High Degree Of Substitution Research Articles

Turning trash into treasure: conversion of agroresidue rice straw into carboxymethylcellulose biopolymer

AbstractIn the present study, rice straw‐derived cellulose was converted into carboxymethylcellulose (CMC) using alkalization followed by an etherification reaction. The synthesis conditions for this chemical modification were optimized such that CMC with a high degree of substitution (1.02) was obtained. Infrared spectra of the synthesized CMC clearly showed an increased intensity of the C═O bond at 1600 cm−1, confirming successful carboxymethylation. Further, X‐ray diffraction analysis demonstrated a decrease in cellulose crystallinity owing to partial rearrangement from a crystalline to an amorphous phase during initial alkalization reaction. The obtained CMC biopolymer was subsequently cross‐linked to form a composite hydrogel matrix reinforced with bentonite clay. The hydrogel showed about 91% adsorption capacity for methylene blue dye as a model contaminant in aqueous media. Therefore, this study shows that lignocellulosic agrowaste is a rich source of cellulose, and its derivatives such as CMC possess the potential to realize the waste to wealth sustainability goal.

Microwave-functionalized natural tannic acid as an anticorrosive UV-curable coating

Corrosion causes serious steel deterioration with consequent negative impacts on the environment and economy. Organic coatings are widely exploited to provide corrosion protection on low-carbon steel. However, the raw materials and preparation methods for common anticorrosive coatings are not sustainable. In this framework, the efficient microwave-assisted methacrylation of a natural polyphenolic compound, tannic acid (TA), provided a UV-curable monomer with a high degree of substitution. The produced methacrylated tannic acid (MTA) was characterized by means of 31P NMR and FTIR spectroscopies. The UV-curing of MTA by radical photopolymerization was deeply investigated via the real-time FTIR, photo-DSC, and photo-rheological analyses, confirming the high photo-reactivity of MTA with a conversion of 80 % and a gel point at 2.5 s. The UV-cured MTA showed good thermal stability and a glass transition temperature (Tg) of 133 °C. Furthermore, UV-cured MTA coating exhibited high hardness and hydrophobicity. The zeta potential measurement indicated a negatively charged surface with an isoelectric point (IEP) at pH 2.7. Finally, the good corrosion protection performance of UV-cured MTA coating on plasma pre-treated steel surface was assessed through electrochemical impedance spectroscopy.

A deep eutectic solvent with bifunctional acid sites treatment to upgrade a bamboo kraft pulp into a cellulose-acetate grade dissolving pulp

Valorization of non-wood pulp, such as bamboo bleached kraft pulp into high-purity cellulose acetate (CA)-grade dissolving pulp is crucial but challenging in China. Herein, a series of metal salt-based deep eutectic solvents (MSDESs) involving various ZnCl2-urea (U), ZnCl2-glycerol (G), and ZnCl2-lactic acid (LA) are comparatively investigated for this purpose. Thanks to the bifunctional acid sites of Lewis acid ZnCl2 and Brønsted acid LA, the ZnCl2-LA MSDES has the highest acidity (2.62) and interaction affinity to bamboo fibers, leading to the highest efficiency in simultaneous pulp purification and activation. As a result, the resultant upgraded pulp from ZnCl2-LA (DES3-F) features remarkable improvements in purity (from 80.8 % to 93.1 %), intrinsic viscosity (from 897 to 419 mg/L), and reactivity (from 18.1 % to 80.8 %). Moreover, the modified acetate product has a high degree of substitution of 2.84 and a yield of 75.5 %. In short, such a proposed MSDES treatment can offer a promising and alternative approach for the manufacture of high-quality dissolving pulp and its derivatives.

Effect of NaCl replacement by other salt mixtures on myofibrillar proteins: Underlining protein structure, gel formation, and chewing properties.

