Starch-Based Composite Films with Enhanced Hydrophobicity, Thermal Stability, and UV-Shielding Efficacy Induced by Lignin Nanoparticles

Versatile corn starch-based sustainable food packaging with enhanced antimicrobial activity and preservative properties

Biodegradable active packaging has garnered significant research interest owing to growing concerns over plastic pollution and food safety. However, current food packaging materials still suffer from drawbacks such as complex synthesis processes, high production costs, and inadequate safety performance in terms of antimicrobial resistance and biodegradability. Typically, their performance in preserving fresh food is also inferior to that of plastics. Herein, a versatile corn starch-based sustainable food packaging (DC) was proposed, utilizing natural corn starch (CS) and carboxymethyl chitosan (CMCS) as raw materials. The focus was on evaluating the mechanical properties, antioxidant properties, and antimicrobial activity, and to further explore the degradability and biocompatibility of the DC films, as well as their application in fruit preservation. The results confirmed the good water vapor barrier properties, antioxidant activity (DPPH scavenging of the DC4 film reached 98.10 ± 0.32 %), Ultraviolet (UV) resistance (more than 99.8 % absorption of both UV-A and UV-B radiation), water resistance, mechanical properties, and bacteriostatic and bactericidal effect (the DC4 film reached 99.67 ± 0.58 % against Escherichia coli and 99.83 ± 0.29 % against Staphylococcus aureus) of the DC. Meanwhile, the DC exhibited favorable biodegradability in the natural environment. Finally, fruit preservation experiments confirmed that the DC could significantly extend the shelf life of fresh fruits at room temperature. Overall, this research presented a sustainable and cost-effective biomass-derived packaging film that could replace conventional petroleum-based plastics, thereby reducing environmental pollution and showing significant potential for use in food packaging.

The preparation of starch-based green adsorption gel with tunable water channels through extrusion-dual cross-linking method

In addressing the challenges of recovery and microparticle residue associated with biochar, loading biochar with starch presents a viable solution. However, starch's high hydrophilicity and viscosity introduce water resistance and uniform loading issues. This study proposes an innovative ionically synergistic dual crosslinking modification method, utilizing an extruder barrel as a novel reactor. This method enables the construction of highly water-resistant starch gels and the uniform and robust loading of biochar micro-nanoparticles within the gel matrix, achieving the "one-step" preparation of starch-biochar-based adsorptive gels. The starch-biochar-based adsorptive gel (Bc-S-D) exhibits excellent removal efficiency for the hazardous waste methylene blue (MB) with a qe value of 549.45 mg/g. This removal efficiency is maintained at 85.37 ± 0.08 % even after five cycles. The textural results indicate that Bc-S-D maintains a high recovery performance of 91.51 % after prolonged water immersion. Scanning Electron Microscopy (SEM) reveals that it has the lowest porosity (47 ± 3.36 %) and micropore size (16.53 ± 2.71 μm). Furthermore, the specific surface area was determined using the Brunauer-Emmett-Teller (BET) model, which is 7.46 ± 0.03 m2/g, representing a 448.53 % increase compared to the unmodified state. A quasi-primary kinetic model for the adsorption of MB on the adsorbent follows the Langmuir model. The starch-biochar-based adsorption gel is also appropriate for high-temperature dyeing wastewater adsorption situations because of its superior water resistance, structural recoverability, and high-temperature stability, which allow rapid, residue-free separation and recovery. This research provides a new reaction method for preparing modification biological macromolecules and loading new biological macromolecule functional materials to achieve the full-cycle green treatment of dyeing wastewater.

