A versatile method for the surface tailoring of cellulose nanocrystal building blocks by acylation with functional vinyl esters

SI-ATRP grafting of polymers from polydopamine-modified cellulose nanocrystals

This work reports on the possibility of using polydopamine (PDA) as a tool to immobilize bromoisobutyryl moieties at the surface of cellulose nanocrystals (CNCs) and initiate Surface Intitiated Atom Transfer Radical Polymerization (SI-ATRP) reactions from these sites. Two different strategies based on i) the stepwise modification of the CNCs with dopamine (DA) and α-bromoisobutyryl bromide (BiBB) (Protocol 1) and ii) the one-step treatment of the CNCs with a mixture of DA and BiBB-modified DA (Protocol 2), were compared. Only the CNC particles treated according to Protocol 1 guaranteed efficient anchoring of the SI-ATRP initiating sites in our experimental conditions (with limited impact on the CNCs crystalline structure), the coated layer being leached out by certain solvents in the case of Protocol 2. The brominated particles displaying the best performances were subsequently tested as potential ATRP macroinitiators, using methyl methacrylate (MMA) and styrene (St) as model monomers. Polymer-grafted particles were successfully obtained, with a grafting density twice as high for Sty as for MMA, demonstrating the validity of this strategy.

Passive anti-leakage of blue light for phosphor-converted white LEDs with crystal nanocellulose materials

A phenomenon known as "blue-light leakage" caused by overheating pcW-LEDs has recently been identified, and it poses a risk to users. This study focuses on investigating and optimizing a solution to address this issue. To tackle the problem of overheating and blue light leakage, we explored the application of a specific thermochromic material called crystal nano cellulose (CNC). We introduced CNC inside the epoxy lens of white LEDs. Importantly, under standard conditions, CNC has a negligible impact on the optical properties of the output white light. However, when overheating conditions arise, leading to blue light leakage, the temperature increase triggers a darkening effect in CNC. This thermochromic behavior of CNC allows it to strongly absorb the blue light, resulting in a significant suppression of the output luminous flux. As a result, the lamp dims, which not only prevents the user's eyes from being exposed to harmful bluish light but also serves as an indicator of aging in the pcW-LED. By implementing CNC as a responsive material in the design of white LEDs, this study offers a practical and effective solution to mitigate the negative effects of blue-light leakage caused by overheating. This improvement enhances the safety and comfort of users while also providing an early warning system for the aging of pcW-LEDs.

Effect of Environment on Acetylated Cellulose Nanocrystal-Reinforced Biopolymers Films

Cellulose nanocrystals (CNCs) were acetylated to the various parametrised degrees of substitution (DS), determined through attenuated total reflection Fourier transform infrared spectroscopy (ATR–FTIR) and incorporated into alginate (ALG) and chitosan (CH) film-forming solutions. An investigation of morphology with scanning electron microscopy (SEM) revealed increased chemical compatibility with the CH matrix after acetylation, producing a smooth surface layer, while ALG mixed better with pristine CNCs. The ATR–FTIR analysis of films demonstrated inter-diffusional structural changes upon the integration of pristine/modified CNCs. Films were evaluated in terms of water contact angle (WCA), which decreased upon CNC addition in either of the biocomposite types. The H2O barrier assessed through applicative vapour transmission (WVT) rate increased with the CNC esterification in CH, but was not influenced in ALG. To evaluate the relationship between environmental humidity and mechanical properties, conditioning was applied for 48 h under controlled relative humidity (33%, 54% and 75%) prior to the evaluation of the mechanical properties and moisture content. It was observed that tensile strength was highest upon specimens being dry (25 ± 3 MPa for ALG, reinforced with neat CNCs, or 16 ± 2 MPa in the CH with CNCs, reacting to the highest DS), lowering with dewing, and the elongation at break exhibited the opposite. It is worth noting that the modification of CNCs improved the best base benchmark stress–strain performance. Lastly, (thermal) stability was assessed by means of the thermogravimetric analysis (TGA) technique, suggesting a slight improvement.

