Introducing covalently crosslinked network to polymer matrix can merge the advantages in reprocessing and durability of polymers.In this contribution,a series of high-performance vitrimeric elastomers were achieved vi...Introducing covalently crosslinked network to polymer matrix can merge the advantages in reprocessing and durability of polymers.In this contribution,a series of high-performance vitrimeric elastomers were achieved via polycondensation.The topological structures of polymers were tuned by varying the feeding ratios of bisacetoacetate,hex–substituted bisacetoacetate,bisamine and tris(2-aminoethyl)amine.With these structural manipulations,the vitrimeric elastomers presented great elastic recovery properties(strain recovery value up to 80%)benefiting from the introduction of long chain branch.Furthermore,the elastomers exhibited excellent reprocessing property,water vapor/oxygen barrier and adhesive properties.Specially,the elastomers could be degraded into monomer under acid conditions which enabled the elastomer synthesis again in closed loop recycling system.The ease of the polycondensation in this work to prepare highly elastic and recyclable vitrimeric elastomers demonstrated exciting opportunities for the synthesis of sustainable polymers.展开更多
Poly(butylene succinate)(PBS)exhibits many advantages,such as renewability,biodegradability,and impressive thermal and mechanical properties,but is limited by the low melt viscosity and strength resulted from the line...Poly(butylene succinate)(PBS)exhibits many advantages,such as renewability,biodegradability,and impressive thermal and mechanical properties,but is limited by the low melt viscosity and strength resulted from the linear structure.To address this,vitrimeric network was introduced to synthesize PBS vitrimers(PBSVs)based on dynamic imine bonds through melt polymerization of hydroxyl-terminated PBS with vanillin derived imine containing compound and hexamethylene diisocyanate using trimethylolpropane as a crosslinking monomer.PBSVs with different crosslinking degrees were synthesized through changing the content of the crosslinking monomer.The effect of crosslinking degree on the thermal,theological,mechanical properties,and stress relaxation behavior of the PBSVs was studied in detail.The results demonstrated that the melt viscosity,melt strength,and heat resistance were enhanced substantially without obvious depression in crystallizability,thermal stability,and mechanical properties through increasing crosslinking degree.In addition,the PBSVs exhibit thermal reprocessability with mechanical properties recovered by more than 90%even after processing for three times.Furthermore,PBSV with improved melt properties shows significantly improved foamability compared to commercial PBS.This research contributes to the advancement of polymer technology by successfully developing PBS vitrimers with improved properties,showcasing their potential applications in sustainable and biodegradable materials.展开更多
The most widely used bisphenol A-type epoxy resin(DGEBA)in electrical engineering demonstrates excellent mechanical and electrical properties.However,the insoluble and infusible characteristics of cured DGEBA make it ...The most widely used bisphenol A-type epoxy resin(DGEBA)in electrical engineering demonstrates excellent mechanical and electrical properties.However,the insoluble and infusible characteristics of cured DGEBA make it difficult to efficiently degrade and recycle decommissioned electrical equipment.In this study,a degradable itaconic acid-based epoxy resin incorporating dynamic covalent bonds was prepared through the integration of ester bonds and disulfide bonds,with itaconic acid as the precursor.The covalent bonding effects on the mechanical,thermal,electrical,and degradation characteristics were systematically evaluated.The experimental results revealed that the introduction of dynamic ester bonds enhanced the mechanical properties and thermal stability of the resin system,achieving a flexural strength of 141.57 MPa and an initial decomposition temperature T_(5%)of up to 344.9℃.The resin system containing dynamic disulfide bonds exhibited a dielectric breakdown strength of 41.11 k V/mm.Simultaneously,the incorporation of disulfide bonds endowed the epoxy resin with remarkable degradability,enabling complete dissolution within 1.5 h at 90℃ in a mixed solution of dithiothreitol(DTT)and N-methylpyrrolidone(NMP).This research provides a valuable reference for the application of itaconic acid-based vitrimer with dynamic covalent bonds in electrical materials,contributing to the development and utilization of environmentally friendly electrical equipment.展开更多
