Renewable Natural Polymer Research Articles

Preparation and properties of room temperature foaming lignin-based non-isocyanate polyurethane foams

The preparation and application of biomass-based non-isocyanate polyurethane (NIPU) is an essential and meaningful hot topic research work in the field of polyurethane industry, due to its advantages of sustainability of raw materials and no highly toxic isocyanate used in the synthesis. Lignin, as the second most renewable natural polymer on earth, was used in this paper to synthesize lignin-based non-isocyanate polyurethane (L-NIPU) resins. Subsequently, L-NIPU foams were prepared by self-foaming at room temperature with the addition of maleic acid as an initiator and glutaraldehyde as a cross-linker, and their properties were investigated. Results show that L-NIPU foams are lightweight (0.11–0.18 g/cm3), have low thermal conductivity (0.033–0.04 W/m·K), and have excellent compressive strength. When the addition of maleic acid and glutaraldehyde is respectively 18 % and 25 % (based on L-NIPU resin quality), the compressive strength can be as high as 0.5 MPa, and the thermal conductivity is only 0.03559 W/m·K, so it can be used as an insulating board in buildings. In addition, FT-IR and XPS analyses showed that maleic acid and glutaraldehyde can react with the amino group in L-NIPU to form a cross-linked network structure, which ensures the favorable mechanical properties of the foam.

Recent Advances in Natural-Polymer-Based Hydrogels for Body Movement and Biomedical Monitoring.

In recent years, the interest in medical monitoring for human health has been rapidly increasing due to widespread concern. Hydrogels are widely used in medical monitoring and other fields due to their excellent mechanical properties, electrical conductivity and adhesion. However, some of the non-degradable materials in hydrogels may cause some environmental damage and resource waste. Therefore, organic renewable natural polymers with excellent properties of biocompatibility, biodegradability, low cost and non-toxicity are expected to serve as an alternative to those non-degradable materials, and also provide a broad application prospect for the development of natural-polymer-based hydrogels as flexible electronic devices. This paper reviews the progress of research on many different types of natural-polymer-based hydrogels such as proteins and polysaccharides. The applications of natural-polymer-based hydrogels in body movement detection and biomedical monitoring are then discussed. Finally, the present challenges and future prospects of natural polymer-based hydrogels are summarized.

A high-sensitive capacitive humidity sensor based on chitosan-sodium chloride composite material

Chitosan, as a hydrophilic, renewable, biodegradable, and cost-effective natural polymer, holds great promise in humidity sensor applications. This study proposes a green high-performance capacitive humidity sensor based on chitosan (CS)-sodium chloride (NaCl) composites. The CS-NaCl films were fabricated through a simple drip coating method, and their surface morphology and structure were characterized using SEM, XRD, FTIR and XPS techniques. The pure chitosan humidity sensor demonstrates an impressive response of 1180.17 % with excellent linearity. The introduction of NaCl markedly boosted the sensor response, with CS-50 wt% NaCl composites exhibiting a 72-fold increase (86, 492.84 %) in capacitance response compared to pure CS films. The contact angle test demonstrated that the chitosan film exhibited good hydrophilicity, which was further enhanced by the addition of NaCl. XRD and FTIR characterization confirmed that NaCl altered the structural properties of chitosan, disrupted hydrogen bonds, and consequently increased the mobility of polarizing groups and the dielectric constant. A water adsorption model was developed to elucidate the humidity sensing mechanism of the CS-NaCl sensor. The CS-NaCl composite material presents advantages such as easy preparation, high sensitivity, eco-friendliness, and promising practical applications in humidity sensing.

