Borohydride reduction of dialdehyde cellulose (DAC) is a promising strategy to generate dialcohol cellulose as bio-based alternative to petroleum-based materials. However, the degradation of the polymer backbone according to β-elimination mechanisms limits the practical applications of the reaction. Therefore, we aimed at optimizing the process to suppress degradation reactions by varying reaction time, pH, and reagent stoichiometry. The degree of oxidation (DO) of the DAC intermediates significantly impacts the yields and molecular weights of the isolated dialcohol celluloses, with a “leveling-off” effect at higher DO values. Increasing the amount of sodium borohydride can minimize—but not entirely prevent—chain scissions. Lowering the pH value during reduction slows down the degradation but results in incomplete conversion of the aldehyde functionalities. Our study provides valuable insights into the consequences of side reactions during borohydride reduction of DAC as well as into chemistry and analysis of the dialdehyde cellulose/dialcohol cellulose system.Graphical abstractAbout a dilemma in cellulose chemistry: Dialcohol cellulose derived by periodate oxidation and subsequent borohydride reduction of cellulose has received increasing attention in the development of sustainable thermoplastic materials. The present study highlights the challenge of suppressing β-elimination and favoring the reduction pathway to optimize reaction conditions and minimize chain degradation.

Soybean hulls (SBHs) are one of the main by-products of soybean crushing, usually destined for animal feeding or to become a putrescible waste. In this work, we upgraded the SBHs to materials with antimicrobial properties. After the extraction of soybean peroxidase from SBHs, an enzyme applicable in different technological sectors and naturally present in soybean hulls, the exhausted biomass was subjected to an acid–base treatment to isolate cellulose. The obtained material was, in turn, functionalized with 3-aminopropyl triethoxysilane (APTES) to achieve new hybrids with antimicrobial properties. The synthetic procedure was optimized by varying the solvent type (ethanol or toluene) and APTES amount. Overall, the amino-functionalization process was effective and the activity was outstanding against both gram-positive and gram-negative bacteria, reaching complete disinfection practically in all cases. The samples were studied by means of several characterization techniques, demonstrating that the solvent and cellulose types had a significant influence on the physical–chemical features, together with the eco-sustainability of the process. In particular, the use of greener ethanol and waste cellulose (with respect to a commercial one) resulted in a higher APTES immobilization efficiency and superior thermal stability of the final materials. Interestingly, the presence of various unremoved compounds from the lignocellulosic SBH matrix, although in small quantities, emerged as a crucial factor, also in terms of antibacterial activity, hypothesizing a role of residual phytochemicals.

The occurrence of oil spills has severe damage upon both the environment and human health. Hence, the development of a green, recyclable, complex environment resistant, and efficient oil–water separation aerogel is required in order to effectively absorb marine or industrial oil. In this study, modified cellulose/N,N'-methylenebisacrylamide/tannin (PCMT) composite porous materials were prepared utilizing the sol–gel method and were modified with tertbutyl acrylate. PCMT possesses a three-dimensional interpenetrating porous structure, exhibiting remarkable oil–water separation performance and excellent compressive strength (PCMT can capable of bearing 7000 times its own weight; PCMT can endure 290.3 kPa pressure at 80% strain when the amount of tannin is 0.2 g). The unique pore structure of PCMT engenders differential oil adsorption capacities (PCMT0, PCMT0.05, PCMT0.1, and PCMT0.2 evince higher adsorption capacities for petroleum ether and dichloromethane, n-hexane and dichloromethane, toluene, and toluene and dichloromethane, respectively). Of critical import, PCMT demonstrates exceptional adaptability to complex environments, wherein the porous materials maintain good hydrophobicity and oil absorption capacity under conditions of vigorous stirring, a wide pH range (1–14), a wide temperature range (4–160 °C), ultraviolet irradiation (8 h), and tape peeling (10 times). Moreover, the porous materials may be employed for the recovery of oil through simple mechanical extrusion, thus demonstrating certain economic significance and the application potential in the treatment of oil spills.

