Cellulose Films Research Articles

Dissolution and regeneration of cellulose using superbase-based dicarboxylic ionic liquids with tailored amphiphilicity

The processes of dissolving and regenerating cellulose are crucial for transforming cellulose into products with added value. Due to the cellulose’s inherent amphiphilic characteristics, both its dissolution and the physical and mechanical properties of the regenerated materials can vary depending on the amphiphilicity of solvent used. Innovative solvent designs that offer precise manipulation of these processes are key in developing regenerated materials with specific desired properties. Here we show that modifying the amphiphilicity of superbase-based ionic liquids (SILs) with dicarboxylates allows for the control of the solubility, crystal structure and film-forming capability of cellulose. Notably, the solubility of microcrystalline cellulose (MCC) in the optimized SILs can exceed 10 wt% at 95 °C. In addition, regenerated cellulose films (RCFs) with a lower (1–10) crystal plane-oriented structure from SIL solution, using water as coagulation bath, possess not only exceptional mechanical properties (tensile strength: 103.63 MPa, elongation at break: 11.89 %), but also transparency (ca. 90 % under visible light) and flexibility. We anticipate that the tailored amphiphilicity design of SILs in this study offers a promising and effective solution for dissolution, modification, and reconstruction of cellulose materials.

Indicative bacterial cellulose films incorporated with curcumin-embedded Pickering emulsions: Preparation, antibacterial performance, and mechanism

Biodegradable, sustainable, and multifunctional intelligent food packaging has attracted extensive attention due to the concerns about the environmental pollution, the health hazard, and the food safety of plastic packaging. Herein, a multifunctional bacterial cellulose (BC)-based film (termed BC-PE-Cur) was fabricated for intelligent food packaging. The film was simply prepared by vacuum filtration and compression of a mixture of the BC and the curcumin (Cur)-embedded Pickering emulsion (PE) stabilized with the natural protein-polysaccharide hybrid nanoparticles (PPH NPs). The Pickering emulsion droplets containing Cur were uniformly distributed within the film and adhered to the film surface, resulting in a uniform dispersion of Cur in the film, and a thicker, rougher film with a laminated pore structure. The BC-PE-Cur film showed excellent antibacterial, antioxidant, UV-shielding, water vapor barrier, and mechanical properties. BC-PE-Cur film can extend the shelf life of basa fish by delaying the lipid peroxidation and inhibiting the growth of spoilage microorganisms. Moreover, during the storage of basa fish, BC-PE-Cur films underwent significant color change due to the production of alkaline substances, which could indicate the freshness of basa fish. This study provides an attractive strategy to construct multifunctional smart bio-based composite films containing non-water-soluble active ingredients for food packaging and freshness monitoring.

In-situ synthesis of zinc oxide-tannic acid-waste bagasse with antibacterial activity as multifunctional additive for packaging film

The resource utilization of waste bagasse (SB) is a green and effective solution to reduce environmental pollution. However, traditional methods for recycling of bagasse have the technical bottlenecks, including, secondary pollution, low efficiency, high cost and small production scale. Here, we develop a novel mechanical activation technology to convert SB in situ into zinc oxide-tannic acid-SB (ZnO-TA-SB) with antibacterial activity as multifunctional additives for packaging films. Unlike traditional methods that demand harsh reaction conditions, this novel strategy for the resource utilization of SB is convenient, green, efficient and large-scale. The results show that the bactericidal activities of ZnO-TA-SB against E. coli and S. aureus are >99 %, confirming the strong spectral antibacterial activity of ZnO-TA-SB. With the addition of ZnO-TA-SB to carboxymethyl cellulose (CMC) film, the tensile strength, elongation at break, O2 barrier property of ZnO-TA-SB/CMC film are increased by 1.43, 2.49, 2.09 times compared with CMC film, respectively. Furthermore, ZnO-TA-SB/CMC film effectively keeps the appearance and freshness of strawberries for more than 18 days. Notably, ZnO-TA-SB/CMC film is easily degraded in soil and used as a nutrient for crop growth without secondly pollution. Therefore, this work develops a new strategy for the resource utilization of waste biomass, and obtains green, clean and high-value products from waste biomass.

