Using the reaction of Ar(3Po,2) + PCl3 as a source of PCl(b1 +), we have measured the quenching rate constants of PCl(b,v'=0) for more than 20 quenchers. The E-V model is used to calculate the rate constants. The ...Using the reaction of Ar(3Po,2) + PCl3 as a source of PCl(b1 +), we have measured the quenching rate constants of PCl(b,v'=0) for more than 20 quenchers. The E-V model is used to calculate the rate constants. The comparison of the calculated values with the experimental ones shows that the quenching of PCl(b) by the reagent molecules results from the electronic to vi-brational energy near resonance transfer and has been related to the Franck-Condon factors for the PCl(b,v'=0-a,v'=m) transition and to the anharmonicities of the terminal bonds of the quenchers. In addition, the influence of the polarizability of the reagent molecule on the quenching rate constant is discussed.展开更多
Lamellar crystals of diblock, triblock and four-arm poly（ethylene glycol）-b-poly（ε-caprolactone） （PEG-b-PCL） crystalline-crystalline copolymers were successfully obtained from their solution. Morphology and str...Lamellar crystals of diblock, triblock and four-arm poly（ethylene glycol）-b-poly（ε-caprolactone） （PEG-b-PCL） crystalline-crystalline copolymers were successfully obtained from their solution. Morphology and structure of lamellar crystals of crystalline-crystalline copotymers were investigated using tapping-mode atomic force microscopy （AFM） and selected area electron diffraction （SAED）. All of these samples showed the truncated-lozenge multilayer basal shapes with central screw dislocation or central stack, which were all obtained simultaneously from the oil bath. The diffraction pattern of PEG block lamellar crystal is attributed to the （120） diffracting planes and the pattern of PCL block lamellar crystal is attributed to the （1 I0） diffracting planes and （200） diffracting planes according to the SAED results. Four （110） crystal growth planes and two （200） crystal growth planes are discovered for the PCL blocks, but the （120） crystal growth planes of PEG blocks are hided in the figure of AFM. The crystalline structure of the four-arm copolymers （FA） is more disorder and confused than that of the diblock （DI） copolymer and the striated fold surface structures of lamellar crystals of four-arm copolymers （FA） are smoother than these of linear analogues, owing to the confused crystallization of blocks caused by the mutual restriction of blocks and the hindrance of the dendritic cores. In addition, the aspect ratio of FA is greater than that of the others. It is hypothesized that there are two reasons for the change of aspect ratios. First, the （200） diffracting planes of PCL crystals grew slowly compared to their （110） diffracting planes because of difference in the energy barrier. Secondly, edge dislocations on the （200） diffracting planes are also responsible for the variation of the aspect ratio. Consequently, the crystalline defects are augmented by the competing blocks crystallized simultaneously and the hindrance of the dendritic cores.展开更多
Atomic force microscopy （AFM）, wide-angle X-ray diffraction （WAXD） and differential scanning calorimetry are used to analyze the crystallization morphology and melting behavior of 4-arm PEO-b-PCL under high-pressu...Atomic force microscopy （AFM）, wide-angle X-ray diffraction （WAXD） and differential scanning calorimetry are used to analyze the crystallization morphology and melting behavior of 4-arm PEO-b-PCL under high-pressure CO2. It is demonstrated that CO2 has certain effect on the melting and crystallization behavior of the samples. After crystallization under CO2 at 4 MPa, spherulites with concentric ring-banded structure are formed which are composed of crystals with periodic thickness variation, and the band distance decreases with increasing treatment pressure. Due to the plasticization effect of CO2, depression of the melting temperature is observed with sorption of CO2 in polymers.展开更多
基金Project supported by the National Natural Science Foundation of China and by the Cross-Century Talent Foundation of Shandong University.