Plant-based cellulose owing to its biocompatibility, slow in vivo degradability, chemical modifiability, mechanical properties and low cost of production represents an attractive biomaterial for tissue engineering applications. This study aimed at synthesizing probe-sonicated cellulose (PSC), followed by functionalization via bone-conditioned medium (BCM) and examining the in silico binding affinity of protein-based active components of BCM with cellulose subunits. Furthermore, the in vitro bioactivity i.e., cell proliferation, viability and mineralization of the BCM-treated PSC were also investigated. Cotton cellulose (CC) was first treated with sulfuric acid and subjected to probe sonication to reduce the reaction time, fiber length and enhance the surface roughness for improved surface adsorption potential. BCM was prepared by conditioning the serum-free media with pre-osteoblasts. Then, PSC was exposed to BCM. The successful functionalization of PSC was characterized by Fourier transform infrared (FTIR), Raman spectroscopy and scanning electron microscopy (SEM) with energy-dispersive X-ray spectroscopy (EDX). Molecular docking and molecular simulation results confirmed the high binding affinity of active components of BCM including bone morphogenetic protein-2 (BMP-2) and transforming growth factor beta 1 (TGF-β1) with cellulose subunits. Biochemical analysis demonstrated favorable biocompatibility and non-toxicity of BCM-functionalized PSC which promoted the proliferation, viability and mineralization of pre-osteoblast cells. These promising results suggest that BCM-functionalized PSC can be explored as a potential candidate for providing a conducive environment for cells as well as scaffolding in bone tissue engineering applications.Graphical abstract

In this study, a green and effective stepwise catalytic system for cellulose conversion to 5-hydroxymethylfurfural (HMF) is reported. In a pretreatment process, very fast (15 min) dissolution of cellulose was achieved at a low temperature of 70 °C, utilizing ZnBr2·4H2O as the best dissolution solvent, which to improve the reactivity of cellulase for raw cellulose and increase efficiency of cellulose degradation. Enzyme-inorganic hybrid nanoflowers (Cellulase@β-glucosidase/Zn3(PO4)2-NF and Glucose isomerase@Zn3(PO4)2-NF) with different morphological structures were prepared to act as biocatalyst in the sequential conversion of pretreated cellulose to glucose and glucose to fructose. HCl was applied catalyst for dehydration of fructose to 5-HMF in a water/tert-butanol biphasic system. Under optimal reaction conditions, the yield of 5-HMF for the overall reaction from cellulose was about 21.6%. A feasibility route for green conversion of cellulose to 5-HMF is reported.Graphical abstract

The utilization of cellulosic fibers is becoming increasingly widespread worldwide as promising raw material in polymer composite reinforcement. However, and despite the multiple advantages of cellulosic fibers like the lower density, cheap cost and biodegradability, their use is limited due to hydrophilic character which reduces their affinity with hydrophobic matrices. A natural fiber treatment, whether chemical or physical, is advised to address this issue. The purpose of this study is to characterize the Ampelodesmos mauritanicus plant (AM) fibers extracted by the chemical method (2% NaOH for 48 h) and treated (chemically and physically). We carried out acetylation, mercerization and microwaves modification of the AM plant fibers to reduce their hydrophilic character. The influence of chemical and physical treatments on the structure and morphology of AM plant fibers was characterized by analytical techniques as per International Standard. X-ray diffraction confirmed that the AM fibers have a good crystallinity index (52.4%). Microwave physical treatment at 550 W increased their density from 1.00 to 1.55 g/cm3, their Young’s modulus and tensile strength from 11.0 to 18.6 GPa and from 155 to 290 MPa, respectively, giving the highest values. It is followed by chemical treatments: first with acetic anhydride (C4H6O3) for 4 h and then with 3% NaOH also for 4 h. It should be observed that the data have a very considerable dispersion that calls for statistical analysis (method of Weibull with two and three parameters was utilized).