Anti-SARS-CoV-2 activity of microwave solvolysis lignin from woody biomass

The global pandemic caused by the novel coronavirus, severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2), has had profoundly detrimental effects on our society. To combat this highly pathogenic virus, we turned our attention to an abundant renewable natural aromatic polymer found in wood. Through a chemical modification of Eucalyptus and Japanese cedar wood via acidic microwave solvolysis in equivolume mixture of 2 % (w/w) aqueous H2SO4, ethylene glycol, and toluene at 190 °C. Subsequently, we separated the resulting solvolysis products through extractions with toluene, ethyl acetate, and ethanol. Among these products, the ethyl acetate extract from Eucalyptus wood (eEAE) demonstrated the highest inhibition effects against the novel SARS-CoV-2. We further divided eEAE into four fractions, and a hexane extract from the ethanol-soluble portion, termed eEAE3, exhibited the most substantial inhibitory rate at 93.0 % when tested at a concentration of 0.5 mg/mL. Analyzing eEAE3 using pyrolysis gas chromatography–mass spectrometry revealed that its primary components are derived from lignin. Additionally, 1H–13C edited-heteronuclear single quantum coherence nuclear magnetic resonance analysis showed that the solvolysis process cleaved major lignin interunit linkages. Considering the abundance and renewability of lignin, the lignin-derived anti-SARS-CoV-2 agent presents a promising potential for application in suppressing infections within our everyday environment.

Dramatic improvement in corrosion inhibition effect of carboxymethyl cellulose by modified with levodopa: Experimental study and first-principles calculations

Cellulose, as a kind of renewable natural polymer, has great potential as green corrosion inhibitor. However, the low inhibition effect is the obstacle to its practical application. Herein we developed a high efficiency green cellulose derivative corrosion inhibitor, levodopa-carboxymethyl cellulose (LDCMC), by modifying carboxymethyl cellulose (CMC) with levodopa (LD) through a simple amidation reaction. The inhibition effect of CMC for mild steel in HCl medium is dramatically improved with an increase in inhibition efficiency from 56.98% of CMC to 97.27% of LDCMC. The intrinsic nature of the dramatically improved inhibition effect is in-depth unraveled by first-principles calculations based on density functional theory (DFT). CMC and LDCMC can adsorb on the mild steel surface through -OH, -COOH and LD fragment by forming the covalent bonds with steel surface. Benefiting from the additional strong adsorption of the benzene ring in LD fragment, the introduction of LD can significantly enhance the adsorption capacity of LDCMC, which is the intrinsic nature of the dramatical improvement in the inhibition effect of LDCMC.

The Efficiency of κ-Carrageenan-Chitosan-PVA-MWCNTs Membranes in Removing Methylene Blue, Rhodamine B, Bromocresol Purple, and Murexid from Water

The electrocoagulation method has been proven to be highly effective in removing metal ions from water, with a removal efficiency of over 97%. However, in terms of removing organic pollutants such as synthetic dyes, the efficiency of electrocoagulation is still relatively low. A hybrid approach combining electrocoagulation with membrane filtration has been proposed to enhance the removal of organic contaminants. Eco-friendly membranes made from renewable natural polymers like carrageenan and chitosan, reinforced with synthetic polymers such as polyvinyl alcohol and carbon nanotubes, have shown to be promising for this application. In this study, membranes with varying chitosan/carrageenan ratios of 0.2, 0.33, 0.5, and 0.71 (g/g) were used to remove synthetic dyes, including methylene blue, rhodamine B, bromocresol purple, and murexid, at a concentration of 200 ppm from 8.5 ml of water. From the SEM images, the four membranes have almost the same surface and cross-section morphology. The results showed that the membrane with a chitosan/carrageenan ratio of 0.71 exhibited the highest removal efficiency for all synthetic dyes. The parameter affecting the membrane’s removal efficiency is the interaction between the membrane and synthetic dyes. Murexid, an anionic dye, achieved a 100% removal efficiency, surpassing cationic dyes such as rhodamine B and methylene blue. Besides interactions, the dye’s molecular size determines the removal’s efficiency. The molecular size of rhodamine B is larger than that of methylene blue, and the removal efficiency of rhodamine B (98.4%) is greater than methylene blue (91%). Bromocresol purple is almost the same size as rhodamine B but not ionic because it has the lowest removal efficiency of 34.55%.

