POLYMER
·
2021
·
IF 4.43
Yadi Liu,Sheng Zhou,Ning Zhao,Jian Xu,Zhihao Shen,Xing-He Fan,Qi-Feng Zhou
A series of aramids containing hydroxyl side group (NOM-OH c , where c is the molar fraction of hydroxyl substitution in the polymer, and c = 0, 10, 20, 40, 60, 80, 100) were synthesized by direct high-temperature polycondensation . The synthesis employed a facile process. The monomer , 4,4'-(terephthaloylbis(azanediyl))bis(2-hydroxybenzoic acid), was prepared simply via an esterification reaction. The chemical structures of the soluble aramids were confirmed by 1 H NMR. And the molecular weight and mass dispersity of the aramids were obtained by size exclusion chromatography , instead of the traditional intrinsic viscosity method. The use of unsymmetrical monomers and the introduction of hydroxyl side group into the aramid structure decrease the conjugation of the polymer main chain, and thus the resulting aramid has excellent solubility in relatively polar solvents , such as N -methy-2-pyrrolidone, dimethylsulfoxide , N , N -dimethylacetamide, and N , N -dimethylformamide. As a result, the molding processability of the aramids and their composites is greatly improved. For example, films can be made by solution spinning and casting. The films have good mechanical strength , with tensile strength , tensile modulus , and elongation at break in the range of 68–95 MPa, 2.65–3.12 GPa, and 5–10%. The thermal resistance of the aramids is still quite good, with 5% weight loss temperatures in nitrogen and in air in the range of 360–430 °C.
研究领域:
材料科学
·
化学工程
✓ 已验证
DOI
高影响因子
Coatings
·
2019
·Vol. 9
·期 10
·605
·
IF 2.33
Jianye Ji,Xin Ge,Weijie Liang,Xiaoyan Pang,Ruoling Liu,Shuyi Wen,Jiaqi Sun,Xunjun Chen,Jianfang Ge
To overcome the inherent limitation that the preparation of high molecular weight MQ copolymers (Mw ≥ 30,000 g/mol) via the hydrolysis and condensation of solicate salts generally results in an intractable gel, vinylphenyl-containing MQ silicone resin with a high molecular weight was designed and synthesized through the hydrosilylation reaction of vinyl-containing MQ silicone resin and linear poly(diphenylsiloxane) with two terminal Si–H bonds. The weight average molecular weight of these modified copolymers reported here is at least 30,000 dal·mol−1. These polymers have favorable thermal stability and a higher refractive index than that of the base resin due to the formation of novel regular macromolecular structures and the introduction of phenyl groups. These inorganic/organic hybrid materials could be used as a potential component for temperature-resistance electronics adhesive, heat-resistant coatings and high-performance liquid silicone rubber. Moreover, the proposed process also provides a possibility to choose higher molecular weight MQ silicones according to application requirements.Keywords:MQ silicone resin;modified;hydrosilylation;high molecular weight
研究领域:
材料科学
·
有机化学
✓ 已验证
产品关联
DOI
高影响因子
JOURNAL OF INDUSTRIAL AND ENGINEERING CHEMISTRY
·
2021
·
IF 6.064
Xiaoling Qu,Guangyuan Zhou,Rui Wang,Haiyan Zhang,Zhipeng Wang,Min Jiang,Jun Tang
In pursuit of poly(ethylene 2,5-furandicarboxylate) PEF materials with high molecular weight, satisfactory appearance and faster crystallization rate, its preparation from dimethyl furan-2,5-dicarboxylate (DMFD) with ethylene glycol (EG) in the trace presence of metal zinc was performed via transesterification method. Optimization of the main polymerization parameters enabled Zn-catalyzed PEF to gain high molecular weight ( M n , 5.40 × 10 4 g mol −1 ) and low content of diethylene glycol furandicarboxylate unit (DEGF, 2.91%). On the basis of experimental phenomena and high performance liquid chromatography (HPLC), the actual catalytic active species of metal zinc in the polymerization was speculated to be a salt of 2, 5-furandicarboxylate derivative (Zn(II)). The in-stiu catalyst can efficaciously inhibit the influence of by-product FDCA on the color of PEF, which displayed quite better appearance (close to white). Differential Scanning Calorimetry (DSC) showed that the in-stiu catalytic system acted as nucleating agent (NA) and the crystallization half-time (t 1/2 ) of PEFs-Zn was only 1/4 of that of PEF-tin. Additionally, series of high molecular weight furan-based polyesters from DMFD and diols with different methylene (3, 5, 6 and 8) were obtained by zinc powder as in-stiu catalyst, which further evidenced it to be efficiency and universality.