Hydrogels are attracting widespread attention due to their unique mechanical flexibility, which holds great promise for application in various fields. However, the high water-richness of hydrogels make them inevitably freeze at sub-zero temperatures conditions and severely limit the range of applications. Herein, we presented a novel anti-freezing strategy based on betaine/CaCl2 and CNCs as both reinforcing agent and physical cross-linking agent to achieve the simultaneous upgrading of anti-freezing and mechanical properties of hydrogels. Under the synergistic effect of betaine and CaCl2, the GA/PAA-CNC/betaine/CaCl2 hydrogels maintained exceptional fracture toughness (1.5 MPa) and tensile properties (1000%) even at − 30 °C. This work offers a neoteric antifreeze strategy to design self-healing, high intensity and anti-freezing arabic gum hydrogels.

Ion pair self-assembly (IPSAM) responsive to temperature and oxidation was prepared using quaternium hydroxyethyl cellulose ethoxylate (QHECE) as a cationic hydrophilic polymer and (phenylthio) acetic acid (PTA) as a hydrophobic counter ion. The IPSAM was spontaneously formed when the quaternium to carboxylic group molar ratio was 1/9–2/8. QHECE/PTA IPSAM was found as sphere-like nanoparticles whose diameter was tens of nanometers on the TEM micrograph. The ion pair showed the upper critical solution temperature (UCST) that increased with increasing the PTA content and decreased when the PTA of the ion pair was oxidized by H2O2. The ion pair was interface-active due to its amphiphilic property and the interface activity was decreased upon the PTA oxidation. The critical micelle concentration of the ion pair was about 10.5 mg/ml, determined by a fluorospectroscopic method, and it decreased upon oxidation. The ionic interaction between QHECE and PTA and the oxidation of PTA were confirmed by FT-IR spectroscopy, and the oxidation was re-confirmed by X-ray photoelectron microscopy. The release of a payload (i.e. nile red) in IPSAM was restrained below the UCST but it was triggered above the phase transition temperature possibly due to the disintegration of the IPSAM. The release was expedited by the PTA oxidation, possibly because the UCST shifted downward below the release medium temperature. The release was somewhat dependent on the pH value but it was not affected by pH value as much as by temperature and oxidation.

During the last decade, the usage of geotextiles has tremendously grown into a needful auxiliary, particularly regarding soil protection. Although geotextiles made of natural fibers blended with synthetic materials are considered a modern achievement, backing up the basic concept of increasing the stability of roads and soils, they suffer from severe degradation. It includes the environmental exposure such as hydrolysis, and thermal, chemical, and biological degradation, affecting their long-term performance. This paper focuses on the jute-based geotextile having outstanding water repellency with a water contact angle of 169° and immutable tensile strength (~ 12 MPa) when incorporated with hexadecyltrimethoxysilane (HDTMS) modified titanium dioxide (TiO2) nanoparticles (nps) via drop casting technique. Herein, the durability of the coating was examined by sand (dropping sand particles) and impact (driving two-wheeler) tests on the coated jute sample. In addition, the coated samples were immersed in different aqueous mediums, and the behaviour in the tensile strength was noted. Similarly, the thermal degradation affecting the tensile strength was also evaluated. Lastly, biodegradability was judged by burying the samples for different periods in the soil. These outcomes demonstrate the potential of the HDTMS-TiO2 nps coating on jute geotextile having a suitable mechanically durable and sustainable superhydrophobic property that could be successfully used in roadway applications.

To realize the biocompatibility, mechanical strength, and sustained antibacterial properties of medical materials, it is feasible to introduce antibacterial material components into biomass matrix to prepare medical materials. Herein, zinc oxide (ZnO) was in-situ synthesized in bacterial cellulose (BC) dispersion and filtered into a film, and the BC/ZnO composite film was further immersed in sodium alginate (Alg) solution to construct the second layer structure. The microstructure, mechanical strength, and antibacterial properties of the composite films were investigated systematically. The tensile strength of the BC/ZnO/CAlg sample was achieved at 16.5 ± 2.4 MPa, much higher than that of the Zn2+ crosslinked CAlg film of 11.5 ± 1.2 MPa. The Zn2+ cross-linked Alg in the outer layer and the BC/ZnO composite film in the inner layer combined to create a synergistic effect. This secondary structure design ensures good hydrophilicity and hygroscopicity of the material which enables the sustained-release migration of Zn2+ from the inner layer to the outer layer. Finally, the BC/ZnO/CAlg composite film possesses excellent antibacterial performance against Staphylococcus aureus and Escherichia coli. In addition, this work systematically expounds on the antibacterial and slow-release mechanism of secondary structure composite membranes. The results will provide a database and theoretical reference for applying BC/ZnO/CAlg composite membranes in the medical field.