Sodium carboxymethyl cellulose and MXene reinforced multifunctional conductive hydrogels for multimodal sensors and flexible supercapacitors

With the growing demand for eco-friendly materials in wearable smart electronic devices, renewable, biocompatible, and low-cost hydrogels based on natural polymers have attracted much attention. Cellulose, as one of the renewable and degradable natural polymers, shows great potential in wearable smart electronic devices. Multifunctional conductive cellulose-based hydrogels are designed for flexible electronic devices by adding sodium carboxymethyl cellulose and MXene into polyacrylic acid networks. The multifunctional hydrogels possess excellent mechanical property (stress: 310 kPa; strain: 1127 %), toughness (206.67 KJ m−3), conductivity (1.09 ± 0.12 S m−1) and adhesion (82.19 ± 3.65 kPa). The multifunctional conductive hydrogels serve as strain sensors (Gauge Factor (GF) = 5.79, 0–700 % strain; GF = 14.0, 700–900 % strain; GF = 40.36, 900–1000 % strain; response time: 300 ms; recovery time: 200 ms) and temperature sensors (Temperature coefficient of resistance (TCR) = 2.5755 °C−1 at 35 °C- 60 °C). The sensor detects human activities with clear and steady signals. A distributed array of flexible sensors is created to measure the magnitude and distribution of pressure and a hydrogel-based flexible touch keyboard is also fabricated to recognize writing trajectories, pressures and speeds. Furthermore, a flexible hydrogel-based supercapacitor powers the LED and exhibits good cyclic stability over 15,000 charge-discharge cycles.

Environmentally friendly separators based on cellulose diacetate-based crosslinked networks for lithium-ion batteries

Biomass fibers are recognized as degradable and renewable green natural polymer materials. However, research on biomass fiber-based lithium battery separators is still relatively limited. Here, a kind of cellulose diacetate-based composite separator for lithium batteries was investigated via electrostatic spinning technology. In this study, M-CDA/PEO/BM composite separators were obtained by modifying fiber-based nonwovens through deacetylation, followed by an infiltration process and thermal cross-linking reaction to introduce boehmite (BM) and polyethylene oxide (PEO). Wherein the infiltrating solution is composed of polyethylene glycol diglycidyl ether (PEGDE), polyetheramine (DPPG), and boehmite particles. The results demonstrate that this nanofibre composite separator exhibits good heat tolerance (no shrinkage at 200 °C), excellent wettability (contact angles only 15.1°), and high ionic conductivity (2.83 mS cm−1) in electrolytes. Additionally, the cells utilizing the composite separator exhibited superior cycle performance and better multiplier performance (170 mAh·g−1 at 0.5C) compared to the polypropylene separator that is currently available in the market, under identical circumstances. This renewable composite possesses remarkable properties that position it as a highly promising option for lithium-ion battery separators with exceptional performance.

Effectiveness of modified lignin on poly(butylene adipate‐co‐terephthalate)/poly(lactic acid) mulch film performance

AbstractIn this work, the biodegradable poly(butylene adipate‐co‐terephthalate) (PBAT)/poly(lactic acid) (PLA) blend (ECOVIO®) and lignin, a renewable and biodegradable natural polymer with high UV absorption and modified by gamma radiation were used to produce agriculture mulch films. Lignin was gamma‐irradiated at 30 and 60 kGy. The irradiated and non‐irradiated lignin content of 2 wt% was incorporated into PBAT/PLA blend matrix using a twin‐screw extruder and extrusion blown film to prepare flexible films. PBAT/PLA/LIGNIN films were characterized by Fourier transform infrared (FTIR) spectroscopy, differential scanning calorimetry (DSC), x‐ray diffraction (XRD), field emission scanning electron microscopy (FESEM), tensile tests, contact angle, and UV–Vis analysis. FTIR spectra showed partial miscibility between PBAT/PLA and lignin, being intensified in irradiated lignin compounds. The DSC and XRD results confirmed that the degree of crystallinity of the blends was not significantly influenced by lignin addition. FE‐SEM images showed better dispersion and miscibility in PBAT/PLA/Irradiated lignin. Miscibility improvement provided by irradiated lignin promoted better mechanical properties, mainly with lignin irradiated at 60 kGy. PBAT/PLA/LIGNIN films containing 2 wt% showed excellent UV‐barrier property and greater hydrophobicity. Summing up, incorporation of low contents of irradiated lignin could be an interesting alternative to produce biodegradable UV‐blocking agriculture mulch films.

Research Progress and Prospect of Stimuli-Responsive Lignin Functional Materials.

