The insertion of elemental selenium into the Csp(2)-Zr bond of alkenylchloro-zirconocenes affords (E)-vinylseleno zirconocenes, which were trapped by alkyl halides giving (E)-vinylic selenides in moderate to good yields.
Transition-metal-catalyzed C–H bond activation represents one of the most attractive research areas in organic synthesis.In contrast to the great developments made in directed C–H bond functionalization of arenes,th...Transition-metal-catalyzed C–H bond activation represents one of the most attractive research areas in organic synthesis.In contrast to the great developments made in directed C–H bond functionalization of arenes,the directing group-assisted activation of non-aromatic vinylic C–H bonds still remains challenging.During the recent years,significant progress has been made in this fascinating field with various functionalized alkenes,heterocycles and carbocycles being obtained.This article will focus on the recent achievements in the field of directing-group-assisted vinylic C–H bond functionalization.展开更多
This letter describes a method for the stereoselective synthesis of polymer supported vinylic selenides and their applications to synthesis of ( E ) and ( Z ) 1,2 disubstituted ethenes on solid phase by the ...This letter describes a method for the stereoselective synthesis of polymer supported vinylic selenides and their applications to synthesis of ( E ) and ( Z ) 1,2 disubstituted ethenes on solid phase by the coupling reaction with Grignard reagents under the catalysis of NiCl 2(PPh 3) 2.展开更多
Chemical warfare agents(CWAs)remain a persistent hazard in many parts of the world,necessitating a deeper exploration of their chemical and physical characteristics and reactions under diverse conditions.Diisopropyl m...Chemical warfare agents(CWAs)remain a persistent hazard in many parts of the world,necessitating a deeper exploration of their chemical and physical characteristics and reactions under diverse conditions.Diisopropyl methylphosphonate(DIMP),a commonly used CWA surrogate,is widely studied to enhance our understanding of CWA behavior.The prevailing thermal decomposition model for DIMP,developed approximately 25 years ago,is based on data collected in nitrogen atmospheres at temperatures ranging from 700 K to 800 K.Despite its limitations,this model continues to serve as a foundation for research across various thermal and reactive environments,including combustion studies.Our recent experiments have extended the scope of decomposition analysis by examining DIMP in both nitrogen and zero air across a lower temperature range of 175??C to 250??C.Infrared spectroscopy results under nitrogen align well with the established model;however,we observed that catalytic effects,stemming from decomposition byproducts and interactions with stainless steel surfaces,alter the reaction kinetics.In zero air environments,we observed a novel infrared absorption band.Spectral fitting suggests this band may represent a combination of propanal and acetone,while GCMS analysis points to vinyl formate and acetone as possible constituents.Although the precise identity of these new products remains unresolved,our findings clearly indicate that the existing decomposition model cannot be reliably extended to lower temperatures or non-nitrogen environments without further revisions.展开更多
Phenanthridine is a key structural motif in numerous natural products and biologically active compounds,making it an attractive target for pharmaceuticals and advanced materials.Recently,visible-light-induced cyclizat...Phenanthridine is a key structural motif in numerous natural products and biologically active compounds,making it an attractive target for pharmaceuticals and advanced materials.Recently,visible-light-induced cyclization through radical process has emerged as a powerful and sustainable strategy for building such a core under mild and environmentally friendly conditions,paving the way for new applications in synthetic and medicinal chemistry.This review highlights recent progress in the photochemical synthesis of phenanthridines,mainly focusing on various radical acceptors,including 2-isocyanobiaryls,cyanides,vinyl azides and vinyl benzotriazoles.展开更多
Chain-growth radical polymerization of vinyl monomers is essential for producing a wide range of materials with properties tailored to specific applications.However,the inherent resistance of the polymer's C―C ba...Chain-growth radical polymerization of vinyl monomers is essential for producing a wide range of materials with properties tailored to specific applications.However,the inherent resistance of the polymer's C―C backbone to degradation raises significant concerns regarding long-term environmental persistence,which also limits their potential in biomedical applications.To address these challenges,researchers have developed strategies to either degrade preexisting vinyl polymers or incorporate cleavable units into the backbone to modify them with enhanced degradability.This review explores the various approaches aimed at achieving backbone degradability in chain-growth radical polymerization of vinyl monomers,while also highlighting future research directions for the development of application-driven degradable vinyl polymers.展开更多