The crystallinity of cellulose decreases when bundled microfibrils are dispersed in water as cellulose nanofibers (CNFs) or physically separated into finer nanoscale fibrils or single microfibrils. The crystallinity of these CNFs is recovered when they become densely assembled through the dehydration of the dispersion. In this process, multiple CNFs are assumed to partially fuse, leading to the enlargement of crystallite widths. The mechanism of this CNF fusion is, however, not well understood. In this study, the recovery process of the crystallinity of CNFs was monitored by sampling wet CNF gels during condensation from a dilute dispersion to a dense aggregate, followed by wide-angle X-ray diffractometry (WAXD) and solid-state 13C nuclear magnetic resonance (NMR) spectroscopy analyses after supercritical drying. In the WAXD analysis, a two-step enlargement in the (2 0 0) crystal size was observed: the first step was a rapid increase in the range of solid content up to 1%, followed by a gradual increase in the range of 1–85%. The crystallinity index estimated by NMR hardly changed in the range of 0.5–30% but gradually increased in the range of 30–85%. A portion of the CNF samples, without drying, were also subjected to small-angle X-ray scattering and viscoelasticity analyses, indicating that the inter-CNF contact points in water significantly increased until reaching a solid content of 1%, and then at solid contents higher than 1%, the contact areas of each point gradually expanded. Finally, a mechanism of CNF fusion was proposed based on these results.

We exploited organic photo-redox-catalyzed atom transfer radical polymerization (O-ATRP) to synthesize a thermo-responsive polymer with a narrow molecular weight distribution. Poly(methyl methacrylate) (PMMA) chains were polymerized from a hydroxypropyl cellulose (HPC)-based macroinitiator using metal-free O-ATRP under visible-light irradiation. This O-ATRP is mediated by 1,2,3,5-tetrakis (carbazol-9-yl)-4,6-dicyanobenzene (4CzIPN), a photoredox catalyst with a substantial excited-state reduction potential, low cost, and ease of preparation. The synthesis of a series of PMMA-grafted HPC (PMMA-g-HPC) was characterized by various analytical methods, including FTIR spectroscopy, NMR spectroscopy, TGA, and GPC analysis. The lower critical solution temperature (LCST) of the polymers was determined by measuring the transmittance of the polymer solution as a function of the temperature at various pH values. Consequently, we expanded the LCST window of the HPC-based polymers and generated the opposite pH dependency of the LCST by forming PMMA-g-HPCs. Our “grafting-from” synthetic approach and thermo-responsive polymers, which are controllable in full range of physiological conditions, are promising in a variety of biological, electronics, and biosensor applications, particularly in drug delivery systems.

Phosphoric acid is widely used for the swelling and hydrolysis of cellulose. The detailed description of molecular interactions between cellulose and phosphoric acid is essential for understanding and controlling these processes. Here, to obtain structural insights into the swelling behavior, we investigated the structural evolution of cellulose swollen in concentrated phosphoric acid solution using X-ray fiber diffraction and solid-state NMR spectroscopy. We observed the formation of a crystalline complex of cellulose and phosphoric acid at − 40 °C, where cellulose molecules adopt a seven-fold helical conformation. This structure is the second known cellulose-acid crystalline complex and the first cellulosic crystal consisting of seven-fold helical chains. Our observation highlights the conformational flexibility of cellulose molecules in the solvated states and the strong influence of cellulose-acid interactions on the packing and conformation of cellulose molecules.Graphical abstract

