The preparation of high-performance thermal conductive composites containing liquid metals(LM)has attracted significant attention.However,the stable dispersion of LM within polymer solution and effective property cont...The preparation of high-performance thermal conductive composites containing liquid metals(LM)has attracted significant attention.However,the stable dispersion of LM within polymer solution and effective property contribution of liquid metals remains significant challenges that need to be overcome.Inspired by the properties of the dendritic structure of the tree root system in grasping the soil,“shear-induced precipitation-interfacial reset-reprotonation”processing strategy is proposed to prepare nanocomposites based on aramid micron fibers(AMFs)with hierarchical dendritic structure.Thanks to the combination of van der Waals force provided by hierarchical dendritic structure,electrostatic interaction between AMFs and LM,coordinative bonding of―NH to LM,together with interfacial re-setting and multi-step protonation,several features can be achieved through such strategy:conducive to the local filler network construction,improvement of interfacial interaction,improvement of the stability of filler dispersion in the solvent,and enhancement of mechanical and thermal properties of the films.The resulting AMFsp H=4/LM films demonstrate a thermal conductivity of 10.98 W·m^(-1)·K^(-1)at 70%filler content,improvement of 126.8%compared to ANFs/LM film;while maintaining a strength of~85.88 MPa,improvement of 77%compared to AMFs/LM film.They also possess insulation properties,enable heat dissipation for high power electronics.This work provides an effective strategy for the preparation of high performance polymer composites containing liquid metal.展开更多
L-Heptopyranoses are important components of bacterial polysaccharides and biological active secondary metabolites like septacidin(SEP),which represents a group of nucleoside antibiotics with antitumor,antifungal,and ...L-Heptopyranoses are important components of bacterial polysaccharides and biological active secondary metabolites like septacidin(SEP),which represents a group of nucleoside antibiotics with antitumor,antifungal,and pain-relief activities.However,little is known about the formation mechanisms of those L-heptose moieties.In this study,we deciphered the biosynthetic pathway of the L,L-gluco-heptosamine moiety in SEPs by functional characterizing four genes and proposed that SepI initiates the process by oxidizing the 4’-hydroxyl of L-glycero-α-D-manno-heptose moiety of SEP-328(2)to a keto group.Subsequently,SepJ(C5 epimerase)and SepA(C3 epimerase)shape the 4’-keto-L-heptopyranose moiety by sequential epimerization reactions.At the last step,an aminotransferase SepG installs the 4’-amino group of the L,L-gluco-heptosamine moiety to generate SEP-327(3).An interesting phenomenon is that the SEP intermediates with 4’-keto-L-heptopyranose moieties exist as special bicyclic sugars with hemiacetal-hemiketal structures.Notably,L-pyranose is usually converted from D-pyranose by bifunctional C3/C5 epimerase.SepA is an unprecedented monofunctional L-pyranose C3 epimerase.Further in silico and experimental studies revealed that it represents an overlooked metal dependent-sugar epimerase family bearing vicinal oxygen chelate(VOC)architecture.展开更多
基金financially supported by the National Key Research&Development Plan(No.2022YFA1205200)。
文摘The preparation of high-performance thermal conductive composites containing liquid metals(LM)has attracted significant attention.However,the stable dispersion of LM within polymer solution and effective property contribution of liquid metals remains significant challenges that need to be overcome.Inspired by the properties of the dendritic structure of the tree root system in grasping the soil,“shear-induced precipitation-interfacial reset-reprotonation”processing strategy is proposed to prepare nanocomposites based on aramid micron fibers(AMFs)with hierarchical dendritic structure.Thanks to the combination of van der Waals force provided by hierarchical dendritic structure,electrostatic interaction between AMFs and LM,coordinative bonding of―NH to LM,together with interfacial re-setting and multi-step protonation,several features can be achieved through such strategy:conducive to the local filler network construction,improvement of interfacial interaction,improvement of the stability of filler dispersion in the solvent,and enhancement of mechanical and thermal properties of the films.The resulting AMFsp H=4/LM films demonstrate a thermal conductivity of 10.98 W·m^(-1)·K^(-1)at 70%filler content,improvement of 126.8%compared to ANFs/LM film;while maintaining a strength of~85.88 MPa,improvement of 77%compared to AMFs/LM film.They also possess insulation properties,enable heat dissipation for high power electronics.This work provides an effective strategy for the preparation of high performance polymer composites containing liquid metal.
基金financially supported by the Ministry of Science and Technology of China(2020YFA0907703)the National Natural Science Foundation of China(32025002,31870043)。
文摘L-Heptopyranoses are important components of bacterial polysaccharides and biological active secondary metabolites like septacidin(SEP),which represents a group of nucleoside antibiotics with antitumor,antifungal,and pain-relief activities.However,little is known about the formation mechanisms of those L-heptose moieties.In this study,we deciphered the biosynthetic pathway of the L,L-gluco-heptosamine moiety in SEPs by functional characterizing four genes and proposed that SepI initiates the process by oxidizing the 4’-hydroxyl of L-glycero-α-D-manno-heptose moiety of SEP-328(2)to a keto group.Subsequently,SepJ(C5 epimerase)and SepA(C3 epimerase)shape the 4’-keto-L-heptopyranose moiety by sequential epimerization reactions.At the last step,an aminotransferase SepG installs the 4’-amino group of the L,L-gluco-heptosamine moiety to generate SEP-327(3).An interesting phenomenon is that the SEP intermediates with 4’-keto-L-heptopyranose moieties exist as special bicyclic sugars with hemiacetal-hemiketal structures.Notably,L-pyranose is usually converted from D-pyranose by bifunctional C3/C5 epimerase.SepA is an unprecedented monofunctional L-pyranose C3 epimerase.Further in silico and experimental studies revealed that it represents an overlooked metal dependent-sugar epimerase family bearing vicinal oxygen chelate(VOC)architecture.