As the world's second most abundant renewable natural phenolic polymer after cellulose, lignin is an extremely complex, amorphous, highly cross-linked class of aromatic polyphenolic macromolecules. Due to its special aromatic structure, lignin is considered to be one of the most suitable candidates to replace fossil materials, thus the research on lignin functional materials has received extensive attention. Because lignin has stimuli-sensitive groups such as phenolic hydroxyl, hydroxyl, and carboxyl, the preparation of stimuli-responsive lignin-based functional materials by combining lignin with some stimuli-responsive polymers is a current research hotspot. Therefore, this article will review the research progress of stimuli-responsive lignin-based functional materials in order to guide the subsequent work. Firstly, we elaborate the source and preparation of lignin and various types of lignin pretreatment methods. We then sort out and discuss the preparation of lignin stimulus-responsive functional materials according to different stimuli (pH, light, temperature, ions, etc.). Finally, we further envision the scope and potential value of lignin stimulus-responsive functional materials for applications in actuators, optical coding, optical switches, solar photothermal converters, tissue engineering, and biomedicine.

Catalytic Strategies and Mechanism Analysis Orbiting the Center of Critical Intermediates in Lignin Depolymerization

Lignin, as a precious resource given to mankind by nature with abundant functional aromatic structures, has drawn much attention in the recent decade from academia to industry worldwide, aiming at harvesting aromatic compounds from this abundant and renewable natural polymer resource. How to efficiently depolymerize lignin to easy-to-handle aromatic monomers is the precondition of lignin utilization. Many strategies/methods have been developed to effectively degrade lignin into monomers, such as the traditional methods of pyrolysis, gasification, liquid-phase reforming, solvolysis, chemical oxidation, hydrogenation, reduction, acidolysis, alkaline hydrolysis, alcoholysis, as well as the newly developed redox-neutral process, biocatalysis, and combinatorial strategies. Therefore, there is a strong demand to systemically summarize these developed strategies and methods and reveal the internal transformation principles of the lignin. Focusing on the topic of lignin depolymerization to aromatic chemicals, this review reorganizes and categorizes the strategies/methods according to their mechanisms, orbiting the center of critical intermediates during the lignin linkage transformation, which includes the critical anionic intermediates, cationic intermediates, organometallic intermediates, organic molecular intermediates, aryl cation radical intermediates, and neutral radical intermediates. The corresponding introduction involves the generation and the transformation chemistry of the critical intermediates via the corresponding C-H/O-H/C-C/C-O chemical bond transformations, leading to the cleavage of the C-C/C-O linkage bonds. Accompanying the brief introduction of lignin chemistry and the final concluding remarks and perspectives on lignin depolymerization, this review aims to provide a current research process of lignin depolymerization, which may provide useful suggestions for this vigorous research field.

Characterization of chestnut starch acetate with different degrees of substitution

Abstract Chestnut starch acetates (CSA) with different degrees of substitution (DS) were prepared. The structure and physicochemical properties of CSA were then determined, with scanning electron microscopy showing that most of the CSA granules were damaged and dented, and adhered with increased in DS. X-ray diffraction results indicated that the crystal form of CS and CSA was type C. Chemical structure analysis showed that the starch molecule was grafted with acetyl groups. The transparency, freeze–thaw stability, solubility and swelling power of CSA improved with an increase in DS. The viscosity and stability of CSA were significantly improved and pasting temperatures reduced compared with native CS. The cohesion, hardness, gumminess, chewiness and springiness of CSA decreased with an increase in DS, whereas adhesiveness increased. By comparing the properties of CSA with different DS, a new option was provided for the application of renewable natural polymer CSA in food fields.

Biomimetic Bridging for Reconstructing Biomass Components toward Significantly Enhanced Films from the Full Composition of Bamboo

Bamboo is a kind of renewable natural polymer resource. Using bamboo biomass without a component isolation process can be a sustainable route for the preparation of an eco-friendly biomass film. Inspired by the natural structure of plant biomass, we designed to introduce a bionic interaction, being akin to the role of hemicellulose in natural biomass, for connecting the cellulose and lignin components using tannic acid-modified cellulose nanocrystals (TA@CNCs) as the bridging molecules. In order to make up for the size difference between the cellulosic molecules and lignin particles, cellulose nanocrystals (CNCs) served as the carriers of TA. Core–shell hybrids of TA@CNCs were prepared and added into the solution of bamboo powder dissolved in a tetrabutylammonium hydroxide/dimethyl sulfoxide aqueous solvent (TBAH/H2O/DMSO) followed by gelation in air and regeneration in water to prepare the bamboo-derived biomass films with high strength. The results showed that the tensile strength of the as-prepared films was effectively improved from 55.4 to 127.2 MPa by adding 5 wt % TA@CNCs. Structural analyses indicated that TA@CNCs serve as an excellent modifier for the enhancement of cellulose–lignin interfaces by rationally reconstructing the biomimetic hydrogen-bonded system.

