Search

The increasing environmental burden generated by disposable plastic wastes makes the development of sustainable substitute materials an emergent task. As one of the most abundant bioresources, chitosan (CS) has been considered as a potential candidate for plastic substitution. Conventionally, CS-based materials are fabricated through a solution-processing procedure due to the high crystallinity of CS. Herein, we designed a CS-based material via integrating CS into the network of polyimine (PI), which shows thermomechanical processability similar to plastics. Strong interactions were achieved through dynamic imine bond and hydrogen bond and thus formed a thermo-processable dynamic composite network. These CS-based plastic substitutes exhibit exceptional mechanical performances, excellent thermal/chemical stability, and a series of self-adaptiveness, including re-healing, reprocessing and multi-layer laminating. Notably, CPs can be easily degraded and 100% recycled for the production of next-generation materials. This work provides an alternative route to produce green and sustainable biomass materials as a plastic substitute.

Ancient papers, facing the threat of acidification, aging and microbial corrosion, need to be repaired due to their significance of history, art and culture research. In this work, a new and highly efficient approach was proposed to deacidify and strengthen aging paper by in-situ quaternization for the conservation, in which MgO nanoparticles dispersed in hexamethyldisiloxane was coated on the paper surface and the aqueous alkaline solution and the 2, 3-epoxypropyl trimethyl ammonium chloride/isopropyl alcohol/water mixture were sprayed in a closed reactor. Results showed that properties of ageing papers were improved after MSCE-8/2 treatment. The pH value was in the range of 7.5–9.0 and the maximum amount of alkali storage was 220 mmol/Kg. The tensile strength and folding endurance were increased by 28.05% and 80%, respectively. The fluctuation range of brightness and chromatic aberration was 0.14 and 1.27. Moreover, treated paper also had the great anti-bacteria and anti-aging effects.

Traditional preparation methods of the hydrogel are not only tedious but also requiring external stimuli. Here, a plant catechol-inspired self-catalytic system (sulfonated lignin and iron ion) has been introduced to rapidly trigger the graft polymerization of vinyl monomers on the carboxymethyl xylan (CMX) at room temperature, generating an elastic, UV-shield, and conductive hydrogel. The rapid preparation process can be finished at room temperature in 5 min without the removal of oxygen. The hydrogel shows charming extension ratio (up to 460%) and tensile stress (up to 23 kPa), which can be ascribed to the double network structure constructed from Fe

In this work, a series of amphiphilic hemicellulose-based grafting polymers are synthesized by homogeneous esterification with various hydrophobic chain fatty acids. With the flexible chain conformation of hemicelluloses, the hemicellulose-graft-fatty acid is self-assembled into hard sphere micelles in aqueous solution through hydrophobic interactions. The resultant micelles show apparent hydrodynamic radius (Rh) varying in the range of 34-57 nm and radius of gyration (Rg) varying from 30 to 44 nm. Moreover, the Rh, Rg, zeta potential and critical micelle concentration (CMC) of the micelles gradually decreases with the increasing hydrophobic chain length. The aggregation number of micelles can be tuned by varying alkyl chain lengths. Taking curcumin (Cur) as a model drug, the hemicellulose micelles were investigated as drug carriers, which exhibit a chain length-controlled drug release behavior. Taken together, structure and property tunable hemicellulose-based micelles were obtained, and showed potential of application in pharmaceutical, food, and cosmetics fields.

Traditional preparation methods of the hydrogel are not only tedious but also requiring external stimuli. Here, a plant catechol-inspired self-catalytic system (sulfonated lignin and iron ion) has been introduced to rapidly trigger the graft polymerization of vinyl monomers on the carboxymethyl xylan (CMX) at room temperature, generating an elastic, UV-shield, and conductive hydrogel. The rapid preparation process can be finished at room temperature in 5 min without the removal of oxygen. The hydrogel shows charming extension ratio (up to 460%) and tensile stress (up to 23 kPa), which can be ascribed to the double network structure constructed from Fe3+ and CMX. The hydrogel exhibits great transparency (up to 85.37%), fascinating UV-blocking (up to 99%), and conductive features, thereby serving as potential human body sensors. The rapid preparation of xylan-derived hydrogels via dynamic lignin catechol chemistry may open up a new approach to high-valued utilization of biomass.