文摘Using the reaction of Ar(3Po,2) + PCl3 as a source of PCl(b1 +), we have measured the quenching rate constants of PCl(b,v'=0) for more than 20 quenchers. The E-V model is used to calculate the rate constants. The comparison of the calculated values with the experimental ones shows that the quenching of PCl(b) by the reagent molecules results from the electronic to vi-brational energy near resonance transfer and has been related to the Franck-Condon factors for the PCl(b,v'=0-a,v'=m) transition and to the anharmonicities of the terminal bonds of the quenchers. In addition, the influence of the polarizability of the reagent molecule on the quenching rate constant is discussed.
基金National Basic Research Program of China (973Program,Grant No. 2007CB935800 and 2009CB930300)Program forNew Drug R&D (Grant No. 2009ZX09310-001)+2 种基金NSFC projects(Grant No. 81072597)Beijing NSF project (Grant No. 7112089)Programs from Ministry of Education (Grant No. BMU20110268and BMU20110263)
基金the National Natural Science Foundation of China(Nos.21004073 and 51003117)Zhejiang Province Innovative Research Team(No.2009R50013)+2 种基金Ningbo Innovative Research Team(No.2009B21008)Ningbo Key Lab of Polymer Materials(No.2010A22001)Zhejiang Provincial Natural Science Foundation(No.Y4100517)
文摘Lamellar crystals of diblock, triblock and four-arm poly（ethylene glycol）-b-poly（ε-caprolactone） （PEG-b-PCL） crystalline-crystalline copolymers were successfully obtained from their solution. Morphology and structure of lamellar crystals of crystalline-crystalline copotymers were investigated using tapping-mode atomic force microscopy （AFM） and selected area electron diffraction （SAED）. All of these samples showed the truncated-lozenge multilayer basal shapes with central screw dislocation or central stack, which were all obtained simultaneously from the oil bath. The diffraction pattern of PEG block lamellar crystal is attributed to the （120） diffracting planes and the pattern of PCL block lamellar crystal is attributed to the （1 I0） diffracting planes and （200） diffracting planes according to the SAED results. Four （110） crystal growth planes and two （200） crystal growth planes are discovered for the PCL blocks, but the （120） crystal growth planes of PEG blocks are hided in the figure of AFM. The crystalline structure of the four-arm copolymers （FA） is more disorder and confused than that of the diblock （DI） copolymer and the striated fold surface structures of lamellar crystals of four-arm copolymers （FA） are smoother than these of linear analogues, owing to the confused crystallization of blocks caused by the mutual restriction of blocks and the hindrance of the dendritic cores. In addition, the aspect ratio of FA is greater than that of the others. It is hypothesized that there are two reasons for the change of aspect ratios. First, the （200） diffracting planes of PCL crystals grew slowly compared to their （110） diffracting planes because of difference in the energy barrier. Secondly, edge dislocations on the （200） diffracting planes are also responsible for the variation of the aspect ratio. Consequently, the crystalline defects are augmented by the competing blocks crystallized simultaneously and the hindrance of the dendritic cores.
基金supported by the National Natural Science Foundation of China(No.21004073)Natural Science Foundation of Ningbo Municipal(Nos.2009A610050,2008A610063,2010A610193,2011A610116)+2 种基金State Key Laboratory of Polymer Materials Engineering(Sichuan University)(KF201004)Program for Ningbo Innovative Research Team (2009B21008)Ningbo Key Lab of Polymer Materials(No.2010A22001).
文摘Atomic force microscopy （AFM）, wide-angle X-ray diffraction （WAXD） and differential scanning calorimetry are used to analyze the crystallization morphology and melting behavior of 4-arm PEO-b-PCL under high-pressure CO2. It is demonstrated that CO2 has certain effect on the melting and crystallization behavior of the samples. After crystallization under CO2 at 4 MPa, spherulites with concentric ring-banded structure are formed which are composed of crystals with periodic thickness variation, and the band distance decreases with increasing treatment pressure. Due to the plasticization effect of CO2, depression of the melting temperature is observed with sorption of CO2 in polymers.
