^13C spin-lattice relaxation times （T1） of a conjugated polymer MEH-PPV in polymer/ layered silicate nanocomposites together with the steady state fluorescence emission and transient fluorescence decay measurements ...^13C spin-lattice relaxation times （T1） of a conjugated polymer MEH-PPV in polymer/ layered silicate nanocomposites together with the steady state fluorescence emission and transient fluorescence decay measurements have been investigated. The T1 values of the conjugated carbons decrease dramatically according to the reduction of polymer concentration in the nano composites, while the fluorescence life times （τ） show a linear prolonging tendency. The results are explained from the point of view of molecular dynamics.展开更多
Lithium perchlorate/poly（ethylene oxide）complex,as potential polymer electrolytes,has attracted much research interests in the past decades,due to its great applicational significance.However,despite of great effort...Lithium perchlorate/poly（ethylene oxide）complex,as potential polymer electrolytes,has attracted much research interests in the past decades,due to its great applicational significance.However,despite of great efforts,the mechanism of ion conducting of the system is still a topic with debates.In this work,the（）13C CP/MAS spectra of a series of PEO/LiClO4 complexes were measured with different compositions.It is found that for the extensively dried samples,the（）13C CP/MAS spectrum can exhibit up to 11 narrow peaks and the characteristics of the spectrum varies greatly with the composition.The（）13C spin-lattice relaxation time（T1）of these narrow peaks are found to be comparable to that of the neat PEO crystalline region,indicating these narrow peaks are corresponding to the complexed crystalline structures.On the other hand,the（）1H T1ρ of the narrow peaks are much longer than that of the neat PEO crystalline region,suggesting that the chain motion of PEO in the complex is greatly restricted due to the interaction between the oxygen of PEO and Li+.The aforementioned 11 peaks are assigned to three complexed crystalline structures.The conductivity of the complex sample decreases greatly when [O]∶ molar ratio decreases to 4∶1,while half of the （）13C peaks that are attributed to one crystalline structure varnish,indicating that there should exist certain kind of correlation between the complexed crystalline structure and the conductivity.展开更多
Ethylene-octene copolymer (POE) samples exposed to γ-radiation under a series doses were investigated using solid state ~ 13 C-NMR.The chemical shifts of POE were assigned, and the peak evolution as a function of rad...Ethylene-octene copolymer (POE) samples exposed to γ-radiation under a series doses were investigated using solid state ~ 13 C-NMR.The chemical shifts of POE were assigned, and the peak evolution as a function of radiation dose was discussed.An obviously chain scission was found near the branch carbons, and the ~ 13 C-NMR spectra of the corresponding gels confirmed the result.Linewidths of irradiated POE samples of various absorbed doses were observed to which were related to the molecular mobility of the radiation-crosslinked polymer.展开更多
基金supported by the National Natural Science Foundation of China(Grant No.20023003).
文摘^13C spin-lattice relaxation times （T1） of a conjugated polymer MEH-PPV in polymer/ layered silicate nanocomposites together with the steady state fluorescence emission and transient fluorescence decay measurements have been investigated. The T1 values of the conjugated carbons decrease dramatically according to the reduction of polymer concentration in the nano composites, while the fluorescence life times （τ） show a linear prolonging tendency. The results are explained from the point of view of molecular dynamics.
文摘Lithium perchlorate/poly（ethylene oxide）complex,as potential polymer electrolytes,has attracted much research interests in the past decades,due to its great applicational significance.However,despite of great efforts,the mechanism of ion conducting of the system is still a topic with debates.In this work,the（）13C CP/MAS spectra of a series of PEO/LiClO4 complexes were measured with different compositions.It is found that for the extensively dried samples,the（）13C CP/MAS spectrum can exhibit up to 11 narrow peaks and the characteristics of the spectrum varies greatly with the composition.The（）13C spin-lattice relaxation time（T1）of these narrow peaks are found to be comparable to that of the neat PEO crystalline region,indicating these narrow peaks are corresponding to the complexed crystalline structures.On the other hand,the（）1H T1ρ of the narrow peaks are much longer than that of the neat PEO crystalline region,suggesting that the chain motion of PEO in the complex is greatly restricted due to the interaction between the oxygen of PEO and Li+.The aforementioned 11 peaks are assigned to three complexed crystalline structures.The conductivity of the complex sample decreases greatly when [O]∶ molar ratio decreases to 4∶1,while half of the （）13C peaks that are attributed to one crystalline structure varnish,indicating that there should exist certain kind of correlation between the complexed crystalline structure and the conductivity.
文摘Ethylene-octene copolymer (POE) samples exposed to γ-radiation under a series doses were investigated using solid state ~ 13 C-NMR.The chemical shifts of POE were assigned, and the peak evolution as a function of radiation dose was discussed.An obviously chain scission was found near the branch carbons, and the ~ 13 C-NMR spectra of the corresponding gels confirmed the result.Linewidths of irradiated POE samples of various absorbed doses were observed to which were related to the molecular mobility of the radiation-crosslinked polymer.
