A novel method of controlling the shape memory properties of shape memory polyurethane （SMPU） by addition of micro-phase separation promoters including 1-octadecanol （ODO） and liquid paraffin （LP） is reported. T...A novel method of controlling the shape memory properties of shape memory polyurethane （SMPU） by addition of micro-phase separation promoters including 1-octadecanol （ODO） and liquid paraffin （LP） is reported. The results indicate that the strain recovery temperature and the strain modulus rate （Eg/Er） were increased significantly with addition of small amount of micro-phase separation promoters. Thus it can increase the shape memory fixity rate and other shape memory behaviors of SMPU.展开更多
Sub-micron sized phenolic epoxy resin waterborne particles were prepared by phase inversion emulsification. Micro-phase separation occurred during the curing process at high temperature. The as-prepared samples posses...Sub-micron sized phenolic epoxy resin waterborne particles were prepared by phase inversion emulsification. Micro-phase separation occurred during the curing process at high temperature. The as-prepared samples possessed one glass transition temperature （Tg） and two exothermal processes during DSC heating scannings. After being thermally treated above the exothermal peak temperature, they possessed two glass transition temperatures with the disappearance of exothermal peaks, whilst a core/shell structure was formed. This was likely related with the outward diffusion of reactive oligomers to the outer layer of particles.展开更多
Two series of polyurethanes based on mixed polychloromethyl methyl siloxane and poly-tetramethylene oxide in different weight fractions were synthesized. The phase separation ofsamples was studied using DSC and dynami...Two series of polyurethanes based on mixed polychloromethyl methyl siloxane and poly-tetramethylene oxide in different weight fractions were synthesized. The phase separation ofsamples was studied using DSC and dynamic mechanical property analysis. The results showedthat the introduction of chloromethyl group into polysiloxane increased its polarity and henceimproved the miscibilities with polytetramethylene oxide and polyurethane hard segment.Particularly, in the case of N-methyldiethanolamine extended materials, the surface and tensileproperties of these samples can be adjusted by various ratios of two soft segments.展开更多
Self-organization in thin micro-films has shown potential for the production of microelements with specific structures and functions; however, little is known about its mechanism of formation. A 2-D molecular dynamics...Self-organization in thin micro-films has shown potential for the production of microelements with specific structures and functions; however, little is known about its mechanism of formation. A 2-D molecular dynamics (MD) simulation on this process is carried out in this paper for films between two parallel walls (substrates) under different initial conditions. The films consist of two immiscible components (A and B). The simulation results in alternative columns perpendicular to the walls, which are rich either in A or in B molecules, respectively, apparently owing to their different interactions with the walls. The characteristic breadths of the columns depend on the distance between the two walls. By providing microscopic details of the self-organization processes and the resulted structures, MD simulation proves itself as a unique way for analyzing the dynamics of thin films.展开更多
Directed Self-Assembly(DSA)of block copolymers(BCPs)is a promising technique for sub-10 nm nanofabrication,which is highly compatible with conventional lithography.DSA relies on the microphase separation of block copo...Directed Self-Assembly(DSA)of block copolymers(BCPs)is a promising technique for sub-10 nm nanofabrication,which is highly compatible with conventional lithography.DSA relies on the microphase separation of block copolymers to form nanostructures of different morphologies.The pitch size of the obtained nanostructure depends largely on the intrinsic properties of BCPs and is usually fixed when BCPs are produced.One effective way of tuning the pitch size of BCPs is by blending BCPs of different molecular weight.In this paper,we have demonstrated the pitch tuning capability by blending the triblock poly(2-vinyl pyridine-bpolystyrene-b-poly 2-vinyl)pyridine(P2VP-b-PS-b-P2VP)with another triblock P2VP-b-PS-b-P2VP or diblock copolymer(PS-b-P2VP)at various volume ratios by solvent annealing.The nanopatterns of blended BCPs after sequential infiltration synthesis(SIS)and plasma etching process,were characterized by scanning electron microscopy.It’s observed that the blended BCPs can form highly ordered lamellar nanostructures of different pitch sizes at different blending ratios.The method of blending BCPs of varying molecular weights greatly extends the functionality of existing BCPs,with the capability of fine-tuning nanopatterning pitch at nanometer resolution.展开更多
High-impedance faults(HIFs)in distribution networks may result in fires or electric shocks.However,considerable difficulties exist in HIF detection due to low-resolution measurements and the considerably weaker time-f...High-impedance faults(HIFs)in distribution networks may result in fires or electric shocks.However,considerable difficulties exist in HIF detection due to low-resolution measurements and the considerably weaker time-frequency characteristics.This paper presents a novel HIF detection method using synchronized current information.The method consists of two stages.In the first stage,joint key characteristics of the system are extracted with the minimal system prior knowledge to identify the global optimal micro-phase measurement unit(μPMU)placement.In the second stage,the HIF is detected through a multivariate Jensen-Shannon divergence similarity measurement using high-resolution time-synchronized data inμPMUs in a high-noise environment.l2,1 principal component analysis(PCA),i.e.,PCA based on the l2,1 norm,is applied to an extracted system state and fault features derived from different resolution data in both stages.An economic observability index and HIF criteria are employed to evaluate the performance of placement method and to identify HIFs.Simulation results show that the method can reliably detect HIFs with reasonable detection accuracy in noisy environments.展开更多
基金We are grateful to the Natural Science Foundation of Hunan Province(Project no.01JJY33011)for financial support for this work.We also thank Dr.Yuan Li Cai for his assistance.
