Construction of Real-time Pulsed NMR System and Its Application to the Study of Polymers

构建了实时脉冲核磁共振测量系统。该系统由脉冲核磁共振仪、瞬变记录仪和连接高速输入输出接口的高速微型计算机组成网络。编制了计算自旋-晶格驰豫时间、自旋-晶格驰豫时间和自旋-晶格驰豫时间及其信号强度的软件程序，可用于固体回波和Carr-Purcell-Meiom-Gill脉冲序列的高速实时测量。通过在计算机上连接来自每个脉冲序列的信号，可以获得固体非均相样品的真实自由感应衰减信号。对于&lt；T_(1(Rho))&gt；测量，固体回波序列脉冲序列被发现比正常的自旋锁定序列更好。为了更好地分析非均相体系中的自旋扩散，采用改进的Goldman-shen脉冲序列研究了微相分离嵌段共聚物的结晶过程(聚己内酯/聚苯乙烯/聚苯乙烯/聚乙烯基甲醚等)的结晶过程、水/聚丙烯酰胺体系的凝胶化过程和自旋扩散过程。主要结果是晶化程度、分子在晶相、非晶相和界面相中的运动程度随时间的变化。该系统还监测了结晶过程中各相含量的变化。从自旋扩散我们甚至可以估计微相分离的大小和形状。将脉冲核磁共振用作非破坏性显微镜是可能的。我们正计划将该系统应用于更实际的问题，并测量聚合物体系中的扩散常数。

Real-time pulsed nuclear magnetic resonance measurement system has been constructed. The system is composed of a network of <^1H> -pulsed NMR instrument, transient recorder, and high speed microcomputer connected with high speed input and output interface. Soft ware programm to calculate multiple spin-spin relaxation time <T_2> , spin-lattice relaxation time <T_1> , and spin-lattice relaxation time in the rotating frame <T_(1(rho))> and their signal intensity has been developed.For the high speed real time measurement of <T_2> , solid echo and Carr-Purcell-Meiboom-Gill pulse sequence was effective. By connecting the signal from each pulse sequence on the computer, it has become possible to obtain real free induction decay signal for solid heterogeneous samples. For <T_(1(rho))> measurement, solid echo train pulse sequence was found to be better compared to normal spin-locking sequence. For the analysis of spin diffusion in heterogeneous system, modified Goldman-Shen pulse sequence was found to be better.The above system was applied to study crystallization process(crystallization of poly ( <epsilon> - caprolactone)(PCL)/polystyrene/poly(vinyl methyl ether) mixtures et al), gelation process of water/poly(acryl amide) system, and spin diffusion process in micro-phase separated block copolymers. Main results are the change of the degree of crystallization, degree of molecular motion in the crystalline, amorphous, and interface phase with time. Change of the amount of each phase during crystallization was also monitored by this system. From the spin diffusion we can even estimate the size and shape of the micro-phase separation. It may be possible to use pulsed NMR as a non-destructive microscope.We are planning to apply the system to more practical problems and to measure the diffusion constants in polymer systems.