Wood cellulose films with different foldabilities triggered by dissolution and regeneration from concentrated H2SO4 and NaOH/urea aqueous solutions

Forests are a major source of wealth for Canadians, and cellulose makes up the “skeleton” of wood fibers. Concentrated H2SO4 and NaOH/urea aqueous solutions are two efficient solvents that can rapidly dissolve cellulose. Our preliminary experiment obtained regenerated wood cellulose films with different mechanical properties from these two solvents. Therefore, herein, we aim to investigate the effects of aqueous solvents on the structure and properties of wood cellulose films. Regenerated cellulose (RC) films were produced by dissolving wood cellulose in either 64 wt% H2SO4 solution (RC-H4) or NaOH/urea aqueous solution (RC-N4). RC-H4 showed the higher tensile strength (109.78 ± 2.14 MPa), better folding endurance (20–28 times), and higher torsion angle (42°) than RC-N4 (62.90 ± 2.27 MPa, un-foldable, and 12°). The increased cellulose contents in the H2SO4 solutions from 3 to 5 wt% resulted in an improved tensile strength from 102.61 ± 1.99 to 132.93 ± 5.64 MPa and did not affect the foldability. RC-H4 also exhibited better water vapor barrier property (1.52 ± 0.04 × 10−7 g m−1 h−1 Pa−1), superior transparency (~90 % transmittance at 800 nm), but lower thermal stability compared to RC-N4. This work provides special insights into the regenerated wood cellulose from two aqueous solvents and is expected to facilitate the development of high-performance RC films from abundant forestry resources.

In situ alkali‐free growth of octahedral Ag2O nanoparticles by bacterial cellulose for efficient antibacterial application

AbstractUniform octahedral Ag2O nanoparticles were in situ synthesized within natural bacterial cellulose (BC) films without any inorganic alkali. The morphological transformation of Ag2O from nanoparticles and small nanoplates to an octahedral structure was well controlled by varying the UV exposure time. To reduce and anchor Ag2O nanoparticles, abundant hydroxyl groups on the surface of natural BC fibers ensured an ideal environment for the mild redox reaction between Ag+ and –OH groups. The structural features and structure–activity relationship of Ag2O/BC films were confirmed through TEM, energy dispersive spectroscopy assisted SEM analysis, Fourier transform IR, X‐ray photoelectron spectroscopy, TGA and XRD. The structure–antibacterial activity relationship of the Ag2O/BC films was proved against both Gram‐positive (Staphylococcus aureus) and Gram‐negative (Escherichia coli) bacteria. They also showed excellent performance in the photocatalytic degradation of organic dyes. Ag2O/BC films have potential bactericidal applications in the field of pharmacy, specifically for wound dressing and flexible wearable materials. © 2024 Society of Chemical Industry.

Flexible Ag-AgCl/TiO2/cellulose biocomposite film for solar photocatalytic degradation of VOCs

Photocatalyst immobilization on biopolymers presents a promising avenue for air purification, yet achieving efficient immobilization and purification methods remains a challenge. In this study, we develop a novel, straightforward sequential coating technique to fabricate cellulose film embedded with uniformly dispersed TiO2 submicrospheres and Ag-AgCl nanoparticles (NPs), tailored for effective indoor air purification under sunlight exposure. The obtained Ag-AgCl/TiO2/cellulose film exhibit remarkable photocatalytic prowess in degrading various volatile organic compounds (VOCs, including ethanol, 1-propanol, 1-butanol, propylamine, and propanethiol) under simulated sunlight, owing to the enhanced separation of charge carriers facilitated by the presence of plasmonic Ag-AgCl NPs. Notably, the nature of the functional groups and the carbon atom count within the VOCs molecular structures exert significant influence on the overall photocatalytic performance. Furthermore, our investigation into the reusability of this biocomposite film confirms its durability, particularly in mineralizing alcoholic compounds during VOC oxidization, and the deactivation primarily occurs with VOCs containing heteroatoms that can be residual on biocomposite surface. This study represents a significant step towards practical applications of biocomposite films with efficient photocatalytic activities for real-world air purification and environmental remediation.

Structure Formation by 3D-Printing of Cellulose from Cellulose-NMMO-Water Solutions: Analysis of Extrusion, Regeneration, and Drying Stages.

