatment and contact angle measurements showed that the contact angles against water increased significantly after this treatment. AFM force measurements were performed with a PS probe to study the adhesive properties. The adhesion increased with increasing contact time for the treated surfaces, probably due to entanglements between the polystyrene blocks at the treated surface and the probe. This demonstrates that the use of this type of amphiphilic block copolymer is a promising route to improve the compatibility between charged reinforcing materials, such as cellulose-based fibers/fibrils, and hydrophobic matrices in composite materials. [Copyright &y& Elsevier]

• Anionic PEDOT:PSS adsorbs spontaneously on anionically charged cellulose. • Temperature-dependent QCM-D suggests the larger entropic contribution to adsorption. • Low pH, high ionic strength and multivalent counterions favor PEDOT:PSS adsorption on CNF. • PEDOT:PSS and CNF show higher adhesion at low pH in colloidal probe measurements. • PEDOT:PSS organizes differently on 3D and 2D cellulose surfaces. Poly(3,4-ethylenedioxythiophene):poly(styrenesulfonate) (PEDOT:PSS) is a conducting polymer frequently used with cellulose, to develop advanced electronic materials. To understand the fundamental interactions between cellulose and PEDOT:PSS, a quartz crystal microbalance with dissipation (QCM-D) was used to study the adsorption of PEDOT:PSS onto model films of cellulose-nanofibrils (CNFs) and regenerated cellulose. The results show that PEDOT:PSS adsorbs spontaneously onto anionically charged cellulose wherein the adsorbed amount can be tuned by altering solution parameters such as pH, ionic strength and counterion to the charges on the CNF. Temperature-dependent QCM-D studies indicate that an entropy gain is the driving force for adsorption, as the adsorbed amount of PEDOT:PSS increased with increasing temperature. Colloidal probe AFM, in accordance with QCM-D results, also showed an increased adhesion between cellulose and PEDOT:PSS at low pH. AFM images show bead-like PEDOT:PSS particles on CNF surfaces, while no such organization was observed on the regenerated cellulose surfaces. This work provides insight into the interaction of PEDOT:PSS/cellulose that will aid in the design of sustainable electronic devices. [ABSTRACT FROM AUTHOR]

• Wood-based cellulose fibers are used to prepare well-defined cellulose gel beads. • The beads are used as platform for deposition of LbL flame-retardant nanocoatings. • An optimal range of 10–20 BL is observed for cellulose char forming ability. • A micro-intumescent behavior is easily identified as main flame-retardant mechanism. Layer-by-Layer (LbL) assembled nanocoatings are exploited to impart flame-retardant properties to cellulosic substrates. A model cellulose material can make it possible to investigate an optimal bilayer (BL) range for the deposition of coating while elucidating the main flame-retardant action thus allowing for an efficient design of optimized LbL formulations. Model cellulose gel beads were prepared by dissolving cellulose-rich fibers followed by precipitation. The beads were LbL-treated with chitosan (CH) and sodium hexametaphosphate (SHMP). The char forming properties were studied using thermal gravimetric analysis. The coating increased the char yield in nitrogen to up to 29 % and showed a distinct pattern of micro intumescent behavior upon heating. An optimal range of 10–20 BL is observed. The well-defined model cellulose gel beads hence introduce a new scientific route both to clarify the fundamental effects of different film components and to optimize the composition of the films. [ABSTRACT FROM AUTHOR]