Herein the use of rare-earth compounds in catalytic reduction systems for the end-group functionalization of carboxyl-terminated low-molecularweight fluoropolymers was explored.Leveraging the high catalytic activity a...Herein the use of rare-earth compounds in catalytic reduction systems for the end-group functionalization of carboxyl-terminated low-molecularweight fluoropolymers was explored.Leveraging the high catalytic activity and selectivity of rare-earth compounds along with no residual impact on polymer product's performance,highly efficient catalytic reduction systems containing sodium borohydride(NaBH_(4))and rare-earth chloride(RECl_(3))were specifically designed for a telechelic carboxyl-terminated liquid fluoroeslastomer,aiming to facilitate the conversion of chainend carboxyl groups into hydroxyl groups and improvement in end-group reactivity.To achieve this,lanthanum chloride(LaCl_(3)),cerium chloride(CeCl_(3)),and neodymium chloride(NdCl_(3))were used separately to form catalytic reduction systems with NaBH_(4).The effects of solvent dosage,reaction temperature,reaction time length,and reductant dosage on carboxylic conversion were investigated,and the molecular chain structure,molecular weight,and functional group content of the raw materials and the products were analyzed and characterized by means of infrared spectroscopy(FTIR),proton nuclear magnetic resonance(^(1)H-NMR),fluorine-19 nuclear magnetic resonance(^(19)F-NMR),gel permeation chromatography(GPC),and chemical titration.Moreover,the catalytic activity and selectivity of the rare-earth chlorides,as well as the corresponding underlying interactions were discussed.Results indicated that the rare-earth-containing catalytic reduction systems studied in this work could efficiently convert the chain-end carboxyl groups into highly active hydroxyl groups,with a highest conversion up to 87.0%and differing catalytic reduction activities ranked as NaBH_(4)/CeCl_(3)>NaBH_(4)/LaCl_(3)>NaBH_(4)/NdCl_(3).Compared with the conventional lithium aluminum hydride(LiAIH_(4))reduction system,the NaBH_(4)/RECl_(3)systems provide multiple advantages such as mild reaction conditions,high conversion ratio with good selectivity,and environmental innocuity,and are potentially applicable as new reduction-catalysis combinations for the synthesis and functionalization of polymer materials.展开更多
In this study,we prepared unentangled and slightly entangled poly(L-lactic acid)telechelic ionomer samples(Mn=5 and 16 kg/mol)based on sodium sulfonate groups.The telechelic samples exhibit extremely slow crystallizat...In this study,we prepared unentangled and slightly entangled poly(L-lactic acid)telechelic ionomer samples(Mn=5 and 16 kg/mol)based on sodium sulfonate groups.The telechelic samples exhibit extremely slow crystallization kinetics below the melting temperature T_(m) and above the glass transition temperature T_(g),which enables us to examine the linear viscoelasticity of the ionomer melt samples therein.The application of either the shear flow(at 85℃)or elongational flow(between 70 and 90℃)strongly accelerates the crystallization,leading to strong strain hardening and formation of highly orientedαcrystals.Depending on the relative average rates of the strain-induced dissociation and strain-induced crystallization,the stress evolution can be classified into two cases,and the critical work for strain-induced crystallization is higher in case where the strain-induced dissociation occurs earlier than the strain-induced crystallization.展开更多
Synthesis of telechelic trans-1,4-polyisoprenes（TPI： trans-structure ＆gt; 95%） was evaluated based on two different methods of oxidative cleavage（indirect cleavage： first epoxidation of TPI, then the selective c...Synthesis of telechelic trans-1,4-polyisoprenes（TPI： trans-structure ＆gt; 95%） was evaluated based on two different methods of oxidative cleavage（indirect cleavage： first epoxidation of TPI, then the selective cleavage of epoxidized units in epoxidized trans-1,4-polyisoprene（ETPI） and direct cleavage of isoprene units in TPI）. The influence of solvents and the ratio of oxidative agents was investigated by 1H-NMR and 13C-NMR. A series of well-defined telechelic TPI with double terminated functional groups and less side reaction（molecular weight distribution range： 1.96？2.26） were synthesized by indirect cleavage in chloroform. Telechelic TPI showed similar crystallization behavior with TPI and interesting cold crystallization behavior characterized by DSC.展开更多