研究领域:
材料科学
·
聚合物化学
✓ 已验证
DOI
高影响因子
Heliyon
·
2023
·
IF 4
Yuanyuan An,Cuifang Lu,Mengmeng You,Xinshuo Liu,Wenqiang Yao,Yitao Li
Prior to crosslinking and vulcanization, fluorosilicone rubber is a linear polymer. This linear polymer contains 3,3,3,-trifluoropropyl methyl siloxane links, a few methyl vinyl siloxane links, and is formed by co-polymerization of 1,3,5-trimethyl-1,3,5-tris(3,3,3-trifluoropropyl) cyclotrisiloxane (D 3 F) with 2,4,6,8-tetramethyl-2,4,6,8-tetravinylcyclotetrasiloxane (V 4 ) under alkaline conditions. To improve the performance of fluorosilicone rubber, three key points should be considered during the synthesis of vinyl-containing high-molecular-weight linear fluorosilicone polymers (fluorosilicone raw rubber): first, avoid the generation of low molecular weight equilibrium by-products; second, eliminate the influence of impurities; and third, increase the copolymerization participation rate of monomer V 4 . From the three aspects above, this study optimized the reaction conditions for the synthesis of high-molecular-weight linear fluorosilicone polymers containing vinyl. Various factors influencing polymerization were thoroughly investigated. These factors include the initiation system, accelerator, equilibrium reaction, feeding ratio, feeding sequence, neutralization mode, impurity content, etc.
研究领域:
材料科学
·
化学工程
✓ 已验证
DOI
高影响因子
Green Energy & Environment
·
2020
·
IF 6.395
Jiake Wang,Yan Wang,Zhongzheng Ma,Lifeng Yan
Green solvents for cellulose dissolution is a key topic for green chemistry, especially natural cellulose with high molecular weight, and there are scarce solvents reported. Deep eutectic solvent (DES) is a typical kind of green solvent that has been attracted much attention recently. Here, high molecular weight natural cellulose (DP > 3000) was first isolated from wheat straw and then be directly dissolved in the choline/ l -lysine (Ch/Lys) DES. The solution owns excellent stability, and the solubility reaches ∼5%. Rheological studies revealed that the natural cellulose can be well dispersed in the DES solution and showed gelation at high concentrations. The dissolved cellulose can be regenerated when the dilute acid aqueous solution was added into the solution. It provides an energy conversation and an environmentally friendly route to prepare a cellulose solution, which makes it possible to convert cellulose to valuable chemicals and materials in its homogeneous solution.
研究领域:
化学工程
·
材料科学
✓ 已验证
DOI
高影响因子
JOURNAL OF CATALYSIS
·
2018
·
IF 6.759
Wei Li,Lei Hui,Bing Xue,Chuanding Dong,Yuming Chen,Linxi Hou,Binbo Jiang,Jingdai Wang,Yongrong Yang
A Polyhedral oligomeric silsesquioxane (POSS) modified Ziegler-Natta catalyst is reported to synthesize the weakly entangled ultra-high molecular weight polyethylene at a high temperature and with a high activity. Incorporation of POSS can form numbers of aggregates with a mean size of 48 nm adsorbing on the surface of SiO 2 . The structure of nanoaggregates is evidenced by the experiments and theoretical calculations where one POSS can coordinate with multiple MgCl 2 molecules serving as an electric donor to the further immobilized TiCl 4 . The catalyst is thus featured by two distinct active regions positioned in the POSS/MgCl 2 nanoaggregates and δ -MgCl 2 , respectively. The former regions present extremely low activity on ethylene polymerization, which function as horizontal separators for isolating the active TiCl 4 sites and the growing chains. This catalyst exhibits an exceptional activity ( i.e. 1.3 × 10 6 gPE mol Ti −1 h −1 bar −1 ) for the synthesis of weakly entangled polyethylene at 60 °C.