The protein structure, gel changes, and chewing properties of low-sodium myofibrillar protein (MP) prepared by compound chloride salts (KCl/MgCl2, KCl/CaCl2, and KCl/MgCl2/CaCl2) and different substitution degrees (10%, 25%, and 40%) at same ionic strength (0.6M) were investigated. The results revealed that the low-sodium MP gels containing CaCl2 manifested more liquid loss and less moisture content accompanied by obvious morphological shrinkage, while KCl/MgCl2 contributed to the gel juiciness. At high substitution degree of 40%, KCl/CaCl2 substitution rendered the gel with dense structure and highest strength, but worse water retention capacity. Using other compound chloride salts influenced the chewing efficiency, and CaCl2 substitution made the gel relatively hard to chew. The inhomogeneous structure accompanied by cluster blocks in KCl/CaCl2-substituted MP gel accelerated the overall fracture rate. During heating process, more proteins in CaCl2-substituted MP did not participate in gel formation, intervening the final gel properties. The chloride salt mixtures containing MgCl2, rather than CaCl2, avoided or alleviated the liquid loss and shrinkage of low-sodium MP gel within the substitution degree of 10%-40%, and substitution degree not exceeding 25% was more reasonable for the controlled qualities.

Synthesis, characterization, and application of films made from highly substituted N-perfluoroacylated chitosan

Highly substituted perfluoroacylated chitosan can alter the physicochemical properties of chitosan; however, the currently synthesized perfluoroacylated chitosan has a low degree of substitution. In this study, we present a simple method for the homogeneous preparation of highly substituted N-perfluoroacylated chitosan, conducted at room temperature without requiring strict anhydrous or oxygen-free conditions. Various perfluorocarbon chains were successfully attached to chitosan through a reaction between perfluorinated acid esters and amines, catalyzed by DBU. The synthesized N-perfluoroacylated chitosan, with high degree of substitution, demonstrated excellent solubility in common organic solvents. Comprehensive characterization was performed using elemental analysis, nuclear magnetic resonance (including two-dimensional NMR), gel permeation chromatography, infrared spectroscopy, X-ray diffraction, and thermal analysis. The resulting films exhibited high water contact angles. Notably, as the fluorocarbon chain length increased, tensile strength gradually decreased, while elongation at break improved. Additionally, water uptake, water vapor transmission rate, and oxygen transmission rate all exhibited a declining trend. The films exhibited good biocompatibility, and in the grape preservation experiment, HFBC treatment effectively delayed grape aging and deterioration while enhancing quality preservation. These results suggest that HFBC film holds promising potential for food packaging applications.

Octenylsuccinated alginate as a delivery agent for encapsulation of bergamot essential oil: Preparation, functional properties and release behavior

This study evaluate the effect of succinylation of sodium alginate (ALG) by octenyl succinic anhydride (OSA) and its effect on the bergamot essential oil (BEO)-loaded ALG beads. The physico-chemical, antioxidant, antibacterial, and in vitro release properties of BEO-loaded ALG beads were assessed. The presence of BEO in alginate beads was assessd using Fourier transform-infrared (FT-IR) spectroscopy, X-ray diffraction (XRD), and differential scanning calorimetry (DSC) experiments. The higher amount of BEO in modified alginate beads at higher degree of substitution (DS) has been confirmed. Accordingly, it was discovered that the DS has notable effects on encapsulation efficiency (EE), loading capacity (LC) of beads, so that the values of EE and LC were about 31–75 % and 19–45 %, respectively, when the DS value of ALG was 0.00–0.022. Besides, BEO-loaded beads prepared using high DS, exhibited higher total phenolic compound (TPC = 21.101 mg garlic acid/g brad), good antioxidant activity (DPPH radical scavenging activity ≈ 69 %) and antibacterial properties (against E. coli and S. aureus). In vitro release analysis showed the initial fast release followed by a slow-release. OSA modification slowed down the release rate of bergamot essential oil from alginate beads. Also, the release of BEO from the beads followed Fickian diffusion.

Highly phosphorylated cellulose toward efficient removal of cationic dyes from aqueous solutions

Highly phosphorylated cellulose was produced under different processing parameters and used as an effective adsorbent for methylene blue (MB) dye removal from aqueous systems. The characteristics of the designed adsorbent were analyzed using different technics. The zeta potential measurement of the developed adsorbents was negative (−11.3 to −49.4 mV) in the pH range of 4 to 11. Batch removal tests were performed under different processing parameters of contact time, initial concentration, phosphorylation degree and pH. The developed adsorbent with a high substitution degree of 1.07 (13.22 % of P), revealed an outstanding retention capacity for MB dye (up to 3153.5 mg/g) during an extremely low equilibrium adsorption time (∼30 min), which is 130-fold higher than pure MCC (15.3 mg/g). Interestingly, this capacity raised up to 3236.6 mg/g when raising the pH of the solution (from 7 to 11). The experimental adsorption data in the examined conditions were well fitted by the Langmuir type isotherm and pseudo-second-order kinetic models, highlighting the significance of the reaction medium and phosphate content in determining the adsorbent's retention capacity. This investigation has demonstrated the potential of converting pure MCC into high value-added adsorbent for the efficient purification of organic dye from aqueous solutions.