A feasible approach to produce xylooligosaccharides (XOS) using organic acids as catalysts by microwave-induced hydrolysis of different hemicelluloses was developed. The effects of different acids (oxalic acid, maleic acid, citric acid and sulfuric acid), acid concentration, reaction temperature and reaction time on the hemicelluloses hydrolysis were investigated. Results demonstrated that organic acid was more beneficial to the XOS production than the conventional sulfuric acid. Higher acid concentration, higher reaction temperature and longer reaction time accelerated the further depolymerization of XOS to form monosaccharide. Response surface methodology was employed to optimize the reaction conditions (temperature and time) for the production of XOS from beechwood xylan (BX), corncob hemicelluloses (CH) and recovered hemicelluloses from the industrial waste liquor of dissolving pulp (RH), respectively. The predicted highest XOS yields were achieved to 39.31% (126.54°C-7.95min), 27.29% (120.00°C-0min), 30.32% (122.63°C-15.85min), respectively, being close to the experimental value (39.42%, 27.46% and 30.89%) from BX, CH and RH, indicating the fitted models of XOS yield were in good agreement with the experimental results.

Natural active compounds with antioxidant properties and other potential health benefits, like quercetin (Qu), have aroused wide concern for developing bio-functional products. However, their applications are hindered by their intrinsic poor water solubility and chemical instability. In this paper, a natural antioxidant alpha lipoic acid (ALA) was grafted onto chitosan (CS) to synthesize a novel graft polymer (CS-graft-ALA). In particular, this graft-polymer could self-assemble into spherical nanomicelles in water, with a low critical micelle concentration (CMC) of 0.0076 mg/mL. As a robust and active nanocarrier, the CS-graft-ALA micelles showed high efficiency in encapsulating Qu and dispersing Qu in water. As found, the antioxidant activity of Qu was effectively enhanced when entrapped within CS-graft-ALA micelles. Moreover, CS-graft-ALA micelles could significantly improve the photo-stability and temperature-stability of Qu. The Qu/CS-graft-ALA micelles with excellent water dispersability, stability and improved antioxidant activity hold a great potential for wide applications.

In the present study, a graded ethanol precipitation technique was employed to obtain hemicelluloses from the alkali-extracted corncob liquid. The relationship between the structural characteristics of alkali-soluble corncob hemicelluloses and the production of furfural was investigated by a heterogeneous process in a biphasic system. Results showed that alkali-soluble corncob hemicelluloses mainly consisted of glucuronoarabinoxylans and L-arabino-(4-O-methylglucurono)-D-xylans, and the drying way had less influence on the sugar composition, molecular weights and the functional groups of hemicelluloses obtained by the different ethanol concentration precipitation except for the thermal property, the amorphous structure and the ability for the furfural production. Furthermore, alkali-soluble corncob hemicelluloses with higher xylose content, lower branch degree, higher polydispersity and crystallinity contributed to the furfural production. A highest furfural yield of 45.41% with the xylose conversion efficiency of 99.06% and the furfural selectivity of 45.84% was obtained from the oven-dried hemicelluloses precipitated at the 30% (v/v) ethanol concentration.

High strength and self-healing properties of hydrogels are of great interest in tissue engineering and biomedical fields. In this paper, nanocomposite hydrogels were prepared by freeze-thaw cycle method via fabricating physical cross-links into chemical-crosslinked formed polymer network. The properties of nanocomposite hydrogels were characterized by FTIR, XRD, SEM, rheological analysis, swelling analysis and mechanical test. The results showed that the electrostatic interaction between CNC and QAX and the high amount of PVA (20 wt%) were favorable to improve the mechanical properties of nanocomposite hydrogels, in which the maximum compressive strength and elongation at break of nanocomposite hydrogels were 1.56 MPa and 771 %, respectively. Prepared hydrogels achieved self-healing without any external stimuli at room temperature with the help of hydrogen bonds and the entanglement of long polymer chains, the healing efficiency was 37.03 % within 48 h. These hydrogels with high strength and self-healing properties will offer new insights for xylan application.