研究领域:
材料科学
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催化化学
✓ 已验证
产品关联
DOI
高影响因子
ACS Omega
·
2021
·
IF 3.512
Tianyu Lan,Na Zhang,Liduo Chen,Cuiqin Li,Jun Wang
The 1.0G dendrimer polyamidoamine (PAMAM), 3,5-dichlorosalicylaldehyde, and TiCl4·2THF were used as synthetic materials, and the dendritic salicylaldehyde imide ligand with substituent hindrance and its titanium catalyst were synthesized by the condensation reaction of Schiff base. The structure of the synthesized products was characterized by infrared spectroscopy, nuclear magnetic resonance hydrogen spectroscopy, ultraviolet spectroscopy, electrospray mass spectrometry, and inductively coupled plasma-mass spectrometry. Activated methylaluminoxane (MAO) was used as a catalyst precursor for ethylene polymerization in the process of ethylene catalytic. The effects of ethylene polymerization were studied in terms of the Al/Ti molar ratio, reaction time, reaction temperature, polymerization pressure, and ligand structure of the catalyst. The results show good catalytic performance (70.48 kg PE/mol Ti·h) for ethylene polymerization because of the existence of ortho substituent hindrance on the salicylaldehyde skeleton. Furthermore, high-temperature gel permeation chromatography (GPC)-IR, differential scanning calorimetry (DSC), and torque rheometer were used to characterize the microstructure, thermal properties, and viscoelastic state of the polyethylene samples obtained. The results showed that the product was ultrahigh-molecular-weight polyethylene.
研究领域:
化学
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材料科学
✓ 已验证
产品关联
DOI
PubMed
高影响因子
Processes
·
2023
·Vol. 11
·期 1
·255
·
IF 3.5
Ke Chen,Jingyun Zhang,Xing Liu,Peiyuan Zhang,Wenlong Yue,Zhiqiang Cai
Aspergillussp. D-23 was obtained by ultraviolet-diethyl sulfate (UV-DES) compound mutagenesis fromAspergillussp. C18 that the α-galactosidase was purified from. According to sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE) and non-denaturing polyacrylamide gel electrophoresis (Native-PAGE), the purified enzyme demonstrated apparent homogeneity. The monomeric α-galactosidase’s native molecular weight was 125 kDa. The optimal temperature of α-galactosidase was 65 °C, and 75% of the initial enzyme activity could be maintained between 45 and 55 °C. Its optimal pH was 5.0 with good pH stability. After incubating for 2 h at pH 3.0–8.0, it could retain more than 80% of its original activity. Different concentrations of metal ions had different effects on the α-galactosidase activity. High concentrations of Cu2+could strongly inhibit enzyme activity and low concentrations of Fe2+could promote enzyme activity. Additionally, as shown by thin layer chromatography and high-performance liquid chromatography, the enzyme also had good hydrolysis ability, which could efficiently hydrolyze melibiose and raffinose by more than 95%. Therefore, these excellent characteristics could make α-galactosidase a good candidate for the food and feed industries.Keywords:α-galactosidase;enzymatic characterization;Aspergillussp.;enzymatic hydrolysis;higher molecular weight
研究领域:
生物化学
·
食品科学
·
微生物学
✓ 已验证
产品关联
DOI
高影响因子
Polymers
·
2023
·Vol. 15
·期 11
·2501
·
IF 5
Panpan Zhang,Qiongqiong Xu,Wenyu Mao,Jiaxing Lv,Haodong Tang,Huadong Tang
A novel synthesis of ultrahigh molecular weight poly(methyl methacrylate) (PMMA) using organosulfur compounds combined with a catalytical amount of transition metal carboxylates as an initiator has been developed. The combination of 1-octanethiol with palladium trifluoroacetate (Pd(CF3COO)2) was found to be a very efficient initiator for the polymerization of methyl methacrylate (MMA). An ultrahigh molecular weight PMMA with a number-average molecular weight of 1.68 × 106Da and a weight-average molecular weight of 5.38 × 106Da has been synthesized at the optimal formulation of [MMA]:[Pd(CF3COO)2]:[1-octanethiol] = 94,300:8:23 at 70 °C. A kinetic study showed that the reaction orders with respect to Pd(CF3COO)2, 1-octanethiol, and MMA are 0.64, 1.26, and 1.46, respectively. A variety of techniques such as proton nuclear magnetic resonance spectroscopy (1H NMR), electrospray ionization mass spectroscopy (ESI-MS), size exclusion chromatography (SEC), X-ray photoelectron spectroscopy (XPS), transmission electron microscopy (TEM), and electron paramagnetic resonance spectroscopy (EPR) were employed to characterize the produced PMMA and palladium nanoparticles (Pd NPs). The results revealed that Pd(CF3COO)2was firstly reduced by the excess of 1-octanethiol to form Pd NPs at the early stage of the polymerization, followed by the adsorption of 1-octanethiol on the surface of nanoparticles and subsequent generation of corresponding thiyl radicals to initiate the polymerization of MMA.Keywords:ultrahigh molecular weight;PMMA;polymerization;kinetics;mechanism
