The application of mass spectrometry to investigations o{ gas-phase photochemistry and kinetics by flash photolysis was first reported in 1957. Mass spectrometry is advantageous and versatile for kinetics and mechani...The application of mass spectrometry to investigations o{ gas-phase photochemistry and kinetics by flash photolysis was first reported in 1957. Mass spectrometry is advantageous and versatile for kinetics and mechanism studies since it is capable of detecting many different chemical species during the course of the reaction and one can determine kinetic rates of reactant decay and product growth. When the mass spectrometer is used to determine kinetic decays and growths following pulsed photolysis, it may be called flash photolysis with time-resolved mass spectrometry(FPTRMS). While experiments using FPTRMS can obtain direct and valuable information on kinetics and mechanism o[ chemical reactions, they are limited in some cases. For example, experiments can be conducted only at limited temperature and pressure ranges. Moreover,the experimental investigation alone does not always provide sufficient information for the reaction mecha-nism study, especially for a complex reaction system. The theoretical investigations including Ab Initio cal-culations, RRKM calculations and numerial simulations are useful and supplemental tools to the experimen-tal studies. Ab initio and RRKM calculations can be used to predict rate coefficients of chemical reactions ina much wider ranges of temperature and pressure. Important information on the mechanism can also be obtained from the theoretical studies. However, the validation and accuracy of the results from the theoreticalinvestigations need to be verified or adjusted by experimental results. As an example, a study of kinetics and mechanism of CF3CHC10 radical reactions using FPTRMS combining with the theoretical calculations is reported.展开更多
The melting and recrystallization behaviour of poly（vinylcyclohexane）-b-poly（ethylene）-b-poly（vinylcyclohexane）（PVCH-PE-PVCH） triblock copolymer in supercritical carbon dioxide(CO2) was investigated by（using...The melting and recrystallization behaviour of poly（vinylcyclohexane）-b-poly（ethylene）-b-poly（vinylcyclohexane）（PVCH-PE-PVCH） triblock copolymer in supercritical carbon dioxide(CO2) was investigated by（using） of DSC.The effect of the rate of the depressurization of CO2 on the crystallization of the samples was also examined.It is found that there are three melting peaks on each DSC curve of the samples treated in supericritical CO2 at the temperature above tm of the untreated PVCH-PE-PVCH.They corresponded to the 'hard' confined crystallization of PE blocks homogeneous nucleation,the 'soft' confined crystallization of PE blocks homogeneous nucleation and the self-seeding nucleation free crystallization of PE blocks respectively.Furthermore,these three kinds of crystallization could be controlled by changing the competition between the crystallization of PE block and the vitrifaction of PVCH block in the samples,which depended on the rate of the depressurization of CO2.展开更多
文摘The application of mass spectrometry to investigations o{ gas-phase photochemistry and kinetics by flash photolysis was first reported in 1957. Mass spectrometry is advantageous and versatile for kinetics and mechanism studies since it is capable of detecting many different chemical species during the course of the reaction and one can determine kinetic rates of reactant decay and product growth. When the mass spectrometer is used to determine kinetic decays and growths following pulsed photolysis, it may be called flash photolysis with time-resolved mass spectrometry(FPTRMS). While experiments using FPTRMS can obtain direct and valuable information on kinetics and mechanism o[ chemical reactions, they are limited in some cases. For example, experiments can be conducted only at limited temperature and pressure ranges. Moreover,the experimental investigation alone does not always provide sufficient information for the reaction mecha-nism study, especially for a complex reaction system. The theoretical investigations including Ab Initio cal-culations, RRKM calculations and numerial simulations are useful and supplemental tools to the experimen-tal studies. Ab initio and RRKM calculations can be used to predict rate coefficients of chemical reactions ina much wider ranges of temperature and pressure. Important information on the mechanism can also be obtained from the theoretical studies. However, the validation and accuracy of the results from the theoreticalinvestigations need to be verified or adjusted by experimental results. As an example, a study of kinetics and mechanism of CF3CHC10 radical reactions using FPTRMS combining with the theoretical calculations is reported.
文摘The melting and recrystallization behaviour of poly（vinylcyclohexane）-b-poly（ethylene）-b-poly（vinylcyclohexane）（PVCH-PE-PVCH） triblock copolymer in supercritical carbon dioxide(CO2) was investigated by（using） of DSC.The effect of the rate of the depressurization of CO2 on the crystallization of the samples was also examined.It is found that there are three melting peaks on each DSC curve of the samples treated in supericritical CO2 at the temperature above tm of the untreated PVCH-PE-PVCH.They corresponded to the 'hard' confined crystallization of PE blocks homogeneous nucleation,the 'soft' confined crystallization of PE blocks homogeneous nucleation and the self-seeding nucleation free crystallization of PE blocks respectively.Furthermore,these three kinds of crystallization could be controlled by changing the competition between the crystallization of PE block and the vitrifaction of PVCH block in the samples,which depended on the rate of the depressurization of CO2.