Poly(vinyl alcohol)(PVA)is a biodegradable and environmentally friendly material known for its gas barrier characteristics and solvent resistance.However,its flammability and water sensitivity limit its application in...Poly(vinyl alcohol)(PVA)is a biodegradable and environmentally friendly material known for its gas barrier characteristics and solvent resistance.However,its flammability and water sensitivity limit its application in specialized fields.In this study,phytic acid(PA)was introduced as a halogen-free flame retardant and biochar(BC)was introduced as a reinforcement to achieve both flame resistance and mechanical robustness.We thoroughly investigated the effects of BC particle sizes(100-3000 mesh)and addition amounts(0 wt%-10 wt%),as well as PA addition amounts(0 wt%-15 wt%),on the properties of PVA composite films.Notably,the PA10/1000BC5 composite containing 10 wt%PA and 5 wt%1000 mesh BC exhibited optimal properties.The limiting oxygen index increased to 39.2%,and the UL-94 test achieved a V-0 rating.Additionally,the PA10/1000BC5 composite film demonstrated significantly enhanced water resistance,with a swelling ratio reaching 800%without dissolving,unlike that of the control PVA.The water contact angle was 70°,indicating that hydrophilic properties remained essentially unaffected.Most importantly,the tensile modulus and elongation at break were 213 MPa and 281.7%,respectively,nearly double those of the PVA/PA composite film.This study presents an efficient and straightforward method for preparing PVA composite films that are flame-retardant,tough,and waterresistant,expanding their potential applications in various fields.展开更多
Poly(vinyl chloride)(PVC)materials are produced with high smoke and toxic gases during combustion,when commercial flame-retardant additives are incorporated.Here,rare-earth yttrium stannate(Y_(2)Sn_(2)O_(7)),which is ...Poly(vinyl chloride)(PVC)materials are produced with high smoke and toxic gases during combustion,when commercial flame-retardant additives are incorporated.Here,rare-earth yttrium stannate(Y_(2)Sn_(2)O_(7)),which is superior to commercial flame retardants,was designed to enhance the smoke suppression and toxicity reduction performance of PVC materials without damaging their mechanical properties.After the addition of 15 wt%Y_(2)Sn_(2)O_(7)(PVC/Y_(2)Sn_(2)O_(7)),the PVC composites achieved a V-0 rating,whereas the pure PVC material achieved a V-2 rating.The peak heat release rate of PVC/Y_(2)Sn_(2)O_(7) composite was reduced from 282.7 kW/m^(2)(pure PVC)to 243.6 kW/m^(2).In addition,the maximum smoke density(Ds-max)of PVC/Y_(2)Sn_(2)O_(7) was 263 m^(2)/m^(2),a decrease of 48.5%compared to pure PVC materials(511 m^(2)/m^(2)),indicating its outstanding ability for smoke suppression.Compared to Sb_(2)O_(3),Y_(2)Sn_(2)O_(7) can effectively reduce the release of the toxic gas CO(decreasing by 37.5%).Furthermore,the tensile strength of PVC can reach as high as 16.1 MPa.Compared with five widely used commercial flame retardants,Y_(2)Sn_(2)O_(7) demonstrates superior performance,positioning it as a promising alternative to prospective candidates.Therefore,this study developed a rare-earth flame retardant and offers a promising design to improve the fire safety of PVC composites.展开更多
Different reactive flame retardants have been extensively developed for vinyl ester resins(VERs),but very few of them can yield a flame-retardant resin that meets defined standards(e.g.UL-94 V-0 rating).In this work,p...Different reactive flame retardants have been extensively developed for vinyl ester resins(VERs),but very few of them can yield a flame-retardant resin that meets defined standards(e.g.UL-94 V-0 rating).In this work,phosphorous-containing 1-vinylimidazole salts(called VIDHP and VIDPP)were synthesized through the facile neutralization of the acid and 1-vinylimidazole.VIDHP and VIDPP were then applied as flame-retardant crosslinking agents of VERs,by which phosphorus-containing groups could be incorporated into the resin chain via ionic bonds.VIDHP/VER and VIDPP/VER showed a high curing activity and can be well cured in moderate temperatures.With 20 wt.%additions of VIDHP and VIDPP,VIDHP20/VER,and VIDPP20/VER presented a limiting oxygen index value of 29.7%and 28.4%,respectively,with the latter achieving a UL 94 V0 rating.In the cone calorimetric test,compared to the unmodified VERs,VIDPP20/VER exhibited large reductions in the peak heat release rate,total heat release rate,and total smoke release rate while VIDHP20/VER demonstrated comparatively inferior performance in terms of the heat release.VIDHP20/VER and VIDPP20/VER showed good thermal stability and presented a little lower glass transition temperature than the control sample.VIDPP with a low phosphorus oxidation state(+1)demonstrated high flame-retardant activities in the gaseous phase,whereas VIDHP with a high phosphorus oxidation state(+5)primarily exhibited efficacy in the condensed phase.展开更多
