CELLULOSE
·
2025
·
IF 4.8
Zhao Yao,Wang Xueping,Li Bowen,Si Tian,Gao Xin,Peng Lincai,Zhang Heng
The cellulose catalytic oxidation system mainly comprises inorganic ion-based oxidants. Hence, the selective oxidation of C 6- primary hydroxy groups (C 6 -OH) of cellulose, catalyzed by piperidine free radicals, was limited to the homogeneous cellulosic system containing protic solvents or heterogeneous system. In this work, the use of the catalytic system containing 4-acetamido-2,2,6,6-tetramethylpiperidine 1-oxyl (4-AcNH-TEMPO) was extended to the cellulosic solution in N, N-dimethylacetamide (DMAc) and combined with chlorine dioxide. Results showed that the carboxyl content was 0.832 mmol/g. Meanwhile, the degree of polymerization decreased from 900 to 489. This study provides an effective route for the homogeneous selective oxidation of primary hydroxy groups in cellulose and explored its oxidation mechanism in DMAc solvent. Furthermore, studies showed that the reactive chlorine species- ClO·, Cl·, and ClO 2 played a crucial role in the oxidation process. The methodology developed here displayed great potential to be utilized to various biomolecules in aprotic solvents homogeneous system based on 4-AcNH-TEMPO as oxidation catalysts.
研究领域:
化学工程
·
材料科学
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DOI
高影响因子
NEW JOURNAL OF CHEMISTRY
·
2018
·Vol. 42
·期 8
·6274-6282
·
IF 3.201
Shuang Chen,Hao Wu,Jing-han Hua,Jing-wen Yang,Hong-bin Zhang,Xue-qin Hu
Dextran is a polysaccharide with a high medicinal value. Thus, the chemical modifications of dextran, and the structural and physicochemical properties of its derivatives should be given focus. Dextran (Mw 5000 Da to 7500 Da) can complex with iron. In this study, dextran (Mw 5400 Da) was modified at different pH levels (8–14) by using NaOH and NaClO/NaBr. The carboxyl groups of the modified dextran were determined using infrared spectroscopy, and the carboxyl contents were compared. The results of high-performance liquid chromatography indicated that dextran was degraded during the modification. The crystallization and the structure of the carboxyl-modified dextran were investigated using X-ray diffraction, nuclear magnetic resonance, and quadrupole time-of-flight mass spectrometry. The physicochemical properties, i.e., solubility, and granule morphology, of the carboxyl-modified dextran were carefully characterized and compared. This work provides a theoretical foundation for the accurate selection of carboxyl-modified dextran and the development of a novel strategy for the preparation of metal complexes.
研究领域:
生物化学
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材料科学
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DOI
高影响因子
POLYMER DEGRADATION AND STABILITY
·
2025
·
IF 7.4
Ranran Qi,Ziwen Gan,Qi Wang,Xiaojie Zhang,Mingyi Liao
In this study, microwave (MW)-assisted oxidative degradation of poly(vinylidene fluoride-tetrafluoroethylene-hexafluoropropylene) (P(VDF-TFE-HFP)) was applied to synthesize carboxy-terminated liquid fluororubber, referred to as LTCFs-246. The resulting product has a carboxyl content of 3.01%, a number-average molecular weight (Mn) of 2100 g/mol, and a polydispersity index (PDI) of 1.61. The product's structure was characterized and analyzed in detail using techniques such as 19 F NMR, UV–Vis, and FTIR spectroscopy. Results indicate that the selective dehydrofluorination reaction (K HF reaction) primarily occurs on four sequence structures: HFP-VDF-HFP, HFP-VDF-TFE, TFE-VDF-HFP, and TFE-VDF-TFE, with similar degrees of reactivity across these structures. Two types of C=C bonds were formed in the LTCFs-246 backbone, primarily through Hofmann elimination and, to a lesser extent, Zaitsev elimination. The oxidative reaction (K C-C reaction) was temperature-dependent. At lower temperatures, H 2 O 2 decomposed slowly, limiting the K C-C reaction; as the temperature increased, H 2 O 2 rapidly decomposed, actively engaging in the K C-C reaction and extensively consuming C=C bonds. Once H 2 O 2 was fully consumed, the K C-C reaction ceased, while the K HF reaction continued uninterrupted. In conclusion, this study provides strong evidence to advance the understanding of the oxidative degradation mechanism of MW-assisted P(VDF-TFE-HFP).
