The heterogeneous free-radical polymerization of methyl methylacrylate (MMA) and divinylbenzene (DVB) as cross-linker within supercritical carbon dioxide-swollen silicon rubber (SR) has been studied as an approach to ...The heterogeneous free-radical polymerization of methyl methylacrylate (MMA) and divinylbenzene (DVB) as cross-linker within supercritical carbon dioxide-swollen silicon rubber (SR) has been studied as an approach to preparing semi-interpenetrating polymer network (semi-IPN) of SR and poly(methyl methylacrylate) (PMMA). The SR/PMMA semi-IPNs were characterized by scanning electron microscopy (SEM) and dynamic mechanical analyzer (DMA).展开更多
Two cyclic olefin copolymers with the same comonomers and different monomer molar ratios were blended,and then the blends were satura ted in supercritical CO 2 at 20?MPa and various temperatures to prepare microc ellu...Two cyclic olefin copolymers with the same comonomers and different monomer molar ratios were blended,and then the blends were satura ted in supercritical CO 2 at 20?MPa and various temperatures to prepare microc ellular cyclic olefin copolymer blends by means of pressure quench.The cell dens ity and cell diameter of microcellular polymers were calculated to investigate t he effects of temperature and blending ratio on cell structures.The higher tempe rature results in larger cell sizes and smaller cell densities.The cell density increases remarkably and cell diameter decreases with increase in the content of the ingredient with higher T g.It is found that the stiffness of the matri x is the only possible material property that accounts for the differences in ce ll structure of micorocellular cyclic olefin copolymer blends with different ble nding ratio.展开更多
Three poly(vinyl acetate)(PVAc)oligomers with controlled molecular weight and narrow molecular distribution are synthesized by reversible addition-fragmentation chain transfer(RAFT)polymerization.The effects of the re...Three poly(vinyl acetate)(PVAc)oligomers with controlled molecular weight and narrow molecular distribution are synthesized by reversible addition-fragmentation chain transfer(RAFT)polymerization.The effects of the reaction temperature and the added amount of initiator of the PVAc polymerization are discussed.In addition,the phase behavior of the prepared PVAc in pressured CO2 is determined via the cloud point method.The results indicate that the cloud point of PVAc increases with the increase in the molecular weight,the PVAc concentration,and the temperature.The cloud point pressures for the PVAc mass concentration of 0.12%with the molecular weight of 1 550,2 120,and 2 960 g/mol are 13.48,13.83 and 15.43 MPa,respectively,at the temperature of 35℃.It reveals that the solubility of PVAc in ScCO2 at relatively low pressure is remarkably limited.展开更多
CeO2-ZrO2-Al2O3 ternary oxides were successfully prepared by a green route of supercritical anti-solvent precipitation with supercritical CO2 as anti-solvent and methanol as solvent. The structures and oxygen storage ...CeO2-ZrO2-Al2O3 ternary oxides were successfully prepared by a green route of supercritical anti-solvent precipitation with supercritical CO2 as anti-solvent and methanol as solvent. The structures and oxygen storage capacities of these ternary oxides were characterized by XRD, Raman spectra and oxygen storage capacity measurements. It was found that Al3＋ and Zr4＋ inserted into CeO2 lattice, forming CeO2-ZrO2-Al2O3 solid solution. The concentration of aluminium isopropoxide in the solution affected the concentration of oxygen vacancy and the distortion of oxygen sublattice which were responsible for the oxygen storage capacity. The rapidest oxygen uptake/release rate and maximum total oxygen storage capacity （122.0 mmolO2/molCeO2） were obtained with the aluminitun isopropoxide concentration at 0.2 wt.% in the solution.展开更多
This paper used a new approach of preparing poly-composites by covalent linkage between the MWCNT’s by imine group. The Poly (Imine)/MWCNT Composite was synthesized by the solution blending method from reacted amino ...This paper used a new approach of preparing poly-composites by covalent linkage between the MWCNT’s by imine group. The Poly (Imine)/MWCNT Composite was synthesized by the solution blending method from reacted amino multi-walled carbon nanotubes (MWCNT-NH2) with Terephthalaldehyde (TPAL). The obtained poly-composite was characterized by FT-IR, UV-Vis, XRD, TEM, SEM, TGA, DSC and DC electrical conductivity. The formation of Poly (Imine)/MWCNT composite was confirmed. The DC electrical conductivity of poly-composites was within the range 2.3 × 10–4 - 5.3 × 10–4 S/cm due to the interaction between the nanotubes.展开更多
