Journal of Coatings Technology and Research
·
2020
·Vol. 18
·期 1
·259-269
·
IF 1.815
Liu Jieming,Wang Shaoshun,Su Qiuping,He Jiajian,Li Yong,Xie Jing,Yi Guobin
A hyperbranched polyester with carboxyl end group (HPC) was synthesized by using trimellitic anhydride and neopentyl glycol as raw materials via A 2 + B 3 polycondensation. Then, waterborne hyperbranched polyester acrylate (WHPC) was synthesized by partially modifying the carboxylic groups of HPC with glycidyl methacrylate. In order to explore the influence of molecular weight, acrylate groups content, and ion groups content on performances, a series of WHPC films with different molecular weight, acrylate groups content, and ion groups content were prepared. The dynamic light scattering spectrometer analysis shows that the higher ionic groups content and the lower molecular weight cause the smaller particle size. The ionic group content has a positive effect on the solubility. The smaller molecular weight and particle size cause the lower viscosity. The Fourier-transform IR spectrophotometer reveals that the double bond final conversion increased with increasing acrylate groups content. The final conversion is between 69 and 86%. The curing speed is fast, and the curing time is about 70 s due to the numerous end groups owned by the hyperbranched structure. The dynamic mechanical thermal analysis coupled with end-use mechanical property tests illustrates that the crosslink density has a positive effect on the storage modulus and a negative effect on the flexibility. It is also found that glass transition temperature and pencil hardness are determined by the balance between crosslink segment and hyperbranched polyester segment. The thermogravimetric analysis proves that increased crosslink density and molecular weight promote the heat resistance of films. This work utilizes a novel hyperbranched structure that excels in viscosity, flexibility, and water solubility. Furthermore, the preparation process is convenient.
研究领域:
材料科学
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化学工程
✓ 已验证
产品关联
DOI
高影响因子
COMPOSITES PART B-ENGINEERING
·
2021
·
IF 9.078
Bo-Wen Liu,Yu-Fei Lei,Xiao-Feng Liu,Li Chen,De-Ming Guo,Yu-Zhong Wang
The use of conventional flame-retardant elements such as Cl, Br, P for carbon-based polymers usually leads to the deterioration of smoke and toxic gas release, and possesses serious environmental and ecological issues. Herein, we proposed a facile strategy to largely improve the flame-retardant efficiency of an eco-friendly flame-retardant method. By simply tailoring the substitution position of the functional polymerization monomer , the corresponding copolymer exhibited extremely high flame retardancy , including a 59% lower peak heat release rate (pHRR), a 48% lower smoke density, a high limiting oxygen index (LOI) of 30%, and passed the UL-94 V-0 rating without dripping. More importantly, the para -substitution copolymer showed a much higher flame-retardant efficiency than the meta -substitution copolymer, for which the monomer content needed for UL-94 V-0 rating, high LOI value, and low smoke and toxic gas release largely decreased by 25%. The detailed mechanism and the different performance between the two copolymers were comprehensively investigated. The results first confirmed the “end-group-capturing” mechanism, then revealed that the different flame-retardant efficiency was owing to the different thermal rearrangement capability of the two functional monomers . The molecular-level mechanism revealed here provided a novel thinking for designing flame-retardant polymers.
研究领域:
材料科学
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高分子化学
✓ 已验证
产品关联
DOI
高影响因子
JOURNAL OF CHROMATOGRAPHY A
·
2023
·
IF 4.1
Jiayu Yu,Jingdong Peng,Huanjun Peng,Zilong Zhang,Kun Fan,Pan Luo,Jiajia Wu,Hanqi Yang,Hanlin Zeng,Xiang Wang
Three structurally similar silane reagents with different terminal groups were prepared and bonded to silica to obtain three structurally similar stationary phases (Sil-Ph-COOH, Sil-Phe and Sil-Ph-NH 2 ). The prepared stationary phases were characterized through elemental analysis (EA) and Fourier Transform Infrared Spectroscopy (FT-IR). These three stationary phases provided acceptable retention repeatability (relative standard deviations between 0.08% and 0.13%) and high column efficiency (7.3 × 10 4 plates/m for uridine on Sil-Phe). The retention behavior of the three columns was investigated under different chromatographic conditions including different mobile phase ratio, salt concentration, pH etc. The retention mechanisms were explored by linear solvation energy relationships and Van't Hoff plots. Applications in separation under reversed phase liquid chromatography (RPLC), hydrophilic interaction liquid chromatography (HILIC) and ion exchange chromatography (IEC) mode were investigated. The results showed that the retention capacity of the stationary phases with different terminal groups to the analytes is very different, especially for carboxylic acids, because the surface charges of amino groups and carboxyl groups under weakly acidic conditions produce different electrostatic effects with dissociated carboxylic acids. Finally, the Sil-Phe column was employed to detect ibuprofen extracted from pharmaceutical ibuprofen capsules and vitamins extracted from vitamin tablets.