Processing cellulose from 4-methyl morpholine n-oxide (NMMO)-water solutions is a completely circular route that produces biodegradable cellulose fibers or films while recovering reusable NMMO [Guo, Y.; Cai, J.; Sun, T.; Xing, L.; Cheng, C.; Chi, K.; Xu, J.; Li, T. The purification process and side reactions in the N-methylmorpholine-N-oxide (NMMO) recovery system. Cellulose 2021, 28(12), 7609-7617]. Despite proven success in two-dimensional applications, challenges in transitioning to three-dimensional objects arise from the critical changes that cellulose undergoes during deposition, regeneration, and postregeneration stages. While emphasizing the critical diffusion-driven precipitation during regeneration, this investigation explores the influence of extrusion temperature, printing alignment, regeneration, and drying processes on interfilament fusion, bonding, shape integrity, and mechanical properties. Three distinct drying processes: ambient, vacuum, and freeze-drying were investigated. Tensile and flexural bending tests provided insight into the delamination of dried specimens. Ambient and vacuum drying enhanced the properties of specimens, while freeze-drying resulted in a more stable shape. The findings contribute to advancing the understanding of 3D-printing cellulose from NMMO solutions, addressing crucial aspects of the extrusion, regeneration, and drying stages for enhanced applications in sustainable manufacturing.

Development and characterization of cellulose‐based smart films extracted from coconut waste

AbstractThe increasing demands for safe and quality packaged food have diverted all the intentions toward the enhancement of hazard detection and quantification techniques. The integration of smart functions with the novel biomaterials‐based packaging provides an effective approach to deal with the uplifting concerns of food safety and environmental pollution. In the current study, firstly the cellulose was extracted from coconut waste, then it was subjected to prepare biodegradable films and lastly the films were incorporated with curcumin or quercetin dihydrate. The films were characterized for their mechanical, barrier and smart properties. The incorporation of curcumin or quercetin dihydrate improved the physicochemical properties of the cellulose films, including strength, elongation at break (EAB), water vapor permeability (WVP), biodegradability, antioxidant and antimicrobial activity. However, the moisture content and water solubility decreased. The scanning electron microscopy (SEM) images depicted the rough surface of curcumin incorporated smart films which represents successful application of curcumin, while cracks and pits were observed for the films with the higher concentration of quercetin dihydrate. All the smart films showed effective responses against pH ranging from 2 to 14.

Dialdehyde cellulose films covalently crosslinked with porphyrin-based covalent organic polymers for photodynamic sterilization

Foodborne pathogens result in a great harm to human, which is an urgent problem to be addressed. Herein, a novel cellulose-based packaging films with excellent anti-bacterial properties under visible light were prepared. A porphyrin-based covalent organic polymer (Por-COPs) was constructed, then covalently grafted onto dialdehyde cellulose (DAC). The addition of Por-COPs enhanced the mechanical, hydrophobicity, and water resistance of the DAC-based composite films. DAC/Por-COP-2.5 film exhibited outstanding properties for the photodynamic inactivation of bacteria under visible light irradiation, delivering inactivation efficiencies of 99.90 % and 99.45 % towards Staphylococcus aureus and Escherichia coli within 20 min. The DAC/Por-COPs films efficiently generated •O2− and 1O2 under visible light, thereby causing oxidative stress to cell membranes for bacterial inactivation. The prepared composite film forms a protective barrier against bacterial contamination. Results guide the development of high performance and more sustainable packaging films for the food sector.

Preparation of benzothiocyanine‐carboxymethyl cellulose composite film and its antimicrobial properties

AbstractCellulose has a wide range of uses. It could be modified to create cellulose‐based hydrophobic materials and cellulose‐based conductive and stable flexible films, but it did not have antibacterial properties and was susceptible to bacterial erosion. In order to improve the utilization of cellulose materials and broaden the application of cellulose materials, cellulose could be given certain antibacterial properties by combining it with antimicrobial agents. This study focused on creating an organic antimicrobial agent, Benzothiocyanine (TCMTB), from CH2ClBr, and then developing a TCMTB‐CMC composite antimicrobial film by combining TCMTB with CMC. The successful synthesis of TCMTB was confirmed through NMR hydrogen spectroscopy testing. By varying the proportions of TCMTB in CMC, three types of composite antimicrobial cellulose film were produced. The study also assessed the impact of TCMTB on the mechanical strength of CMC film and tested the antimicrobial effectiveness of the composite film using the plate counting method. Results showed that the composite film had high inhibition rates, with 96.2% against Escherichia coli and 98.6% against Staphylococcus aureus. To establish a theoretical foundation for its use in seed encapsulation, leather preservation, and other applications.