The production of C_(2)H_(3)Cl from CH_(3)Cl(MCTV)represents a promising non-petroleum route for synthesizing C_(2)alkenes from C_(1)molecules.Exploration of new MCTV catalysts is crucial for advancing sustainable che...The production of C_(2)H_(3)Cl from CH_(3)Cl(MCTV)represents a promising non-petroleum route for synthesizing C_(2)alkenes from C_(1)molecules.Exploration of new MCTV catalysts is crucial for advancing sustainable chemical production.In this study,we present NaVO_(3)as a surface-confined coupling center for·CH_(2)Cl radicals,demonstrating its superior performance in the selective coupling of methyl chloride to synthesize vinyl chloride.By incorporating NaVO_(3)onto the surface of CeO_(2),the catalyst enables effective capture of·CH_(2)Cl radicals during the CH_(3)Cl oxidative pyrolysis and their subsequent conversion into C_(2)H_(3)Cl.We experimentally validate the capability of highly dispersed Na-VO_(3)to controllably couple·CH_(2)Cl radicals through in-situ synchrotron-based vacuum ultraviolet photoionization mass spectrometry.The results demonstrate that the dispersion of NaVO_(3)on the catalyst surface has a considerable impact on the reaction efficiency of·CH_(2)Cl radicals and the overall MCTV performance.This discovery holds substantial implications for the controlled C_(1)radical transformation and provides a guidance for the design of catalysts for sustainable production of C_(2)H_(3)Cl.展开更多
The deformation mechanism of glycerol plasticized poly(vinyl alcohol)(PVA)with different hydrolyses(88%,92%,98%)at elevated temperatures(60-100℃)was elucidated by in situ synchrotron radiation X-ray scattering.The vi...The deformation mechanism of glycerol plasticized poly(vinyl alcohol)(PVA)with different hydrolyses(88%,92%,98%)at elevated temperatures(60-100℃)was elucidated by in situ synchrotron radiation X-ray scattering.The vinyl acetate(VAc)in PVA acts as a non-crystalline chain defect,which significantly influences the plastic deformation and stretching-induced crystallization behavior of PVA.The key microstructural parameters of PVA during deformation,such as crystallinity(χ_(c)),lateral crystallite size(L),and long period(l),in combination with the stress-strain curves,were obtained.The experimental results show that the deformation process of the plasticized PVA film present a three-stage evolution:(i)a plastic deformation zone.The plastic deformation of the crystallite occurs as evidenced by the apparent decrease in crystallinity and lamellar reorientation induced by stretching;(ii)the stress softening zone.The decreasing trend of crystallinity becomes slow,and the long period becomes smaller,which indicates that PVA crystallization is induced by stretching;and(iii)the strain-hardening zone.There is a synergistic effect between the crystallite destruction and formation.Further research reveals that a high temperature and low degree of alcoholysis favor the stretching-induced crystallization of PVA,while the system with a high degree of alcoholysis shows significant characteristics of preferred crystal growth.展开更多
The Pfitzinger reaction has long served as a notable synthesis pathway for quinoline-4-carboxylic acids.Although recognized for its synthetic potential since its discovery>138 years ago,a truly catalytic variant ha...The Pfitzinger reaction has long served as a notable synthesis pathway for quinoline-4-carboxylic acids.Although recognized for its synthetic potential since its discovery>138 years ago,a truly catalytic variant has remained elusive until now.Herein,we present a novel 2-tert-butyl-1,1,3,3-tetramethylguanidine(BTMG)-catalyzed Pfitzinger reaction that employs N-[(α-trifluoromethyl)vinyl]isatins with amines and alcohols,providing direct routes to 2-CF_(3)-quinoline-4-carboxamides and carboxylic esters.This method is not only green and environmentally benign but also accommodates the introduction of other functional groups like CF_(2)H and CO_(2)Me at the C2 position of quinoline skeleton.The utility of this methodology was demonstrated by the broad substrate scope,the late-stage modification of commercial drugs,and the diverse derivatization of quinoline framework.More importantly,this work not only opens up a new avenue for the activation of amide C-N bonds in catalytic reaction development,but also unlocks the huge potential of some 2-trifluoromethyl quinolines with strong inhibitory activity against PTP1B or optoelectronic application in organic light-emitting diodes.展开更多
Nitrogen‐doped ordered mesoporous carbon （N‐OMC） catalysts were directly synthesized using SBA‐15 as a hard template and sucrose as a carbon source. Urea, which was used as the nitrogen source, was carbonized wit...Nitrogen‐doped ordered mesoporous carbon （N‐OMC） catalysts were directly synthesized using SBA‐15 as a hard template and sucrose as a carbon source. Urea, which was used as the nitrogen source, was carbonized with sucrose. A 3.6 wt% nitrogen doping of the carbon framework was achieved, with more than 70%of the nitrogen incorporated as quaternary nitrogen species. Only 0.2 wt% nitrogen doping, with only 32.7% quaternary nitrogen incorporation was obtained in an N‐OMC catalyst （N‐OMC‐T） prepared using a two‐step post‐synthesis method. The acetylene hy‐drochlorination activities of N‐OMC catalysts prepared via the one‐step method were higher than that of the N‐OMC‐T catalyst because of the higher nitrogen loadings.展开更多
