MACROMOLECULES
·
2016
·
IF 5.554
Shaoning Liang,Xiaohui Li,Wen-Jun Wang,Bo-Geng Li,Shiping Zhu
We report the reversible addition–fragmentation chain transfer (RAFT) solution copolymerization of methyl methacrylate (MMA) with a cleavable divinyl comonomer, bis(2-methacryloyl)oxyethyl disulfide (BMAODS). 2-Cyano-2-propyldodecyl trithiocarbonate was used as a RAFT chain transfer agent and 2,2′-azobis(2-methylpropionitrile) as an initiator. The selective cleavage of BMAODS disulfide bonds was used to collect primary chains for the determination of the branching density (BD). The effects of initial monomer concentration, vinyl/divinyl ratio, and primary chain length on the branching and cyclization reactions were thoroughly investigated. It was found that more than 50% pendent double bonds from BMAODS were consumed in cyclization rather than in branching. The BD increased linearly with the conversion up to approximately 60% conversion. The monomer concentration was found to be the most efficient parameter in promoting branching. Increasing divinyl monomer ratio and primary chain length favored cyclization over branching. The work provides experimental evidence to support the random branching mechanism in RAFT copolymerization of vinyl and divinyl monomers.
研究领域:
高分子化学
·
材料科学
✓ 已验证
产品关联
DOI
高影响因子
ACS Applied Polymer Materials
·
2023
·
IF 5
Le Yang,Yin Qin,Yang Li,Yinhan Xu,Yao Tao,Zhu Luo,Qiang Zheng
Long-chain branch (LCB) structures are critical for upgrading the poly(lactic acid) (PLA) melt performance. Polymer chains that are restructured by introducing LCBs via melt transesterification show higher reactive efficiencies and are environmentally friendly and gel free. Although PLA is environmentally friendly, its low melt strength hinders film blowing, blow molding, foaming, and other processes involving polymer melts. Therefore, the construction of LCBs is the key to solving this problem. However, because PLA easily thermally degrades, severe excessive transesterification-associated polymer degradation via the drastic chain-scission reaction substantially outcompetes the LCB-branching reaction, which substantially narrows the processing window for forming LCBs. Therefore, in this study, a dual hybrid branching (DHB) strategy was proposed to overcome these challenges. Specifically, surface-aminated ZnO (SAN-ZnO) nanoparticles were applied as an accelerant via ester activation by coordinating zinc atoms in ZnO with ester group oxygen atoms in PLA, which promoted transesterification between PLA and a trifunctional ester to form LCB–PLA. Moreover, amidogens on the SAN-ZnO surface could collect degraded PLA chains and react with their terminal carboxyl groups via amidation in situ to form DHB chains and thus restrain polymer overdegradation. Because DHB both facilitated LCB formation and restrained excessive polymer degradation, the PLA melt performance, especially the melt strength, was obviously improved to over 37 cN.
研究领域:
材料科学
·
高分子化学
✓ 已验证
产品关联
DOI
高影响因子
JOURNAL OF FLUORINE CHEMISTRY
·
2021
·
IF 2.05
Nianze Song,Xin Huang,Yifei Li,Kaokao Zhang,Chaihui Wei,Jian Zhang,Yue Zhang
ABSTRACT To deal with the demulsification of emulsion stabilized by naphthenic compounds, a series of multibranched–linear–multibranched (MLM) copolymer were designed and synthesized. The hydrophilic core with MLM structure is constructed by anionic ring-opening multibranching polymerization (ROMBP) of glycidol with poly (ethylene glycol). The amphophobic arms are grafted by atom transfer radical polymerization (ATRP) of 2, 2, 2-trifluoroethyl methacrylate (TFEMA). The demulsification performance of the MLM copolymer in n-octane/water emulsion stabilized by naphthenic acids (NAs) and sodium naphthenates (Na-NAs) were evaluated. The influences of copolymer dosage, temperature and Na-NAs/NAs ratio on the demulsification efficiency were investigated in detail. Compared with the blank sample settled for 90 min, the fluorinated MLM copolymer with medium HLB value promoted the demulsification efficiency from 50% to 92%. By analyzing the correlation between the polymer structure and demulsification performance, it can be considered that the PEG segment improved the low solubility of the fluorinated copolymer caused by the solvophobic nature of fluorinated groups. The amphophobic effect of the fluorinated group not only accelerates the diffusion process of polymer molecules from the bulk to the interface, but also reduces the rigidity of the interface film by repelling the original interface active material, and produces effective demulsification.