Fabrication of lignin nanoparticles with adjustable size, antioxidant, antibacterial, and hydrophobic properties by a two-step fractionation

Lignin nanoparticles (LNPs) are gaining attention for their renewability and environmental friendliness in advanced nanomaterials. To establish a new sustainable value chain, it is vital to fully utilize lignin resources and thoroughly examine the effects of LNPs size and structure on performance. Herein, a two-step fractionation scheme is engineered via combining sequential organic solvent fractionation and acid precipitation methods to obtain four lignin fractions (denoted as F1, F2, F3, and F4) with low heterogeneity, suitable hydroxyl content and the syringyl (S)/guaiacyl (G) ratio for LNPs fabrication. Up to 88.7 % of alkali lignin was collected to prepare LNPs, and the LNPs showed controllable sizes (100-500 nm, denoted as F1-LNP, F2-LNP, F3-LNP, and F4-LNP). The size gradually decreased from F1-LNP to F4-LNP with increasing specific surface area of LNPs, contributing to superior antibacterial and antioxidant properties. Notably, a higher S/G ratio with enriched p-hydroxyphenyl (H) units resulted in a smaller size of LNPs, possibly resulting from the greater attraction and larger binding energy between S-S and H-H than G-G. This work gives insights into the full utilization of technical lignin to nano-particles to meet specific performance requirements, which will particularly broaden the commercialization and high-value utilization of lignin.

Nano structural regulation of lignin and evaluation of its ultraviolet light absorption properties through quantum chemistry calculations

Lignin, a biomass-derived material containing chromophores, possesses the potential to serve as a versatile organic ultraviolet (UV) light screening agent. By employing quantum chemical computation techniques, an amphoteric deep eutectic solvent (DES) based on sulfamic acid was purposefully designed and engineered to create a solvent system tailored for the nanoparticle formation and functionalization of lignin. As confirmed by experimental evidence, the size of the modified lignin nanoparticles (LNPs) varies from 168.4 to 388.8 nm, with molecular weights ranging from 1806 to 2093 g/mol, and a PDI of 1.51 to 1.67. The nano-processing of lignin, along with auxochrome addition, induced a shift in the absorption peak to a longer wavelength spectrum, from 359 to 379 nm. Furthermore, the results confirmed a significant increase in absorption, particularly within the UVA radiation band, for lignin treated in this system. Quantum chemical calculations verified that incorporating a G-type structure with a β-5 bond significantly enhanced lignin's UV absorption in the UVA spectrum, and the presence of auxochrome shifted its absorption peak to longer wavelengths.

Engineered environment-friendly multifunctional food packaging with superior nonleachability, polymer miscibility and antimicrobial activity

This study was conducted primarily to develop an environment-friendly food packaging boasting several advantages, including good water vapor barrier, UV resistance, antimicrobial activity, non-leachability, and polymer miscibility. Initially, the starch-based antimicrobial agent (OCSI) was synthesized through a simple esterification reaction between oxidized corn starch (OCS) and indoleacetic acid (IAA). Subsequently, OCSI was further blended separately with environmentally-friendly materials (PVA, PBAT, PCL), and a series of environment-friendly packaging films were successfully prepared. The resulting films exhibited desirable thermal stability and 100 % barrier against both UV-A and UV-B rays. Moreover, the films presented effective barriers against water vapor, antioxidant, and antimicrobial activity against E. coli and S. aureus. Meanwhile, the films could significantly inhibit the deterioration of fresh fruits and prolong shelf life, considerably expanding their utilization in safe packaging. The environment-friendly packaging not only realized the sustainable utilization of green polymers, but also offered novel insights into the exploration of sustainable packaging.

Crosslinked lignin starch copolymer as a sustainable and thermally stable drilling fluid controller

Fluid loss is a well-known challenge of drilling operations. In this work, a novel sustainable starch-lignin-based polymer was synthesized for possible use in drilling fluid applications. The X-ray photoelectron spectroscopy (XPS) analysis confirmed that kraft lignin was crosslinked with starch via ether covalent bonds. The X-ray diffraction (XRD) analysis confirmed the loss of crystallinity in starch and emerging of new amorphous structures in crosslinked starch-lignin (CSL) polymers after crosslinking with lignin. The incorporation of lignin and new covalent ether bonds improved the thermal stability of starch. The CSL had a rougher surface morphology, higher hydrophilicity, and significantly higher water absorption than starch. CSL-2, with its higher lignin content, demonstrated higher hydrophilicity, better water absorption capacity, and thermal stability than CSL-1. The rheology analysis of the CSL-2 polymer suggested that crosslinking starch with lignin would increase G' more than G" and reduce tan δ of the polymer solution, resulting in more elastic properties and more stability against the angular frequency. Due to its improved swelling, thermal, and rheological properties as compared to native starch, the produced sustainable lignin-starch copolymer could be used as a new viscosity and rheology modifier, such as a fluid loss controller for oil extraction from wells.