It remains a challenge to use a simple approach to fabricate a multi-shape memory material with high mechanical performances.Here,we report a triple crosslinking design to construct a multi-shape memory epoxy vitrimer...It remains a challenge to use a simple approach to fabricate a multi-shape memory material with high mechanical performances.Here,we report a triple crosslinking design to construct a multi-shape memory epoxy vitrimer(MSMEV),which exhibits high mechanical properties,multi-shape memory property and malleability.The triple crosslinking network is formed by reacting diglycidyl ether of bisphenol F(DGEBF)with 4-aminophenyl disulfide,γ-aminopropyltriethoxysilane(APTS)and poly(propylene glycol)bis(2-aminopropyl ether)(D2000).The triple crosslinking manifests triple functions:the disulfide bonds and the silyl ether linkages enable malleability of the epoxy network;the silyl ether linkages impart the network with high heterogeneity and broaden the glass transition region,leading to multi-shape memory property;a small amount of D2000 increases the modulus difference between the glassy and rubbery states,thereby improving the shape fixity ratio.Meanwhile,the high crosslinking density and rigid structure provide the MSMEV with high tensile strength and Young’s modulus.Moreover,integrating carbon fibers and MSMEV results in shape memory composites.The superior mechanical properties of the composites and the recyclability of carbon fiber derived from the dissolvability of MSMEV make the composites hold great promise as structural materials in varied applications.展开更多
Synthesizing orientated liquid crystal elastomers(LCEs)via the two-stage thiol-acrylate Michael addition and photopolymerization(TAMAP)reaction is extensively used.However,excess acrylates,initiators,and strong stimul...Synthesizing orientated liquid crystal elastomers(LCEs)via the two-stage thiol-acrylate Michael addition and photopolymerization(TAMAP)reaction is extensively used.However,excess acrylates,initiators,and strong stimuli are inevitably involved in the second stage crosslinking.Herein,we simplify the strategy through taking advantage of a volatile alkaline(originally added to catalyze the thiol-acrylate addition in the first crosslinking stage).Without excess functional groups,the residual catalyst after annealing is still enough to trigger reactions of dynamic covalent bonds at a relatively mild temperature(80℃)to program the alignment of LCEs.The reversible reaction switches off by itself after this process since the catalyst gradually but totally evaporates upon heating.The obtained soft actuators exhibit robust actuation during repeated deformation(over 1000 times).Many shape-morphing modes can be achieved by rationally designing orientation patterns.This strategy not only facilitates the practical synthesis of LCE actuators,but also balances the intrinsic conflict between stability and reprogrammability of exchangeable LCEs.Moreover,the method of applying volatile catalysts has the potential to be extended to other dynamic covalent bonds(DCBs)applied to crosslinked polymer systems.展开更多
基金supported by National Natural Science Foundation of China(NSFC,Nos.21971230,U19B6001,22201003)Excellent Research and Innovation Team Project of Anhui Province(No.2022AH010001)Anhui Province Key Laboratory of Environment-friendly Polymer Materials。
文摘Introducing covalently crosslinked network to polymer matrix can merge the advantages in reprocessing and durability of polymers.In this contribution,a series of high-performance vitrimeric elastomers were achieved via polycondensation.The topological structures of polymers were tuned by varying the feeding ratios of bisacetoacetate,hex–substituted bisacetoacetate,bisamine and tris(2-aminoethyl)amine.With these structural manipulations,the vitrimeric elastomers presented great elastic recovery properties(strain recovery value up to 80%)benefiting from the introduction of long chain branch.Furthermore,the elastomers exhibited excellent reprocessing property,water vapor/oxygen barrier and adhesive properties.Specially,the elastomers could be degraded into monomer under acid conditions which enabled the elastomer synthesis again in closed loop recycling system.The ease of the polycondensation in this work to prepare highly elastic and recyclable vitrimeric elastomers demonstrated exciting opportunities for the synthesis of sustainable polymers.
基金financially supported by the National Natural Science Foundation of China(No.51973176)the Chongqing Talent Plan for Young Top-Notch Talents(No.CQYC2021059217)the Fundamental Research Funds for the Central Universities(No.SWUXDJH202314)。
文摘Poly(butylene succinate)(PBS)exhibits many advantages,such as renewability,biodegradability,and impressive thermal and mechanical properties,but is limited by the low melt viscosity and strength resulted from the linear structure.To address this,vitrimeric network was introduced to synthesize PBS vitrimers(PBSVs)based on dynamic imine bonds through melt polymerization of hydroxyl-terminated PBS with vanillin derived imine containing compound and hexamethylene diisocyanate using trimethylolpropane as a crosslinking monomer.PBSVs with different crosslinking degrees were synthesized through changing the content of the crosslinking monomer.The effect of crosslinking degree on the thermal,theological,mechanical properties,and stress relaxation behavior of the PBSVs was studied in detail.The results demonstrated that the melt viscosity,melt strength,and heat resistance were enhanced substantially without obvious depression in crystallizability,thermal stability,and mechanical properties through increasing crosslinking degree.In addition,the PBSVs exhibit thermal reprocessability with mechanical properties recovered by more than 90%even after processing for three times.Furthermore,PBSV with improved melt properties shows significantly improved foamability compared to commercial PBS.This research contributes to the advancement of polymer technology by successfully developing PBS vitrimers with improved properties,showcasing their potential applications in sustainable and biodegradable materials.