Polyester-Based Coatings for Corrosion Protection

The article is the first review encompassing the study and the applications of polyester-based coatings for the corrosion protection of steel. The impact of corrosion and the challenges encountered thus far and the solutions encountered in industry are addressed. Then, the use of polyesters as a promising alternative to current methods, such as phosphating, chromating, galvanization, and inhibitors, are highlighted. The classifications of polyesters and the network structure determine the overall applications and performance of the polymer. The review provides new trends in green chemistry and smart and bio-based polyester-based coatings. Finally, the different applications of polyesters are covered; specifically, the use of polyesters in surface coatings and for other industrial uses is discussed.

Recent Advances in Chemically Modified Cellulose and Its Derivatives for Food Packaging Applications: A Review

The application of cellulose in the food packaging field has gained increasing attention in recent years, driven by the desire for sustainable products. Cellulose can replace petroleum-based plastics because it can be converted to biodegradable and nontoxic polymers from sustainable natural resources. These products have increasingly been used as coatings, self-standing films, and paperboards in food packaging, owing to their promising mechanical and barrier properties. However, their utilization is limited because of the high hydrophilicity of cellulose. With the presence of a large quantity of functionalities within pristine cellulose and its derivatives, these building blocks provide a unique platform for chemical modification via covalent functionalization to introduce stable and permanent functionalities to cellulose. A primary aim of chemical attachment is to reduce the probability of component leaching in wet and softened conditions and to improve the aqueous, oil, water vapor, and oxygen barriers, thereby extending its specific use in the food packaging field. However, chemical modification may affect the desirable mechanical, thermal stabilities and biodegradability exhibited by pristine cellulose. This review exhaustively reports the research progress on cellulose chemical modification techniques and prospective applications of chemically modified cellulose for use in food packaging, including active packaging.

Lignocellulosic Biomass-Derived Nanocellulose Crystals as Fillers in Membranes for Water and Wastewater Treatment: A Review

The improvement of membrane applications for wastewater treatment has been a focal point of research in recent times, with a wide variety of efforts being made to enhance the performance, integrity and environmental friendliness of the existing membrane materials. Cellulose nanocrystals (CNCs) are sustainable nanomaterials derived from microorganisms and plants with promising potential in wastewater treatment. Cellulose nanomaterials offer a satisfactory alternative to other environmentally harmful nanomaterials. However, only a few review articles on this important field are available in the open literature, especially in membrane applications for wastewater treatment. This review briefly highlights the circular economy of waste lignocellulosic biomass and the isolation of CNCs from waste lignocellulosic biomass for membrane applications. The surface chemical functionalization technique for the preparation of CNC-based materials with the desired functional groups and properties is outlined. Recent uses of CNC-based materials in membrane applications for wastewater treatment are presented. In addition, the assessment of the environmental impacts of CNCs, cellulose extraction, the production techniques of cellulose products, cellulose product utilization, and their end-of-life disposal are briefly discussed. Furthermore, the challenges and prospects for the development of CNC from waste biomass for application in wastewater treatment are discussed extensively. Finally, this review unraveled some important perceptions on the prospects of CNC-based materials, especially in membrane applications for the treatment of wastewater.

Elaboration of capsules from Pickering double emulsion polymerization stabilized solely by cellulose nanocrystals

Pickering double oil-in-water-in-oil emulsions O/W/O were stabilized using solely cellulose nanocrystals (CNCs), which were modified by introducing surface brominated functions. The emulsions were formulated using only bio-friendly components, among which isopropyl myristate as oil phase, hydroxyl oligoethylene glycol methacrylate (OEGMA) as macromonomer, tetraethylene glycol diacrylate (TEGDA) as cross-linker, and CNCs as stabilizing particles. Formulation parameters could be tuned easily to modulate the fraction of inner emulsion droplets within the double emulsion drops or change the monomer(s) composition within the aqueous phase. The latter was further polymerized to synthesize matrix capsules. The obtained objects showed good resistance to the vacuum and were efficiently used as promising encapsulation vessels. Both hydrophobic and hydrophilic model dyes were encapsulated, with an encapsulation efficiency of about 90%.

