JOURNAL OF THERMAL ANALYSIS AND CALORIMETRY
·
2014
·Vol. 119
·期 1
·597-603
·
IF 2.206
Xu Xiaopeng,Chen Si,Wu Bozhen,Ma Meng,Shi Yanqin,Wang Xu
The influence of allantoin (ALL) combined with zinc stearate (ZnSt 2 ), calcium stearate (CaSt 2 ), and ZnSt 2 –CaSt 2 (1:1), respectively, in different mass ratios on thermal stability of poly(vinyl chloride) (PVC) was investigated by Congo red test, discoloration test, and thermogravimetric analysis. The results indicated that ALL behaved as a good long-term thermal stabilizer for PVC, which was attributed to its ability to absorb hydrogen chloride released from the degradation of PVC. Moreover, ALL was able to extend the stabilization time of PVC containing ZnSt 2 –CaSt 2 and postpone “zinc burning.” Fourier transform infrared spectra confirmed that ALL can react with ZnCl 2 to produce an inert complex, which is responsible for postponing “zinc burning.”
研究领域:
材料科学
·
化学工程
✓ 已验证
产品关联
DOI
高影响因子
CRYSTAL GROWTH & DESIGN
·
2025
·
IF 3.4
Dongling Yang,Hongyuan Sha,Qinghe Li,Lilin Yang,Zujian Wang,Rongbing Su,Chao He,Bin Su,Xiaoming Yang,Xifa Long
Birefringent crystals are important optical functional materials widely used in light polarization modulation. Generally, the larger the birefringence, the higher the modulation efficiency. Thus, it is necessary to develop crystals with a large birefringence. Herein, two planar groups, phenyl and acyl, were adopted to generate strong optical anisotropy. Then, three urea-based crystals, N-phenylurea, N,N′-diphenylurea, and acetylurea, were found, all of which exhibit a large birefringence of 0.169, 0.266, and 0.315 (at 546 nm), respectively. Although the birefringence improvement is facilitated by phenyl groups, it is restricted by their incomplete coplanar arrangement, while it achieves the maximum by acyl groups and their coplanar arrangement with urea. Moreover, these crystals all exhibit a wide ultraviolet transparency window. Therefore, this work develops three birefringent crystal candidates and also provides some new insights, which will facilitate the exploration of novel birefringent crystals.
研究领域:
材料科学
·
光学
✓ 已验证
产品关联
DOI
高影响因子
JOURNAL OF CHEMICAL THERMODYNAMICS
·
2016
·
IF 2.196
Yaotai Jiang,Xiaobang Liu,Dongshun Deng
The solubilities of SO 2 in three dipolar aprotic urea diversities, 1,1,3,3-tetramethylurea (TMU), 1,3-dimethyl-2-imidazolidinone (DMI), and 1,3-dimethyl-3,4,5,6-tetrahydro-2 (1H)-pyrimidinone (DMPU) was measured at temperatures ranging from (293.15 to 323.15) K and pressure up to 120 kPa. By correlating the solubility results with a reaction equilibrium thermodynamic model (RETM), Henry’s constants ( H m ), reaction equilibrium constants ( K °), and enthalpy (Δ H r ) in the absorption process were obtained. The results indicate that the three solvents exhibit both strong physical and weak chemical interactions with SO 2 . Further comparison of the capture performance with ILs, deep eutectic solvents (DESs), and several organic solvents, DMI, DMPU and TMU are noted to be excellent absorbents for acidic SO 2 .