Active bio-nanocomposites from litchi seed starch, tamarind kernel xyloglucan, and lignin nanoparticles to improve the shelf-life of banana (Musa acuminata)

Valorization of agricultural byproducts to biodegradable packaging films aids in reducing plastic dependency and addressing plastic perils. Herein, starch (LSS) from litchi seeds and xyloglucan (XG) from tamarind kernels were recovered, and composite films were developed. The XG addition strengthened the weak polymer networks of LSS and improved rheological, molecular, morphological, mechanical, and water vapor barrier properties. The incorporation of lignin nanoparticles (LNPs) into the LSS-XG network further increased the tensile strength (14.83 MPa), elastic modulus (0.41 GPa), and reduced surface wettability (80.07°), and water vapor permeability (5.63 ± 0.38 × 10-7 g m-1s-1Pa-1). The phenolic hydroxyls of LNPs imparted strong UV-shielding and free radical scavenging abilities to films. These attributes aided in preserving the quality of coated banana fruits with minimal weight loss and color change. Overall, this research highlights the potential transformation of underutilized abundant byproducts into sustainable active bio-nanocomposites for food packaging and shelf-life extension of fruits.

Flame-Resistant Inorganic Films by Self-Assembly of Clay Nanotubes and their Conversion to Geopolymer for CO2 Capture

Self-assembling of very long natural clay nanotubes represents a powerful strategy to fabricate thermo-stable inorganic thin films suitable for environmental applications. In this work, self-standing films with variable thicknesses (from 60 to 300 µm) are prepared by the entanglement of 20-30 µm length Patch halloysite clay nanotubes (PT_Hal), which interconnect into fibrosus structures. The thickness of the films is crucial to confer specific properties like transparency, mechanical resistance, and water uptake. Despite its completely inorganic composition, the thickest nanoclay film possesses elasticity comparable with polymeric materials as evidenced by its Young's modulus (ca. 1710 MPa). All PT_Hal-based films are fire resistant and stable under high temperature conditions preventing flame propagation. After their direct flame exposure, produced films do not show neither deterioration effects nor macroscopic alterations. PT_Hal films are employed as precursors for the development of functional materials by alkaline activation and thermal treatment, which generate highly porous geopolymers or ceramics with a compact morphology. Due to its high porosity, geopolymer can be promising for CO2 capture. As compared to the corresponding inorganic film, the CO2 adsorption efficiency is doubled for the halloysite geopolymeric materials highlighting their potential use as a sorbent.

Effect of different initiators on the properties of diacetone acrylamide grafted starch-based adhesive

Environmentally friendly and non-toxic bio-based adhesives are emerging as the most promising substitutes for petroleum-based adhesives, attracting increasing attention. This work involved the synthesis of a starch-based adhesive for particleboards by grafting diacetone acrylamide (DAAM) onto starch. The graft polymerization was initiated using three different initiators: ammonium persulfate (APS), hydrogen peroxide (H2O2)/ammonium ferrous sulfate system, and ceric ammonium nitrate (CAN). A comparative study was conducted to assess the varying effects of these initiators. The results showed that in the graft copolymerization of starch with DAAM, different initiators produced different types of free radicals, and CAN initiation produced alkyl radicals and long-chain alkyl radicals with a peak total spin value of 3.96 × 1015, and thus had the highest grafting efficiency and grafting rate of 72.59 % and 16.75 %, respectively. From the comparison of the total number of spins, it can be seen that CAN is more targeted for starch initiation. In addition, characterization results from Fourier transform infrared spectroscopy and confocal Raman spectroscopy showed that DAAM underwent a graft copolymerization reaction with starch. Notably, the adhesive initiated by CAN demonstrated the highest water resistance and mechanical strength, with an absorption thickness expansion and static bending strength of 8.52 % and 10.56 MPa, respectively.