A La-modified Al2O3 catalyst was prepared with deposition-precipitation method. The effect of calcination temperature on the reactivity for vapor phase hydrofluorination of acetylene to vinyl fluoride. The catalysts c...A La-modified Al2O3 catalyst was prepared with deposition-precipitation method. The effect of calcination temperature on the reactivity for vapor phase hydrofluorination of acetylene to vinyl fluoride. The catalysts calcined at different temperatures were characterized using NH3-TPD, pyridine-FTIR, X-ray diffraction, and Raman techniques. It was found that the calcination process could not only change the structure of these catalysts but also modify the amount of surface acidity on the catalysts. The catalyst calcined at 400 ℃ exhibited the highest conversion of acetylene （94.6%） and highest selectivity to vinyl fluoride （83.4%） and lower coke deposition selectivity （0.72%）. The highest activity was related to the largest amount of surface acidity on the catalyst, and the coke deposition was also related to the total amount of surface acidic sites.展开更多
Copolymer of maleic acid and acrylic acid （PMA-100）, combining with polyvinyl butyral （PVB） ultrafiltration membrane was used for the removal of Mn（II） from waste water by complexation-ultrafiltration. The carbo...Copolymer of maleic acid and acrylic acid （PMA-100）, combining with polyvinyl butyral （PVB） ultrafiltration membrane was used for the removal of Mn（II） from waste water by complexation-ultrafiltration. The carboxylic group content of PMA-100 and the rate of complexation reaction were measured. Effects of the mass ratio of PMA-100 to Mn（II） （n）, pH, background electrolyte, etc on the rejection rate （R） and permeate flux （J） were investigated. The results show that carboxylic group content of PMA-100 is 9.5 mmol/g. The complexation of Mn（II） with PMA-100 is rapid and completed within 5 min at pH 6.0. Both R and J increase with pH increasing in the range of 2.5-7.0, and R increases with the increase of n at pH 6.0 while J is little affected. The background electrolyte leads to the decrease of R, and CaCl2 has much greater effect on R than NaCl at the same ionic strength.展开更多
[Objective] The aim was to explore release characteristics of vinyl chlo- ride-vinyl acetate copolymer controlled-release N fertilizer and the effects on minerat nitrogen in soils. [Method] Vinyl chloride-vinyl acetat...[Objective] The aim was to explore release characteristics of vinyl chlo- ride-vinyl acetate copolymer controlled-release N fertilizer and the effects on minerat nitrogen in soils. [Method] Vinyl chloride-vinyl acetate copolymer and hydroxyl-modi- fied VCNAc were taken as coating materials to prepare slow release fertilizer. Nutri- ent release characteristics of VC/VAc slow release fertilizer was evaluated by water immersion method and the effects of VC/VAc slow release fertilizer on mineral ni- trogen were researched by pot experiment. [Result] The release periods of VC-VAc controlled-release urea and hydroxyl-modified VC/VAc coated urea were 60 and 50 d, respectively. Furthermore, the content of ammonium nitrogen reached the peak on the 30th d and the content of nitrate nitrogen reached the peak on the 60th d in soils in treatments with VCNAc and hydroxyl-modified VC/VAc; the content of nitrate nitrogen rose again on the 120th d in the treatment with VC/VAc. In terms of wheat yield, different treatments showed insignificant differences and rice yield in the treatment with VCNAc was significantly higher than that in the treatment with hy- droxyl-modified VCNAc （P〈0.05）. [Conclusion] The release days of slow controlled- release fertilizer vary upon pot experiment method and water immersion method. Slow controlled-release fertilizer is not suitable for monoculture, due to long fertilizer efficiency, but multiple cropping would be optimal for its role to be fully exploited.展开更多
On the basis of the Michael-addition mechanism of classical proteasome inhibitors, six dipeptide vinyl sulfonamide and dipeptide vinyl sulfonate derivatives were designed and synthesized. Moreover, an efficient method...On the basis of the Michael-addition mechanism of classical proteasome inhibitors, six dipeptide vinyl sulfonamide and dipeptide vinyl sulfonate derivatives were designed and synthesized. Moreover, an efficient method for the synthesis of g-amino vinyl sulfonamides, key intermediates to the target molecules, was developed via the Wittig-Horner reaction of peptide aldehyde with Wittig reagents derived from methanesulfonamides.展开更多
文摘The insertion of elemental selenium into the Csp(2)-Zr bond of alkenylchloro-zirconocenes affords (E)-vinylseleno zirconocenes, which were trapped by alkyl halides giving (E)-vinylic selenides in moderate to good yields.