研究领域:
化学工程
·
物理化学
✓ 已验证
产品关联
DOI
高影响因子
JOURNAL OF CHROMATOGRAPHY A
·
2022
·
IF 4.601
Xiangqiong He,Adeel Ahmed,Shuaibing Guo,Chuankui Kang,Youqing Shen,Hailin Cong,Bing Yu
Recently, the design and development of efficient chiral stationary phases is still the core and goal of chiral chromatography. In order to quickly separate chiral drugs, we designed and prepared an environmentally friendly small particle chiral stationary phase: p-methylphenylurea-β-cyclodextrin chiral stationary phase (SiO 2 @PMPU-β-CD). Firstly, p-methylphenylurea-β-cyclodextrin (PMPU-β-CD) was connected to the surface of mesoporous silica microspheres by diazoresin (DR) to prepare a SiO 2 @PMPU-β-CD. In reverse elution mode, the column temperature was set at 25 °C, the flow rate was 0.2 mL/min, and ACN H 2 O (v/ v = 70:30) was used as the elution condition of the mobile phase. The enantiomers of chlorpheniramine maleate, 2-phenylcyclohexanone, and promethazine were separated within 5 min. In addition, the addition of TEAA buffer to the mobile phase improved the enantiomer resolution of chlorpheniramine maleate from 1.03 to 5.69. The experimental results show that the SiO 2 @PMPU-β-CD column can be used for the separation of appellant chiral drugs with good repeatability, and the use of DR instead of silane coupling agent has the advantages of being non-toxic, environmentally protected, and easy to operate, which is of great significance for the development of chiral stationary phase.
研究领域:
色谱学
·
药物化学
·
分析化学
✓ 已验证
DOI
PubMed
高影响因子
CHINESE JOURNAL OF POLYMER SCIENCE
·
2019
·Vol. 37
·期 12
·1205-1214
·
IF 2.804
Jiang Zhuo-Lun,Zhao Jun-Peng,Zhang Guang-Zhao
Highly potent ionic organocatalyst is developed for room-temperature controlled ring-opening polymerization (ROP) of lactones, including δ -valerolactone, ε -caprolactone, and δ -hexalactone. The catalysts are prepared by simply mixing tetra- n -butyl ammonium hydroxide and a (thio)urea at elevated temperature under vacuum, and used in cooperation with an alcoholic initiator. The performance of the catalyst is readily adjusted and optimized through variation of the (thio)urea precursor, catalyst composition, and reaction condition. Urea-derived catalysts are generally superior to thiourea-derived ones. Provided with proper N -substituents, the catalyst affords both high polymerization efficiency and high selectivity for monomer enchainment over macromolecular transesterification, even at high monomer conversion and/or substantially extended reaction time. In addition to acidity, structural symmetry of the urea also proves decisive for the catalytic activity, which enables a catalyst-assisted proton transfer process for the ring-opening of lactone and thus provides a novel mechanistic insight for ROP catalyzed by hydrogen-bonding type bifunctional ionic organocatalysts.
研究领域:
高分子化学
·
有机化学
✓ 已验证
DOI
高影响因子
CHEMICAL ENGINEERING JOURNAL
·
2023
·
IF 15.1
Shangyu Hu,Yaxiong Zhan,Peilei Wang,Jingfei Yang,Fengxiu Wu,Meng Dan,Zhao-Qing Liu
The production of hydrogen peroxide (H 2 O 2 ) by electrochemical oxygen reduction is a clean and convenient route. Here, we develop a universal urotropine (hexamethylenetetramine) modified carbon-based catalyst strategy. Both experimental results and theoretical calculations proved that the introduction of urotropine not only provides the isolating O 2 active sites to protect OOH* from being further split, but also excites carbon nanotube matrix to produce rich secondary O 2 active sites. More importantly, the end-on type of adsorption of O 2 on excited secondary reactive sites can be stabilized by the hydrogen bond effect, which greatly increases the productivity of H 2 O 2 . As a result, the urotropine (hexamethylenetetramine) modified commercial carbon nanotubes (denoted as H-CNTs) catalyst achieved 95% selectivity and 748 mmol·g catalyst ·h −1 yield of H 2 O 2 at 0.7 V vs . RHE. Therefore, this work provides a highly potential urotropine modification strategy towards efficient electrochemical H 2 O 2 synthesis.