A strategy to prolong cheese shelf-life: Laminated films of bacterial cellulose and chitosan loaded with grape bagasse antioxidant extract for effective lipid oxidation delay

This study presents an innovative approach to developing bioactive composite films for food packaging applications. Laminated films composed of bacterial cellulose (BC) and chitosan were enriched with grape bagasse extract (GE) and glycerol. GE provides antioxidant capacity. Glycerol was added as plasticizer. The formulations were systematically varied to assess their mechanical and thermal properties. The assembly of the films demonstrated robust interaction between components, resulting in enhanced mechanical strength. Tensile tests revealed that GE and glycerol concentrations significantly influenced the tensile strength and elongation properties Films were obtained with Tensile Strength values that ranged between 16.92 and 32.71 MPa, but with an increase of up to 4 times in the percentage of elongation (from 2.33 to 8.63%) compared to films without GE. Puncture tests indicated that the incorporation of GE and glycerol played pivotal roles in improving puncture resistance. Predictive models were developed for better understanding. The laminated films were applied as separators for Havarti cheese, demonstrating their ability to mitigate lipid oxidation and maintaining antioxidant properties during storage. After 60 days of cheese storage, 67.3% decrease in the lipid oxidation was obtained. The findings suggest that laminated BC-chitosan films enriched with GE and glycerol could serve as effective, eco-friendly packaging materials with enhanced mechanical strength and antioxidant functionality for extending the shelf life of food products.

Cellulose-based film with stable fluorescent, antibacterial, and UV-shielding performance fabricated via Biginelli reaction and enamine functionalization

Cellulosic multifunctional films offer extensive versatility and hold potential for diverse applications across multiple domains. However, the majority of cellulose-based multifunctional film studies have indicated issues with inadequate stability and consistency. Herein, a cellulose-based multifunctional film with exceptional stability was fabricated using multiple chemical modifications. Firstly, the solvent exchange method was used to prepare a cellulose acetoacetate (CAA) hydrogel film. Then, the fluorescent group and gentamicin sulfate (antibacterial group) were bonded to the CAA hydrogel film through Biginelli reaction and the formation of enamine bond, respectively. The resulting film exhibited photoluminescent, high transparency (above 80%), UV-shielding (blocking 90.9% UVA), and antibacterial properties, which are also very stable to external solvents. Hence, the multifaceted films made from cellulose displayed immense promise in various areas including eco-friendly packaging for perishables, ensuring authenticity, and in manufacturing unique types of films.

Antimicrobial topical polymeric films loaded with Acetyl-11-keto-β-boswellic acid (AKBA), boswellic acid and silver nanoparticles: Optimization, characterization, and biological activity

The study examined the antimicrobial and antioxidant potential of pure Acetyl-11-keto-β-boswellic acid (AKBA), boswellic acid (70%) and AKBA loaded nanoparticles as topical polymeric films. The optimized concentration (0.05 % w/v) of pure AKBA, boswellic acid (BA), and AKBA loaded silver nanoparticles were used to study its impact on film characteristics. Carboxymethyl cellulose (CMC), sodium alginate (SA), and gelatin (Ge) composite films were prepared in this study. The polymeric films were evaluated for their biological (antioxidant and antimicrobial activities) and mechanical characteristics such as tensile strength (TS) and elongation (%). Moreover, other parameters including water barrier properties and color attributes of the film were also evaluated. Furthermore, assessments were conducted using analytical techniques like FTIR, XRD, and SEM. Surface analysis revealed that AgNP precipitation led to a few particles in the film structure. Overall, the results indicate a relatively consistent microstructure. Moreover, due to the addition of AKBA, BA, and AgNPs, a significant decrease in TS, moisture content, water solubility, and water vapor permeation was observed. The films transparency also showed a decreasing trend, and the color analysis revealed decreasing yellowness (b*) of the films. Importantly, a significant increase in antioxidant activity against DPPH free radicals and ABTS cations was observed in the CSG films. Additionally, the AgNP-AKBA loaded films displayed significant antifungal activity against C. albicans. Moreover, the molecular docking analysis revealed the inter-molecular interactions between the AKBA, AgNPs, and composite films. The docking results indicate good binding of AKBA and silver nanoparticles with gelatin and carboxymethyl cellulosemolecules. In conclusion, these polymeric films have potential as novel materials with significant antioxidant and antifungal activities.