Objectives:Interdroplet interactions affect the properties and textures of emulsions.In this study,we creatively introduced telechelic DNA to link oil droplets directly at molecular scale to further improve the viscoe...Objectives:Interdroplet interactions affect the properties and textures of emulsions.In this study,we creatively introduced telechelic DNA to link oil droplets directly at molecular scale to further improve the viscoelastic properties of emulsions.Materials and Methods:A stable emulsion with 70%oil fraction was prepared by adding 40 mg/mL of whey protein isolate and peach gum polysaccharide complex(WPI–PGP complex).The addition of telechelic DNA(0.125–0.375μmol/L)made the emulsion change from a cream-like state to a self-supporting gel.Results:Rheological experiments confirmed that the telechelic DNA could improve the yield stress,storage modulus/loss modulus(Gʹ/Gʹʹ)and apparent viscosity of the emulsion gel in a concentration-dependent manner(0–0.375μmol/L).Inverted fluorescence images clearly showed the interdroplet network of the emulsion gel linked by telechelic DNA.For 3D printing,the emulsion gel with a higher concentration(0.375μmol/L)of telechelic DNA displayed better surface quality and dimensional resolution,indicating improved printability.Conclusion:This study successfully designed a novel telechelic DNA-bridged emulsion gel,which showed great potential as edible ink for 3D printing.展开更多
Comprehensive Summary Introducing covalently crosslinked network to telechelic polymers can enable the formation of advanced polymeric materials with enhanced material properties.In this contribution,well-defined tele...Comprehensive Summary Introducing covalently crosslinked network to telechelic polymers can enable the formation of advanced polymeric materials with enhanced material properties.In this contribution,well-defined telechelic polymers bearing acetoacetate groups were synthesized via Ru-catalyzed ring-opening metathesis polymerization of cyclooctene in the presence of chain transfer agents.Given the unique feature of muti-site reactive acetoacetate end groups,several crosslinked networks were constructed using different crosslinkers under mild conditions.In the Michael addition reaction system,the introduction of di/trifunctional aliphatic acrylate as crosslinkers significantly enhanced the mechanical properties of the generated crosslinked network(tensile strength up to 27 MPa,elongation at break up to 500%).On the other hand,vitrimers with dynamic covalent crosslinked networks were accessed via transamination of vinylogous urethane reaction using telechelic polymers and tris(2-aminoethyl)amine.展开更多
Poly(ethylene methyl phosphate)-poly(ethylene glycol)-poly(ethylene methyl phosphate)triblock copolymers carrying hydroxyl group at both chain ends were synthesized with sodium poly(ethylene glycol)ate as initiator.Th...Poly(ethylene methyl phosphate)-poly(ethylene glycol)-poly(ethylene methyl phosphate)triblock copolymers carrying hydroxyl group at both chain ends were synthesized with sodium poly(ethylene glycol)ate as initiator.The effects of the factors such as solvent,amount of the initiator and reaction time were investigated.The copolymers were characterized by IR,^(1)H-NMR,^(1)H{^(31)P}-NMR,^(13)C-NMR,^(31)P{^(1)H}-NMR,and DSC.High molecular weight of the copolymer and high yield of the polymerization were achieved within 3 min at 25 degrees C.The polymerization process was studied by^(31)P{^(1)H}-NMR and transesterification was found during longer polymerization time.展开更多
文摘Herein the use of rare-earth compounds in catalytic reduction systems for the end-group functionalization of carboxyl-terminated low-molecularweight fluoropolymers was explored.Leveraging the high catalytic activity and selectivity of rare-earth compounds along with no residual impact on polymer product's performance,highly efficient catalytic reduction systems containing sodium borohydride(NaBH_(4))and rare-earth chloride(RECl_(3))were specifically designed for a telechelic carboxyl-terminated liquid fluoroeslastomer,aiming to facilitate the conversion of chainend carboxyl groups into hydroxyl groups and improvement in end-group reactivity.To achieve this,lanthanum chloride(LaCl_(3)),cerium chloride(CeCl_(3)),and neodymium chloride(NdCl_(3))were used separately to form catalytic reduction systems with NaBH_(4).The effects of solvent dosage,reaction temperature,reaction time length,and reductant dosage on carboxylic conversion were investigated,and the molecular chain structure,molecular weight,and functional group content of the raw materials and the products were analyzed and characterized by means of infrared spectroscopy(FTIR),proton nuclear magnetic resonance(^(1)H-NMR),fluorine-19 nuclear magnetic resonance(^(19)F-NMR),gel permeation chromatography(GPC),and chemical titration.Moreover,the catalytic activity and selectivity of the rare-earth chlorides,as well as the corresponding underlying interactions were discussed.Results indicated that the rare-earth-containing catalytic reduction systems studied in this work could efficiently convert the chain-end carboxyl groups into highly active hydroxyl groups,with a highest conversion up to 87.0%and differing catalytic reduction activities ranked as NaBH_(4)/CeCl_(3)>NaBH_(4)/LaCl_(3)>NaBH_(4)/NdCl_(3).Compared with the conventional lithium aluminum hydride(LiAIH_(4))reduction system,the NaBH_(4)/RECl_(3)systems provide multiple advantages such as mild reaction conditions,high conversion ratio with good selectivity,and environmental innocuity,and are potentially applicable as new reduction-catalysis combinations for the synthesis and functionalization of polymer materials.
基金This work was financially supported by the National Natural Science Foundation of China(No.22173095).