研究领域:
高分子化学
·
材料科学
✓ 已验证
产品关联
DOI
PubMed
高影响因子
ACS Applied Materials & Interfaces
·
2025
·
IF 8.2
Ke Han,Rui Li,Yule Lu,Xin Sun,Jie Cui,Yin-Zhu Wang,Yong Wang,Hao Lv,Yonghong Hu,Li Mi
Due to the low bioavailability and insolubility of high molecular weight polycyclic aromatic hydrocarbons (HMW-PAHs) in aqueous solutions, their degradation efficiency is significantly limited in wastewater treatment and environmental remediation. To address this challenge, we designed oil-in-water (O/W) macroemulsion (ME) bioreactors with mixed surfactants (Tween-80 and Triton X-100), n-butanol, corn oil, and Burkholderia vietnamiensis (BVs) to enhance the degradation efficiency of pyrene. Owing to the higher solubility of pyrene in MEs, it could be easily adsorbed onto hydrophobic groups on the cell surface. Furthermore, the fluorescence images showed that the BVs were adsorbed on the surface of the MEs, increasing the contact frequency and interactions between pyrene and BVs. Meanwhile, the degradation efficiency of the prepared ME bioreactor was improved by up to 198% compared to that of the conventional surfactant. Therefore, the constructed ME bioreactors can provide green guidance for HMW-PAH biodegradation in industrial wastewater and environmental remediation.
研究领域:
环境科学
·
微生物学
✓ 已验证
产品关联
DOI
PubMed
高影响因子
JOURNAL OF ELECTRONIC MATERIALS
·
2021
·Vol. 50
·期 5
·2789-2799
·
IF 1.938
Fahad Shah,Yu Haojie,Wang Li,Wang Yang,Lin Tengfei,Amin Bilal Ul,Naveed Kaleem-Ur-Rahman,Khan Rizwan Ullah,Mehmood Sahid,Haq Fazal,Xing Yusheng,Usman Muhammad
High molecular weight polyvinylpyrrolidone (PVP) and seeding conditions are considered to have important roles in the synthesis of AgNWs. In this work, we report a versatile synthesis of AgNWs in a salt-free environment and under Ar inert atmosphere using high molecular weight PVP and seeding step during the synthetic process. The high molecular weight PVP was found to efficiently promote the preparation of AgNWs via supporting the proper growth control of AgNWs on {111} facets and selective growth on {100} facets. The seeding step facilitates the formation of seeds such as multiple twinned nanoparticles (MTPs) and single crystal seeds, which promoted the feasible formation of AgNWs. The shape and size of the synthesized AgNWs were characterized by SEM and TEM. The crystalline nature of the synthesized AgNWs was characterized by HRTEM, SAED and XRD, and their LSPR peaks were confirmed by UV-Vis spectroscopy. The conductive properties of the synthesized AgNWs were determined by preparing their thin conductive film on a PET substrate. The prepared AgNWs thin films exhibited good sheet resistance.
研究领域:
材料科学
·
纳米技术
✓ 已验证
产品关联
DOI
高影响因子
MACROMOLECULAR RAPID COMMUNICATIONS
·
2022
·Vol. 43
·期 20
·2200341
·
IF 5.006
Yongjia Lou,Jialin Xu,Luyan Xu,Zhuo Chen,Bo-Lin Lin
Synthesizing chemically recyclable solid polymeric materials is a significant strategy to potentially achieve carbon neutral production of new polymers and alleviate plastic pollution, especially when the synthesis is based on CO 2 and inexpensive co-feedstocks available in large scales. Additionally, polymeric materials should have high enough molecular weight to exhibit distinguished properties from low molar mass polymers to serve for a broader range of application scenarios. However, up to now, strategies for developing solid-state CO 2 -based chemically recyclable polyesters with both high molecular weight and facile property tunability are still unprecedented. Herein, a brand-new synthetic route is developed to synthesize chemically recyclable CO 2 -based solid polyesters with high molecular weight ( M n up to 587.7 kg mol −1 ) and narrow dispersity ( Đ < 1.2), which should further broaden the potential application scenarios of new CO 2 -based polyesters. Additionally, complete monomer recovery from poly( δLH 2 ) material is also achieved. The preserved terminal alkene groups allow facile property tuning of the polyesters via photo-initiated thiol-ene click reactions, enabling more potential utilities and further functionalizations.
研究领域:
材料科学
·
化学工程
·
环境科学
✓ 已验证
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）