Electromagnetic (EM) wave pollution causing damage to precision equipment and threatening thehealth of living organisms has attracted considerable attention. Herein, promising microcellular foamedpolyamide 6 (PA6)/car...Electromagnetic (EM) wave pollution causing damage to precision equipment and threatening thehealth of living organisms has attracted considerable attention. Herein, promising microcellular foamedpolyamide 6 (PA6)/carbon nanotube (CNT) composites for highly efficient EM wave absorption were successfully fabricated using supercritical CO_(2) foaming. Nanocomposites foams with a void fraction rangingfrom 38.7% to 85.1% were achieved, providing a platform to assess the correlation of the electrical conductivity, the dielectric permittivity and the EM wave absorption properties with porosity. Notably, theFoam-257.5C sample with a void fraction of 38.7% exhibited outstanding EM wave absorption characteristics at a thickness of only 1.59 mm and an ultra-low reflection loss value of -55.3 dB (99.9997% wave absorption). Most importantly, the effective absorption bandwidth (EAB) of the Foam-257.5C sample couldcover the entire Ku band (12.4–18 GHz) by slightly adjusting the thickness from 1.20 to 1.60 mm. Thesuperior EM wave absorption performance of the Foam-257.5C sample was attributed to multiple reflections and scattering at the solid-gas interfaces, favorable impedance matching due to the existence ofa large polymer-air interface area, conductive loss near the interfaces and interfacial polarization. Thus,this study offers an eco-friendly, simple and versatile methodology to develop high-efficiency, flexiblepolymer-based EM wave absorbents.展开更多
基金This work was supported by the National Natural Science Foundation of China (50173030).
文摘The heterogeneous free-radical polymerization of methyl methylacrylate (MMA) and divinylbenzene (DVB) as cross-linker within supercritical carbon dioxide-swollen silicon rubber (SR) has been studied as an approach to preparing semi-interpenetrating polymer network (semi-IPN) of SR and poly(methyl methylacrylate) (PMMA). The SR/PMMA semi-IPNs were characterized by scanning electron microscopy (SEM) and dynamic mechanical analyzer (DMA).
文摘Two cyclic olefin copolymers with the same comonomers and different monomer molar ratios were blended,and then the blends were satura ted in supercritical CO 2 at 20?MPa and various temperatures to prepare microc ellular cyclic olefin copolymer blends by means of pressure quench.The cell dens ity and cell diameter of microcellular polymers were calculated to investigate t he effects of temperature and blending ratio on cell structures.The higher tempe rature results in larger cell sizes and smaller cell densities.The cell density increases remarkably and cell diameter decreases with increase in the content of the ingredient with higher T g.It is found that the stiffness of the matri x is the only possible material property that accounts for the differences in ce ll structure of micorocellular cyclic olefin copolymer blends with different ble nding ratio.
基金The Natural Science Foundation of Jiangsu Province(No.BK20130602)the Applied Basic Research Program of Suzhou(No.SYG201836)the Project of the Collaborative Innovation Center of Suzhou Nano Science and Technology
文摘Three poly(vinyl acetate)(PVAc)oligomers with controlled molecular weight and narrow molecular distribution are synthesized by reversible addition-fragmentation chain transfer(RAFT)polymerization.The effects of the reaction temperature and the added amount of initiator of the PVAc polymerization are discussed.In addition,the phase behavior of the prepared PVAc in pressured CO2 is determined via the cloud point method.The results indicate that the cloud point of PVAc increases with the increase in the molecular weight,the PVAc concentration,and the temperature.The cloud point pressures for the PVAc mass concentration of 0.12%with the molecular weight of 1 550,2 120,and 2 960 g/mol are 13.48,13.83 and 15.43 MPa,respectively,at the temperature of 35℃.It reveals that the solubility of PVAc in ScCO2 at relatively low pressure is remarkably limited.