Strategies for the incorporation of organosolv lignin in hydroxypropyl methylcellulose-based films: A comparative study

Organosolv lignin extracted from vine pruning residues was added to hydroxypropyl methylcellulose (HPMC)-based films using three strategies: i) lignin incorporated into the film (lignin-based film), ii) lignin nanoparticles (LNPs) incorporated into the film (LNPs-based film), and iii) lignin coated on HPMC films' surface (lignin-coated film). The films obtained were evaluated in terms of morphology, water barrier and mechanical properties, and antioxidant capacity. Results showed that LNPs incorporation did not affect the films´ water vapour permeability (WVP). Nonetheless, the lignin-based and lignin-coated films improved the water barrier properties of HPMC-based films, achieving a 31.5 and 36 % reduction of WVP, respectively. The morphological evaluation, performed by scanning electron microscopy, revealed films' morphology changes with the lignin incorporation, which was more evident in the lignin-based films. Fourier transform infrared spectroscopy (FTIR) showed minor changes in the film's structure using the different lignin incorporation methods. The mechanical properties were improved, including a significant increase in the tensile strength in the lignin-based and lignin-coated films. All films showed high radical scavenging activity (RSA) after 24 h, with a gradual increase in the lignin-coated films over time. The lignin-coated films showed to be the most promising incorporation strategy to improve the HPMC-based film's properties.

Lignin-Based Composite Film and Its Application for Agricultural Mulching

Agricultural mulching is an important input for modern agricultural production and plays an important role in guaranteeing food security worldwide. At present, polyethylene (PE) mulching is still commonly used in agricultural production in most countries around the world, which is non-biodegradable, and years of mulching have caused serious agricultural white pollution. Lignin is one of the three major components of plant cell walls, and it is also the main renewable natural aromatic compounds in nature. Lignin-based composite film materials are green, biodegradable, and show good prospects for development in the field of agricultural mulch. This paper introduces the types, structure, and application status of lignin, summarizes the preparation of lignin-based composite film materials and its latest research progress, focuses on the types, preparation methods, and application examples of lignin-based agricultural mulching, and looks forward to the future development prospects of lignin-based agricultural mulching.

Benefits of Incorporating Lignin into Starch-Based Films: A Brief Review

Polysaccharides are an excellent renewable source for developing food-packing materials. It is expected that these packages can be an efficient barrier against oxygen; can reduce lipid peroxidation, and can retain the natural aroma of a food commodity. Starch has tremendous potential to be explored in the preparation of food packaging; however, due to their high hydrophilic nature, packaging films produced from starch possess poor protective moisture barriers and low mechanical properties. This scenario limits their applications, especially in humid conditions. In contrast, lignin's highly complex aromatic hetero-polymer network of phenylpropane units is known to play a filler role in polysaccharide films. Moreover, lignin can limit the biodegradability of polysaccharides films by a physical barrier, mainly, and by non-productive bindings. The main interactions affecting lignin non-productive bindings are hydrophobic interactions, electrostatic interactions, and hydrogen-bonding interactions, which are dependent on the total phenolic -OH and -COOH content in its chemical structure. In this review, the use of lignin as a reinforcement to improve the biodegradability of starch-based films in wet environments is presented. Moreover, the characteristics of the used lignins, the mechanisms of molecular interaction among these materials, and the sensitive physicochemical parameters for biodegradability detection are related.