A new 3D printing strategy by enhancing shear-induced alignment of gelled nanomaterial inks resulting in stronger and ductile cellulose films

Cellulose nanofibrils (CNFs) are derived from biomass and have significant potential as fossil-based plastic alternatives used in disposable electronics. Controlling the nanostructure of fibrils is the key to obtaining strong mechanical properties and high optical transparency. Vacuum filtration is usually used to prepare the CNFs film in the literature; however, such a process cannot control the structure of the CNFs film, which limits the transparency and mechanical strength of the film. Here, direct ink writing (DIW), a pressure-controlled extrusion process, is proposed to fabricate the CNFs film, which can significantly harness the alignment of fibrils by exerting shear stress force on the filaments. The printed films by DIW have a compact structure, and the degree of fibril alignment quantified by the small angle X-ray diffraction (SAXS) increases by 24 % compared to the vacuum filtration process. Such a process favors the establishment of the chemical bond (or interaction) between molecules, therefore leading to considerably high tensile strength (245 ± 8 MPa), elongation at break (2.2 ± 0.5 %), and good transparency. Thus, proposed DIW provides a new strategy for fabricating aligned CNFs films in a controlled manner with tunable macroscale properties. Moreover, this work provides theoretical guidance for employing CNFs as structural and reinforcing materials to design disposable electronics.

Water-induced controllable deswelling strategy enabled rapid fabrication of transparent cellulose film for plastics replacement

Plastic pollution has posed significant impacts on the ecosystem. While biodegradable transparent cellulose films are considered ideal alternatives, they still grapple with issues of high energy consumption and low production efficiency. In this study, we proposed a water-induced fiber deswelling strategy to expedite the fabrication of transparent cellulose films from wood pulp. Raw cellulose fibers were firstly disintegrated into micro-sized fibers via cold alkali swelling and mild mechanical blending. Subsequently, water was introduced to govern the swelling and aggregation behavior of these treated cellulose fibers, reducing their water retention and facilitating the rapid preparation of cellulose films. By regulating the amount of water added, cellulose film can be prepared within 1 min using vacuum filtration. Furthermore, the resulting film exhibits good wet strength, surpassing most previously reported cellulose-based films, with a wet strength exceeding 30 MPa and a wet strength retention of up to 65.7 %. With these advantageous features, the cellulose film was demonstrated for packaging and fruits preservation, showing a great potential to replace conventional plastics in the packaging applications. In addition, the life cycle environmental impacts of 1.0 kg cellulose film production (cradle-to-gate system boundary) were 12.63 kg CO2-eq, 0.04 kg SO2-eq, and 397 MJ energy use.

Ultrathin Freestanding Nanocellulose Film Prepared from TEMPO-Mediated Oxidation and Homogenized Hydrogel.

This paper presents a versatile method to fabricate ultrathin nanofibrillated cellulose (NFC) films as thin as 800 nm by blade coating, which is compatible with a roll-to-roll process on a large scale. Our approach allows obtaining a dried nanocellulose film within a span of 1 h subsequent to 2,2,6,6-tetramethylpiperidine-1-oxyl radical-assisted oxidation and homogenization procedures. One of the thinnest freestanding NFC films with a thickness of 800 nm is achieved using a blade coating of nanocellulose after 72 h of oxidation followed by homogenization with a channel size of 65 μm. Incorporating water-soluble CdTe core-type quantum dots into the nanocellulose film led to a uniform emission under 385 nm UV irradiation, indicating excellent material compatibility. We anticipate nanocellulose developed in our study to be beneficial in biomimicry flying objects, environmentally friendly encapsulation, color filters, and energy storage device membranes, to name a few.

