Cellulose nanofibrils (CNFs) in uniform diameter: Capturing the impact of carboxyl group on dispersion and Re-dispersion of CNFs suspensions

Pickering emulsions as an effective route for the preparation of bioactive composites: A study of nanocellulose/polyaniline particles with immunomodulatory effect

Several studies have reported on application of cellulose particles for stabilizing Pickering emulsions (PE). Here we employ an original approach that involves using these particles as a part of advanced composite colloids made of conducting polymer polyaniline (PANI) and cellulose nanocrystals (CNC) or nanofibrils (CNF). PANI/cellulose particles were prepared using oxidative polymerization of aniline in situ in the presence of CNC or CNF. The type and amount of celluloses (CNC vs CNF) and concentration of precursors (aniline monomer and oxidant) used in the reaction determined properties of the colloidal particles, such as size, morphology and content of PANI. The particles demonstrated intriguing biological characteristics, including no cytotoxicity, antibacterial activity against Staphylococcus aureus and Escherichia coli, antioxidant activity and related immunomodulatory activity. For the first time, such composites were used to successfully stabilize oil-in-water PE with undecane or capric/caprylic triglyceride oils. The properties of the emulsions were determined by the PANI/cellulose particles and oil used. The key finding of the study is the demonstrated ability of PANI/cellulose particles to stabilize PE, as well as the excellent antioxidant activity and ROS scavenging action originating from PANI presence, indicating potential of such systems for use in biomedicine, particularly for wound healing.

Compressible, anti-freezing, and ionic conductive cellulose/polyacrylic acid composite hydrogel prepared via AlCl3/ZnCl2 aqueous system as solvent and catalyst

From the perspective of environmental sustainability, introducing cellulose into ionic conductive hydrogel is an inevitable trend for the development of flexible conductive materials. We report a double-network cellulose/polyacrylic acid (Cel/PAA) composite hydrogel based on the dissolving of cellulose by AlCl3/ZnCl2 aqueous system. The Cel/PAA composite hydrogel consists of rigid cellulose chains and flexible polyacrylic acid, which synergistically realize the improvement of the mechanical properties. The AlCl3/ZnCl2 aqueous system not only serves as the green solvent for cellulose, but also the Al3+ and Zn2+ metal ions can be served as a catalyst to activate the initiator for polymerization of acrylic acid. Compared with pure cellulose hydrogel, the compression strain of the Cel/PAA composite hydrogel was significantly improved to 80 %, and its conductivity increased by 28.1 %. In addition, its compression stress was enhanced over 2 times than pure PAA hydrogel. The Cel/PAA composite hydrogel exhibits excellent anti-freezing (-45 °C), weight retention (90 %), and conductivity (2.70 S/m) properties, still maintaining transparency and storage stability in the extreme environment. This work presents a facile strategy to develop an ionic conductive cellulose-based composite hydrogel with good conductivity and mechanical properties, which shows potential for the application fields of flexible sensors and 3D-printing functional materials.

Chemistry of Hydroxypropyl Cellulose Oxidized by Two Selective Oxidants

Along with the increased usage of cellulose in the manufacture of novel materials, those of its derivatives that have good solubility in water or organic solvents have become increasingly important. In this study, hydroxypropyl cellulose (HPC), a cellulosic derivative with distinct features, was utilized to investigate how two of the most-selective oxidation methods currently available in the literature act on the constituent OH groups of both the side chain and the anhydroglycosidic unit in HPC. The oxidation reactions were carried out first using TEMPO, sodium hypochlorite, and sodium bromide, then sodium periodate (NaIO4), for 5 h. A combination of these two protocols was applied. The amount of aldehyde and number of carboxylic groups introduced after oxidation was determined, while the changes in the morphological features of oxidized HPC were, additionally, assessed. Furthermore, utilizing Fourier-transform infrared spectra, X-ray diffraction, and thermogravimetric studies, the chemical structure, crystallinity, and thermal stability of the oxidized HPC samples were examined and compared.