研究领域:
化学工程
·
材料科学
✓ 已验证
产品关联
DOI
高影响因子
Macromolecular Reaction Engineering
·
2014
·Vol. 9
·期 2
·90-99
·
IF 1.543
Xiaohui Li,Wen-Jun Wang,Bo-Geng Li,Shiping Zhu
This work reported branching studies in reversible addition-fragmentation chain transfer (RAFT) miniemulsion copolymerization of styrene and triethylene glycol dimethacrylate (TEGDMA), and control of branching density distribution using a model-based computer-programed monomer feeding strategy. Highly branched polystyrenes (PS) were produced with small amount of TEGDMA. The branching density experienced drifting in a batch operation. A semi-batch kinetic model by combining the kinetic model for RAFT miniemulsion copolymerization with a semi-batch reactor model was used to design the monomer feeding rate profiles for targeted branching density distributions. A series of hyperbranched PSs with the designed branching density distributions were synthesized.
研究领域:
高分子化学
·
材料科学
✓ 已验证
产品关联
DOI
高影响因子
Polymer Chemistry
·
2015
·Vol. 6
·期 20
·3747-3753
·
IF 5.52
Bo Zhao,Yaochen Zheng,Zhulin Weng,Shengying Cai,Chao Gao
This paper firstly revealed the electrophilic effect of thiol groups on thiol–yne polymerization. For this, we designed and synthesized five kinds of α-thiol-ω-alkynyl AB2 type intermediates with thiols with different electrophilicities. The thiol electrophilic effect can be assessed by chemical shift (δ) and measured directly by nuclear magnetic resonance (NMR) spectroscopy. As the evidence from gel permeation chromatography (GPC) and NMR tracking measurements shows, the polymerization rate and molecular weight (MW) were significantly enhanced as the thiol electrophilic effect reduced. On the contrary, with increasing electrophilicity of the thiol, the resultant degrees of branching (DBs) increased. The semiquantitative relation between reactive rate constant (k) and δ (or electrophilicity of thiol) can be expressed by k = 2.41–1.34δ. Therefore, important features of thiol–yne polymerization and HPTEs, such as rate constant (k), MW, DB, etc., can be roughly estimated in advance by the NMR measurement of the thiol's electrophilic effect.
研究领域:
材料科学
·
化学
✓ 已验证
产品关联
DOI
高影响因子
Autophagy
·
2023
·
IF 13.3
Chaonan Sun,Yuxin Chen,Qianqian Gu,Yuanyuan Fu,Yao Wang,Cui Liu,Huazhong Xie,Yong Liao,Zhihua Zheng,Peiqing Liu,Min Li
ATG4B is a core protein and essential for cleaving precursor MAP1LC3/LC3 or deconjugating lipidated LC3-II to drive the formation of autophagosomes. The protein stability and activity of ATG4B regulated by post-translational modification (ubiquitination) will directly affect macroautophagy/autophagy. However, the mechanism involved in ATG4B ubiquitination is largely unclear. In this study, a new E3 ligase of ATG4B, UBE3C, was identified by mass spectra. UBE3C mainly assembles K33-branched ubiquitin chains on ATG4B at Lys119 without causing ATG4B degradation. In addition, the increased ubiquitination of ATG4B caused by UBE3C overexpression inhibits autophagy flux in both normal and starvation conditions, which might be due to the reduced activity of ATG4B and ATG4B-LC3 interaction. This reduction could be reversed once the lysine 119 of ATG4B was mutated to arginine. More important, under starvation conditions the interaction between ATG4B and UBE3C apparently decreased followed by the removal of the K33-branched ubiquitin chain of ATG4B. Thus, starvation-induced autophagy could be partially suppressed by an increased ubiquitination level of ATG4B. In conclusion, our research reveals a novel modification mode of ATG4B in which UBE3C can fine tune ATG4B activity by specific ubiquitination regulating autophagy without causing ATG4B degradation.