Covalent Immobilization of Natural Biomolecules on Chitin Nanocrystals.

As a highly crystalline and renewable natural polymer nanomaterial, chitin nanocrystals (ChNCs) have attracted intense interest in the biomedical field. The structure of a ChNC is composed of an acetylglucosamine unit containing two hydroxyl groups and an acetyl group. The acetyl group can be converted to the active amino group through deacetylation, which is under the condition of maintaining the rod-like morphology and high crystalline property and is beneficial for the following modification and potential application. We investigated the relationship between different treatments and varied crystallinities of the modified ChNC, which obtained surface amino groups and aldehyde groups and retained high crystallinity. The natural biomolecules were covalently immobilized on the surface of the ChNC. The etherification was performed based on the hydroxyl groups. Based on the amino groups and the aldehyde groups, the carboxyamine and Knoevenagel condensation reactions were realized on ChNCs. Finally, natural biomolecule-modified ChNCs showed no or low cytotoxicity, antibacterial properties, and high antioxidant properties, which extended their potential biomedical applications.

Application of three types of aminated lignins for efficient removal of Cd(II) and Pb(II) ions in aqueous solution

Lignin is a renewable natural aromatic polymer that is generated as a co-product during lignocellulosic biorefinery processes, and it has been applied widely as a functional biomaterial. In this study, the adsorption behavior of Cd(II) and Pb(II) metal ions was investigated via ion chelation using aminated lignins (ALs) with primary, secondary, and tertiary amine groups. ALs exhibited optimal Cd(II) and Pb(II) adsorption capacities in solution under neutral conditions due to their chelating, electrostatic, and cationic–π interactions with metal ions. The AL with the primary amine group showed the highest adsorption capacities for both Cd(II) and Pb(II), reaching 83.2 and 159.7 mg·g-1, respectively, followed by the ALs with secondary and tertiary amine groups. The adsorption kinetics and isotherm analysis demonstrated that all adsorption behaviors followed the Langmuir isotherm and pseudo-second-order kinetics. Thermodynamic studies revealed that the adsorption processes of Cd(II) and Pb(II) using the ALs were spontaneous and endothermic. These results demonstrate that ALs are promising adsorbents for the removal of Cd(II) and Pb(II) metal ions.

About Hydrophobicity of Lignin: A Review of Selected Chemical Methods for Lignin Valorisation in Biopolymer Production

Lignin is the second most abundant renewable natural polymer that occurs on Earth, and as such, it should be widely utilised by industries in a variety of applications. However, these applications and possible research seem to be limited or prevented by a variety of factors, mainly the high heterogeneity of lignin. Selective modifications of the structure and of functional groups allow better properties in material applications, whereas the separation of different qualitative lignin groups permits selective application in industry. This review is aimed at modification of the lignin structure, increasing the hydrophobicity of the produced materials, and focusing on several perspective modifications for industrial-scale production of lignin-based polymers, as well as challenges, opportunities, and other important factors to take into consideration.

Cellulose-based composite scaffolds for bone tissue engineering and localized drug delivery.