Crystalline polysaccharides: A review

The biodegradability and mechanical properties of polysaccharides are dependent on their architecture (linear or branched) as well as their crystallinity (size of crystals and crystallinity percent). The amount of crystalline zones in the polysaccharide significantly governs their ultimate properties and applications (from packaging to biomedicine). Although synthesis, characterization, and properties of polysaccharides have been the subject of several review papers, the effects of crystallization kinetics and crystalline domains on the properties and application have not been comprehensively addressed. This review places focus on different aspects of crystallization of polysaccharides as well as applications of crystalline polysaccharides. Crystallization of cellulose, chitin, chitosan, and starch, as the main members of this family, were discussed. Then, application of the aforementioned crystalline polysaccharides and nano-polysaccharides as well as their physical and chemical interactions were overviewed. This review attempts to provide a complete picture of crystallization-property relationship in polysaccharides.

Hydrophobic functionalization reactions of structured cellulose nanomaterials: Mechanisms, kinetics and in silico multi-scale models

Nanoscale-interfaced cellulose nanomaterials are extracted from polysaccharides, which are widely available in nature, biocompatible and biodegradable. Moreover, the latter have a potential to be recycled, upcycled, and formulate therefore a great theoretical predisposition to be used in a number of applications. Nanocrystals, nano-fibrils and nanofibers possess reactive functional groups that enable hydrophobic surface modifications. Analysed literature data, concerning mechanisms, pathways and kinetics, was screened, compared and assessed with regard to the demand of a catalyst, different measurement conditions and added molecule reactions. There is presently only a scarce technique description for carbonOH bond functionalization, considering the elementary chemical steps, sequences and intermediates of these (non)catalytic transformations. The overview of the prevailing basic research together with in silico modelling approach methodology gives us a deeper physical understanding of processes. Finally, to further highlight the applicability of such raw materials, the review of the development in several multidisciplinary fields was presented.

Development of composite hydrogel based on hydroxyapatite mineralization over pectin reinforced with cellulose nanocrystal

Hydrogels based on pectin and cellulose nanocrystals (CNC) were used in our study to nucleation and growth of hydroxyapatite (HAp) by the biomimetic method. In this study, we evaluated the direct impact of the different percentages of CNC on pectin hydrogel and the influence of HAp obtained through two methods. CNC were obtained from HCl hydrolysis following chemical functionalization through vinyl groups. The percentage of CNC positively induces thermal stability, mechanical properties and HAp mineralization from biomimetic using simulated body fluid (1.5 SBF). Hydrogels with 5% of CNC showed a higher amount of HAp immersed for 14 days, about 28% of HAp. The obtained hydrogels were compared with hydrogels containing 20% of HAp nanoparticles obtained by chemical precipitation. Biocompatibility of the hydrogels was evaluated by cell viability using fibroblasts (L929). In general, the hydrogels obtained through the biomimetic method show slightly larger biocompatibility compared to the hybrid hydrogels obtained from chemical precipitation.

Improving the Anti-Pilling Performance of Cellulose Fiber Blended Knitted Fabrics with 2,4,6-Trichloropyrimidine Treatment

Pilling is a common and unresolved problem in knitted fabrics, especially for the cellulose fiber blended fabrics, which not only causes an unattractive appearance and an uncomfortable handle, but also reduces the added value of the products. In this study, four different kinds of knitted fabrics were treated with 2,4,6-trichloropyrimidine (TLP) alkaline emulsion by dipping and pad–dry–cure modification processes. The surface morphology and chemical structure of original and treated fabrics were characterized by scanning electron microscopy (SEM), Fourier transform infrared spectroscopy (FTIR) and X-ray diffraction (XRD). The anti-pilling performance, thermal properties, physical and mechanical properties and color features of treated fabrics were also evaluated. The results indicated that TLP was successfully covalently crosslinked onto the surface of the cellulose fibers. The dipping process resulted in a better anti-pilling property than that of the pad–dry–cure process, and both treatments could bring about an excellent anti-pilling property and outstanding laundering durability. A pilling grade of 4.5 was achieved for the treated polyester/viscose (T/V) fabric with the dipping process even after 20 washing cycles. In addition, the treated fabrics displayed an enhanced antistatic property and still maintained a soft handle. Besides, the bursting strength and air permeability of treated samples were found to have a slight deterioration, while no apparent differences were found in the color parameters and colorfastness of dyed fabrics. The above results demonstrate that 2,4,6-trichloropyrimidine has the potential application prospect in the functional finishing and home-caring of textiles.