Photo-responsive decellularized small intestine submucosa hydrogels.

Decellularized small intestine submucosa (dSIS) is a promising biomaterial for promoting tissue regeneration. Isolated from the submucosal layer of animal jejunum, SIS is rich in extracellular matrix (ECM) proteins, including collagen, laminin, and fibronectin. Following mild decellularization, dSIS becomes an acellular matrix that supports cell adhesion, proliferation, and differentiation. Conventional dSIS matrix is usually obtained by thermal crosslinking, which yields a soft scaffold with low stability. To address these challenges, dSIS has been modified with methacrylate groups for photocrosslinking into stable hydrogels. However, dSIS has not been modified with clickable handles for orthogonal crosslinking. Here, we report the development of norbornene-modified dSIS, named dSIS-NB, via reacting amine groups of dSIS with carbic anhydride in acidic aqueous reaction conditions. Using triethylamine (TEA) as a mild base catalyst, we obtained high degrees of NB substitution on dSIS. In addition to describing the synthesis of dSIS-NB, we explored its adaptability in orthogonal hydrogel crosslinking and used dSIS-NB hydrogels for cancer and vascular tissue engineering. Impressively, compared with physically crosslinked dSIS and collagen matrices, orthogonally crosslinked dSIS-NB hydrogels supported rapid dissemination of cancer cells and superior vasculogenic and angiogenic properties. dSIS-NB was also exploited as a versatile bioink for 3D bioprinting applications.

Impact of the degree of substitution on the enantioseparation of anionic β-cyclodextrin in liquid‒liquid extraction and countercurrent chromatography: Insights from molecular docking simulations

Five types of sulfobutylether-β-cyclodextrin (SBE-β-CD) and carboxymethyl-β-cyclodextrin (CM-β-CD) with different degrees of substitution were synthesized, and six and five racemates were respectively chosen to study the influence of the degree of substitution on the enantioseparation factor. The synthesized SBE-β-CD and CM-β-CD were characterized using 1H NMR spectroscopy and mass spectrometry. The results indicated that the influence of the degree of substitution on enantioseparation for distinct racemates exhibited significant variability. Increasing the degree of substitution of CM-β-CD led to an increasing enantioseparation factor, while SBE-β-CD with a specific degree of substitution provided the optimum enantioseparation factor for some racemates. The optimum enantioseparation factors of N-methyl duloxetine and duloxetine were obtained when a relatively low degree of substitution (DS = 3.5) was selected. And the optimum enantioseparation factor was obtained with a relatively high degree of substitution (DS = 7.5). SBE-β-CD with a low substitution degree of 3.5 was chosen to optimize the countercurrent chromatographic enantioseparation of N-methyl-duloxetine, which resulted in a significant improvement in peak resolution from 0.51 to 0.83. Molecular docking was used to construct three SBE-β-CDs with different degrees and distributions of substitution, and a good agreement was found between the docking results and the experimental results.

Bushy-Tailed QACs: The Development of Multicationic Quaternary Ammonium Compounds with a High Degree of Alkyl Chain Substitution.

Quaternary ammonium compounds have served as a first line of protection for human health as surface disinfectants and sanitizers for nearly a century. However, increasing levels of bacterial resistance have spurred the development of novel QAC architectures. In light of the observed reduction in eukaryotic cell toxicity when the alkyl chains on QACs are shorter in nature (≤10 C), we prepared 47 QAC architectures that bear multiple short alkyl chains appended to up to three cationic groups, thus rendering them "bushy-tailed" multiQACs. Antibacterial activity was strong (often ~1-4 μM) in a varied set of bushy-tailed architectures, though observed therapeutic indices were not significantly improved over QAC structures bearing fewer and longer alkyl chains.