研究领域:
细胞生物学
·
分子生物学
·
生物化学
✓ 已验证
DOI
PubMed
高影响因子
LANGMUIR
·
2024
·
IF 3.7
Jiahang Zhou,Minqiang Xia,Lingui Hu,Yunbo Li
Herein, a novel method is presented for the in situ growth of gold nanofilms with branched structures in the presence of organosulfur. The key feature in this approach is the Rayleigh instability of ultrathin gold nanowires (AuNWs) without oleylamine (OAm), which allows the ultrathin AuNWs to decompose into gold nanoparticles (AuNPs) and the AuNPs to in situ grow into branched structures for high-performance stability and electrical conductivity. The sheet resistance of the gold nanofilms initially sharply decreased, whereas it subsequently slightly increased with the concentration of CS(NH2)2 until it exceeded the optimal range. After undergoing a 10 min heat treatment at 150 °C, the sheet resistance of the nanofilms was further reduced to 18 Ω/sq, which could be maintained for more than five months. The internal structure becomes fully grown and denser, forming a branched structure after heat treatment. Only certain organosulfurs can improve the electrical properties of the gold nanofilms, and the mechanism of organosulfur in the in situ growth of gold nanofilms with branched structures has also been presented. Overall, this novel method provides a straightforward and convenient approach to obtaining gold nanomaterials with branched structures, holding great potential promise for applications in flexible electronics, catalysis, and energy fields.
研究领域:
材料科学
·
纳米技术
·
电子工程
✓ 已验证
产品关联
DOI
PubMed
高影响因子
Cell Reports Physical Science
·
2020
·
IF 0
Pengfei Zhang,Zhangliu Tian,Chin-Te Hung,Yong Liu,Bingquan Jia,Kun Lan,Biao Kong,Fuqiang Huang,Liqiang Mai,Dongyuan Zhao
The understanding and control of the structural complexity of mesoporous semiconductors with single-crystal-like nature are both attractive and challenging. Here, we report a crystallization-driven epitaxial assembly from monomicelles to construct branched mesoporous TiO 2 mesocrystals (m-TiO 2 MCs) with coherent atomic domains. The star-shaped multipods are obtained by two-step evaporation with nanocrystal mediation, primarily consisting of arms along < 001 >, < 101 >, and < 111 > crystal directions. For each arm, ordered open mesochannels arrange in parallel along the growth direction. The m-TiO 2 MC multipods have a surface area of ∼116 m 2 /g and single-crystal-like frameworks and are good hydrogen evolution photocatalysts. Under full-spectrum irradiation, the branched m-TiO 2 MCs exhibit a hydrogen evolution rate of 8 mmol h −1 g −1 , which is more than four times higher than that of commercial TiO 2 P25. This crystallization-driven self-assembly approach may provide valuable insight into designing programmable mesoporous mesocrystals by controlling the oriented assembly of monomicelle building blocks.
研究领域:
材料科学
·
化学
✓ 已验证
DOI
BIOMACROMOLECULES
·
2021
·
IF 6.988
Ronghua Yin,Lutan Zhou,Na Gao,Lisha Lin,Huifang Sun,Dingyuan Chen,Ying Cai,Zhili Zuo,Kaifeng Hu,Shengxiong Huang,Jikai Liu,Jinhua Zhao
Glycosaminoglycans (GAGs) are conserved polysaccharides composed of linear repeating disaccharides and play crucial roles in multiple biological processes in animal kingdom. However, saccharide-branched GAGs are rarely found, except the fucose-branched one from sea cucumbers. There was conjecture about the presence of disaccharide-branched GAG since 30 years ago, though not yet confirmed. Here, we report a GAG containing galactose-fucose branches from Thelenota ananas. This unique branch was confirmed as d-Gal4S(6S)-α1,2-l-Fuc3S by structural elucidation of oligosaccharides prepared from T. ananas GAG. Bioassays indicated that oligomers with a larger degree of polymerization exhibited a potent anticoagulation by targeting the intrinsic tenase. Heptasaccharide was proven as the minimum fragment retaining the anticoagulant potential and showed 92.6% inhibition of venous thrombosis in vivo at sc. of 8 mg/kg with no obvious bleeding risks. These results not only solve a long-standing question about the presence of disaccharide-branched GAG in Holothuroidea, but open up new opportunities to develop safer anticoagulants.