A review of starch/polyvinyl alcohol (PVA) blend film: A potential replacement for traditional plastic-based food packaging film

In recent years, the development of environmentally friendly packaging materials using biodegradable polymers has emerged as a key challenge for scientists and consumers in response to resource depletion and environmental issues caused by plastic packaging materials. Starch and polyvinyl alcohol (PVA) are being recognized as excellent candidates for producing biodegradable food packaging films. Polymer blending has emerged as a practical approach to overcome the limitations of biopolymer films by developing films with unique properties and enhancing overall performance. This review briefly introduces the molecular structure and properties of starch and PVA, summarizes the common preparation methods and properties of starch/PVA blend films, and focuses on different strategies used to enhance starch/PVA blend films, including nanoparticles, plant extracts, and cross-linking agents. Additionally, this study summarizes the application of starch/PVA blend films as active and smart packaging in food preservation systems. This study demonstrates that starch and PVA blends have potential in manufacturing biodegradable food films with excellent properties due to their excellent compatibility and intermolecular interactions, and can be used as packaging films for a variety of foods to extend their shelf life.

The application of starch-based edible film in food preservation: a comprehensive review

Using renewable resources for food packaging not only helps reduce our dependence on fossil fuels but also minimizes the environmental impact associated with traditional plastics. Starch has been a hot topic in the field of current research because of its low cost, wide source and good film forming property. However, a comprehensive review in this field is still lacking. Starch-based films offer a promising alternative for sustainable packaging in the food industry. The present paper covers various aspects such as raw material sources, modification methods, and film formation mechanisms. Understanding the physicochemical properties and potential commercial applications is crucial for bridging the gap between research and practical implementation. Finally, the application of starch-based films in the food industry is discussed in detail. Different modifications of starch can improve the mechanical and barrier properties of the films. The addition of active substances to starch-based films can endow them with more functions. Therefore, these factors should be better investigated and optimized in future studies to improve the physicochemical properties and functionality of starch-based films. In summary, this review provides comprehensive information and the latest research progress of starch-based films in the food industry.

Lignin-xylan nanospheres prepared by green and quick method from lignocellulose and used as additive in PVA films

Lignin, as an amorphous three-dimensional aromatic polymer, was able to self-assemble into lignin nanoparticles (LNPs) to realize valorization of lignin. Here, lignin-xylan extractives were extracted from grape seed (GS) and poplar by acidic THF at room temperature, and effectively produced lignin-xylan nanospheres via spin evaporation. The morphology and chemical properties of nanospheres were determined by its natural origins, consequently influencing its application. For the lignin-xylan extractive from grape seed, the lignin was composed of guaiacyl (G) and p-hydroxylphenyl (H) units and the hollowed nanospheres (GS-LNPs) with 362.72 nm diameter was produced. The extractive from poplar was composed of G-syringyl (S) typed lignin (80.30 %) and xylan (12.33 %), that can assemble into LNPs with smaller size (229.87 nm), better PDI (0.1), and light color. The hybrid particles showed the qualities of lignin and xylan, that properties led to the LNPs@PVA composite films with UV-blocking capability, strong mechanical strength and hydrophobicity, and transparency ability of visible light. P-LNPs showed better performance as the film additives, due to its lower particles size and high content of unconjugated -OH from xylan. Xylan was significant in the composite films, and lowering the xylan content resulted in the decrease of the composite film's mechanical properties and hydrophobicity.

Nanotechnology in wood science: Innovations and applications

Application of nanomaterials is gaining tremendous interest in the field of wood science and technology for value addition and enhancing performance of wood and wood-based composites. This review focuses on the use of nanomaterials in improving the properties of wood and wood-based materials and protecting them from weathering, biodegradation, and other deteriorating agents. UV-resistant, self-cleaning (superhydrophobic) surfaces with anti-microbial properties have been developed using the extraordinary features of nanomaterials. Scratch-resistant nano-coatings also improve durability and aesthetic appeal of wood. Moreover, nanomaterials have been used as wood preservatives for increasing the resistance against wood deteriorating agents such as fungi, termites and borers. Wood can be made more resistant to ignition and slower to burn by introducing nano-clays or nanoparticles of metal-oxides. The use of nanocellulose and lignin nanoparticles in wood-based products has attracted huge interest in developing novel materials with improved properties. Nanocellulose and lignin nanoparticles derived/synthesized from woody biomass can enhance the mechanical properties such as strength and stiffness and impart additional functionalities to wood-based products. Cellulose nano-fibres/crystals find application in wide areas of materials science like reinforcement for composites. Incorporation of nanomaterials in resin has been used to enhance specific properties of wood-based composites. This review paper highlights some of the advancements in the use of nanotechnology in wood science, and its potential impact on the industry.