研究领域:
材料科学
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化学工程
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DOI
高影响因子
Discover Applied Sciences
·
2024
·Vol. 6
·期 4
·1-16
·
IF 0
Liu Xiaohong,Basta Altaf H.,Liu Rui,Fu Shiyu
This study describes the preparation of cellulose nanofibers (CNFs) with varying amounts of carboxyl groups from rice straw pulp using the TEMPO/NaBr/NaClO oxidation system. The resulting CNFs were found to be in the form of nanofibers with an average diameter of 6 nm and an average length of 160 nm. To further enhance their properties, the CNFs were grafted with polycaprolactone (PCL) to create CNFs-g-PCL, which was then blended with shape memory polyurethane (SMPU) to produce CNFs-g-PCL/SMPU composites. It was observed that as the carboxyl content in CNFs increased from 0.35 to 1.14 mmol/g, the graft ratio of PCL on CNFs decreased from 24.6 to 10.7%. Consequently, the hydrophobicity of the grafted product (CNFs-g-PCL) also decreased. When 10% CNFs-g-PCL was added to the SMPU matrix, the elastic modulus and tensile stress of the resulting composite were both higher than those of the pure SMPU, increasing by up to 54.4% and 67.3%, respectively. Additionally, the shape retention and shape recovery rates of the composite remained stable after addition of CNFs-g-PCL. In conclusion, incorporating CNFs-g-PCL into SMPU can improve its mechanical properties while maintaining its shape memory properties. Graphical abstract
研究领域:
材料科学
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高分子化学
·
纳米技术
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DOI
INTERNATIONAL JOURNAL OF BIOLOGICAL MACROMOLECULES
·
2025
·
IF 8.5
Yuying Zhang,Na Li,Lianmei Chen,Xueru Sheng,Bing Wang,Jian Zhang,Qingwei Ping,Yan Shi
In this paper, bamboo biochar was prepared and used for laccase immobilization. Biochar was prepared under different conditions (pyrolysis temperature, heating rate and dwell time) to understand biochar characteristics impacts on enzyme activity. The results showed that the preparation conditions had an important effect on the content of carboxyl groups on biochar. And the specific surface area is not the key factor affecting laccase immobilization in this study, which is a little different than before. The highest immobilized laccase activity (1404.17 U/g) was obtained when the biochar was heated to 300 °C at the rate of 15 °C/min and stayed for 1.5 h, and the carboxy group concentration was 0.490 mmol/g. Compared with free laccase (FL), the immobilized laccase on bamboo biochar (LBC) showed higher thermo-tolerant performance, more excellent acid-proof ability and reusability. Without any mediators, LBC displayed high degradation efficiency (74.72 %, 85.88 % and 94.53 %, respectively) for bisphenol A (BPA), malachite green (MG) and methyl orange (MO) in water. Our research demonstrates that the content of carboxyl group in biochar plays a decisive role in the immobilization of laccase and LBC has excellent performance in the effective removal of toxicant in water, which makes it a promising candidate for environmental recovery.
研究领域:
环境科学
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生物技术
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DOI
PubMed
高影响因子
CELLULOSE
·
2022
·Vol. 30
·期 3
·1623-1636
·
IF 6.123
Xue Jianghua,Zhu Enwen,Zhu Hengfeng,Liu Dongning,Cai Haopeng,Xiong Chuanxi,Yang Quanling,Shi Zhuqun
The problems caused by water pollution are increasingly serious, wastewater contains a lot of heavy metal ions, textile dyes, medicines, etc. However, most adsorption materials usually face problems such as inefficient recycling, high cost, and secondary pollution. As a natural polymer, cellulose has low cost, degradability and good biocompatibility. In this work, by changing the addition amount of sodium hypochlorite during 2,2,6,6-Tetramethylpiperidine-1-oxyl radical (TEMPO) oxidation, nanocellulose with different carboxyl content could be prepared, which is expected to be a good high-efficiency cationic adsorbent due to its rich in hydroxyl groups on the surface and negatively charged. Then the calcium chloride solution was used as the cross-linking agent to prepare TEMPO-oxidized cellulose nanofibril beads (TOCNB) by the dropping solidification method. As the content of carboxyl groups increases, the Zeta potential value of the nanocellulose dispersion became increasingly negative. The nanocellulose beads all presented a good three-dimensional network porous structure. With the increase of carboxyl group content, the specific surface area increases from 173 to 367 m 2 g −1 , and the adsorption capacity for methylene blue (MB) also gradually strengthened. The saturated adsorption capacity of TOCNB on MB was calculated as high as 925.93 mg g −1 . The nanocellulose bead was a cationic adsorbent with highly efficient adsorption and adjustable specific surface area, and the preparation method was simple, fast, efficient and green.