文摘A novel method of controlling the shape memory properties of shape memory polyurethane （SMPU） by addition of micro-phase separation promoters including 1-octadecanol （ODO） and liquid paraffin （LP） is reported. The results indicate that the strain recovery temperature and the strain modulus rate （Eg/Er） were increased significantly with addition of small amount of micro-phase separation promoters. Thus it can increase the shape memory fixity rate and other shape memory behaviors of SMPU.
基金This work was financially supported by the National Natural Science Foundation of China(No.20104008).
文摘Sub-micron sized phenolic epoxy resin waterborne particles were prepared by phase inversion emulsification. Micro-phase separation occurred during the curing process at high temperature. The as-prepared samples possessed one glass transition temperature （Tg） and two exothermal processes during DSC heating scannings. After being thermally treated above the exothermal peak temperature, they possessed two glass transition temperatures with the disappearance of exothermal peaks, whilst a core/shell structure was formed. This was likely related with the outward diffusion of reactive oligomers to the outer layer of particles.
文摘Two series of polyurethanes based on mixed polychloromethyl methyl siloxane and poly-tetramethylene oxide in different weight fractions were synthesized. The phase separation ofsamples was studied using DSC and dynamic mechanical property analysis. The results showedthat the introduction of chloromethyl group into polysiloxane increased its polarity and henceimproved the miscibilities with polytetramethylene oxide and polyurethane hard segment.Particularly, in the case of N-methyldiethanolamine extended materials, the surface and tensileproperties of these samples can be adjusted by various ratios of two soft segments.
文摘Self-organization in thin micro-films has shown potential for the production of microelements with specific structures and functions; however, little is known about its mechanism of formation. A 2-D molecular dynamics (MD) simulation on this process is carried out in this paper for films between two parallel walls (substrates) under different initial conditions. The films consist of two immiscible components (A and B). The simulation results in alternative columns perpendicular to the walls, which are rich either in A or in B molecules, respectively, apparently owing to their different interactions with the walls. The characteristic breadths of the columns depend on the distance between the two walls. By providing microscopic details of the self-organization processes and the resulted structures, MD simulation proves itself as a unique way for analyzing the dynamics of thin films.
基金This work was supported by the Awards No.SXH1232030,IDH1232054 and KBH1232189 from the Shanghai Municipal Science and Technology CommissionThis work is partially supported by the National Natural Science Foundation of China(General program).Y.C would like to thank the Shanghai super postdoc award for supporting this workThe authors declare no competing financial interest.
文摘Directed Self-Assembly(DSA)of block copolymers(BCPs)is a promising technique for sub-10 nm nanofabrication,which is highly compatible with conventional lithography.DSA relies on the microphase separation of block copolymers to form nanostructures of different morphologies.The pitch size of the obtained nanostructure depends largely on the intrinsic properties of BCPs and is usually fixed when BCPs are produced.One effective way of tuning the pitch size of BCPs is by blending BCPs of different molecular weight.In this paper,we have demonstrated the pitch tuning capability by blending the triblock poly(2-vinyl pyridine-bpolystyrene-b-poly 2-vinyl)pyridine(P2VP-b-PS-b-P2VP)with another triblock P2VP-b-PS-b-P2VP or diblock copolymer(PS-b-P2VP)at various volume ratios by solvent annealing.The nanopatterns of blended BCPs after sequential infiltration synthesis(SIS)and plasma etching process,were characterized by scanning electron microscopy.It’s observed that the blended BCPs can form highly ordered lamellar nanostructures of different pitch sizes at different blending ratios.The method of blending BCPs of varying molecular weights greatly extends the functionality of existing BCPs,with the capability of fine-tuning nanopatterning pitch at nanometer resolution.
基金supported in part by the National Key Research and Development Program of China(No.2017YFB0902800)Science and Technology Project of the State Grid Corporation of China(No.52094017003D)。
文摘High-impedance faults(HIFs)in distribution networks may result in fires or electric shocks.However,considerable difficulties exist in HIF detection due to low-resolution measurements and the considerably weaker time-frequency characteristics.This paper presents a novel HIF detection method using synchronized current information.The method consists of two stages.In the first stage,joint key characteristics of the system are extracted with the minimal system prior knowledge to identify the global optimal micro-phase measurement unit(μPMU)placement.In the second stage,the HIF is detected through a multivariate Jensen-Shannon divergence similarity measurement using high-resolution time-synchronized data inμPMUs in a high-noise environment.l2,1 principal component analysis(PCA),i.e.,PCA based on the l2,1 norm,is applied to an extracted system state and fault features derived from different resolution data in both stages.An economic observability index and HIF criteria are employed to evaluate the performance of placement method and to identify HIFs.Simulation results show that the method can reliably detect HIFs with reasonable detection accuracy in noisy environments.
