Material design of nanocellulose/polymer composites via Pickering emulsion templating

Nanocellulose-stabilized nanocomposites for effective Hg(II) removal and detection: a comprehensive review

Mercury pollution, with India ranked as the world's second-largest emitter, poses a critical environmental and public health challenge and underscores the need for rigorous research and effective mitigation strategies. Nanocellulose is derived from cellulose, the most abundant natural polymer on earth, and stands out as an excellent choice for mercury ion remediation due to its remarkable adsorption capacity, which is attributed to its high specific surface area and abundant functional groups, enabling efficient Hg(II) ion removal from contaminated water sources. This review paper investigates the compelling potential of nanocellulose as a scavenging tool for Hg(II) ion contamination. The comprehensive examination encompasses the fundamental attributes of nanocellulose, its diverse fabrication techniques, and the innovative development methods of nanocellulose-based nanocomposites. The paper further delves into the mechanisms that underlie Hg removal using nanocellulose, as well as the integration of nanocellulose in Hg detection methodologies, and also acknowledges the substantial challenges that lie ahead. This review aims to pave the way for sustainable solutions in mitigating Hg contamination using nanocellulose-based nanocomposites to address the global context of this environmental concern.

Rheology of cellulose nanocrystal and nanofibril suspensions

Nanocellulose is a sustainable nanomaterial and a versatile green platform that has attracted increasing attention. Although the wide applications of its aqueous suspensions are closely related to rheology, comprehensive studies of their rheological behavior, especially the yielding behavior, are still limited. Herein, to investigate the relationship between structure and rheological properties, the viscoelasticity, thixotropy and yielding behavior of two commonly used nanocelluloses, rod-shaped cellulose nanocrystals (CNCs) and filamentous cellulose nanofibrils (CNFs), were systematically investigated. The viscosity, viscoelasticity and thixotropic behavior of the suspensions were analyzed by steady-state shear, frequency sweep, creep-recovery, hysteresis loop, and three-interval thixotropic recovery tests. The yielding behaviors were evaluated through creep, steady-state shear, step shear rate, stress ramps, amplitude sweep, and large amplitude oscillatory shear tests. The rheological properties of the two typical suspensions showed a strong dependence on concentration and time. However, compared to CNC suspensions, CNF suspensions exhibited stronger thixotropy and higher yield stress due to the higher aspect ratio of CNF and the stronger structural skeleton of the suspensions as supported by Simha's equation and micromorphology analysis. This work provides a theoretical rheology basis for the practical applications of nanocellulose suspensions in various fields.

Structured Emulgels by Interfacial Assembly of Terpenes and Nanochitin

Interfacial assemblies formed by colloidal complexation are effective in multiphase stabilization, as shown in structured liquids and Pickering emulgels. Herein, we demonstrate a type of biobased colloidal system that spontaneously stabilizes an organic phase in a continuous hydrogel phase. Specifically, a triterpene extracted from bark (betulin, BE) is added to an organic phase containing a coniferous resin (rosin acid, a diterpene). BE is shown to take part in strong noncovalent interactions with the nanochitin dispersed in the aqueous (hydrogel) phase, leading to a complex of high interfacial activity. The viscoelastic response of the system is rationalized by the presence of a superstable structured dual network. When used as a templating material, the emulgel develops into structured liquids and cryogels. The herein introduced all-biobased type of nanoparticle surfactant system forms a gel ("emulsion-filled" with "aggregated droplets") that features the functional benefits of both betulin and nanochitin.

Tough and strong sustainable thermoplastic elastomers nanocomposite with self-assembly of SI-ATRP modified cellulose nanofibers

The ingenious design of sustainable thermoplastic elastomers (STPEs) is of great significance for the goal of the sustainable development. However, the preparation of STPEs with good mechanical performance is still complicated and challenging. Herein, to achieve a simple preparation of STPEs with strong mechanical properties, two biobased monomers (tetrahydrofurfuryl methacrylate (THFMA) and lauryl methacrylate (LMA)) were copolymerized into poly (THFMA-co-LMA) (PTL) and grafted onto TEMPO oxidized cellulose nanofiber (TOCN) via one-pot surface-initiated atom transfer radical polymerization (SI ATRP). The grafting modified TOCN could be self-assembled into nano-enhanced phases in STPEs, which are conducive to the double enhancement of the strength and toughness of the STPEs, and the size of nano-enhanced phases is mainly affected by TOCN fiber length and molecular weight of grafting chains. Especially, with the addition of 7 wt% TOCN, tensile strength, tensile strain, toughness, and glass transition temperature (Tg) of TOCN based STPEs (TOCN@PTL) exhibited 140 %, 36 %, 215 %, and 6.8 °C increase respectively, which confirmed the leading level in the field of bio-based elastomers. In general, this work constitutes a proof for the chemical modification and self-assembly behavior of TOCN by one-pot SI ATRP, and provides an alternative strategy for the preparation of high-performance STPEs.

