波谱学杂志 ›› 2008, Vol. 25 ›› Issue (2): 159-164.

• 研究论文 • 上一篇    下一篇

聚乙烯结晶区的交叉极化动力学研究

刘志建; 舒婕; 张莉莉; 陈群   

  1. 华东师范大学 物理系, 上海市功能磁共振成像重点实验室, 上海 200062
  • 收稿日期:2007-04-12 修回日期:2007-05-21 出版日期:2008-06-05 发布日期:2009-12-05
  • 通讯作者: 陈群

A Study on the Cross-Polarization Kinetics of Polyethylene Crystals

LIU Zhi-jian; SHU Jie; ZHANG Li-li; CHEN Qun   

  1. Shanghai Key Laboratory of Functional Magnetic Resonance Imaging,Department of Physics,East China Normal University, Shanghai 200062, China
  • Received:2007-04-12 Revised:2007-05-21 Online:2008-06-05 Published:2009-12-05
  • Contact: Chen Qun

摘要: 研究了单轴拉伸的聚乙烯(PE)纤维结晶区的1H-13C交叉极化(CP)动力学,发现在魔角旋转(MAS)条件下,质子的同核偶极相互作用变弱,其CP动力学可以用I-I*-S模型描述. 沿MAS转轴整齐排列的纤维样品CP动力学曲线随接触时间的增加振荡上升,与斜方晶相比,单斜晶曲线的振荡更为明显, 而非取向样品的CP动力学曲线则单调上升. 说明经过单轴拉伸的PE样品中斜方晶和单斜晶都在一定程度上沿着拉伸方向排列,而单斜晶的取向度高于斜方晶,上述结果表明测量在MAS条件下的CP动力学可以成为表征分子取向度的一种新方法.

关键词: 固体NMR, 交叉极化动力学, 聚乙烯, 取向

Abstract:

The kinetics of cross-polarization (CP) between 1H and 13C nuclei in the crystalline regions of elongated polyethylene fiber was studied. It was found that, with a moderate magic angle spinning (MAS) rate, the CP build-up curves of both orthorhombic and monoclinic crystals of PE can be described by I-I*-S- model. For the fiber sample aligning with the MAS axis in the rotor, the CP build-up curves of both orthorhombic and monoclinic crystals exhibit oscillation, while those of the disoriented samples exhibit monotonic increase. These results demonstrated that, to a certain extent, both orthorhombic and monocline crystals are oriented along the direction of elongation. The degree of orientation of the monoclinic crystal is higher than that of the orthorhombic crystal. Measurement of the kinetics of cross-polarization can be employed as a new technique to determine the degree of orientation of polymer chain.

Key words: solid state NMR, kinetics of cross-polarization, crystalline polyethylene, orientation