Polymer Chemistry
·
2015
·Vol. 6
·期 20
·3747-3753
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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
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DOI
高影响因子
FOOD HYDROCOLLOIDS
·
2022
·
IF 11.504
Ding-Tao Wu,Yuan He,Qin Yuan,Shengpeng Wang,Ren-You Gan,Yi-Chen Hu,Liang Zou
In this study, the microbial fermentation characteristics of okra pectic-polysaccharide (OPP) and its degraded products (DOPP-1 and DOPP-3) with different molecular weights ( M w ) and degrees of branching (DB) were investigated, and related impacts on gut microbial composition were also revealed. Results indicated that microbial fermentation characteristics of OPP were obviously affected by its different structural features. The fermentabilities of OPP (high M w and DB), DOPP-1 (middle M w and DB), and DOPP-3 (low M w and DB) were measured to be 49.49%, 58.34%, and 48.16%, indicating that the utilization of total carbohydrates of DOPP-1 was relatively higher compared to OPP and DOPP-3. The ways in which gut bacteria metabolized OPP, DOPP-1 and DOPP-3 were quite different, and a lower M w and a higher DB were more beneficial to the fermentation by intestinal bacteria. Additionally, selective modulations of gut microbial composition by different types of okra pectic-polysaccharides were observed. Both OPP and DOPP-1 could increase relative abundances of several beneficial bacteria, such as Bacteroides and Phascolarctobacterium . While DOPP-3 could notably improve relative abundances of Megasphaera and Megamonas. Results suggested that the modulation of gut microbiota by okra pectic-polysaccharide was structure-dependent, and both DB and M w played critical roles in the selective modulation of gut microbial composition. Collectively, our findings are beneficial to revealing the potential relationship between chemical structures of OPP and its gut microbial fermentation characteristics, which are also helpful for the design of potential OPP for selective modulation of beneficial bacteria in the gut.
研究领域:
食品科学
·
微生物学
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DOI
高影响因子
EUROPEAN POLYMER JOURNAL
·
2020
·
IF 3.862
Mei Chen,Yuming Chen,Wei Li,Chuanding Dong,Peng Liang,Ning Wang,Binbo Jiang,Jingdai Wang,Yongrong Yang
We report a selective immobilization strategy to control the catalytic performance of the target active species in hybrid multisite catalysts. The sterically bulky and electronically donated polyhedral oligomeric silsesquioxane (POSS) is introduced onto the support and offers extra immobilization sites for the target pre-catalyst. DFT and CO low-temperature adsorption facilitate to understand the distribution of active sites. The nickel pre-catalyst can interact with the POSS, endowing the scattered distribution of nickel sites. The large steric and electronic donated iron pre-catalyst exhibits the inertness to POSS, confining iron species on the POSS-free space. The selective dispersion of nickel species enhances its contribution in the synthesis of UHMWPE fraction with an exceptional activity, a much higher molecular weight and branching degree. This promoted contribution synchronously enhances the impact resistance (+27%), tensile strength (+53%), Young’s modulus (+111%) and elongation ratio (+37%) of the synthesized bimodal PE compared to those of commercial UHMWPE.
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
RSC Advances
·
2025
·Vol. 15
·期 8
·5801-5807
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IF 4.6
Zeen Zhang,Tianjiao Li,Yong Dong,Yangcheng Lu
This study focuses on ethylene homopolymerization catalyzed by α-diimine catalysts within a designed microfluidic system. Distinct from conventional batch reactors, this microfluidic configuration effectively eradicates the reaction environment heterogeneity, thereby guaranteeing homogeneous reaction conditions and decoupling the mass transfer from the reaction process. This unique setup enables precise modulation of ethylene concentration, facilitating the isolation of variables to scrutinize the effects of temperature and pressure on the polymerization. By varying residence times, it's revealed that the reaction rate is ethylene concentration-independent. Variable separation studies between concentration and temperature show an inverse relationship between temperature and branching degree (BD), contrasting traditional batch reactions due to ethylene concentration changes. Pressure studies indicate that higher pressure leads to lower BD. Different product structures' steric hindrances influence the reaction rate; greater hindrance slows it down. These novel findings suggest microreactors offer new perspectives on late transition metal-catalyzed ethylene homopolymerization, potentially enabling breakthroughs in mass production.
研究领域:
化学工程
·
高分子科学
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DOI
PubMed
高影响因子
JOURNAL OF ORGANOMETALLIC CHEMISTRY
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2013
·
IF 2
Lei Xue,Zhizhou Yang,Dengxu Wang,Yike Wang,Jie Zhang,Shengyu Feng
Novel hyperbranched organosilicon polymers were successfully prepared via step-growth thiol-ene click reaction using mercaptopropylmethyldiallylsilane (AB 2 ) and mercaptopropyltriallylsilane (AB 3 ) as hyperbranched monomers . The structures of the prepared polymers were characterized by Fourier transform infrared spectroscopy and nuclear magnetic resonance spectroscopy . The degree of branching (DB) of the polymers was determined using quantitative 29 Si NMR spectroscopy. The DB of the polymers from AB 2 and AB 3 was 0.60 and 0.22, respectively. The results of thermogravimetric analysis showed that the presence of thioether does not affect the thermal stability of the resulting silicon-containing hyperbranched polymers (Si-HBs). The resulting Si-HBs can be used as promising candidate materials for heavy metal adsorption because of the thioether bond.