Exploring the potential of lignin nanoparticles in enhancing the mechanical, thermal, and bioactive properties of poly (butylene adipate-co-terephthalate)

The preparation and characterization of lignin nanoparticles (LNPs) were described. LNPs were produced via the precipitation technique. Nanocomposites of LNPs with poly (butylene adipate-co-terephthalate) (PBAT) were prepared by melt mixing with various concentrations up to 6 wt% of LNPs. The assessment of the effects of LNP addition on the mechanical, thermal, morphological, cytotoxicity, antioxidant, antibacterial, and antiviral properties of nanocomposites was carefully performed. The addition of LNPs to PBAT enhances the thermal stability of the nanocomposites. The antioxidant effect of LNPs on PBAT increased with increasing filler content. LNPs showed higher efficiency as antioxidant agents than lignin particles (LP). The tensile modulus increased by 20 % for the nanocomposites with 6 % LNPs in comparison with neat PBAT. The crystallization peak temperature of PBAT was 80 °C, which increased to 104.6 °C with the addition of 6 wt% of LNPs, suggesting their strong nucleation activity. Antibacterial tests demonstrated the bacteriostatic activities of LNP, LP, and nanocomposites. Both LP and LNP showed considerable antiviral activity against herpes simplex virus type 1 and human coronavirus 229e. The antiviral activity of LNP was concentration-dependent. The findings suggest that LNP is a promising bio-additive for PBAT and can enhance its properties for various applications, including food packaging.

Bioinspired multiscale cellulose/lignin-silver composite films with robust mechanical, antioxidant and antibacterial properties for ultraviolet shielding

Constructing a high-performance ultraviolet shielding film is an effective way for addressing the growing problem of ultraviolet radiation. However, it is still a great challenge to achieve a combination of multifunctional, excellent mechanical properties and low cost. Here, inspired by the multiscale structure of biomaterials and features of lignin, a multifunctional composite film (CNF/CMF/Lig-Ag) is constructed via a facile vacuum-filtration method by introducing micron-sized cellulose fibers (CMF) and lignin-silver nanoparticles (Lig-Ag NPs) into the cellulose nanofibers (CNF) film network. In this composite film, the microfibers interweave with nanofibers to form a multiscale three-dimensional network, which ensures satisfactory mechanical properties of the composite film. Meanwhile, the Lig-Ag NPs are employed as a multifunctional filler to enhance the composite film's antioxidant, antibacterial and ultraviolet shielding abilities. As a result, the prepared CNF/CMF/Lig-Ag composite film demonstrates excellent mechanical properties (with tensile strength of 133.8 MPa and fracture strain of 7.4 %), good biocompatibility, high thermal stability, potent antioxidant and antibacterial properties. More importantly, such composite film achieves a high ultraviolet shielding rate of 98.2 % for ultraviolet radiation A (UVA) and 99.4 % for ultraviolet radiation B (UVB), respectively. Therefore, the prepared CNF/CMF/Lig-Ag composite film shows great potential in application of ultraviolet protection.

Production and characterization of starch-lignin based materials: A review

In their pristine state, starch and lignin are abundant and inexpensive natural polymers frequently considered green alternatives to oil-based and synthetic polymers. Despite their availability and owing to their physicochemical properties; starch and lignin are not often utilized in their pristine forms for high-performance applications. Generally, chemical and physical modifications transform them into starch- and lignin-based materials with broadened properties and functionality. In the last decade, the combination of starch and lignin for producing reinforced materials has gained significant attention. The reinforcing of starch matrices with lignin has received primary focus because of the enhanced water sensitivity, UV protection, and mechanical and thermal resistance that lignin introduces to starch-based materials. This review paper aims to assess starch-lignin materials' production and characterization technologies, highlighting their physicochemical properties, outcomes, challenges, and opportunities. First, this paper describes the current status, sources, and chemical modifications of lignin and starch. Next, the discussion is oriented toward starch-lignin materials and their production approaches, such as blends, composites, plasticized/crosslinked films, and coupled polymers. Special attention is given to the characterization methods of starch-lignin materials, focusing on their advantages, disadvantages, and expected outcomes. Finally, the challenges, opportunities, and future perspectives in developing starch-lignin materials, such as adhesives, coatings, films, and controlled delivery systems, are discussed.