FACILE SYNTHESIS OF CARBOXYMETHYL CELLULOSE (CMC) FROM AGRICULTURAL RESIDUES

Cellulose derivative products, such as carboxymethyl cellulose (CMC), which are used in the food, cosmetics, and pharmaceutical industries, but still rely on cotton-derived cellulose, can be made from oil palm fruit empty bunches (OPEFB) and rice straw. This study examined how sodium monochloroacetic acid (NaMCA) concentration (3, 6, and 9 g) affected the simple synthesis and characteristics of CMC from OPEFB and rice straw cellulose. OPEFB-derived CMC produced with NaMCA (9 g) had the lowest of brightness, while rice straw CMC was brighter. NaMCA modifications altered the onset temperature (Tonset), but not maximum degradation temperature (Tmax), according to thermal analysis. The onset temperatures of OPEFB and rice straw CMC were 40–62 °C and 67–183 °C, respectively. Commercial CMC has an onset temperature of about 27 °C. The EDX analysis showed that rice straw CMC had a higher degree of substitution (DS) of 0.34–1.37 than OPEFB CMC, which had 0.30-0.70. Oil palm empty fruit bunch (OPEFB) cellulose and rice straw cellulose offer a viable carboxymethyl cellulose (CMC) alternative. This process turns agricultural waste into valuable products and enables for their usage in numerous applications.

Sustainable Light‐Assisted 3D Printing of Bio‐Based Microwave‐Functionalized Gallic Acid

AbstractThe development of 3D printing technologies and the requirement for more sustainable 3D printing materials is constantly growing. However, ensuring both sustainability and performance of the new materials is crucial to replace current fossil‐based polymers. Here, a bio‐based UV‐curable resin is produced in high yield from gallic acid (GA), a natural polyphenolic compound, by means of rapid and efficient microwave‐assisted methacrylation (5 min heating time and 10 min at 130 °C). The successful microwave‐assisted methacrylation with a high degree of substitution is confirmed by Fourier transform infrared (FTIR) spectroscopy and proton nuclear magnetic resonance spectroscopy. The radical UV‐photopolymerization of the methacrylated gallic acid (MGA) is further investigated by real‐time FTIR and differential scanning photo calorimetry (photo‐DSC) analyses, clearly demonstrating the high photo‐reactivity of MGA. Moreover, the %gel assessment demonstrates the formation of highly insoluble fractions after the UV‐curing, with 98% gel content. The photo‐rheology and rheology support the suitability of MGA for light‐assisted 3D printing. Indeed, a honeycomb and a hollow cube are 3D printed by means of the digital light processing 3D printing technique with high accuracy in a small scale. Finally, the cured‐MGA illustrates high Tg and thermal stability.

Exploring Sintered Fe-(Ce, Nd)-B with High Degree of Cerium Substitution as Potential Gap Magnet.

The more effective use of readily available Ce in FeNdB sintered magnets is an important step towards more resource-efficient, sustainable, and cost-effective permanent magnets. These magnets have the potential to bridge the gap between high-performance FeNdB and hard ferrite magnets. However, for higher degrees of cerium substitution (>25%), the magnetic properties deteriorate due to the lower intrinsic magnetic properties of Fe14Ce2B and the formation of the Laves phase Fe2Ce in the grain boundaries. In this paper, sintered magnets with the composition Fe70.9-(CexNd1-x)18.8-B5.8-M4.5 (M = Co, Ti, Al, Ga, and Cu; with Ti, Al, Ga, and Cu less than 2.0 at% in total and Cobal; x = 0.5 and 0.75) were fabricated and analyzed. It was possible to obtain coercive fields for higher degrees of Ce substitution, which previous commercially available magnets have only shown for significantly lower degrees of Ce substitution. For x = 0.5, coercivity, remanence, and maximum energy product of µ0Hc = 1.29 T (Hc = 1026 kA/m), Jr = 1.02 T, and (BH)max = 176.5 kJ/m3 were achieved at room temperature for x = 0.75 µ0Hc = 0.72 T (Hc = 573 kA/m), Jr = 0.80 T, and (BH)max = 114.5 kJ/m3, respectively.