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
JOURNAL OF POLYMER SCIENCE PART A-POLYMER CHEMISTRY
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2010
·Vol. 48
·期 23
·5364-5374
·
IF 3.971
You-Mei Bao,Xiao-Hui Liu,Xiu-Lan Tang,Yue-Sheng Li
A series of novel hyperbranched poly(ester-amide)s (HBPEAs) based on neutral α-amino acids have been synthesized via the “AD + CBB′” couple-monomer approach. The ABB′ intermediates were stoichiometrically formed through thio-Michael addition reaction because of reactivity differences between functional groups. Without any purification, in situ self-polycondensations of the intermediates at elevated temperature in the presence of a catalyst afforded HBPEAs with multihydroxyl end groups. The degrees of branching (DBs) of the HBPEAs were estimated to be 0.40–0.58 and 0.24–0.54 by quantitative 13 C NMR with two different calculation methods, respectively, depending on polymerization conditions and structure of monomers. The influences of catalyst, temperature, and intermediate structure on the polymerization process and molecular weights as well as properties of the resultant polymers were investigated. FTIR, NMR, and DEPT-135 NMR analyses revealed the branched structure of the resultant polymers. The HBPEAs possess moderately high molecular weights with broad distributions, glass transition temperatures in the range of −25.5 to 36.5 °C, and decomposition temperatures at 10% weight loss under nitrogen and air in the regions of 243.4–289.1 °C and 231.4–265.6 °C, respectively. Among them, those derived from D , L -phenylalanine display the lowest degree of branching, whereas the highest glass transition temperature and the best thermal stability. © 2010 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2010
研究领域:
高分子化学
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材料科学
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高影响因子
INDUSTRIAL & ENGINEERING CHEMISTRY RESEARCH
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2019
·
IF 3.375
Liang Xiang,Yang Song,Min Qiu,Yuanhai Su
Solution polymerization of butyl acrylate and divinylbenzene (DVB) in toluene, initiated with 2,2′-azobisisobutyronitrile and mediated with chain transfer agent dodecanethiol (DDT), was carried out in a capillary microreactor with a 1 mm inner diameter. Through the Strathclyde method, branched poly(butyl acrylate) with different molecular weight distributions (MWDs) was prepared by adjusting the feed formulation and the residence time. The dosages of DVB and DDT were controlled to avoid gelation, and their effects on the branching degree of the products were investigated. The multimodal MWDs were deconvoluted to quantitatively study the branching process. The kinetics in batch and continuous operation are compared. Aqueous miniemulsion polymerization with a similar feed formulation was also conducted in the microreactor, enabling faster reaction rate, lower solution viscosity, and higher branching efficiency. This study demonstrated the feasibility to use commercial monomers to prepare branched polymers with high functionality and a dense architecture in continuous-flow mode.
研究领域:
高分子化学
·
材料科学
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DOI
高影响因子
POLYMER BULLETIN
·
2015
·Vol. 72
·期 8
·2105-2125
·
IF 1.438
Liu Yuhong,Wang Yichao,Jiang Xue,Zhang Xiying
Abstract In the study, we investigated the influence of degree of branching (DB) of isocyanate-functionalized hyperbranched polyurethanes (HPU –NCOX ) on the cure and thermal property of phenol-terminated benzoxazine oligomer (BZ –OH ). The structure of the as-synthesized HPU –NCOX was confirmed by proton nuclear magnetic resonance ( 1 H NMR and 13 C NMR), gel permeation chromatography (GPC) and Fourier transform infrared spectra (FT-IR). Thermally activated cross-linking behavior as well as the thermal stability of HPU –NCOX /BZ –OH blend was investigated by differential scanning calorimetry (DSC) and thermal gravimetric analysis (TGA). HPU –NCOX can covalently incorporate into BZ –OH via urethane reaction. Both the cure kinetics and the weight residue of HPU –NCOX /BZ –OH copolymer reveal a gradual increase with the improvement of DB of HPU –NCOX . Graphical abstract A novel isocyanate-functionalized hyperbranched polyurethanes (HPU –NCOX ) with degree of branching (DB) ranging from 25.1 to 51.1 % were successfully synthesized. The HPU –NCOX and benzoxazine copolymers exhibit enhanced cure kinetics with the increase of DB of HPU –NCOX .
研究领域:
材料科学
·
高分子化学
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DOI
高影响因子
FOOD CHEMISTRY
·
2017
·
IF 4.529
Ting Hu,Qilin Huang,Kahing Wong,Hong Yang,Jingsi Gan,Yanru Li
An alkali-soluble polysaccharide was extracted from Lignosus rhinocerotis sclerotia (LRP). Its structural characteristics were determined by GC–MS, FT-IR, GC, 1D and 2D NMR combined with Smith degradation and methylation analysis. The LRP had a (1 → 3)-β- d -Glcp backbone with every three residues bearing a (1 → 6)-linked and hyperbranched side chain that contained three (1 → 6)-β- d -Glcp residues as secondary main chain and two terminal β- d -Glcp residues linked at O3. The degree of branching was 0.76 from GC–MS analysis, implying a highly branched structure for LRP. The M w , < S 2 > z 1/2 , R h and [ η ] values of LRP in 0.25 M LiCl/DMSO were measured by SEC-MALLS-Vis-RI combination technology to be 2.88 × 10 5 g/mol, 30.36 nm, 22.34 nm and 131.50 ml/g, respectively. Furthermore, the exponent α of [ η ] –M w , β of < S 2 > z 1/2 –M w , the fractal dimension d f and molecular parameter ρ were determined to be 0.20, 0.33, 2.50 and 1.36, demonstrating that the LRP was a hyperbranched polysaccharide and adopted a compact coil conformation in LiCl/DMSO.
研究领域:
生物化学
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多糖化学
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药学化学
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分析化学
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DOI
PubMed
高影响因子
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