基金financially supported by the National Natural Science Foundation of China(No.52377025)。
文摘The most widely used bisphenol A-type epoxy resin(DGEBA)in electrical engineering demonstrates excellent mechanical and electrical properties.However,the insoluble and infusible characteristics of cured DGEBA make it difficult to efficiently degrade and recycle decommissioned electrical equipment.In this study,a degradable itaconic acid-based epoxy resin incorporating dynamic covalent bonds was prepared through the integration of ester bonds and disulfide bonds,with itaconic acid as the precursor.The covalent bonding effects on the mechanical,thermal,electrical,and degradation characteristics were systematically evaluated.The experimental results revealed that the introduction of dynamic ester bonds enhanced the mechanical properties and thermal stability of the resin system,achieving a flexural strength of 141.57 MPa and an initial decomposition temperature T_(5%)of up to 344.9℃.The resin system containing dynamic disulfide bonds exhibited a dielectric breakdown strength of 41.11 k V/mm.Simultaneously,the incorporation of disulfide bonds endowed the epoxy resin with remarkable degradability,enabling complete dissolution within 1.5 h at 90℃ in a mixed solution of dithiothreitol(DTT)and N-methylpyrrolidone(NMP).This research provides a valuable reference for the application of itaconic acid-based vitrimer with dynamic covalent bonds in electrical materials,contributing to the development and utilization of environmentally friendly electrical equipment.
基金by the State Key Scientific Special Project of China(No.2016ZX05017-002)the National Natural Science Foundation of China(No.51873110).
文摘It remains a challenge to use a simple approach to fabricate a multi-shape memory material with high mechanical performances.Here,we report a triple crosslinking design to construct a multi-shape memory epoxy vitrimer(MSMEV),which exhibits high mechanical properties,multi-shape memory property and malleability.The triple crosslinking network is formed by reacting diglycidyl ether of bisphenol F(DGEBF)with 4-aminophenyl disulfide,γ-aminopropyltriethoxysilane(APTS)and poly(propylene glycol)bis(2-aminopropyl ether)(D2000).The triple crosslinking manifests triple functions:the disulfide bonds and the silyl ether linkages enable malleability of the epoxy network;the silyl ether linkages impart the network with high heterogeneity and broaden the glass transition region,leading to multi-shape memory property;a small amount of D2000 increases the modulus difference between the glassy and rubbery states,thereby improving the shape fixity ratio.Meanwhile,the high crosslinking density and rigid structure provide the MSMEV with high tensile strength and Young’s modulus.Moreover,integrating carbon fibers and MSMEV results in shape memory composites.The superior mechanical properties of the composites and the recyclability of carbon fiber derived from the dissolvability of MSMEV make the composites hold great promise as structural materials in varied applications.
基金supported by the National Natural Science Foundation of China(Nos.51722303,21674057 and 21788102).
文摘Synthesizing orientated liquid crystal elastomers(LCEs)via the two-stage thiol-acrylate Michael addition and photopolymerization(TAMAP)reaction is extensively used.However,excess acrylates,initiators,and strong stimuli are inevitably involved in the second stage crosslinking.Herein,we simplify the strategy through taking advantage of a volatile alkaline(originally added to catalyze the thiol-acrylate addition in the first crosslinking stage).Without excess functional groups,the residual catalyst after annealing is still enough to trigger reactions of dynamic covalent bonds at a relatively mild temperature(80℃)to program the alignment of LCEs.The reversible reaction switches off by itself after this process since the catalyst gradually but totally evaporates upon heating.The obtained soft actuators exhibit robust actuation during repeated deformation(over 1000 times).Many shape-morphing modes can be achieved by rationally designing orientation patterns.This strategy not only facilitates the practical synthesis of LCE actuators,but also balances the intrinsic conflict between stability and reprogrammability of exchangeable LCEs.Moreover,the method of applying volatile catalysts has the potential to be extended to other dynamic covalent bonds(DCBs)applied to crosslinked polymer systems.