A new xylan ester (xylan 3,5-dinitrobenzoate) as a creatinine adsorbent was prepared by the homogeneous acylation of xylan with 3,5-dinitrobenzoyl chloride in 1-butul-3-methylimidazolium chloride ionic liquid. The influences of reaction conditions on the degree of substitution values of xylan esters were discussed. Results indicated that xylan esters with the degree of substitution range from 1.34 to 1.77 were obtained under the given conditions. The FTIR and 13 C NMR spectroscopies provided the evidence of grafting 3,5-dinitrobenzoyl groups onto the backbone of xylan. Moreover, the adsorption properties of the xylan ester for creatinine were also investigated. Isotherm studies showed that the sorption capacities for creatinine were 2.45, 2.08 and 1.86 mg/g for 23, 30 and 37 °C, respectively. Thermodynamic studies performed indicated the sorption process mainly was controlled by the chemical adsorption. Therefore, xylan 3,5-dinitrobenzoate displayed the promising application in the treatment of chronic renal failure by the creatinine adsorption as the new oral adsorbent.

Composite films of xylan and polyvinyl alcohol were produced with citric acid as a new plasticizer or a cross-linking agent. The effects of citric acid content and polyvinyl alcohol/xylan weight ratio on the mechanical properties, thermal stability, solubility, degree of swelling and water vapor permeability of the composite films were investigated. The intermolecular interactions and morphology of composite films were characterized by FTIR spectroscopy and SEM. The results indicated that polyvinyl alcohol/xylan composite films had good compatibility. With an increase in citric acid content from 10% to 50%, the tensile strength reduced from 35.1 to 11.6 MPa. However, the elongation at break increased sharply from 15.1% to 249.5%. The values of water vapor permeability ranged from 2.35 to 2.95 × 10−7 g/(mm2 h). Interactions between xylan and polyvinyl alcohol in the presence of citric acid become stronger, which were caused by hydrogen bond and ester bond formation among the components during film forming.

Here, we designed a self-healing composite hydrogel with antioxidant and antibacterial activities by using cellulose nanofibrils (CNF) and tannic acid (TA) as functional additives. Excellent mechanical stability, moldability, stretchability and rapid self-healing ability without any external intervention were realized in one system due to the combined dynamic borate ester bonding between polyvinyl alcohol-borax (PB) and multi-hydrogen bonding between different components. The rheological measurements indicated the incorporation of CNF and TA to PB system substantially affected the viscoelasticity of hydrogels. The unique antioxidant and antibacterial properties were achieved due to the complexation of TA. These high performance multifunctional hydrogels opens a window for a broad application in the field of smart devices and surface engineering.

Xylan-based temperature/pH sensitive hydrogels were prepared by the crosslinking copolymerization of xylan with N-isopropylacrylamide (NIPAm) and acrylic acid (AA) using N,Ń-methylenebis-acrylamide (MBA) as a cross-linker and 2,2-dimethoxy-2-phenylacetophenone as a photoinitiator via ultraviolet irradiation. The influence of the NIPAm, AA and MBA amount on properties of xylan-based hydrogels was discussed. The morphology and interactions of hydrogels were characterized by SEM and FTIR. The lower critical solution temperature (LCST) of hydrogels was investigated by DSC. The results indicated that the LCST of hydrogels emerged at around 34°C and increased with increasing the AA content. The drug encapsulation efficiency of as-prepared hydrogels reached to 97.60% and the cumulative release rate of acetylsalicylic acid was 90.12% and 26.35% in the intestinal and gastric fluid, respectively. Xylan-based hydrogels were proved to be biocompatible with NIH3T3 cell by MTT assay and showed the promising application as drug carriers for the intestinal-targeted oral drug delivery.

In this study, hemicelluloses were isolated from the apical, middle and basal segments of N. cadamba using a 2N KOH extraction procedure. Chemical composition and structural characterization of the three hemicellulosic fractions obtained were comparatively investigated by a combination of HPLC, GPC, FTIR, 1H,13C, HSQC NMR and TGA techniques. According to the sugar analysis and spectral results, (4-O-methyl) glucuronoxylan was the primary hemicellulose identified in the samples with trace levels of mannan also present. All of the three samples showed spherical polymers in 0.005M sodium phosphate solution (containing 0.02N NaCl). Xylan in the middle and basal segment stems had higher molecular weights. Our findings show that during xylogenesis in N. cadamba, changes are observed in xylan content and molecular weight.