Advances in Organic-Inorganic Hybrid Latex Particles via In Situ Emulsion Polymerization

Hybrid latex particles combine the unique properties of inorganic nano/micro particles with the inherent properties of polymers, exhibiting tremendous potential for a variety of applications. Recent years have witnessed an increased interest in the design and preparation of hybrid latex particles with well-defined size, structure and morphology. Due to its simplicity, versatility and environmental friendliness, the in situ (Pickering) emulsion polymerization has been demonstrated to be a powerful approach for the large-scale preparation of hybrid latex particles. In this review, the strategies and applications of in situ (Pickering) emulsion polymerization for the preparation of hybrid latex particles are systematically summarized. A particular focus is placed on the strategies for the preparation of hybrid latex particles with enhanced properties and well-defined core-shell, yolk-shell, multinuclear, raspberry-like, dumbbell-shaped, multipod-like or armored morphologies. We hope that the considerable advances, examples and principles presented in this review can motivate future contributions to provide a deeper understanding of current preparation technologies, develop new processes, and enable further exploitation of hybrid latex particles with outstanding characteristics and properties.

Challenges associated with cellulose composite material: Facet engineering and prospective

Cellulose is the most abundant polysaccharide on earth. It has a large number of desirable properties. Its low toxicity makes it more useful for a variety of applications. Nowadays, its composites are used in most engineering fields. Composite consists of a polymer matrix and use as a reinforcing material. By reducing the cost of traditional fibers, it has an increasing demand for environment-friendly purposes. The use of these types of composites is inherent in moisture absorption with hindered natural fibers. This determines the reduction of polymer composite material. By appropriate chemical surface treatment of cellulose composite materials, the effect could be diminished. The most modern and advanced techniques and methods for the preparation of cellulose and polymer composites are discussed here. Cellulosic composites show a reinforcing effect on the polymer matrix as pointed out by mechanical characterization. Researchers tried their hard work to study different ways of converting various agricultural by-products into useful eco-friendly polymer composites for sustainable production. Cellulose plays building blocks, that are critical for polymer products and their engineering applications. The most common method used to prepare composites is in-situ polymerization. This help to increase the yields of cellulosic composites with a significant enhancement in thermal stability and mechanical properties. Recently, cellulose composites used as enhancing the incorporation of inorganic materials in multi-functional properties. Furthermore, we have summarized in this review the potential applications of cellulose composites in different fields like packaging, aerogels, hydrogels, and fibers.

Utilization of different wood-based microfibril cellulose for the preparation of reinforced hydrophobic polymer composite films via Pickering emulsion: A comparative study

Pickering emulsion is a promising strategy for the preparation of hydrophobic polymer composite using hydrophilic nanocellulose. Herein, two types of microfibril cellulose, pure mechanical pretreated microfibril cellulose (P-MFC) and Deep eutectic solvents pretreated microfibril cellulose (DES-MFC), were used to fabricate reinforced hydrophobic polystyrene (PS) composites (MFC/PS) with the aid of Pickering emulsion. The results showed that both oil/water ratio and the content as well as surface hydrophilicity of MFC were playing an important role in emulsifying capacity. 8 % MFC/PS emulsion showed the smallest and most uniform emulsion droplets which is similar to nanofibril cellulose (NFC)/PS at the oil/water ratio of 3:1. The mechanical performance of MFC/PS composites verified that the reinforcement effect was closely related to the emulsifying capacity of MFC. Specially, when the content of P-MFC was 8 wt%, the composite exhibited the best mechanical properties with the tensile strength of 44.7 ± 4.4 MPa and toughness of 1162 ± 52.8 kJ/m³ and Young's modulus of 13.5 ± 0.8 GPa, which was comparable to NFC/PS composite. Moreover, the effective enhancement role of P-MFC in hydrophobic polymethyl methacrylate and polycarbonate composites were also realized via Pickering emulsion strategy. Overall, this work constituted a proof of concept of the potential application of P-MFC in nano-reinforced hydrophobic composite.