文摘In this study,we prepared unentangled and slightly entangled poly(L-lactic acid)telechelic ionomer samples(Mn=5 and 16 kg/mol)based on sodium sulfonate groups.The telechelic samples exhibit extremely slow crystallization kinetics below the melting temperature T_(m) and above the glass transition temperature T_(g),which enables us to examine the linear viscoelasticity of the ionomer melt samples therein.The application of either the shear flow(at 85℃)or elongational flow(between 70 and 90℃)strongly accelerates the crystallization,leading to strong strain hardening and formation of highly orientedαcrystals.Depending on the relative average rates of the strain-induced dissociation and strain-induced crystallization,the stress evolution can be classified into two cases,and the critical work for strain-induced crystallization is higher in case where the strain-induced dissociation occurs earlier than the strain-induced crystallization.
基金financially supported by the Natural Science Foundation of Shandong Province(No.ZR2014BQ022)the National Natural Science Foundation of China(No.51273100)a Project of Shandong Province Higher Educational Science and Technology Program(No.J14LA12)
文摘Synthesis of telechelic trans-1,4-polyisoprenes（TPI： trans-structure ＆gt; 95%） was evaluated based on two different methods of oxidative cleavage（indirect cleavage： first epoxidation of TPI, then the selective cleavage of epoxidized units in epoxidized trans-1,4-polyisoprene（ETPI） and direct cleavage of isoprene units in TPI）. The influence of solvents and the ratio of oxidative agents was investigated by 1H-NMR and 13C-NMR. A series of well-defined telechelic TPI with double terminated functional groups and less side reaction（molecular weight distribution range： 1.96？2.26） were synthesized by indirect cleavage in chloroform. Telechelic TPI showed similar crystallization behavior with TPI and interesting cold crystallization behavior characterized by DSC.
基金the Key Research and Development Program of Zhejiang Province(No.2023C02042)the Wenzhou Agricultural Development Research Program(No.ZN2020001)the Cultivation Plan Project for the National Science Fund for Distinguished Young Scholars(No.00323133AL),China.
文摘Objectives:Interdroplet interactions affect the properties and textures of emulsions.In this study,we creatively introduced telechelic DNA to link oil droplets directly at molecular scale to further improve the viscoelastic properties of emulsions.Materials and Methods:A stable emulsion with 70%oil fraction was prepared by adding 40 mg/mL of whey protein isolate and peach gum polysaccharide complex(WPI–PGP complex).The addition of telechelic DNA(0.125–0.375μmol/L)made the emulsion change from a cream-like state to a self-supporting gel.Results:Rheological experiments confirmed that the telechelic DNA could improve the yield stress,storage modulus/loss modulus(Gʹ/Gʹʹ)and apparent viscosity of the emulsion gel in a concentration-dependent manner(0–0.375μmol/L).Inverted fluorescence images clearly showed the interdroplet network of the emulsion gel linked by telechelic DNA.For 3D printing,the emulsion gel with a higher concentration(0.375μmol/L)of telechelic DNA displayed better surface quality and dimensional resolution,indicating improved printability.Conclusion:This study successfully designed a novel telechelic DNA-bridged emulsion gel,which showed great potential as edible ink for 3D printing.
基金National Natural Science Foundation of China(NSFC,21971230 and U19B6001)the mentorship and strong support from Professor Changle Chen(USTC).
文摘Comprehensive Summary Introducing covalently crosslinked network to telechelic polymers can enable the formation of advanced polymeric materials with enhanced material properties.In this contribution,well-defined telechelic polymers bearing acetoacetate groups were synthesized via Ru-catalyzed ring-opening metathesis polymerization of cyclooctene in the presence of chain transfer agents.Given the unique feature of muti-site reactive acetoacetate end groups,several crosslinked networks were constructed using different crosslinkers under mild conditions.In the Michael addition reaction system,the introduction of di/trifunctional aliphatic acrylate as crosslinkers significantly enhanced the mechanical properties of the generated crosslinked network(tensile strength up to 27 MPa,elongation at break up to 500%).On the other hand,vitrimers with dynamic covalent crosslinked networks were accessed via transamination of vinylogous urethane reaction using telechelic polymers and tris(2-aminoethyl)amine.
基金Supported by the National Natural Science Foundation of China.
文摘Poly(ethylene methyl phosphate)-poly(ethylene glycol)-poly(ethylene methyl phosphate)triblock copolymers carrying hydroxyl group at both chain ends were synthesized with sodium poly(ethylene glycol)ate as initiator.The effects of the factors such as solvent,amount of the initiator and reaction time were investigated.The copolymers were characterized by IR,^(1)H-NMR,^(1)H{^(31)P}-NMR,^(13)C-NMR,^(31)P{^(1)H}-NMR,and DSC.High molecular weight of the copolymer and high yield of the polymerization were achieved within 3 min at 25 degrees C.The polymerization process was studied by^(31)P{^(1)H}-NMR and transesterification was found during longer polymerization time.