Chemical modification is the most important means to obtain novel biopolymers and biomaterials from the abundant biomacromolecules. In this paper, hemicellulosic succinate, which is very important biomacromolecule for the preparation of functional materials, was homogeneously prepared in 1-butyl-3-methylimidazolium chloride ([BMIM]Cl) ionic liquid. The influence of reaction conditions used in this work on the degree of substitution (DS) was investigated, and the chemical structure and the thermal stability of hemicellulosic succinate were characterized by FT-IR and 13 C NMR spectroscopies as well as thermogravimetry. A high DS of up to 1.80 could be achieved at short time scale in [BMIM]Cl ionic liquid without any catalysts, which is probably due to the excellent dissolving capacity and catalytic effect of ionic liquid. These results indicate that ionic liquids open up totally new opportunities for chemically functionalization of hemicelluloses.

Chemical modification is the most important method to design novel biopolymer and biomaterials from the abundant and biocompatible hemicelluloses. In this paper, an efficient method to synthesize hemicellulosic derivatives with bifunctional groups was developed by the etherification of hemicelluloses with acrylamide in the butanol/water medium. Varying the reaction condition such as reaction time, reaction temperature, and the amount of acrylamide and so on, the optimized hemicellulosic derivative with a higher total degree of substituent (DS) of 0.92 and with the 0.43 ratio of carbamoylethy groups and carboxyethyl groups was obtained. 13C NMR analysis showed that the etherification occurred preferably at C-3 position of xylose. A significant degradation of the polymers occurred during the etherification. The shear-thinning of the hemicellulosic derivatives became more dramatic. The solution of the hemicellulosic derivatives showed lower viscosity and modulus as compared with the native hemicelluloses, exhibiting a less elastic behavior.

Three organic solvents and one aqueous alkaline solution for fully fractional dissolving hemicelluloses from mild ball-milled cell wall of lignified barley straw and maize stems are described: 90% neutral dioxane, 80% dioxane containing 0.05 M HCl, dimethyl sulfoxide (DMSO), and 8% aqueous KOH. The four successive extractions resulted in dissolution of 94.6% and 96.4% of the original hemicelluloses and 93.7% and 95.3% of the original lignin from barley straw and maize stems, respectively. The structures of the hemicellulosic fractions released during the treatment with the neutral solvents of 90% dioxane and DMSO was found to remain intact, while the extractions with 80% acidic dioxane and 8% KOH under the conditions used resulted in a partial depolymerization of dissolved polysaccharides by cleavage of the glycosidic bonds and saponification of the ester groups in the polymers. The 90% neutral dioxane-soluble hemicellulosic fractions consisted mainly of the more branched arabinoxylans and mixed-linkage glucans such as β-glucans, whereas the hemicellulosic fractions solubilized during the sequential treatments with 80% acidic dioxane, DMSO, and 8% KOH are composed of arabino-(4-O-methyl-d-glucurono) xylans as the major hemicellulosic materials. In addition, the hemicellulosic polymers contained small amounts of ferulic and p-coumaric acids and lignins, revealing that the hemicelluloses removed are mostly unbound to the lignins in the cell walls of cereal straws. This non-degradative cell wall dissolution offers the potential to analyze polysaccharide components for the first time, and improve current hemicellulosic isolation method by using high concentration of aqueous alkali from the delignified cell walls.

In this work the application of different hemicellulosic derivatives including different degrees of substitution (DS) cationic hemicelluloses and carboxymethyl hemicelluloses in sulfate kraft pulp were investigated in detail. It was found that cationic hemicelluloses and carboxymethyl hemicelluloses could improve the physical properties of hand sheets, while the cooperation of cationic hemicelluloses and carboxymethyl hemicelluloses could enhance sharply the physical properties of hand sheets. When the dosages of cationic hemicelluloses with DS of 0.37 and carboxymethyl hemicelluloses with DS of 0.35 were 1.0% and 1.0% (based on dry pulp weight), respectively, the physical properties of hand sheets was significantly improved, breaking lengthen and tear index of hand sheets increased by 21.1% and 54.6% compared with the control hand sheets without any additives added. The fiber intertexture of the hand sheets was observed by SEM. The results indicated that hemicelluloses could be used as the source for the production of wet-end additives in papermaking, which might represent an important strategy for sustainable use of the agricultural residue.