Sulfonamide modified chitosan oligosaccharide with high nematicidal activity against Meloidogyne incognita

Chitosan oligosaccharide (COS) modification is a feasible way to develop novel green nematicides. This study involved the synthesis of various COS sulfonamide derivatives via hydroxylated protection and deprotection, which were then characterized using NMR, FTIR, MS, elemental analysis, XRD, and TG/DTG. In vitro experiments found that COS-alkyl sulfonamide derivatives (S6 and S11–S13) exhibited high mortality (>98 % at 1 mg/mL) against Meloidogyne incognita second-instar larvaes (J2s) among the derivatives. S6 can cause vacuole-like structures in the middle and tail regions of the nematode body and effectively inhibit egg hatching. In vivo tests have found that S6 has well control effects and low plant toxicity. Additionally, the structure-activity studies revealed that S6 with a high degree of substitution, a low molecular weight, and a sulfonyl bond on the amino group of the COS backbone exhibited increased nematicidal activity. The sulfonamide group is a potential active group for developing COS-based nematicides.

Effect of amylose partial extraction on citrate esterification of potato starch and its role in structure and physicochemical modification

This study examines the impact and influence of amylose on the starch esterification reaction through partial extraction of amylose. Citric acid was added for the esterification reaction, and then the esterified starches' multiscale structure, physicochemical, and functional properties were evaluated. As the extraction time of amylose increased, the amylose content in the starch decreased. Higher concentrations of citric acid will lead to samples with a higher degree of substitution, with DS rising from 0.203 % (0 h) to 0.231 % (3.5 h) at CA3 treatment. While removing amylose had minimal effects on the crystal structure of starch granules, it did decrease the ratio of A and B1 chains and the molecular weight of amylose. Acid hydrolysis exacerbated these changes upon the addition of citric acid. Furthermore, removing amylose followed by citrate esterification resulted in lower pasting viscosity, enthalpy of gelatinization (from 13.37 J to 2.83 J), and degree of short-range ordering. Also, digestion shows a decrease caused by the increasing content of slow-digesting starch. The presence of amylose in starch granules does affect the formation of starch esters, and removing it before esterification modification may improve production efficiency and reduce costs to some extent.

Synthesis and characterization of polysaccharide carbamates and mixed carbamates with tunable water solubility

Polysaccharide derivatives with two types of functionalities were synthesized; reactive groups for click-chemistry approaches and groups that can tune the water solubility of the products. Xylan phenylcarbonates (XPCs) and cellulose phenylcarbonates (CPCs) with degrees of substitution (DS) ranging from 0.6 to 3.0 were prepared as starting materials. In a modular synthesis approach, these carbonate derivatives were converted with different amines to obtain functional xylan carbamates (XCs) and cellulose carbamates (CCs) with (i) reactive alkynyl- or furfuryl groups and / or (ii) hydrophilic hydroxyalkyl or tertiary amino groups. Both types of functionalities were introduced separately or simultaneously in a convenient one-pot-approach. Mixed polysaccharide carbamates with low, intermediate, and high DS values (0.6 to 2.5) were successfully prepared and characterized. The water solubility of the carbamates and mixed carbamates was tuned by variation of the type and DS of the two hydrophilic substituents. Surprisingly, some of the products showed lower or upper critical solution temperatures (LCSTs, UCSTs). Thus, the thermoreversible phase transition in aqueous solutions was studied. The products obtained in this work are very promising for the preparation of hydrogels through selective covalent crosslinking as well as for the fabrication of thermoresponsive biomaterials.

Insight into the Feasibility of Fatty Acyl Chlorides with 10-18 Carbons for the Ball-Milling Synthesis of Thermoplastic Cellulose Esters.

Fatty acid cellulose esters (FACE) are common cellulose-based thermoplastics, and their thermoplasticity is determined by both the contents and the lengths of the side chains. Herein, various FACE were synthesized by the ball-milling esterification of cellulose and fatty acyl chlorides containing 10-18 carbons, and their structures and thermoplasticity were thoroughly studied. The results showed that FACE with high degrees of substitution (DS) and low melting flow temperatures (Tf) were achieved as the chain lengths of the fatty acyl chlorides were reduced. In particular, a cellulose decanoate with a DS of 1.85 and a Tf of 186 °C was achieved by feeding 3 mol of decanoyl chloride per mole anhydroglucose units of cellulose. However, cellulose stearate (DS = 1.53) synthesized by the same protocols cannot melt even at 250 °C. More interestingly, the fatty acyl chlorides with 10 and 12 carbons resulted in FACE with superior toughness (elongation at break up to 94.4%). In contrast, due to their potential crystallization of the fatty acyl groups with 14-18 carbons, the corresponding FACE showed higher tensile strength and Young's modulus than the others. This study provides some theoretical basis for the mechanochemical synthesis of thermoplastic FACE with designated properties.