Oil gelling agent serves as potential materials in the treatment of marine oil pollution. However, the reported oil gelling agents have some limitations in practical applications, such as the high cost, complex synthesis, secondary pollution, and the lack of enough storage space for the inorganic oil gelling agents. Here, a novel powdery oil gelling agent with a hierarchical porous structure was developed and used in remediating oil pollution on the water surface. Based on the three-dimensional (3D) network of cellulose nanofibrils/silicon dioxide (CNFs/SiO2), it was found that GO acted as a larger skeleton and formed a double skeleton 3D network with CNFs to successfully construct the oil gelling agent (S/GO/CNFs/SiO2, SGCS) with hierarchical porous structure and selective wettability. SGCS can efficiently solidify various oil independent of environmental factors (temperature and pH), especially the accessibility of the large pores and the capillary action of the small pores contribute to the faster solidifying of crude oil. Resulting from the photothermal conversion function of GO, it shows the ability to recovery oil from the solidified state to achieve higher economic benefits. This study overcomes to a certain extent the current limitations of oil gelling agents and will provide powerful support for the application of oil gelling agents in practical marine oil spills.Graphical abstractDouble skeleton powdery oil gelling agent constructed by cellulose nanofibrils and graphene oxide was successfully fabricated and utilized to effectively remove marine oil spill.

Solar-driven absorption has been emerging as a promising technology to clean up crude oil. The photothermal performance of porous absorbents reduces the viscosity of crude oil and allows in-situ oil absorption and desalination when exposed to solar irradiation. However, the process of crude oil recovery (e.g., squeeze) will inevitably damage the properties of the absorbent, seriously reducing its long-term efficacy. Herein, an innovative strategy is designed for in-situ solar-driven crude oil recovery and desalination technology for long-term efficacy without any surface degradation or biofouling. A dual-function photothermal aerogel (PCM@WA) was prepared by modifying delignified wood with polydimethylsiloxane (PDMS), carbon nanotubes (CNTs), and molybdenum dioxide (MoO2). The aerogel displays an efficient crude oil absorption of 35.4 g/g under one sun irradiation. In multiple absorption-recovery cycles, the decline in oil absorption ability promotes the water transport capacity of the aerogel, providing PCM@WA with excellent solar steam generation performance. It exhibits a high and stable evaporation rate of 1.96 kg/m2/h and the total metal removal efficiency is over 99.8%. The strategy combining crude oil absorption with seawater desalination not only extends the device life but also fully exploits the photothermal conversion technology to handle environmental pollution and energy crisis.

Chitosan is a green substance that has antibacterial, non-toxic, and good biocompatibility properties. It is becoming more and more popular in the food, pharmaceutical, and textile industries. In this work, paraffin@chitosan microcapsules were synthesized through a single coacervation method, then modified zinc oxide (ZnO) nanoparticles were grafted onto paraffin@chitosan microcapsules to prepare ZnO/chitosan composite microcapsules through Michael addition reaction. The obtained ZnO/chitosan composite microcapsules were further treated on the wool fabric via a thiol-ene click reaction. After treatment, cuticle layers of wool fibers became tender, and the wool fiber surface was covered with ZnO/chitosan composite microcapsules. The bacterial inhibition rates of treated wool fabric could reach 98.9% and 97.2% against the gram-positive bacteria (Staphylococcus aureus) and gram-negative bacteria (Escherichia coli), which was attributed to the synergistic antibacterial effect of chitosan and ZnO. The treated wool fabric also presented enhancement of superhydrophobicity with a water contact angle of 160.9°. Furthermore, the thermal imager analysis of treated wool fabric illustrated that it had a good thermal energy storage performance due to the loaded paraffin.

Hemicellulose, which is an abundant polysaccharide, has the potential to be an alternative for petroleum-based emulsifiers. In this study, dodecenyl succinic anhydride (DDSA) modified glucuronoxylans (DDSA-GLX) with high degree of substitution (DS) were synthesized through homogeneous esterification. The emulsifying properties of DDSA-GLX were investigated. The influences of pH, DS, calcium and sodium ions, and solvent system on the emulsifying properties (droplet size, zeta potential, emulsifying activity, and emulsion stability) were evaluated. The results indicated that the DS hold positive impact on the emulsifying properties of DDSA-GLX. With the increasing of DS, DDSA-GLX emulsions showed smaller droplet size (~ 0.56 μm), lower zeta potential (− 27.6 mV), higher emulsifying activity (0.989), and better emulsion stability. In addition, DDSA-GLX showed better emulsifying properties at pH 6.5 and pH 8.5. Calcium and sodium ions had negative impacts on the emulsifying properties of DDSA-GLX. Furthermore, DDSA-GLX prepared in water showed better emulsifying properties than those of DDSA-GLX prepared in DMSO (DS = 0.044). To sum up, the DDSA-GLX with high DS (up to 0.328) presented satisfactory emulsifying properties and the potential to be an alternative for petroleum-based emulsifiers.