Evaluation of esterification routes for long chain cellulose esters

Long chain cellulose esters are internally plasticized bio-based materials, which have good future potential in several applications such as coatings, films and plastics. The long chain cellulose esters with different side chain lengths were synthesized using different esterification methods. When homogeneous esterification was used, the acyl chloride method was the most effective esterification method and cellulose esters prepared using this method have the highest degree of substitution values (DS). In this case, the long chain cellulose esters showed DS values from 0.3 to 1.3 depending on the side chain length of cellulose esters. CDI activation, vinyl transesterification and anhydride routes resulted in somewhat lower DS values. The cellulose was also pretreated with ozone, which decreased cellulose molar mass, and resulted in synthesized cellulose esters having higher DS and better reaction efficiency than untreated cellulose. When heterogeneous esterifications were used, only acyl chloride method seemed to work.

Durable Antipilling Modification of Cotton Fabric with Chloropyrimidine Compounds

Cotton fabric, a natural cellulose material, is widely used in the textile industry for its excellent properties. However, its application in some fields are seriously restricted because of its poor antipilling behavior. In this study, cotton fabrics were modified with 2,4,6-trichloropyrimidine (TLP), 2,4-dichloro-5-methoxypyrimidine (DMP), and 2-amino-4,6-dichloropyridine (ADP). The surface morphology and chemical structure of the modified cotton fabric were characterized by scanning electron microscopy (SEM), Fourier transform infrared spectroscopy (FTIR), and X-ray diffraction (XRD). Furthermore, the antipilling behavior, dyeing properties, thermal properties, and mechanical properties of modified cotton fabric were evaluated. The results showed that chloropyrimidine compounds were successfully grafted onto the surface of the cotton fabric, leading to excellent and durable antipilling activity of grade 3-4 even after 10 washes. Moreover, compared with control cotton fabric, the heat release rate (HRR) and total heat release (THR) of TLP-modified cotton fabric decreased to 173.2 W/g (42.3% reduction) and 11.3 KJ/g (13.7% reduction), respectively. In addition, the increased K/S value of modified cotton fabrics dyed with reactive dyes indicated that the modification can enhance the dyability of cotton fabric. This technique provides a simple and versatile method for improving the antipilling behavior of cellulosic materials and supports further preparation of functional textiles.

Convenient Synthesis of Hybrid Polymer Materials by AGET-ATRP Polymerization of Pickering Emulsions Stabilized by Cellulose Nanocrystals Grafted with Reactive Moieties

We report a novel method to prepare capsules, beads, or open-cell materials from Pickering emulsions of monomers, stabilized by cellulose nanocrystals (CNCs) grafted with reactive isobutyrate bromide moieties (CNC-Br). CNC-Br particles with different hydrophilic/hydrophobic balance at their surface were prepared and subsequently used to stabilize direct (O/W), inverted (W/O), or double emulsions of styrene or n-BuA. The different emulsions obtained were subsequently polymerized, by initiating an AGET-ATRP polymerization from the brominated particles surrounding the stabilized droplets. The different hybrid polymer materials obtained were subsequently characterized, and the impact of the CNCs functionalization and polymerization conditions was particularly discussed.

Multifunctional Stimuli-Responsive Cellulose Nanocrystals via Dual Surface Modification with Genetically Engineered Elastin-Like Polypeptides and Poly(acrylic acid)

Cellulose nanocrystals (CNCs) are promising candidates for a myriad of applications; however, successful utilization of CNCs requires balanced and multifunctional properties, which require ever more applied concepts for supramolecular tailoring. We present here a facile and straightforward route to generate dual functional CNCs using poly(acrylic acid) (PAA) and biosynthetic elastin-like polypeptides (ELPs). We utilize thiol-maleimide chemistry and SI-ATRP to harvest the temperature responsiveness of ELPs and pH sensitivity of PAA to confer multifunctionality to CNCs. Cryo-TEM and light microscopy are used to exhibit reversible temperature response, while atomic force microscopy (AFM) provides detailed information on the particle morphology. The approach is tunable and allows variation of the modifying molecules, inspiring supramolecular engineering beyond the currently presented motifs. The surge of genetically engineered peptides adds further possibilities for future exploitation of the potential of cellulose nanomaterials.