研究领域:
材料科学
·
电化学
·
催化反应
✓ 已验证
DOI
高影响因子
ACS Applied Nano Materials
·
2024
·
IF 5.3
Junjie Zhang,Yansheng Wu,Li Zhang,Wenran Gao
Nitrogen-doped graphene has been regarded as one of the most promising materials for nonradical peroxymonosulfate (PMS) activation. However, facile construction of nitrogen-doped graphene and systematic investigation of its nonradical PMS activation in a practical environment still far lag behind. Herein, graphitic N-rich graphene was prepared by one-step pyrolysis of urea. The obtained urea-derived graphitic N-rich graphene (UGNG) possessed a high N content of 12.12 at. % and a graphitic N proportion of 41.12%, giving a high graphitic N content of 4.98 at. %. We confirmed that PMS donated electrons to the graphitic N in UGNG, resulting in the cleavage of PMS to singlet oxygen for nonradical oxidation. The turnover frequency for the oxidation reached the highest value of 10.5 min–1. Also, the reaction could be conducted in a wide temperature (5–45 °C) range, even with the existence of common matrix species and different natural water matrixes. This work presented the direct conversion of N-rich organic urea to UGNG and systematically investigated its nonradical PMS activation, which is believed to be helpful to its further practical use.
研究领域:
环境科学
·
材料科学
✓ 已验证
产品关联
DOI
高影响因子
RSC Advances
·
2022
·Vol. 12
·期 7
·4072-4080
·
IF 4.036
Mengyun Zhang,Ying Liao,Xin Tong,Fuhua Yan
Caries is the most common chronic infectious disease in the human oral cavity and the existing anti-caries agents may lead to drug resistance and microecological imbalance. A novel urea derivative, 1,3-bis[3,5-bis(trifluoromethyl)phenyl]urea, has a potentially prominent antibacterial effect on cariogenic bacterial strain Streptococcus mutans UA159. In this study, we encapsulated the water-insoluble urea derivative in poly(lactic-co-glycolic acid) (PLGA) nanoparticles, performed physicochemical characterizations and explored its potential as a caries-preventive agent. The results showed that the drug-loaded PLGA nanoparticles exhibited satisfying surface morphology, particle size, size distribution and stability. With an optimized theoretical drug loading (10%), the drug-loaded PLGA nanoparticles exhibited negligible cytotoxicity against human oral squamous cell carcinoma cells. We noticed a biphasic drug release in vitro and the rate and cumulative release was higher in an acidic environment (pH 4.5) compared to a neutral environment (pH 7.4). The drug-loaded PLGA nanoparticles significantly inhibited the growth and lactic acid production of planktonic S. mutans as well as S. mutans biofilms. Our results indicate that the novel urea derivative-loaded PLGA nanoparticles serve as a promising anti-caries agent with remarkable pharmaceutical characteristics, low cytotoxicity, and satisfying antimicrobial effect.
研究领域:
口腔医学
·
药剂学
·
材料科学
✓ 已验证
产品关联
DOI
PubMed
高影响因子
GREEN CHEMISTRY
·
2016
·Vol. 18
·期 9
·2851-2863
·
IF 8.506
Mengshuai Liu,Lin Liang,Xin Li,Xiangxiang Gao,Jianmin Sun
Several urea derivative-based ionic liquids (UDILs) with superior thermal stability were facilely synthesized, structurally analyzed, and applied to CO2 capture and conversion under mild conditions. These UDILs reversibly capture CO2 with double molar CO2 absorption and exhibit outstanding catalytic activity for the conversion of CO2 and various epoxides to cyclic carbonates under metal- and solvent-free conditions. The effects of reaction parameters on the catalytic activity for propylene carbonate (PC) synthesis from propylene oxide (PO) and CO2 were thoroughly investigated. Because water is inevitably contained in real gases requiring treatment, the influence of water on CO2 capture and conversion was also studied. Furthermore, reaction kinetic studies were also undertaken and a cation–anion synergistic catalytic mechanism was proposed. The single-component, metal-free, dual functional, stable, and easily recyclable ionic liquids reported herein are interesting materials, displaying a good performance for both CO2 capture and conversion.
研究领域:
化学
·
环境科学
✓ 已验证
产品关联
DOI
高影响因子
危险品化学品经营许可证（带存储）