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

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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.