研究领域:
分析化学
·
色谱学
✓ 已验证
产品关联
DOI
PubMed
高影响因子
JOURNAL OF MOLECULAR LIQUIDS
·
2024
·
IF 5.3
Ran Chen,Junyu Zou,Zihao Mao,Zhongwei An,Pei Chen,Xinbing Chen
Laser display technology can enhance the image quality of liquid–crystal on silicon (LCoS) devices in AR displays. High birefringence (Δ n ), large dielectric anisotropy (Δ ε ), low rotational viscosity ( γ 1 ) and good blue-light stability are inevitable performance requirements for achieving fast response time, low voltage and 2π phase modulation in LCoS devices based on laser display technology. However, people lack attention to how to obtain liquid crystal compounds with above properties. In this work, we propose to utilize one fluorinated terphenyl unit with excellent blue-light stability as the molecular skeleton, and then employ large polar terminal groups to modulate the molecular polarizability and dipole moment , and finally screen to obtain the LCs with high Δ n and large Δ ε . The effects of methyl, fluorinated, chlorinated and cyano terminal groups on the mesomorphic and electro-optical properties of fluorinated terphenyl LCs were systematically studied. Experimental and theoretical results show that the target compounds exhibit wide LC phase intervals, and could enhance the Δ n , Δ ε of the parent LC mixture and reduce its viscoelastic constant, further meaning that they would help to improve the electro-optical properties of LC mixtures for AR displays. Our results would provide experimental data and technical support for the future development of LC mixtures with high blue-light stability for AR displays.
研究领域:
材料科学
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光学
·
显示技术
✓ 已验证
产品关联
DOI
高影响因子
AICHE JOURNAL
·
2024
·
IF 3.5
Jun-Yao Shen,Xin-Yi Gao,Wen-Ze Guo,Jie Jiang,Jin-Jin Li,Ling Zhao,Zhen-Hao Xi,Wei-Kang Yuan
Challenges in the mechanistic and kinetic study on the polymerization with multiple functional monomers hinder the scale-up for the controllable reaction process. Herein, poly (isosorbide carbonate) synthesized from isosorbide (ISB) was employed to investigate the reaction behavior of functional monomers during polymerization. DFT calculations not only determined the energetically preferable pathways but also provided explanations for the significant differences between terminal groups at the molecular level. Subsequently, the characteristic absorption bands were detected from 1000 to 1100 cm −1 for hydroxyls on ISB, providing a quantitative measure for asymmetric hydroxyls. The reaction network indicated that the reactivity was dominated by the types of terminal groups instead of the chain length. Thereafter, a functional group model with six kinetic parameters was built, acting a crucial role in reaction control and reactor design. This method can be promoted to other functional monomers, conducing to the industrialization of high-performance polymers.
研究领域:
高分子化学
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材料科学
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化学工程
✓ 已验证
产品关联
DOI
高影响因子
Materials Today Communications
·
2024
·
IF 3.7
Le Yang,Yin Qin,Yang Li,Bangsheng Wang,Huabi Chen,Zhu Luo
Polylactic acid (PLA) is known for its degradative properties. Since PLA possesses a long chain macromolecular structure, its degradation behavior and characteristics have been the focus of research. In the presence of Lewis acid, the carbonyl oxygen in the ester group of PLA molecular chain can coordinate with it and be activated, so as to break the ester group and cause PLA degradation. However, there is still a lack of research strategies on the evolution of the remote structure of PLA chains, and there were few studies on the long-range degradation of PLA molecular chain in the effect of Lewis acid. In this work, a statistical method, combined with molecular weight testing, was proposed to investigate the long-range degradation behavior of PLA molecular chains. Results showed that in the presence of nano-ZnO, the long-range degradation of PLA molecular chain in solution was initially carried out in the form of terminal group biting-back and exchanging within 4 hours, and the molecular chain with new terminal-group was still long enough after degradation, gradually shortened over time. PLA began to degrade obviously after 8 h reaction. This chain scission method can provide a reaction platform for some reactions such as long-chain branching, which can be utilized to prepare PLA with special molecular chain topology and explore the mechanism of PLA chain structure transformation.