基金supported by the National Basic Research Program of China(2015CB856600)the National Natural Science Foundation of China(21332002,21272010)
文摘Transition-metal-catalyzed C–H bond activation represents one of the most attractive research areas in organic synthesis.In contrast to the great developments made in directed C–H bond functionalization of arenes,the directing group-assisted activation of non-aromatic vinylic C–H bonds still remains challenging.During the recent years,significant progress has been made in this fascinating field with various functionalized alkenes,heterocycles and carbocycles being obtained.This article will focus on the recent achievements in the field of directing-group-assisted vinylic C–H bond functionalization.
基金theNationalNaturalScienceFoundationofChina (No .2 993 2 0 2 0 )
文摘This letter describes a method for the stereoselective synthesis of polymer supported vinylic selenides and their applications to synthesis of ( E ) and ( Z ) 1,2 disubstituted ethenes on solid phase by the coupling reaction with Grignard reagents under the catalysis of NiCl 2(PPh 3) 2.
基金sponsored by the Department of Defense,Defense Threat Reduction Agency under the Materials Science in Extreme Environments University Research Alliance,HDTRA1-20-2-0001。
文摘Chemical warfare agents(CWAs)remain a persistent hazard in many parts of the world,necessitating a deeper exploration of their chemical and physical characteristics and reactions under diverse conditions.Diisopropyl methylphosphonate(DIMP),a commonly used CWA surrogate,is widely studied to enhance our understanding of CWA behavior.The prevailing thermal decomposition model for DIMP,developed approximately 25 years ago,is based on data collected in nitrogen atmospheres at temperatures ranging from 700 K to 800 K.Despite its limitations,this model continues to serve as a foundation for research across various thermal and reactive environments,including combustion studies.Our recent experiments have extended the scope of decomposition analysis by examining DIMP in both nitrogen and zero air across a lower temperature range of 175??C to 250??C.Infrared spectroscopy results under nitrogen align well with the established model;however,we observed that catalytic effects,stemming from decomposition byproducts and interactions with stainless steel surfaces,alter the reaction kinetics.In zero air environments,we observed a novel infrared absorption band.Spectral fitting suggests this band may represent a combination of propanal and acetone,while GCMS analysis points to vinyl formate and acetone as possible constituents.Although the precise identity of these new products remains unresolved,our findings clearly indicate that the existing decomposition model cannot be reliably extended to lower temperatures or non-nitrogen environments without further revisions.
基金financially supported by the National Natural Science Foundation of China(No.21602046)the Zhongjing Youth Talent Project from Henan University of Chinese Medicine(No.03104150-2024-1-52)the Foundation for University Key Teachers from the Education Department of Henan Province(No.2020GGJS107)。
文摘Phenanthridine is a key structural motif in numerous natural products and biologically active compounds,making it an attractive target for pharmaceuticals and advanced materials.Recently,visible-light-induced cyclization through radical process has emerged as a powerful and sustainable strategy for building such a core under mild and environmentally friendly conditions,paving the way for new applications in synthetic and medicinal chemistry.This review highlights recent progress in the photochemical synthesis of phenanthridines,mainly focusing on various radical acceptors,including 2-isocyanobiaryls,cyanides,vinyl azides and vinyl benzotriazoles.
基金funding from the National Natural Science Foundation of China(No.22401037)funding from JST CREST(No.JPMJCR23L1)。
文摘Chain-growth radical polymerization of vinyl monomers is essential for producing a wide range of materials with properties tailored to specific applications.However,the inherent resistance of the polymer's C―C backbone to degradation raises significant concerns regarding long-term environmental persistence,which also limits their potential in biomedical applications.To address these challenges,researchers have developed strategies to either degrade preexisting vinyl polymers or incorporate cleavable units into the backbone to modify them with enhanced degradability.This review explores the various approaches aimed at achieving backbone degradability in chain-growth radical polymerization of vinyl monomers,while also highlighting future research directions for the development of application-driven degradable vinyl polymers.