Influence of dispersion of fibrillated cellulose on the reinforcement of coated papers

The use of cellulose micro/nanofibrils (CMNFs) as reinforcement paper additive at industrial scale is delayed due to inconsistent results, suggesting a lack of proper consideration of some key parameters. The high influence of fibrillated nanocellulose dispersion has been recently identified as a key parameter for paper bulk reinforcement but it has not been studied for surface coating applications yet. This paper studies the effect of CMNF dispersion degree prior to their addition and during mixing with starch on the reinforcement of paper by coating. Results show that this effect depends on the type of CMNFs since it is related to the surface interactions. For a given formulation, a correlation is observed between the CMNF dispersion and the CMNF/starch mixing agitation with the rheology of the coating formulation which highly affects the paper properties. The optimal dispersion degree is different for each nanocellulose, but the best mechanical properties were always achieved at the lowest viscosity of the coating formulation. In general, the initial state of the nanocellulose 3D network, influences the mixing and smooth application of the coating and affects the reinforcement effect. Therefore, the CMNF industrial implementation in coating formulations will be facilitated by the on-line control of formulations prior to their surface application.

Recent advances in qualitative and quantitative characterization of nanocellulose-reinforced nanocomposites: A review

Nanocellulose has received immense consideration owing to its valuable inherent traits and impressive physicochemical properties such as biocompatibility, thermal stability, non-toxicity, and tunable surface chemistry. These features have inspired researchers to deploy nanocellulose as nanoscale reinforcement materials for bio-based polymers. A simple yet efficient characterization method is often required to gain insights into the effectiveness of various types of nanocellulose. Despite a decade of continuous research and booming growth in scientific publications, nanocellulose research lacks a measuring tool that can characterize its features with acceptable speed and reliability. Implementing reliable characterization techniques is critical to monitor the specifications of nanocellulose alone or in the final product. Many techniques have been developed aiming to measure the nano-reinforcement mechanisms of nanocellulose in polymer composites. This review gives a full account of the scientific underpinnings of techniques that can characterize the shape and arrangement of nanocellulose. This review aims to deliver consolidated details on the properties and characteristics of nanocellulose in biopolymer composite materials to improve various structural, mechanical, barrier and thermal properties. We also present a comprehensive description of the safety features of nanocellulose before and after being loaded within biopolymeric matrices.

Preparation of cellulose nanofibers from potato residues by ultrasonication combined with high-pressure homogenization

In this study, the preparation parameters of cellulose nanofibers from potato residues (PCNFs) by ultrasonication combined with high-pressure homogenization were optimized based on yield, zeta-potential and morphology. The optimal parameters were as follows: ultrasonic power of 125 W for 15 min and homogenization pressure of 40 MPa four times. The yield, zeta potential and diameter range of the obtained PCNFs were 19.81 %, -15.60 mV and 20-60 nm, respectively. Fourier transform infrared spectroscopy, X-ray diffraction and nuclear magnetic resonance spectroscopy results showed that part of the crystalline region of cellulose was destroyed, resulting in a decrease in crystallinity index from 53.01 % to 35.44 %. The maximum thermal degradation temperature increased from 283 °C to 337 °C. PCNFs suspensions were non-Newtonian fluids and exhibited rigid colloidal particle properties. In conclusion, this study provided alternative uses for potato residues generated from starch processing and showed great potential for various industrial applications of PCNFs.

Cellulose-based bio-adsorbent from TEMPO-oxidized natural loofah for effective removal of Pb(II) and methylene blue

Excessive discharge of inorganic and organic contaminants in water poses a serious threat to the ecosystems. However, most synthetic adsorbents lack cost-effectiveness in terms of preparation. Interestingly, loofah sponge (LS) was a natural absorbent that could effectively remove pollutions in wastewater, but its adsorption capacity is barely satisfactory. Herein, we present a novel strategy of TEMPO-oxidized loofah sponge (TOLS) to boost the adsorption performance of LS. The batch experiments demonstrated that the maximum removal capacity of TOLS for Pb(II) and methylene blue (MB) was 96.6 mg/g and 10.0 mg/g, respectively, which were 3.5 and 1.3 times that of pristine LS. Notably, the continuous-flow reaction testing of the mixed solution revealed that the elimination rate of Pb(II) and MB was still better than 90 % even after 16 h. Such excellent performance was benefit from the enhanced specific surface area and surface carboxyl content of TOLS. This work offers new insights into the rational development of multifunctional and inexpensive cellulose-based bio-adsorbents for wastewater remediation.