Cationic ring-opening polymerization of 3,3-bis（chloromethyl）oxacyclobutane catalyzed by BF3.OEt2 was carded out in ionic liquids [bmim]BF4 and [bmim]PF6. The influences of BCMO concentration and molar ratio of BCMO...Cationic ring-opening polymerization of 3,3-bis（chloromethyl）oxacyclobutane catalyzed by BF3.OEt2 was carded out in ionic liquids [bmim]BF4 and [bmim]PF6. The influences of BCMO concentration and molar ratio of BCMO/BF3.OEt2 on the molecular weights and yield of PBCMO were investigated. The polymerization in ionic liquids proceed to high conversions, although molecular weights are limited, similar to polymerization in organic solvent such as CH2Cl2. Follow a viewpoint of green chemistry, we feel ionic liquid [bmim]BF4 is superior to [bmim]PF6. Extracting [bmim]PF6 from the product using organic solvent as extractant limits its advantage as a green reaction media.展开更多
A simple method to synthesise hexagonal lead sheets,which belong to the class of two-dimensional materials,is proposed.These objects are collected on a substrate located under two lead electrodes, between which nanose...A simple method to synthesise hexagonal lead sheets,which belong to the class of two-dimensional materials,is proposed.These objects are collected on a substrate located under two lead electrodes, between which nanosecond-pulsed spark discharges are ignited in liquid nitrogen.The hexagonal sheets are single crystals produced by gas phase condensation.Once nitrogen completely evaporates,the sheets change to PbO2by oxidation in air.The oxidation process induces stress that pleats the uppermost sheets or open cracks at the centre.The thickness of the individual objects typically varies from 4to 20nm.When the number of discharges is more than about 2000,in addition to sheets,two types of PbO2 sticks start to form:bundles composed of nanosticks (length 5p.m and diameter 50nm)and isolated sticks (length 20μm and diameter 500nm).These new nanostructures mainly form because of the way the discharge erodes the lead electrodes.Initially,anisotropic erosion driven by the orientation of the crystallographic planes of the lead crystals produces octahedra and nanosticks,and the nanosticks grow on the electrode surfaces as discharge proceeds.After about 2000discharges,the nanosticks are sufficiently long that they can be easily broken,probably by mechanical stress,and they fall onto the underlying substrate.展开更多
基金financially supported by the Key Project of Chinese Ministry of Education(No.105075)the National Natural Science Foundation of China(No.20503016).
文摘Cationic ring-opening polymerization of 3,3-bis（chloromethyl）oxacyclobutane catalyzed by BF3.OEt2 was carded out in ionic liquids [bmim]BF4 and [bmim]PF6. The influences of BCMO concentration and molar ratio of BCMO/BF3.OEt2 on the molecular weights and yield of PBCMO were investigated. The polymerization in ionic liquids proceed to high conversions, although molecular weights are limited, similar to polymerization in organic solvent such as CH2Cl2. Follow a viewpoint of green chemistry, we feel ionic liquid [bmim]BF4 is superior to [bmim]PF6. Extracting [bmim]PF6 from the product using organic solvent as extractant limits its advantage as a green reaction media.
文摘A simple method to synthesise hexagonal lead sheets,which belong to the class of two-dimensional materials,is proposed.These objects are collected on a substrate located under two lead electrodes, between which nanosecond-pulsed spark discharges are ignited in liquid nitrogen.The hexagonal sheets are single crystals produced by gas phase condensation.Once nitrogen completely evaporates,the sheets change to PbO2by oxidation in air.The oxidation process induces stress that pleats the uppermost sheets or open cracks at the centre.The thickness of the individual objects typically varies from 4to 20nm.When the number of discharges is more than about 2000,in addition to sheets,two types of PbO2 sticks start to form:bundles composed of nanosticks (length 5p.m and diameter 50nm)and isolated sticks (length 20μm and diameter 500nm).These new nanostructures mainly form because of the way the discharge erodes the lead electrodes.Initially,anisotropic erosion driven by the orientation of the crystallographic planes of the lead crystals produces octahedra and nanosticks,and the nanosticks grow on the electrode surfaces as discharge proceeds.After about 2000discharges,the nanosticks are sufficiently long that they can be easily broken,probably by mechanical stress,and they fall onto the underlying substrate.