Natural bone constitutes a complex and organized structure of organic and inorganic components with limited ability to regenerate and restore injured tissues, especially in large bone defects. To improve the reconstruction of the damaged bones, tissue engineering has been introduced as a promising alternative approach to the conventional therapeutic methods including surgical interventions using allograft and autograft implants. Bioengineered composite scaffolds consisting of multifunctional biomaterials in combination with the cells and bioactive therapeutic agents have great promise for bone repair and regeneration. Cellulose and its derivatives are renewable and biodegradable natural polymers that have shown promising potential in bone tissue engineering applications. Cellulose-based scaffolds possess numerous advantages attributed to their excellent properties of non-toxicity, biocompatibility, biodegradability, availability through renewable resources, and the low cost of preparation and processing. Furthermore, cellulose and its derivatives have been extensively used for delivering growth factors and antibiotics directly to the site of the impaired bone tissue to promote tissue repair. This review focuses on the various classifications of cellulose-based composite scaffolds utilized in localized bone drug delivery systems and bone regeneration, including cellulose-organic composites, cellulose-inorganic composites, cellulose-organic/inorganic composites. We will also highlight the physicochemical, mechanical, and biological properties of the different cellulose-based scaffolds for bone tissue engineering applications.

Use of a superbase/DMSO/CO2 solvent in order to incorporate cellulose into organic ionogel electrolyte for flexible supercapacitors

The facile preparation of sustainable polymer gel electrolyte by using renewable natural polymers has attracted much attention, and the development of new polymer gel electrolyte materials largely depends on the facile design and preparation of a polymer network capable of effectively loading external high-performance electrolyte. In this study, taking the advantages of a newly developed solvent system superbase/DMSO/CO2 for cellulose, a new and facile “all-in-one” strategy to engineer cellulose into flexible cellulosic poly (protic ionic liquids)/PVA-based composite organic ionogel electrolyte (CPOIE) has been developed through in situ derivatization, chemical cross-linking and compositing strategy using succinic anhydrides, epichlorohydrin, and polyvinyl alcohol, respectively. The findings show that CPOIEs exhibit both excellent mechanical properties and superior electrochemical properties (high ionic conductivity up to 4.2 mS/cm at room temperature with a wide electrochemical window of 2.0 V for C1P1OIE sample). A supercapacitor assembled by using the as-prepared C1P1OIE sample delivers a good specific capacitance of 122 F/g at 0.5 A/g, a high energy density up to 17.38 Wh/Kg at room temperature and an excellent cyclic stability up to 8000 cycles.

Cooperative construction of oil/water separator using renewable lignin and PDMS

Super-hydrophobic materials have played a significant role in the oil/water separation field. The traditional super-hydrophobic materials are prepared by fluorine-containing materials. However, although fluorine-containing materials have lower surface energy, they are expensive and difficult to degrade. Therefore, it's a great challenge for the designed and prepared the super-hydrophobic porous materials with super-oleophilicity to explore an environmentally friendly, easy-to-operate, low-cost, and renewable separator for oil/water mixtures separation. In this work, taking advantage of the microscale of renewable lignin and the low surface energy of polydimethylsiloxane （PDMS）, the porous super-hydrophobic sponge material with super-oleophilicity was prepared by the synergy of polydimethylsiloxane (PDMS) and lignin. After soaking and curing, the porous super-hydrophobic sponge showed a high apparent water contact angle which is up to 160°. The designed porous sponge materials can effectively absorb heavy oil in oil-water mixtures separation. Moreover, the porous sponge materials possess temperature stability, acid and alkali stability, and are easy easily recyclable. As high-efficiency oil-water separation material prepared by the synergy between renewable natural polymers and fluorine-free materials, this technique is not only conducive to remediate environmental problems but also helpful to explore the potentiality of lignin that seemingly bio-waste. At the same time, valuable oil can also be recycled.

Solid State NMR a Powerful Technique for Investigating Sustainable/Renewable Cellulose-Based Materials.

Solid state nuclear magnetic resonance (ssNMR) is a powerful and attractive characterization method for obtaining insights into the chemical structure and dynamics of a wide range of materials. Current interest in cellulose-based materials, as sustainable and renewable natural polymer products, requires deep investigation and analysis of the chemical structure, molecular packing, end chain motion, functional modification, and solvent–matrix interactions, which strongly dictate the final product properties and tailor their end applications. In comparison to other spectroscopic techniques, on an atomic level, ssNMR is considered more advanced, especially in the structural analysis of cellulose-based materials; however, due to a dearth in the availability of a broad range of pulse sequences, and time consuming experiments, its capabilities are underestimated. This critical review article presents the comprehensive and up-to-date work done using ssNMR, including the most advanced NMR strategies used to overcome and resolve the structural difficulties present in different types of cellulose-based materials.