基金National Natural Science Foundation of China(20976120)the Natural Science Foundation of Tianjin(09JCYBJC06200)
文摘CeO2-ZrO2-Al2O3 ternary oxides were successfully prepared by a green route of supercritical anti-solvent precipitation with supercritical CO2 as anti-solvent and methanol as solvent. The structures and oxygen storage capacities of these ternary oxides were characterized by XRD, Raman spectra and oxygen storage capacity measurements. It was found that Al3＋ and Zr4＋ inserted into CeO2 lattice, forming CeO2-ZrO2-Al2O3 solid solution. The concentration of aluminium isopropoxide in the solution affected the concentration of oxygen vacancy and the distortion of oxygen sublattice which were responsible for the oxygen storage capacity. The rapidest oxygen uptake/release rate and maximum total oxygen storage capacity （122.0 mmolO2/molCeO2） were obtained with the aluminitun isopropoxide concentration at 0.2 wt.% in the solution.
文摘This paper used a new approach of preparing poly-composites by covalent linkage between the MWCNT’s by imine group. The Poly (Imine)/MWCNT Composite was synthesized by the solution blending method from reacted amino multi-walled carbon nanotubes (MWCNT-NH2) with Terephthalaldehyde (TPAL). The obtained poly-composite was characterized by FT-IR, UV-Vis, XRD, TEM, SEM, TGA, DSC and DC electrical conductivity. The formation of Poly (Imine)/MWCNT composite was confirmed. The DC electrical conductivity of poly-composites was within the range 2.3 × 10–4 - 5.3 × 10–4 S/cm due to the interaction between the nanotubes.
基金This work was funded by the National Key Research and Development Program of China(No.2016YFB0302200)the Key Research and Development Plan of Anhui Province(No.202104g01020003)+2 种基金the Fundamental Research Funds for the Central Universities(No.JKA012011002)the“111 Project”(No.B20031)Also,this research was supported by the China Scholarship Council(No.201906740084)during the work at the University of Toronto.Additional support was provided by Feringa Nobel Prize Scientist Joint Research Center.We would also like to gratefully thank Dr.Biao Zhao for assistance with electromagnetic data analysis in this research.Supplem。
文摘Electromagnetic (EM) wave pollution causing damage to precision equipment and threatening thehealth of living organisms has attracted considerable attention. Herein, promising microcellular foamedpolyamide 6 (PA6)/carbon nanotube (CNT) composites for highly efficient EM wave absorption were successfully fabricated using supercritical CO_(2) foaming. Nanocomposites foams with a void fraction rangingfrom 38.7% to 85.1% were achieved, providing a platform to assess the correlation of the electrical conductivity, the dielectric permittivity and the EM wave absorption properties with porosity. Notably, theFoam-257.5C sample with a void fraction of 38.7% exhibited outstanding EM wave absorption characteristics at a thickness of only 1.59 mm and an ultra-low reflection loss value of -55.3 dB (99.9997% wave absorption). Most importantly, the effective absorption bandwidth (EAB) of the Foam-257.5C sample couldcover the entire Ku band (12.4–18 GHz) by slightly adjusting the thickness from 1.20 to 1.60 mm. Thesuperior EM wave absorption performance of the Foam-257.5C sample was attributed to multiple reflections and scattering at the solid-gas interfaces, favorable impedance matching due to the existence ofa large polymer-air interface area, conductive loss near the interfaces and interfacial polarization. Thus,this study offers an eco-friendly, simple and versatile methodology to develop high-efficiency, flexiblepolymer-based EM wave absorbents.