Ozone-activated lignocellulose films blended with chitosan for edible film production

This work focuses on the influence of ozone pretreatment on the fractionation and solubilization of sugarcane bagasse and soda bagasse pulp fibers in sodium hydroxide/urea solution, as well as the application of regenerated cellulose for producing edible films. The methodology involved pretreating lignocelluloses with ozone for 20 to 120 min before dissolving in sodium hydroxide/urea solution. The influence of the pretreatment conditions on cellulose dissolution yield was investigated. Regenerated cellulose films were then formed, with and without the addition of 2 % chitosan. Mechanical, physical, structural, thermal, and antimicrobial attributes were determined as a function of ozonation conditions of raw materials and chitosan content. The findings exhibited positive effects of short ozonation on enhancing mechanical strength, cohesion, and hydrophobicity. The prolonged ozonation of 120 min demonstrated optimal improvements in continuity, swelling, and antibacterial resistance of obtained films. Incorporating chitosan enhanced tensile performance, stiffness, and vapor barriers but increased moisture absorption. Tailoring the activation of biomass through ozone pretreatment and chitosan addition resulted in renewable films with adjustable properties to meet diverse packaging requirements, particularly for fruit protective coatings, ensuring the preservation of post-harvest quality.

Influence of acid hydrolysis on the degree of polymerization of cellulose from colored cotton substrates

This study investigated the influence of sulfuric acid hydrolysis on the cellulosic fibers and films’ degree of polymerization (DP). Cotton textile residues (dyed and white) and hydrophilic cotton were used as the raw material. The films were formed by the dissolution of fibers in ionic liquid and regeneration in water. Results showed that dyed cotton residues required hydrolysis at 0.5 M sulfuric acid for 30 min to achieve complete dissolution during viscosimetry assay. Due to different dyeing processes and chemical compositions, the color of the fibers influences the DP. Undyed samples submitted to hydrolysis had DP around 60% lower than samples without pretreatment. This effect was not observed when comparing films with and without hydrolysis, because the depolymerization occurs in the dissolution and regeneration step. This study expands the applicability of viscometry to colored substrates, serving as a starting point for future research on the impact of process parameters and dyes on cellulose polymerization.

Multifunctional composite flexible films of hydroxypropyl cellulose and silver nanowires

Flexible wearable devices have aroused attentions since the booming flexible electronic technologies, as well as the requirements for improved comfortableness and real-time monitoring for complex motion state of human body. Developing a flexible integrated wearable device with multi functions provides a promising route for next-generation wearable devices. Meanwhile, transparency and biocompatibility are also considered a lot. Herein, hydroxypropyl cellulose/silver nanowires (HPC/AgNWs) flexible composite films were fabricated with a facile two-step method. The fabricated composite films exhibited sufficient transparency and mechanical strength. More importantly, the HPC/AgNWs composite films afforded good motion sensing performances with current sensitivity as high as 350 %. It can accurately identify different bending angles and frequencies, and remained stable for more than 1000 bending cycles. Apart from being employed as motion sensors, the fabricated HPC/AgNWs could be also used for electrical heating and electromagnetic shielding. The films could be heated to more than 60°C at 3.0 V in 57 seconds, and the electromagnetic shielding efficiency reached more than 99.9 %. This study contributed a feasible strategy for the preparation of multifunctional flexible films which are expected to be further applicated in the field of wearable devices.

Novel method for screening probiotic candidates tolerant to human gastrointestinal stress

Tolerance to human gastrointestinal stressors is crucial for probiotics to exhibit their health benefits; however, there is no standardised method for screening their stress tolerance. In this study, we proposed a novel method for screening probiotic candidates tolerant to human gastrointestinal stress—gastrointestinal tolerance assay and culture (GTA-C) method—using black polyethylene terephthalate (PET) non-woven fabric as a scaffold to modify the specialized cellulose film (SCF) method. The modified SCF method showed excellent pH-based diffusion of medium components, had minimal effect on the growth of Escherichia coli K12, and improved the visibility of the colonies. Analysis of kimchi samples cultured using the SCF and modified SCF methods revealed that the modified method diversified the cultured bacteria. GTA in a simulated human fasting state using the modified SCF method showed that acid stress significantly affected the growth of four bacteria used as probiotics and that tolerance to acid stress may be species-dependent. Screening of probiotics in kimchi samples resulted in the identification of lactic acid bacteria tolerant to human gastrointestinal stress during fasting. Our results indicate that the modified SCF method (GTA-C method) is useful for screening probiotics resistant to the gastrointestinal environment during fasting.