为了阐明裸子植物中纤维素与木素之间的连接方式,从多糖的角度分析糖单元与木素苯丙烷结构单元之间的共价键连接方式,合成了带6-13 C标记的纤维素前驱物尿苷二磷酸葡萄糖,并将其与PAL酶的抑制剂AOPP及外源性木素前驱物松柏醇-β-D-葡萄...为了阐明裸子植物中纤维素与木素之间的连接方式,从多糖的角度分析糖单元与木素苯丙烷结构单元之间的共价键连接方式,合成了带6-13 C标记的纤维素前驱物尿苷二磷酸葡萄糖,并将其与PAL酶的抑制剂AOPP及外源性木素前驱物松柏醇-β-D-葡萄糖苷一起投入生长中的银杏植物体内。碳13丰度检测得知纤维素在细胞壁的沉积主要是从在初生壁开始,高分辨率固体核磁13 C NMR分析证实了纤维素6位碳与木素以苯甲醚键等方式连接。展开更多
^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
To raise the room temperature ionic conductivity and improve the mechanical strength of a PEO-based polymer electrolyte, a noncrystalline two-component epoxy electrolyte system has been prepared. The diglycidyl ether ...To raise the room temperature ionic conductivity and improve the mechanical strength of a PEO-based polymer electrolyte, a noncrystalline two-component epoxy electrolyte system has been prepared. The diglycidyl ether of polyethylene glycols as precursors of the system were synthesized by a two-step process. The presumed structure of the product was characterized, by ^(13)C, ~1H NMR and IR spectroscopy. It was found that a side-reaction occurred between the secondary hydroxyl group of PEG-chlorohydrin and epichlorohydrin in some degree, resulting in a by- product containing—CH_2Cl side group. By selecting a characteristic signal, which is undistorted by the increase in the length of CH_2 CH_2—O segment, a ~1H NMR approach of determining the equivalent epoxy weight (EEW) was proposed. The method is valid to specimens even though the EEW is as high as 2,000. The examination of the specimens by DSC showed that epoxidation greatly depressed the crystallinity of the PEG's, whereas the T_g was raised.展开更多
The morphology of some polyetherester-ureas were studied by ^(13)C CP/MAS and ~1H wide-line NMR spectroscopy. It was found that the HDI and MDI based polymers have well crystallized hard segments, whereas the TDI and ...The morphology of some polyetherester-ureas were studied by ^(13)C CP/MAS and ~1H wide-line NMR spectroscopy. It was found that the HDI and MDI based polymers have well crystallized hard segments, whereas the TDI and HMDI based ones have not. For HDI/MDI based polymers, the presented results suggest that the distribution of two kinds of hard segment units is mainly in a block form. The influences of the different hard segment and chain length on the mobility of the soft segment were also studied.展开更多
文摘为了阐明裸子植物中纤维素与木素之间的连接方式,从多糖的角度分析糖单元与木素苯丙烷结构单元之间的共价键连接方式,合成了带6-13 C标记的纤维素前驱物尿苷二磷酸葡萄糖,并将其与PAL酶的抑制剂AOPP及外源性木素前驱物松柏醇-β-D-葡萄糖苷一起投入生长中的银杏植物体内。碳13丰度检测得知纤维素在细胞壁的沉积主要是从在初生壁开始,高分辨率固体核磁13 C NMR分析证实了纤维素6位碳与木素以苯甲醚键等方式连接。
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.
基金The project supported by National Natural Science Foundation of China.
文摘To raise the room temperature ionic conductivity and improve the mechanical strength of a PEO-based polymer electrolyte, a noncrystalline two-component epoxy electrolyte system has been prepared. The diglycidyl ether of polyethylene glycols as precursors of the system were synthesized by a two-step process. The presumed structure of the product was characterized, by ^(13)C, ~1H NMR and IR spectroscopy. It was found that a side-reaction occurred between the secondary hydroxyl group of PEG-chlorohydrin and epichlorohydrin in some degree, resulting in a by- product containing—CH_2Cl side group. By selecting a characteristic signal, which is undistorted by the increase in the length of CH_2 CH_2—O segment, a ~1H NMR approach of determining the equivalent epoxy weight (EEW) was proposed. The method is valid to specimens even though the EEW is as high as 2,000. The examination of the specimens by DSC showed that epoxidation greatly depressed the crystallinity of the PEG's, whereas the T_g was raised.
文摘The morphology of some polyetherester-ureas were studied by ^(13)C CP/MAS and ~1H wide-line NMR spectroscopy. It was found that the HDI and MDI based polymers have well crystallized hard segments, whereas the TDI and HMDI based ones have not. For HDI/MDI based polymers, the presented results suggest that the distribution of two kinds of hard segment units is mainly in a block form. The influences of the different hard segment and chain length on the mobility of the soft segment were also studied.