研究领域:
生物化学
·
海洋生物学
·
药理学
✓ 已验证
产品关联
DOI
PubMed
高影响因子
MICROPOROUS AND MESOPOROUS MATERIALS
·
2022
·
IF 5.876
Shuaiqi Wang,Congxin Wang,Hao Liu,Donge Wang,Xiaoping Wang,Lin Yang,Peng Li,Zhijian Tian
In this work, two ZSM-12 zeolites with stellar morphology and dendritic morphology were synthesized from the synthesis system containing nanorod-aggregated hexagonal prism seed and microrod seed, respectively, in the presence of CTAB. The stellar ZSM-12 zeolite was composed of core and branches, while the dendritic ZSM-12 zeolite consisted of stem and branches. For the two zeolites, the branches grew on {310} planes of seed and were in twin relation with the seed. The c -axes of branch and seed were parallel to each other, while the b -axes of them exhibited the angular relation of 65°. The crystallization process of the two zeolites were investigated by using XRD , SEM, and TEM characterizations. It was demonstrated that the branched growth on seeds was controlled by two factors: diffusion of reactive species and adsorption of CTAB. The Mullins-Sekerka instability occurred under the diffusion-limited condition, resulting in the formation of branches on seed. The adsorption of CTAB on side facets of branches inhibited the occurrence of secondary branching.
研究领域:
材料科学
·
结晶学
✓ 已验证
产品关联
DOI
高影响因子
JOURNAL OF APPLIED POLYMER SCIENCE
·
2022
·Vol. 140
·期 5
·e53418
·
IF 3.057
Mengdi Chen,Mingfu Zheng,Lu Zhang,Yunsheng Xu,Xianming Zhang,Wenxing Chen
In this work, multiple rheological and molecular structure characterization methods are utilized to investigate the melt post-polycondensation (MPP) process of polycarbonate (PC) at high temperatures (260–300°C) under a nitrogen atmosphere. We find some unexpected phenomena that the complex viscosity of PC melt rise rapidly and it reaches an extraordinarily high value of about 10 6 Pa·s during the MPP process of 10 h at 300°C. Dissoluble PC and insoluble gel residue are separated and both fractions are analyzed by gel permeation chromatography, 1 H-NMR, and pyrolysis-gas chromatography mass spectrometry. Results show that the molecular weight of dissoluble PC significantly increases at the early stage of the reaction (less than 1 h). After that, it continues to reduce due to the occurrence of branching reactions and degradation reactions caused by high temperature reactions for a long time. Chemical structure analysis indicates that the same two branched structures are discovered in both dissoluble PC and insoluble gel residue, the changes in structures indicate that no new structures are formed during the crosslinking reaction. According to this study's results, we clearly understand the correlation between the rheological properties and structural changes for PC in the MPP progress.
研究领域:
材料科学
·
高分子化学
✓ 已验证
产品关联
DOI
高影响因子
Polymer Chemistry
·
2018
·Vol. 9
·期 23
·3215-3222
·
IF 4.927
Ni Zeng,Yuyan Yu,Junbing Chen,Xiao Meng,Leilei Peng,Yi Dan,Long Jiang
Although branched polymers find widespread applications, the rational design and synthesis of branched vinyl polymers via the conventional radical (co)polymerization of commercially available monomers is still a challenge for researchers in this field. Using branched polyvinyl acetate (PVAc) as a proof-of-concept, we report a facile approach to synthesize branched polymers via redox-initiated radical copolymerization. In this case, the commercially available monomer 2-(dimethylamino)ethyl methacrylate (DMAEMA), containing both a vinyl group and an initiator fragment (tertiary amine group), serves as an inimer in the presence of an oxidant to copolymerize with vinyl acetate (VAc), leading to the formation of branching architectures. The copolymerization kinetics investigation as well as electron paramagnetic resonance (EPR) measurements were conducted to reveal the reactivity of DMAEMA and the development of branching architectures, while TD-SEC and 1H-NMR were employed to study the structures of the resulted polymers. The results confirm that DMAEMA can serve as an inimer for the preparation of branched PVAc. Moreover, balancing the feed ratio of DMAEMA to VAc enables the fine control of branching degree. Within our experimental design, a high feed ratio of DMAEMA to VAc leads to high branching, as demonstrated by the Zimm branching factor, g′. This novel methodology involves only commercially available monomers and conventional radical polymerization and hence offers a promising future for preparing branched vinyl polymers on a large scale and at low cost.
研究领域:
材料科学
·
高分子化学
✓ 已验证
DOI
高影响因子
危险品化学品经营许可证（带存储）