基金supported by the Zhejiang Provincial"Vanguard"and"Leading Goose"R&D Program(No.2025C02203)the Zhejiang Provincial Natural Science Foundation of China(No.LTGS24C130001)the Fund for Key Scientific Research in the Public Interest of Ningbo(No.2024S009)。
文摘Poly(vinyl alcohol)(PVA)is a biodegradable and environmentally friendly material known for its gas barrier characteristics and solvent resistance.However,its flammability and water sensitivity limit its application in specialized fields.In this study,phytic acid(PA)was introduced as a halogen-free flame retardant and biochar(BC)was introduced as a reinforcement to achieve both flame resistance and mechanical robustness.We thoroughly investigated the effects of BC particle sizes(100-3000 mesh)and addition amounts(0 wt%-10 wt%),as well as PA addition amounts(0 wt%-15 wt%),on the properties of PVA composite films.Notably,the PA10/1000BC5 composite containing 10 wt%PA and 5 wt%1000 mesh BC exhibited optimal properties.The limiting oxygen index increased to 39.2%,and the UL-94 test achieved a V-0 rating.Additionally,the PA10/1000BC5 composite film demonstrated significantly enhanced water resistance,with a swelling ratio reaching 800%without dissolving,unlike that of the control PVA.The water contact angle was 70°,indicating that hydrophilic properties remained essentially unaffected.Most importantly,the tensile modulus and elongation at break were 213 MPa and 281.7%,respectively,nearly double those of the PVA/PA composite film.This study presents an efficient and straightforward method for preparing PVA composite films that are flame-retardant,tough,and waterresistant,expanding their potential applications in various fields.
基金financially supported by the Science and Technology Breakthrough Project of Inner Mongolia(Nos.2024KJTW0006 and 2023B2551)Central Guiding Science and Technology Development Fund of Inner Mongolia(No.2022ZY0100)+3 种基金Natural Science Foundation of Anhui Province(No.2408085ME140)National Key Laboratory of Baiyunobo Rare Earth Resource Research and Comprehensive UtilizationExperimental Center of Engineering and Material Science from the University of Science and Technology of ChinaInstruments Center for Physical Science,University of Science and Technology of China。
文摘Poly(vinyl chloride)(PVC)materials are produced with high smoke and toxic gases during combustion,when commercial flame-retardant additives are incorporated.Here,rare-earth yttrium stannate(Y_(2)Sn_(2)O_(7)),which is superior to commercial flame retardants,was designed to enhance the smoke suppression and toxicity reduction performance of PVC materials without damaging their mechanical properties.After the addition of 15 wt%Y_(2)Sn_(2)O_(7)(PVC/Y_(2)Sn_(2)O_(7)),the PVC composites achieved a V-0 rating,whereas the pure PVC material achieved a V-2 rating.The peak heat release rate of PVC/Y_(2)Sn_(2)O_(7) composite was reduced from 282.7 kW/m^(2)(pure PVC)to 243.6 kW/m^(2).In addition,the maximum smoke density(Ds-max)of PVC/Y_(2)Sn_(2)O_(7) was 263 m^(2)/m^(2),a decrease of 48.5%compared to pure PVC materials(511 m^(2)/m^(2)),indicating its outstanding ability for smoke suppression.Compared to Sb_(2)O_(3),Y_(2)Sn_(2)O_(7) can effectively reduce the release of the toxic gas CO(decreasing by 37.5%).Furthermore,the tensile strength of PVC can reach as high as 16.1 MPa.Compared with five widely used commercial flame retardants,Y_(2)Sn_(2)O_(7) demonstrates superior performance,positioning it as a promising alternative to prospective candidates.Therefore,this study developed a rare-earth flame retardant and offers a promising design to improve the fire safety of PVC composites.
基金supported by the National Natural Science Foundation of China(Grant Nos.51991351 and51903132)the Young Elite Scientist Sponsorship Program by CAST(No.2022QNRC001).
文摘Different reactive flame retardants have been extensively developed for vinyl ester resins(VERs),but very few of them can yield a flame-retardant resin that meets defined standards(e.g.UL-94 V-0 rating).In this work,phosphorous-containing 1-vinylimidazole salts(called VIDHP and VIDPP)were synthesized through the facile neutralization of the acid and 1-vinylimidazole.VIDHP and VIDPP were then applied as flame-retardant crosslinking agents of VERs,by which phosphorus-containing groups could be incorporated into the resin chain via ionic bonds.VIDHP/VER and VIDPP/VER showed a high curing activity and can be well cured in moderate temperatures.With 20 wt.%additions of VIDHP and VIDPP,VIDHP20/VER,and VIDPP20/VER presented a limiting oxygen index value of 29.7%and 28.4%,respectively,with the latter achieving a UL 94 V0 rating.In the cone calorimetric test,compared to the unmodified VERs,VIDPP20/VER exhibited large reductions in the peak heat release rate,total heat release rate,and total smoke release rate while VIDHP20/VER demonstrated comparatively inferior performance in terms of the heat release.VIDHP20/VER and VIDPP20/VER showed good thermal stability and presented a little lower glass transition temperature than the control sample.VIDPP with a low phosphorus oxidation state(+1)demonstrated high flame-retardant activities in the gaseous phase,whereas VIDHP with a high phosphorus oxidation state(+5)primarily exhibited efficacy in the condensed phase.