Thermoformable and transparent one-component nanocomposites based on surface grafted cellulose nanofiber

One-component nanocomposites based on poly(methyl methacrylate)(PMMA) and polystyrene (PS) grafted cellulose nanofiber (CNF) with high polymer graft percentage were fabricated. At relative ambient conditions, less active vinyl monomer, MMA, and styrene were grafted from CNF via surface-initiated Cu(0)-mediated reversible deactivation radical polymerizations (RDRP), and PMMA/PS grafted CNFs could reach a graft percentage as high as 7550 % and 3530 %, respectively. The one-component composite films were manufactured by simple hot-pressing subsequentially. Optical transparency, thermal stability, and glass transition temperature of one-component nanocomposites were enhanced dramatically in contrast with the bicomponent nanocomposite. The uniform fracture surface confirmed the uniform dispersity by morphological observation. Mechanical tests indicated that break elongation and tensile strength ascended notably, and tensile modulus slightly descended as the graft percentage increased for PS and PMMA grafted CNF one-component composite. It was concluded that for glassy graft chains, obtaining one-component nanocomposites with high enough graft chain length was essential to achieve moderated mechanical performance without compromising optical properties and thermal manufacturing ability.

Spherical Cellulose Micro and Nanoparticles: A Review of Recent Developments and Applications

Cellulose, the most abundant natural polymer, is a versatile polysaccharide that is being exploited to manufacture innovative blends, composites, and hybrid materials in the form of membranes, films, coatings, hydrogels, and foams, as well as particles at the micro and nano scales. The application fields of cellulose micro and nanoparticles run the gamut from medicine, biology, and environment to electronics and energy. In fact, the number of studies dealing with sphere-shaped micro and nanoparticles based exclusively on cellulose (or its derivatives) or cellulose in combination with other molecules and macromolecules has been steadily increasing in the last five years. Hence, there is a clear need for an up-to-date narrative that gathers the latest advances on this research topic. So, the aim of this review is to portray some of the most recent and relevant developments on the use of cellulose to produce spherical micro- and nano-sized particles. An attempt was made to illustrate the present state of affairs in terms of the go-to strategies (e.g., emulsification processes, nanoprecipitation, microfluidics, and other assembly approaches) for the generation of sphere-shaped particles of cellulose and derivatives thereof. A concise description of the application fields of these cellulose-based spherical micro and nanoparticles is also presented.

Antifungal features and properties of chitosan/sandalwood oil Pickering emulsion coating stabilized by appropriate cellulose nanofiber dosage for fresh fruit application

A novel composite edible coating film was developed from 0.8% chitosan (CS) and 0.5% sandalwood oil (SEO). Cellulose nanofibers (CNFs) were used as a stabilizer agent of oil-in-water Pickering emulsion. We found four typical groups of CNF level-dependent emulsion stabilization, including (1) unstable emulsion in the absence of CNFs; (2) unstable emulsion (0.006-0.21% CNFs); (3) stable emulsion (0.24-0.31% CNFs); and (4) regular emulsion with the addition of surfactant. Confocal laser scanning microscopy was performed to reveal the characteristics of droplet diameter and morphology. Antifungal tests against Botrytis cinerea and Penicillium digitatum, between emulsion coating stabilized with CNFs (CS-SEOpick) and CS or CS-SEO was tested. The effective concentration of CNFs (0.24%) may improve the performance of CS coating and maintain CS-SEO antifungal activity synergistically confirmed with a series of assays (in vitro, in vivo, and membrane integrity changes). The incorporation of CNFs contributed to improve the functional properties of CS and SEO-loaded CS including light transmission at UV and visible light wavelengths and tensile strength. Atomic force microscopy and scanning electron microscopy were employed to characterize the biocompatibility of each coating film formulation. Emulsion-CNF stabilized coating may have potential applications for active coating for fresh fruit commodities.

3D-Printable Nanocellulose-Based Functional Materials: Fundamentals and Applications

Nanomaterials obtained from sustainable and natural sources have seen tremendous growth in recent times due to increasing interest in utilizing readily and widely available resources. Nanocellulose materials extracted from renewable biomasses hold great promise for increasing the sustainability of conventional materials in various applications owing to their biocompatibility, mechanical properties, ease of functionalization, and high abundance. Nanocellulose can be used to reinforce mechanical strength, impart antimicrobial activity, provide lighter, biodegradable, and more robust materials for packaging, and produce photochromic and electrochromic devices. While the fabrication and properties of nanocellulose are generally well established, their implementation in novel products and applications requires surface modification, assembly, and manufacturability to enable rapid tooling and scalable production. Additive manufacturing techniques such as 3D printing can improve functionality and enhance the ability to customize products while reducing fabrication time and wastage of materials. This review article provides an overview of nanocellulose as a sustainable material, covering the different properties, preparation methods, printability and strategies to functionalize nanocellulose into 3D-printed constructs. The applications of 3D-printed nanocellulose composites in food, environmental, and energy devices are outlined, and an overview of challenges and opportunities is provided.