研究领域:
材料科学
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高分子化学
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降解研究
✓ 已验证
产品关联
DOI
高影响因子
SYNTHETIC METALS
·
2013
·
IF 2.109
Hangqi Shi,Zhuowei Gu,Xiao Gu,Hongbin Pan,Junying Pan,Xiaolian Hu,Congcheng Fan,Minmin Shi,Hongzheng Chen
In this work, a diphenyl substituted diketopyrrolopyrrole (DPP) and its two derivatives end-capped with fluorine and n -butyl respectively, namely PDPPP, FPDPPPF, and RPDPPPR, are designed and synthesized. The resulting molecules exhibit similar energy structures, i.e. both relatively narrow optical band gaps (1.75–1.79 eV) and deep highest occupied molecular orbital (HOMO) energy levels (−5.18 to −5.25 eV), implying that all of them are potentially good electron donors for organic solar cells (OSCs). However, three molecules show different photovoltaic performances when they are blended with [6,6]-phenyl-C 61 -butyric acid methyl ester (PC 61 BM) to fabricate OSCs: the RPDPPPR-based device gives the highest power conversion efficiency (PCE) of 1.59%, whereas the PCEs of PDPPP and FPDPPPF-based OSCs are 0.46% and 0.55%, respectively. Through atomic force microscopy (AFM), X-ray diffraction (XRD) and space charge limited current (SCLC) characterizations, the prominent role of end-groups in the photovoltaic properties of DPP derivatives is disclosed: terminal alkyl chains in RPDPPPR can promote molecular crystallization and lead to the formation of finer phase-separation domains in the blended film, which are in favor of charge generation and transportation in the photovoltaic devices. Thus, RPDPPPR provides the best photovoltaic property among three DPP molecules.
研究领域:
材料科学
·
有机电子学
✓ 已验证
产品关联
DOI
高影响因子
Journal of Materials Chemistry C
·
2015
·Vol. 3
·期 33
·8706-8711
·
IF 4.696
Ran Chen,Yi Jiang,Jian Li,Zhongwei An,Xinbing Chen,Pei Chen
Four series of 1,3-dioxolane-terminated liquid crystals were prepared via multi-step reactions based on 4-alkylcyclohexanecarboxylic acids. Their structures were confirmed by infrared spectrometry (IR), nuclear magnetic resonance (NMR) and mass spectrometry (MS). Their properties were measured by differential scanning calorimetry (DSC), polarising optical microscopy (POM), X-ray diffraction (XRD), Abbe refractometer and an electrical constants instrument. The results show that the positive dielectric anisotropy and birefringence of the tolane-liquid crystals are increased significantly by an introduction of 1,3-dioxolane as a terminal group. The application of the 1,3-dioxolane-terminated liquid crystals in the mixture was investigated and the results show that lower threshold voltage, wider nematic range and higher birefringence are obtained when compared to the mixture containing liquid crystals with buty-3-enyl as a terminal group. The lateral fluoro substituent, alkyne-bridge and 1,3-dioxolane terminal group enhance the stability of the nematic mesophase and the solubility of the corresponding compounds in the common host liquid crystal mixture. Meanwhile, DFT calculations of dipole moments and molecular polarizabilities were used to correlate the experimental findings.
研究领域:
材料科学
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化学
✓ 已验证
产品关联
DOI
高影响因子
HIGH PERFORMANCE POLYMERS
·
2016
·
IF 1.045
Shanyou Liu,Shiyang Zhu,Xueping Wang,Haiwei Tan,Shaowei Guan
To investigate the effect of terminal groups on the properties of hyperbranched polyimides (HBPIs) for potential optical applications, a series of HBPIs bearing different terminal groups have been synthesized through a novel aromatic CF3-containing tetra-amine, 4,4′-di[3,5-di(2-trifluoromethyl-4-aminophenoxy)phenoxy] sulfone, and a long chain dianhydride, 2,2-bis[4-(3,4-dicarboxyphenoxy)phenyl]hexafluoropropane, via a two-step polycondensation procedure. The synthesized HBPIs could form flexible and tough polyimide (PI) films, which exhibit good thermal stability with the glass transition temperatures of 191–234°C for differential scanning calorimetry measurement, the 5% weight loss temperatures of 533–610°C, and residual weights of 45.8–58.6% at 800°C under nitrogen atmosphere. The PI films have favorable mechanical properties with tensile strengths of 77–92 MPa, elongation at break of 3.55–7.99%, and initial modulus of 2.05–2.86 GPa. The films also exhibit the good transmittance of higher than 80% at 800 nm. The average refractive indices (nav) and in-plane/out-of-plane birefringence (Δn) measured at 632.8 nm are in the range of 1.5539–1.6022 and 0.0065–0.0077, respectively. The good transmittance in the visible region, tunable nav, and low Δn are very suitable for optical applications.