文摘The production of C_(2)H_(3)Cl from CH_(3)Cl(MCTV)represents a promising non-petroleum route for synthesizing C_(2)alkenes from C_(1)molecules.Exploration of new MCTV catalysts is crucial for advancing sustainable chemical production.In this study,we present NaVO_(3)as a surface-confined coupling center for·CH_(2)Cl radicals,demonstrating its superior performance in the selective coupling of methyl chloride to synthesize vinyl chloride.By incorporating NaVO_(3)onto the surface of CeO_(2),the catalyst enables effective capture of·CH_(2)Cl radicals during the CH_(3)Cl oxidative pyrolysis and their subsequent conversion into C_(2)H_(3)Cl.We experimentally validate the capability of highly dispersed Na-VO_(3)to controllably couple·CH_(2)Cl radicals through in-situ synchrotron-based vacuum ultraviolet photoionization mass spectrometry.The results demonstrate that the dispersion of NaVO_(3)on the catalyst surface has a considerable impact on the reaction efficiency of·CH_(2)Cl radicals and the overall MCTV performance.This discovery holds substantial implications for the controlled C_(1)radical transformation and provides a guidance for the design of catalysts for sustainable production of C_(2)H_(3)Cl.
基金supported by the National Natural Science Foundation of China(No.52422302)Anhui Provincial Natural Science Foundation(Nos.2308085UM02,2408055UM001,and 2308085UM04)the Major Science and Technology Project“Unveiling and Commanding”of Hefei City,Anhui Province(No.2022-SZD-005).
文摘The deformation mechanism of glycerol plasticized poly(vinyl alcohol)(PVA)with different hydrolyses(88%,92%,98%)at elevated temperatures(60-100℃)was elucidated by in situ synchrotron radiation X-ray scattering.The vinyl acetate(VAc)in PVA acts as a non-crystalline chain defect,which significantly influences the plastic deformation and stretching-induced crystallization behavior of PVA.The key microstructural parameters of PVA during deformation,such as crystallinity(χ_(c)),lateral crystallite size(L),and long period(l),in combination with the stress-strain curves,were obtained.The experimental results show that the deformation process of the plasticized PVA film present a three-stage evolution:(i)a plastic deformation zone.The plastic deformation of the crystallite occurs as evidenced by the apparent decrease in crystallinity and lamellar reorientation induced by stretching;(ii)the stress softening zone.The decreasing trend of crystallinity becomes slow,and the long period becomes smaller,which indicates that PVA crystallization is induced by stretching;and(iii)the strain-hardening zone.There is a synergistic effect between the crystallite destruction and formation.Further research reveals that a high temperature and low degree of alcoholysis favor the stretching-induced crystallization of PVA,while the system with a high degree of alcoholysis shows significant characteristics of preferred crystal growth.
基金National Natural Science Foundation of China(Nos.22171056,22122402,21801050)Outstanding Youth Project of Guangdong Natural Science Foundation(Nos.2024B1515020036,2021B1515020048)+3 种基金Guangdong Natural Science Foundation(Nos.2023A1515011313,2021A1515010510,2024A1515030037)Tertiary Education Scientific Research Project of Guangzhou Municipal Education Bureau(No.202235305)the Open Fund from Key Laboratory of Organofluorine ChemistryShanghai Engineering Research Center of Molecular Therapeutics and New Drug Development are gratefully acknowledged for financial support.
文摘The Pfitzinger reaction has long served as a notable synthesis pathway for quinoline-4-carboxylic acids.Although recognized for its synthetic potential since its discovery>138 years ago,a truly catalytic variant has remained elusive until now.Herein,we present a novel 2-tert-butyl-1,1,3,3-tetramethylguanidine(BTMG)-catalyzed Pfitzinger reaction that employs N-[(α-trifluoromethyl)vinyl]isatins with amines and alcohols,providing direct routes to 2-CF_(3)-quinoline-4-carboxamides and carboxylic esters.This method is not only green and environmentally benign but also accommodates the introduction of other functional groups like CF_(2)H and CO_(2)Me at the C2 position of quinoline skeleton.The utility of this methodology was demonstrated by the broad substrate scope,the late-stage modification of commercial drugs,and the diverse derivatization of quinoline framework.More importantly,this work not only opens up a new avenue for the activation of amide C-N bonds in catalytic reaction development,but also unlocks the huge potential of some 2-trifluoromethyl quinolines with strong inhibitory activity against PTP1B or optoelectronic application in organic light-emitting diodes.