Synthesis and characterization of strontium substituted monetite coatings via mild phosphate chemical conversion

Strontium (Sr) substitution into calcium phosphate (CaP) materials has gained acceptance in research into the enhancement of physiochemical and osteogenic potential. Conventional synthesis of metal cationic substitution into CaP coatings on metal substrate usually takes relatively high temperature (﹥100 °C) and hours of processing time. Herein, a mild phosphate chemical conversion method was developed for preparing Sr-substituted CaP coatings on surface of titanium (Ti) in the presence of increasing amount of Sr (40–60 mol%). The results indicated that the complete and even coatings could be produced on the whole surface of Ti only within 50–60 % Sr and the coatings represented a unique lamellar texture in micro/nano-scale. As Sr concentration increased, the phases of coatings were predominantly indexed to monetite and SrHPO4, which presented a highly oriented crystal alignment. With high content of Sr, monetite, instead of brushite, was deposited in the coatings. The possible mechanism of coating formation was proposed that α-SrHPO4 and α-monetite were co-deposited in the acidic phosphating solution and finally a compound of (CaxSr1-x)HPO4 was produced on surface of Ti. Results revealed that coatings formed at high degree of Sr substitution exhibited relative improved mechanical and electrochemical properties. The coatings enhanced the cell focal adhesion and proliferation of BMSCs compared with that of the bare Ti.

Influence of the structure and physicochemical properties of OSA modified highland barley starch based on ball milling assisted treatment

This study aimed to investigate the influence of ball milling assisted treatment on the degree of substitution of octenyl succinic anhydride (OSA) modified highland barley starch (HBS) and on the physicochemical properties and structure of HBS. Scanning electron microscopy (SEM) findings showed that with the increasing of ball milling time, the surface morphology of OSA modified HBS became rougher and rougher and the particle morphology and crystal structure were damaged. When the pretreatment time of ball milling was 40 min, the degree of substitution of OSA modified HBS was 1.32 times higher than that of the conventional modification method. In addition, the longer the ball milling assistant, the longer the short-range ordering of the OSA modified HBS significantly decreased, and the relative crystallinity decreased (from 16.68 % to 7.93 %), leading to a decrease in thermal stability too. However, it greatly enhanced the aging resistance and flowability. In terms of emulsification properties, the emulsification properties of OSA modified HBS increased from 60.67 % to 75.67 %. Therefore, the HBS with better freeze-thaw stability and higher degree of substitution can be prepared by ball milling pretreatment and OSA modification, which provides technical support for further development of starch resources.

Ultrasound and Steam Explosion Treatments on the Quantity and Molecular Size of Soluble Fibre Obtained from Un-purified and Purified Rice Bran

Rice bran (RB) is a major by-product of the rice industry, and the high proportion (~90%) of insoluble fibre (IF) is the main reason limiting its applications in foods. Thus, the objective of this research is to enhance the solubility of rice bran fibre and decrease the molecular weight (MW) of the soluble fibre (SF) fraction through ultrasound (US) and steam explosion (SE) treatments. The main sugars in the RB fibre were xylose and arabinose, with glucose, galactose, and mannose present in the side chains. The ratio of Ara/Xyl was 0.92 for the un-purified and 1.02 for the purified RB, reflecting the high degree of substitution of the xylan backbone. The highest amount of SF was obtained from RB treated at 60% US amplitude, 20 min treatment, where 7.8% (un-purified) and 35.2% (purified), respectively. For SE treatments, the amount of SF in un-purified RB increased as the pressure increased from 0.3 and 0.6 MPa, which were 6.10±0.34 and 8.83±0.56%, respectively. Meanwhile, the highest SF fraction (35.2%) of purified RB was obtained from the SE treatment at 0.6 MPa. The SF produced from both treatments mainly contained oligosaccharides with MW <1 kDa, with those produced by the SE treatment generally smaller than those by the US treatment. Purification of RB significantly enhanced the efficiency of the US and SE treatments in breaking down the IF into the SF.