This work investigated the dissolution rate of flax fibers in the ionic liquid 1-ethyl-3-methylimidazolium acetate [C2mim] [OAc] with the addition of a cellulose anti-solvent, water. The dissolution process was studied as a function of time, temperature and water concentration. Optical microscopy is used to analyse the resultant partially dissolved fibers. Distilled water was added to the solvent bath at the concentrations of 1%, 2% and 4% by weight in order to understand its influence on the dissolution process. The effect of the addition of even small amounts of water was found to significantly decrease the speed of dissolution, decreasing exponentially as a function of water concentration. The resulting data of both pure (as received from the manufacturers) ionic liquid and ionic liquid/anti-solvent mixtures showed the growth of the coagulated fraction as a function of both dissolution time and temperature followed time temperature superposition. An Arrhenius behavior was found, enabling the measurement of the activation energy for the dissolution of flax fiber. The activation energy of the IL as received (0.2% water) was found to be 64 ± 5 kJ/mol. For 1%, 2% and 4% water systems, the activation energies were found to be 74 ± 7 kJ/mol, 97 ± 3 kJ/mol and 116 ± 0.6 kJ/mol respectively. Extrapolating these results to zero water concentration gave a value for the hypothetical dry IL (0% water) of 58 ± 4 kJ/mol. The hypothetical dry ionic liquid is predicted to dissolve cellulose 23% faster than the IL as received (0.2% water).

The purpose of this study is to examine the hornification of enzymatically hydrolyzed high consistency softwood kraft pulp in an experimental defibration dryer. This device dries pulp under turbulent conditions which can prevent interfiber bonding and produce a separated fiber population. This is useful in certain applications, such as composites, which require dry, unbonded pulp fibers. In this study, we examine how fibrillated pulps behave in the dryer with respect to pore expansion in hydrolysis and collapse in drying (hornification). It was found that the endoglucanase cocktail increased the micro-, meso-, and macropore volumes as a function of hydrolysis time. Drying decreased the pore volumes of each size category, with the biggest changes in the macropore region. The pulp with the highest swelling after hydrolysis had the lowest swelling after drying. The mesopores that were formed in hydrolysis were somewhat preserved after drying. After drying, unfibrillated pulp had good fiber separation, while the highly fibrillated samples formed sub-millimeter, spherical particles.

AbstractThermoresponsive hydrogels based on ionic cellulose/chitosan are widely used various fields, such as smart windows and tissue engineering, while the effect of carbohydrate backbones of cellulose/chitosan on the thermal response and mechanical properties of hydrogels has received less attention so far. Herein, poly(2(dimethylamino)ethyl methacrylate) (PDMAEMA)-grafted cellulose sulfate (P-CS) and PDMAEMA-grafted chitosan sulfate (P-CHS) as research models are successfully synthesized through multi-step reactions. The P-CS and P-CHS polymers are further applied in crosslinked polyacrylamide networks, resulting in the P-CS and P-CHS hydrogels. Compared to P-CS hydrogels, P-CHS hydrogels could obviously block the transmission of visible light when the temperature is changed from 25 to 42 °C. In contrast to P-CHS hydrogels, the P-CS hydrogels change easily from soft and weak state to stiff and strong state according to their mechanical behaviors. These results indicate that different carbohydrate backbones of cellulose and chitosan should have caused distinct aggregation behaviors of corresponding P-CS and P-CHS hydrogels, which are accompanied by different light transmittance and mechanical properties.Graphical abstract Thermoresponsive hydrogels using PDMAEMA-grafted ionic cellulose sulfate (P-CS) and chitosan sulfate (P-CHS) are successfully prepared. Distinct carbohydrate backbone displayed different effects on the thermoresponsive and mechanical properties of hydrogels.