Lignins as Promising Renewable Biopolymers and Bioactive Compounds for High-Performance Materials

The recycling of biomass into high-value-added materials requires important developments in research and technology to create a sustainable circular economy. Lignin, as a component of biomass, is a multipurpose aromatic polymer with a significant potential to be used as a renewable bioresource in many fields in which it acts both as promising biopolymer and bioactive compound. This comprehensive review gives brief insights into the recent research and technological trends on the potential of lignin development and utilization. It is divided into ten main sections, starting with an outlook on its diversity; main properties and possibilities to be used as a raw material for fuels, aromatic chemicals, plastics, or thermoset substitutes; and new developments in the use of lignin as a bioactive compound and in nanoparticles, hydrogels, 3D-printing-based lignin biomaterials, new sustainable biomaterials, and energy production and storage. In each section are presented recent developments in the preparation of lignin-based biomaterials, especially the green approaches to obtaining nanoparticles, hydrogels, and multifunctional materials as blends and bio(nano)composites; most suitable lignin type for each category of the envisaged products; main properties of the obtained lignin-based materials, etc. Different application categories of lignin within various sectors, which could provide completely sustainable energy conversion, such as in agriculture and environment protection, food packaging, biomedicine, and cosmetics, are also described. The medical and therapeutic potential of lignin-derived materials is evidenced in applications such as antimicrobial, antiviral, and antitumor agents; carriers for drug delivery systems with controlled/targeting drug release; tissue engineering and wound healing; and coatings, natural sunscreen, and surfactants. Lignin is mainly used for fuel, and, recently, studies highlighted more sustainable bioenergy production technologies, such as the supercapacitor electrode, photocatalysts, and photovoltaics.

Strong, flexible and UV-shielding composite polyvinyl alcohol films with wood cellulose skeleton and lignin nanoparticles

The development of high-performance composite films using biomass materials have become a sought-after direction. Herein, a green method to fabricate strong, flexible and UV-shielding biological composite film from wood cellulose skeleton (WCS), lignin nanoparticles (LNPs) and polyvinyl alcohol (PVA) was described. In the work, WCS and LNPs were prepared by chemical treatment of wood veneer and Enzymatic lignin, respectively. Then, WCS was infiltrated with the LNPs/PVA mixtures and dried to obtain composite films. WCS enhanced the mechanical properties of the composite films, the tensile stress reached to 85.8 MPa and the tensile strain reached to 6.39 %. The composite films with LNPs blocked over 98 % of UV-light, the water absorption decreased by 30 %, and the thermal stabilities were also improved. These findings would provide some references for exploring high quality biological composite films.

Generation of Sulfonated Lignin-Starch Polymer and Its Use As a Flocculant

This paper reports the polymerization of tall oil lignin (TOL), starch, and 2-methyl-2-propene-1-sulfonic acid sodium salt (MPSA), a sulfonate-containing monomer, in a three-component system to generate flocculants for colloidal systems. By utilizing the advanced 1H, COSY, HSQC, HSQC-TOCSY, and HMBC NMR techniques, it was confirmed that the phenolic substructures of TOL and the anhydroglucose unit of starch were covalently polymerized by the monomer to generate the three-block copolymer. The molecular weight, radius of gyration, and shape factor of the copolymers were fundamentally correlated to the structure of lignin and starch, as well as the polymerization outcomes. The deposition behavior of the copolymer, studied by a quartz crystal microbalance with dissipation (QCM-D) analysis, revealed that the copolymer with a larger molecular weight (ALS-5) deposited more and generated more compact adlayer than the copolymer with a smaller molecular weight on a solid surface. Owing to its higher charge density, molecular weight, and extended coil-like structure, ALS-5 produced larger flocs with faster sedimentation in the colloidal systems, regardless of the extent of agitation and gravitational force. The results of this work provide a new approach to preparing a lignin-starch polymer, i.e., a sustainable biomacromolecule with excellent flocculation performance in colloidal systems.

