A new type of aromatic tetraarnine containing biphenyl moiety in the side chain was synthesized via a modified Chichibabin＇s reaction. 3-Nitro-4-acetamidoacetophenone was reacted with 4-phenyl benzaldehyde in the pre...A new type of aromatic tetraarnine containing biphenyl moiety in the side chain was synthesized via a modified Chichibabin＇s reaction. 3-Nitro-4-acetamidoacetophenone was reacted with 4-phenyl benzaldehyde in the presence of ammonium acetate to obtain 2,6-bis（3＇,4＇-diaminophenyl）-4-biphenyl pyridine （DPPA）. A series of polypyrrolones （PPys） were prepared using tetraamine and various aromatic dianhydrides via a two-step cyclization procedure. All the PPys show excellent high temperature stabilities with the initial decomposition temperatures of 530-549℃ and residual weight ratio of 49%-80% at 750℃ in nitrogen. The polymers exhibit no apparent glass transition temperatures （Tgs） except PPy-1 （Tg= 327℃）, which is derived from tetraamine DPPA and 2,2-bis[4-（3＇,4＇-dicarboxyphenoxy）-phenyl]propane dianhydride （BPADA）. In addition, the polymers have acceptable mechanical properties with the tensile strength of 65-94 MPa. The PPy films show excellent hydrolysis-resistance in alkaline aqueous medium and could maintain most of the properties even after boiling in 10% aqueous sodium hydroxide solution for a week.展开更多
Purpose Absolute measurement of radiant power in the X-ray region is essential for many applications in astrophysics,spectroscopy,and X-ray diagnostics.This paper presents a dependable method of absolute measurement o...Purpose Absolute measurement of radiant power in the X-ray region is essential for many applications in astrophysics,spectroscopy,and X-ray diagnostics.This paper presents a dependable method of absolute measurement of radiant power for synchrotron radiation monochromatized X-rays.Methods A free-air ionization chamber was examined closely and employed as the detector in the present work.Its measuring principle was discussed,and the correction factors were determined.Absolute measurement of radiant power for synchro-tron radiation monochromatized X-rays in the region of 6-20 keV was performed using the free-air ionization chamber at Beijing Synchrotron Radiation Facility.As a verification and an important application,photodiodes were calibrated against the free-air ionization chamber.Results Relative standard uncertainties of absolute measurement using free-air ionization chamber are about 1%.Calibration of photodiodes within the photon energy range from 6 to 20 keV has relative standard uncertainties below 1.5%.Conclusion The free-air ionization chamber is qualified to be used in many disciplines to support the measurement of opti-cal radiation.展开更多
基金This project was supported by the National Natural Science Foundation of China(No.50403025).
文摘A new type of aromatic tetraarnine containing biphenyl moiety in the side chain was synthesized via a modified Chichibabin＇s reaction. 3-Nitro-4-acetamidoacetophenone was reacted with 4-phenyl benzaldehyde in the presence of ammonium acetate to obtain 2,6-bis（3＇,4＇-diaminophenyl）-4-biphenyl pyridine （DPPA）. A series of polypyrrolones （PPys） were prepared using tetraamine and various aromatic dianhydrides via a two-step cyclization procedure. All the PPys show excellent high temperature stabilities with the initial decomposition temperatures of 530-549℃ and residual weight ratio of 49%-80% at 750℃ in nitrogen. The polymers exhibit no apparent glass transition temperatures （Tgs） except PPy-1 （Tg= 327℃）, which is derived from tetraamine DPPA and 2,2-bis[4-（3＇,4＇-dicarboxyphenoxy）-phenyl]propane dianhydride （BPADA）. In addition, the polymers have acceptable mechanical properties with the tensile strength of 65-94 MPa. The PPy films show excellent hydrolysis-resistance in alkaline aqueous medium and could maintain most of the properties even after boiling in 10% aqueous sodium hydroxide solution for a week.
基金the National Key R&D Program of China under Grant No.2017YFF0205102the National Natural Science Foundation of China under Grant No.11375227the Joint Funds of the National Natural Science Foundation of China under Grant No.U1632264
文摘Purpose Absolute measurement of radiant power in the X-ray region is essential for many applications in astrophysics,spectroscopy,and X-ray diagnostics.This paper presents a dependable method of absolute measurement of radiant power for synchrotron radiation monochromatized X-rays.Methods A free-air ionization chamber was examined closely and employed as the detector in the present work.Its measuring principle was discussed,and the correction factors were determined.Absolute measurement of radiant power for synchro-tron radiation monochromatized X-rays in the region of 6-20 keV was performed using the free-air ionization chamber at Beijing Synchrotron Radiation Facility.As a verification and an important application,photodiodes were calibrated against the free-air ionization chamber.Results Relative standard uncertainties of absolute measurement using free-air ionization chamber are about 1%.Calibration of photodiodes within the photon energy range from 6 to 20 keV has relative standard uncertainties below 1.5%.Conclusion The free-air ionization chamber is qualified to be used in many disciplines to support the measurement of opti-cal radiation.