Wheat straw hemicelluloses were acetylated with acetic anhydride using iodine as a novel catalyst in 1-butyl-3-methylimidzolium chloride ([C 4 mim]Cl) ionic liquid (IL). Acetylated hemicelluloses with yield and degree of substitution (DS) from 70.5% to 90.8% and between 0.49 and 1.53, respectively, are accessible in a complete homogeneous procedure by changing the reaction temperature, reaction duration, the dosage of catalyst, and the dosage of acetic anhydride. The preferred reaction parameters that resulted in the highest DS were follows: 20:1 reactant molar ratio, 100 °C, 30 min, 15% iodine, in which about 83% hydroxyl groups in native hemicelluloses were esterified. The structural features of the acetylated hemicelluloses were characterized by 13 C NMR and FT-IR spectroscopy. The thermal stability of the acetylated hemicelluloses increased upon chemical modification. It is the first time that we have demonstrated that ILs could be used as an environmentally friendly solvent for the chemical modification of hemicelluloses.

Novel cationic hemicelluloses from sugarcane bagasse were synthesized by quaternization with 3-chloro-2-hydroxypropyltrimethylammonium chloride (CHMAC) using sodium hydroxide as a catalyst in aqueous ethanol solution. The parameters including the molar ratio of NaOH/CHMAC (0.8–2.0), the molar ratio of CHMAC to anhydroxylose units in hemicelluloses (0.5–3.0), reaction time (0.5–2.5 h), and reaction temperature (50–80 °C) were optimized and the extent of quaternization was measured by yield and degree of substitution (DS). A CHMAC/hemicellulose molar ratio of 1.0 and a NaOH/CHMAC molar ratio of 1.2 were found to be an optimum condition for the reaction to proceed smoothly and to yield a product with an expected DS. The structure of the cationic hemicellulosic derivative was characterized by gel permeation chromatography (GPC), Fourier transform infrared (FT-IR), and 13C nuclear magnetic resonance (NMR) spectroscopy as well as thermal analysis. It was found that the thermal stability and weight-average molecular weight of modified hemicelluloses decreased after chemical modification.

One water-soluble and four alkali-soluble hemicellulosic preparations from perennial ryegrass leaves were comparatively studied, and their chemical composition, structural features, and physicochemical properties were examined. The relative monosaccharide compositions of the hemicelluloses were determined by high performance anion exchange chromatography after acid hydroloysis. 13 C NMR and FT-IR spectroscopic methods gave details of the anomeric linkage configuration and confirmed the structure of the hemicelluloses. The results showed that the water-soluble hemicelluloses probably consist of galactoarabinoxylans, β-glucan, and noticeable amounts of pectic polysaccharides, which had a lower molecular weight (19,360 g mol −1 ), while the four alkali-soluble hemicellulosic preparations are presumably composed of galactoarabinoxylans, l -arabino (4- O -methyl- d -glucurono)xylans, and β-glucan, which had higher molecular weights between 31,060 and 36,140 g mol −1 . Galactoarabinoxylans constitute a major fraction of both water- and two alkali-soluble hemicelluloses H 2 and H 3 , isolated with a higher concentration of alkali for a shorter period (18% NaOH or 18% KOH at 22 °C for 2 h). They consist of a linear β-(1 → 4) linked xylan backbone to which α- l -arabinofuranose units and/or short chains of sugar residues containing arabinose and galactose are attached as side residues via α-(1 → 3) and/or α-(1 → 2) linkages. On the other hand, the other two alkali-soluble hemicellulosic preparations H 4 and H 5 , extracted with a relatively lower concentration of alkali for a longer period (10% NaOH or 10% KOH at 22 °C for 16 h), mainly comprised l -arabino (4- O -methyl- d -glucurono)xylans, in which the β-(1 → 4) linked xylan backbone is substituted in O-3 and/or O-2 by signal α- l -arabinose residue and α- d -glucuronic acid or 4- O -methyl-glucuronic acid. β-Glucan, both in water- and alkali-soluble hemicelluloses, was characterized as linear homopolymers consisting of both β-(1 → 3) and β-(1 → 4) glucosidic linkages.