Multiple-Pulse Nuclear Magnetic Resonance of Solid Polymers. Polymer Motions in Crystalline and Amorphous Poly(tetrafluoroethylene)
Multiple-Pulse Nuclear Magnetic Resonance of Solid Polymers. Polymer Motions in Crystalline and Amorphous Poly(tetrafluoroethylene)
复制标题
固体聚合物的多脉冲核磁共振。
DOI：
10.1021/ma60078a051
复制
发表时间：
1980
期刊：
影响因子：
5.5
通讯作者：
A. English
中科院分区：
文献类型：
--
作者：
A. J. Vega;A. English
用多脉冲序列获得的~（19）F NMR化学位移谱可用于测定无规取向聚（α-甲基丙烯酸酯）和聚（α-乙烯-六氟丙烯）的结晶度和检测大分子的运动。观察到了PTFE中的弛豫现象，我们的结果与以前的滞弹性和介电测量结果一致。观察到的y弛豫，并示出是由于在非晶区域的局部链轴的重取向。在非晶区的链轴重取向，这还没有观察到在previousmeasurements，被观察到是非常迅速的（£ 100 MHz），并随着温度的升高而增长的幅度。TFE/HFP共聚物表现出相同类型的大分子运动，但非晶区的局部链轴重取向被低于熔点的空间上较大的CF 3基团抑制。
19F NMR chemical shift spectra obtained with a multiple-pulse sequence are shown to be useful in determining crystallinity and detecting macromolecular motionin randomly oriented poly (tetrafluoroethylene) and poly (tetrafluoroethylene-hexafluoropropylene). The ß relaxation in PTFE is observed and our results are in agreement with previous anelastic and dielectric measurements. The y relaxation is observed and is shown to be due to reorientation about a local chain axis in the amorphous regions. Chain-axis reorientation in the amorphous regions, which has not been observed in previousmeasurements, is observed to be very rapid (£ 100 MHz) and to grow in amplitude with increasing temperature. The TFE/HFP copolymer exhibits the same types of macromolecular motions, but theamorphous-region local chain axis reorientation is inhibited by the sterically larger CF3 groups below the melting point.