Temperature responsive crosslinked starch-kraft lignin macromolecule

Starch is a natural polymer with a relatively simple structure and limited solubility in water. Kraft lignin (KL) is a complex biopolymer obtained as a by-product from the delignification of wood and grasses. The present work reports developing a temperature-responsive high molecular weight macromolecule from crosslinking KL and starch (KLS). The NMR and XPS analyses quantified the changes in the aromatic and anhydroglucose units of KL and starch, observing a higher content of C-O-C bonds, which confirms the presence of glycerol ether cross-linkages between starch and KL in KLS. The rheological analysis of KLS dispersions revealed the formation of a thermo-responsive structured network. The temperature-dependent water solubility and rheological characteristics of KLS were related to the presence of hydrophilic starch chains, crosslinking degree, and physicochemical characteristics of KL. The incorporation of KL and ether crosslinks increased the thermal stability of KLS. Because of its multiple functional groups and large molecular weight (3.6-4.2 × 10⁵ g/mol) that was arranged in an extended globular shape, KLS-5 formed a gel-like structure after a heating-cooling treatment. Overall, the results confirmed that incorporating lignin in starch would fabricate sustainable materials with potentially altered applications, such as temperature-responsive hydrogels and films.

Grafting natural nicotinamide on tempo-oxidized cellulose nanofibrils to prepare flexible and transparent nanocomposite films with fascinating mechanical strength and UV shielding performance

Light pollution from ultraviolet (UV) radiation is gaining growing concerns, as the emissions and burning of fossil fuels destroyed the ozone layer. Seeking a solution against skin exposure to excessive radiation is an urgent requirement. In this study, nicotinamide (NA), the main component of vitamin B3, was introduced as a new modifier into Tempo-oxidized cellulose nanofibrils (TOCNFs) together with the physical cross-linking with tannin acid (TA) to improve anti-UV performance of the nanocomposite films. Incorporation of NA into the films presents distinguished UV shielding capability UVB wavelength range from 200 nm to 320 nm (NTA1-5) due to the introduced functional groups like CO and benzene rings. Moreover, mechanical properties were notably enhanced, which overcome the low strength of common nanocellulosic materials. The stress increased from 69.8 MPa to 116.3 MPa, and the toughness can reach 131.58 MJ/m³ by tuning the additional amount of NA. Meanwhile, TGA and DTG analysis demonstrated that the incorporation of amide bonds and TA into the composite films greatly improved the thermal stability. Thus, the proposed materials fabricated from natural biomolecules show great potential in serving as new kinds of UV-resistant products in the application areas of sunscreen, protective clothing, and building materials.

Stretchable and fatigue resistant hydrogels constructed by natural galactomannan for flexible sensing application

Exploration of sustainable and functional materials from biomolecules has received much interest, while the limited mechanical property and possible bacterial contamination were proved to be their major shortages. Here, we proposed novel double network (DN) hydrogels based on galactomannan (GM) polysaccharide as backbone. Folic acid (FA) and polyacrylamide (PAM) were introduced to form hydrogen bond linkages and covalent bond networks respectively. The three-dimensional hydrogel networks showed greatly improved mechanical strength. Impressive compressive fatigue resistance was present for 100 cycles' compression forming only 0.7 % shape deformation. The phenomenon was mainly attributed to promoted stress-bearing and energy dissipation from the DN cross-linking. The GM hydrogels also exhibited good electronic conductivity and excellent anti-bacterial capabilities with inhibition against more than 80 % of E. coli., attributing to the tunable attachments of FA. Thus, we provided multi-functional hydrogels of high potential serving as anti-fatigue/bacterial and conductive strain sensors on the fields of wearable devices.