研究领域:
环境科学
·
材料科学
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产品关联
DOI
高影响因子
INTERNATIONAL JOURNAL OF BIOLOGICAL MACROMOLECULES
·
2023
·
IF 8.2
Jingwen Wang,Xiaoshuai Han,Weijie Wu,Xiaoyi Wang,Linhu Ding,Yuli Wang,Shanshan Li,Jiapeng Hu,Weisen Yang,Chunmei Zhang,Shaohua Jiang
Wooden building materials have advantages in terms of biodegradability , non-toxicity, pollution-free and recycling. Currently, applications of natural wood are extremely limited because of low density, low strength and toughness. Therefore, we reported an effective modification strategy with nano-scale cellulose nanofibrils design to prepare a synergistically enhanced cellulosic material . Via three steps: i) the secondary alcohol hydroxyl groups in C 2 , C 3 position were cut; ii) oxidize the hydroxyl group at C 2 , C 3 position to achieve dialdehyde cellulose; and iii) oxidized again to obtain dicarboxylic cellulose. Subsequently, thanks to the regulation of the average moisture content, the moisture content in the wood surface and subsurface increased in a short time. The wood softening layer contributes to the hotpressing treatment of the wood. The mechanical properties and dimensionality have been greatly improved. The obtained delignified oxidated hot-pressed wood with 0.55 mmol/g carboxyl group content demonstrates excellent strength of 328.8 ± 7.43 MPa and Young's modulus of 8.1 ± 0.14 GPa, which is twice than that of natural wood. Delignified oxidated hot-pressed wood also shows exceptional toughness of 8.3 ± 0.28 MJ/m 3 . Other than that, the shore hardness indicates 0.55 mmol/g carboxylic group, which could increase the hardness at the wood surface hardness to 72.5 ± 4.29°.
研究领域:
材料科学
·
林业工程
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产品关联
DOI
PubMed
高影响因子
JOURNAL OF APPLIED POLYMER SCIENCE
·
2024
·Vol. 141
·期 23
·e55480
·
IF 2.7
Chuan Yan,HongHua Wang,LiXin Song,GuangYuan Zhou
Aiming at the problem of phase separation between thermoplastic toughener and epoxy after curing, which leads to the reduction of mechanical properties, in this paper we improve the compatibility of the two phases by introducing reactive groups into the molecular chain of thermoplastic resins, thus improving the impact strength of the epoxy system. Phenolphthalein polyether sulfone (C-PESC) with designable and controllable carboxyl group content was prepared via SN 2 nucleophilic substitution copolymerization. Further C-PESC was evaluated for epoxy toughening, and the effects of carboxyl group content of C-PESC on mechanical properties and thermal stability of the resin system were investigated. The results show that C-PESC resin has good compatibility with E51 epoxy resin. Carboxyl group accelerates the dissolution rate of thermoplastic resins in epoxy and also participates in the curing reaction with epoxy to enhance the interfacial bonding ability between the toughening component and the matrix resin. The reactive toughener C-PESC can not only improve the impact properties of E51 epoxy, but also maintain the high T g and thermal properties of the resin system. Among them, the addition of 5 PHR of C-PESC3 increased the impact strength of the modified resin by 45%, with uniform fracture surface and tough fracture shape.
研究领域:
材料科学
·
高分子化学
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DOI
高影响因子
QUIMICA NOVA
·
2022
·Vol. 45
·期 2
·145-151
·
IF 1.145
Sun Fei,Feng Chao,Wang Yang,Yang Xue,Zhao Hong
The fluorescent microspheres are prepared by the swelling-evaporation method. The optimal swelling conditions are obtained by researching related factors, such as types and dosages of swelling agent, dosages of fluorescent substance, swelling time and swelling temperature. Considering that the structure of microspheres can influence the swelling properties, the paper mainly focuses on the effect of molecular weight and surface carboxyl group content of polystyrene microspheres on swelling properties. When the molecular weight of microspheres is 75276 g mol-1, the density of carboxyl group on their surface is 6.94×10-4 mol g-1, and the doping amount of europium complex reaches the maximum of 24.9 mg g-1 with the strongest fluorescence intensity. Meanwhile, the as-prepared fluorescent microspheres have high monodispersity, uniform particles size and high thermal stability (the decomposition temperature is 385oC), which sets up the good foundation for biomolecule detection. So, this work provides a significant experience for the preparation of fluorescent microspheres.