Current characterization methods for cellulose nanomaterials

A new family of materials comprised of cellulose, cellulose nanomaterials (CNMs), having properties and functionalities distinct from molecular cellulose and wood pulp, is being developed for applications that were once thought impossible for cellulosic materials. Commercialization, paralleled by research in this field, is fueled by the unique combination of characteristics, such as high on-axis stiffness, sustainability, scalability, and mechanical reinforcement of a wide variety of materials, leading to their utility across a broad spectrum of high-performance material applications. However, with this exponential growth in interest/activity, the development of measurement protocols necessary for consistent, reliable and accurate materials characterization has been outpaced. These protocols, developed in the broader research community, are critical for the advancement in understanding, process optimization, and utilization of CNMs in materials development. This review establishes detailed best practices, methods and techniques for characterizing CNM particle morphology, surface chemistry, surface charge, purity, crystallinity, rheological properties, mechanical properties, and toxicity for two distinct forms of CNMs: cellulose nanocrystals and cellulose nanofibrils.

Mechanical and dielectric properties of crystalline poly(arylene ether nitrile) copolymers

Poly(arylene ether nitrile) (PEN) copolymers (HQ/RS-PEN) containing different proportions of hydroquinone (HQ-PEN) block and resorcinol (RS-PEN) block were synthesized, and their crystalline, mechanical, and dielectric properties were investigated. Three HQ/RS-PEN copolymers with 10%, 20%, and 30% of RS-PEN blocks were prepared via condensation polymerization of HQ and RS with 2,6-dichlorobenzonitrile. The PEN copolymers were characterized and confirmed by Fourier transform infrared spectroscopy, intrinsic viscosity, and thermal analyses. With the addition of RS-PEN block, the flexibility of PEN copolymers was increased. In addition, even though the high loading content of RS-PEN block was incorporated, the PEN copolymers still exhibited relatively high dielectric constant, whereas the dielectric loss decreased. Furthermore, to investigate the effect of treatment time and temperature on the physical properties of crystalline PEN copolymers, HQ/RS-PEN20 was isothermally treated at different temperatures (280°C, 300°C, 310°C, 320°C, and 330°C) for a constant time and at a constant time for different hours (1, 2, 3, 4, and 5 h). After the optimization of the crystallization of HQ/RS-PEN polymer, excellent mechanical and dielectric properties of copolymers were obtained. The results showed that when isothermally treated at 320°C for 2 h, the HQ/RS-PEN20 showed optimal properties of tensile strength of 117.6 MPa and dielectric constant of 4.07 at 1 kHz.

A new strategy to elaborate polymer composites via Pickering emulsion polymerization of a wide range of monomers

We report a novel strategy to prepare polymer composites reinforced with cellulose nanocrystals (CNCs) via Pickering emulsion polymerization.

Mussel-Inspired Fabrication of Konjac Glucomannan/Poly (Lactic Acid) Cryogels with Enhanced Thermal and Mechanical Properties

Three-dimensional nanofibers cryogels (NFCs) with both thermally-tolerant and mechanically-robust properties have potential for wide application in biomedical or food areas; however, creating such NFCs has proven to be extremely challenging. In this study, konjac glucomannan (KGM)/poly (lactic acid) (PLA)-based novel NFCs were prepared by the incorporation of the mussel-inspired protein polydopamine (PDA) via a facile and environmentally-friendly electrospinning and freeze-shaping technique. The obtained KGM/PLA/PDA (KPP) NFCs were characterized by field emission scanning electron microscopy (FE-SEM), Fourier transform infrared spectroscopy (FTIR), X-ray diffraction (XRD), thermogravimetric analysis (TGA), differential scanning calorimetry (DSC) and compressive and tensile test. The results showed that the hierarchical cellular structure and physicochemical properties of KPP NFCs were dependent on the incorporation of PDA content. Moreover, the strong intermolecular hydrogen bond interactions among KGM, PLA and PDA also gave KPP NFCs high thermostability and mechanically-robust properties. Thus, this study developed a simple approach to fabricate multifunctional NFCs with significant potential for biomedical or food application.

Synthesis of surfactant-free micro- and nanolatexes from Pickering emulsions stabilized by acetylated cellulose nanocrystals

Surfactant-free micro- and nanolatexes from Pickering emulsions stabilized by acetylated cellulose nanocrystals (CNCs).