基金supported by the National Natural Science Foundation of China (20803064)the Natural Science Foundation of Zhejiang Province (Y4090348)~~
文摘Nitrogen‐doped ordered mesoporous carbon （N‐OMC） catalysts were directly synthesized using SBA‐15 as a hard template and sucrose as a carbon source. Urea, which was used as the nitrogen source, was carbonized with sucrose. A 3.6 wt% nitrogen doping of the carbon framework was achieved, with more than 70%of the nitrogen incorporated as quaternary nitrogen species. Only 0.2 wt% nitrogen doping, with only 32.7% quaternary nitrogen incorporation was obtained in an N‐OMC catalyst （N‐OMC‐T） prepared using a two‐step post‐synthesis method. The acetylene hy‐drochlorination activities of N‐OMC catalysts prepared via the one‐step method were higher than that of the N‐OMC‐T catalyst because of the higher nitrogen loadings.
基金ACKNOWLEDGMENT This work was supported by the National Natural Science Foundation of China （No.20873125）,
文摘A La-modified Al2O3 catalyst was prepared with deposition-precipitation method. The effect of calcination temperature on the reactivity for vapor phase hydrofluorination of acetylene to vinyl fluoride. The catalysts calcined at different temperatures were characterized using NH3-TPD, pyridine-FTIR, X-ray diffraction, and Raman techniques. It was found that the calcination process could not only change the structure of these catalysts but also modify the amount of surface acidity on the catalysts. The catalyst calcined at 400 ℃ exhibited the highest conversion of acetylene （94.6%） and highest selectivity to vinyl fluoride （83.4%） and lower coke deposition selectivity （0.72%）. The highest activity was related to the largest amount of surface acidity on the catalyst, and the coke deposition was also related to the total amount of surface acidic sites.
基金Project (21176264) supported by the National Natural Science Foundation of ChinaProject (11JJ2010) supported by Hunan Provincial Natural Science Foundation of ChinaProject (LC13076) supported by Undergraduate Innovation Foundation of Central South University,China
文摘Copolymer of maleic acid and acrylic acid （PMA-100）, combining with polyvinyl butyral （PVB） ultrafiltration membrane was used for the removal of Mn（II） from waste water by complexation-ultrafiltration. The carboxylic group content of PMA-100 and the rate of complexation reaction were measured. Effects of the mass ratio of PMA-100 to Mn（II） （n）, pH, background electrolyte, etc on the rejection rate （R） and permeate flux （J） were investigated. The results show that carboxylic group content of PMA-100 is 9.5 mmol/g. The complexation of Mn（II） with PMA-100 is rapid and completed within 5 min at pH 6.0. Both R and J increase with pH increasing in the range of 2.5-7.0, and R increases with the increase of n at pH 6.0 while J is little affected. The background electrolyte leads to the decrease of R, and CaCl2 has much greater effect on R than NaCl at the same ionic strength.
基金Supported by National Department Public Benefit Research Foundation(201203013)Modern Agricultural Industry Technology System(CARS-11-B-15)+2 种基金IPNI Project(JIANGSU-10)Special Fund for Agro-scientific Research in the Public Interest(201003014-1-2)Jiangsu Agriculture S&T Self-Innovation Project[CX(12)3037]~~
文摘[Objective] The aim was to explore release characteristics of vinyl chlo- ride-vinyl acetate copolymer controlled-release N fertilizer and the effects on minerat nitrogen in soils. [Method] Vinyl chloride-vinyl acetate copolymer and hydroxyl-modi- fied VCNAc were taken as coating materials to prepare slow release fertilizer. Nutri- ent release characteristics of VC/VAc slow release fertilizer was evaluated by water immersion method and the effects of VC/VAc slow release fertilizer on mineral ni- trogen were researched by pot experiment. [Result] The release periods of VC-VAc controlled-release urea and hydroxyl-modified VC/VAc coated urea were 60 and 50 d, respectively. Furthermore, the content of ammonium nitrogen reached the peak on the 30th d and the content of nitrate nitrogen reached the peak on the 60th d in soils in treatments with VCNAc and hydroxyl-modified VC/VAc; the content of nitrate nitrogen rose again on the 120th d in the treatment with VC/VAc. In terms of wheat yield, different treatments showed insignificant differences and rice yield in the treatment with VCNAc was significantly higher than that in the treatment with hy- droxyl-modified VCNAc （P〈0.05）. [Conclusion] The release days of slow controlled- release fertilizer vary upon pot experiment method and water immersion method. Slow controlled-release fertilizer is not suitable for monoculture, due to long fertilizer efficiency, but multiple cropping would be optimal for its role to be fully exploited.
基金Natural Science Foundation of China for the financial support(Grant No.30772626)
文摘On the basis of the Michael-addition mechanism of classical proteasome inhibitors, six dipeptide vinyl sulfonamide and dipeptide vinyl sulfonate derivatives were designed and synthesized. Moreover, an efficient method for the synthesis of g-amino vinyl sulfonamides, key intermediates to the target molecules, was developed via the Wittig-Horner reaction of peptide aldehyde with Wittig reagents derived from methanesulfonamides.