研究领域:
材料科学
·
生物医学
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DOI
高影响因子
CARBOHYDRATE POLYMERS
·
2022
·
IF 10.723
Changxiu Chen,Panyi Xi,Shanbei Zhang,Liming Zhang,Yaning Sun,Jiuyong Yao,Kuanjun Fang,Yijun Jiang
TEMPO oxidized nano-fibrillated cellulose (TONFC) has been used in different applications including biomedical, packing materials, paints and cosmetics because of its higher transparency, mechanical properties and better biocompatibility. However, pulping is always required to remove lignin and hemicellulose , and high-energy homogenization is required to defibrillate cellulose bundle into filament. Therefore, it is desirable to find a novel way to get TONFC with high carboxyl content without intensive mechanical disintegration. In this work, nanocellulose (TOHOLO) with higher carboxyl groups (2.2 ± 0.2 mmol/g) and smaller size (length = 400–685 nm and diameter = 5.9 nm) was prepared by a two-step strategy without intensive mechanical homogenization. In addition to the advantages in terms of diameter and carboxyl groups, TOHOLO showed better transparency and re-dispersibility as well as higher mechanical properties (122.8 MPa) compared to previous reports. Furthermore, for high carboxyl group and dispersibility, the TOHOLO can be used as a reinforcing filler to fabricate nanocomposites. The reinforced PVA fibers show a tensile strength of 484.4 MPa, which is about 170 % higher than comparison samples (PVA/TOCN-M, 291.9 MPa).
研究领域:
材料科学
·
生物医学
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产品关联
DOI
PubMed
高影响因子
INTERNATIONAL JOURNAL OF BIOLOGICAL MACROMOLECULES
·
2023
·
IF 8.2
Ying Li,Jin-Hua Wang,Er-Chun Wang,Zhong-Sheng Tang,Yu Han,Xiu-Er Luo,Xin-An Zeng,Meng-Wai Woo,Zhong Han
The structure and thermal properties of pulsed electric field (PEF) assisted sodium hypochlorite oxidized starch were investigated. The carboxyl content of the oxidized starch was increased by 25 % when compared with the traditional oxidation method. Dents and cracks were evident on the surface of the PEF-pretreated starch. Compared with native starch, the peak gelatinization temperature (T p ) of PEF-assisted oxidized starch (POS) was reduced by 10.3 °C, while that of the oxidized starch without PEF treatment (NOS) was only reduced by 7.4 °C. In addition, PEF treatment further reduces the viscosity and improve the thermal stability of the starch slurry. Therefore, PEF treatment combined with hypochlorite oxidation is an effective method to prepare oxidized starch. PEF showed great potential in expanding starch modification, to promote a wider application of oxidized starch in the paper, the textile and the food industry.
研究领域:
食品科学
·
材料科学
·
化学工程
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产品关联
DOI
PubMed
高影响因子
INTERNATIONAL JOURNAL OF BIOLOGICAL MACROMOLECULES
·
2022
·
IF 8.025
Jie Jiang,Jiaju Zhang,Ting Li,Xuhui Zhang,Yang Wang,Bihua Xia,Jing Huang,Yimin Fan,Weifu Dong
Chitin , a kind of polysaccharide mainly obtained from food waste, has emerged as an important biodegradable biopolymer in composite materials. The difficulty of aldehyde modification, which greatly limited the application of chitin nanocrystals , was addressed by applying a facile route of partial deacetylation followed by periodate oxidation in this study. Deacetylation occurred on the surface of both crystalline and amorphous regions, which were significantly degraded in the following periodate oxidation due to the inevitable cleavage of chitin chains, leading to an increase in the crystallinity index of obtained di-aldehyde chitin. The degree of deacetylation and periodate addition had limited improvement in the aldehyde content of di-aldehyde chitin with a maximum value of around 0.42 mmol/g. With further 2,2,6,6-tetramethylpiperidine-1-oxyl-mediated oxidation, the carboxyl content of tri-carboxyl chitin was improved to 1.58 mmol/g, which played a critical role in the dispersion efficiency and morphology of chitin nanocrystals. The obtained rod-like chitin nanocrystals with a ζ-potential value of −42 mV and an average size of 97 nm have potential application in dye-adsorption and emulsion stabilizers.
研究领域:
生物材料学
·
化学工程
·
环境科学
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产品关联
DOI
PubMed
高影响因子
危险品化学品经营许可证（带存储）