研究领域:
材料科学
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高分子化学
·
光学材料
✓ 已验证
DOI
高影响因子
JOURNAL OF MEMBRANE SCIENCE
·
2024
·
IF 8.4
Na Yang,Keting Li,Yufan Hao,Longfei Zhang,Yongli Sun,Luhong Zhang,Bin Jiang
Polyethyleneimine (PEI) nanofiltration (NF) membranes hold great application prospects in lithium extraction from salt lakes due to their high positive charge properties. However, the poor permeability of the membranes caused by the dense separation layer structure severely hinders their further application. Herein, a functional end-capping strategy was employed to address this problem by adding the effective end-capping reagent, Girard's Reagent T (GRT), to the PEI aqueous phase as the co-reaction reagent. Under the dual functions of the end-capping effect and the quaternary ammonium groups of GRT, the looseness and positive charge of the membrane were simultaneously optimized. After the modification of GRT, the looser structure of the PEI/GRT NF membrane improved its pure water flux (PWF) to 115 L m −2 h −1 at 6 bar, which was around 3.7 times higher than that of the original PEI NF membrane. Meanwhile, the enhanced positive charge (from −8 to 9 mV, pH = 7) of the membrane bottom surface allowed it to maintain the high rejection rate of MgCl 2 at 97.2 %. Besides, the PEI/GRT NF membrane exhibited good Mg 2+ /Li + selectivity (S Mg 2+ /Li + = 22.7, 2000 ppm, Mg 2+ /Li + mass ratio: 20:1). Therefore, this study provides a simple and feasible strategy for the preparation of high-permeable PEI NF membranes with good Mg 2+ /Li + separation performance.
研究领域:
材料科学
·
环境工程
✓ 已验证
DOI
高影响因子
CHINESE JOURNAL OF CHEMISTRY
·
2014
·Vol. 32
·期 2
·123-127
·
IF 1.04
Dongxia Li,Yang Shi,Ling Wang
We demonstrated in this study that mixing two short peptide-based gelators with different aromatic capping groups would result in molecular hydrogels with enhanced mechanical property. We selected gelators of PTZ-GFFY and Nap-GFFY for the study. Both PTZ-GFFY and Nap-GFFY could independently form molecular hydrogel by a heating-cooling process. However, the mechanical property of gels of PTZ-GFFY and Nap-GFFY was relatively weak with storage moduli ( G′ ) of about 500 and 150 Pa, respectively. A two-component gel of PTZ-GFFY and Nap-GFFY could also form by a heating-cooling process. Surprisingly, the G′ value of the two-component gel was about 5000 Pa , which was at least ten times bigger than that of each single-component gel. This is a novel and simple strategy to improve the mechanical property of molecular hydrogels.
研究领域:
材料科学
·
生物化学
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产品关联
DOI
高影响因子
JOURNAL OF APPLIED POLYMER SCIENCE
·
2022
·Vol. 139
·期 43
·e53061
·
IF 3.057
Binglun Gao,Lianwei Sun,Xin Chen,Xiaobo Zhai,Junchi Zheng,Xin Ye,Jianmin Lu,Anchao Feng,Liqun Zhang
The focus of this paper is to report the quantitative synthesis of bis-epoxy end functionalized polyisoprene (BETPI) macromonomers by anionic polymerization and reversible addition fragmentation chain transfer (RAFT) polymerization. For anionic polymerization, more stable and sterically hindered living anions polyisoprene (Li + -PIp-Li + ) react with epichlorohydrin (ECH) for the synthesis of well-defined BETPI. For the high-pressure RAFT polymerization, a novel bis-epoxy end functionalized trithiocarbonate (BODAAT) is designed as RAFT agent for the polymerization of isoprene monomer to obtain well-defined BETPI. The functionalities of the resulting BETPI are analyzed by Fourier transform infrared spectroscopy (FT-IR), NMR, and size exclusion chromatography (SEC). Through two polymerization methods, the BETPI with 600–1000 Da of molecular weight and over 75% of epoxy end capping rate is obtained, which can be further utilized as highly reactive liquid macromonomers.
研究领域:
高分子化学
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材料科学
✓ 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）