ANALYSES OF THE LOCAL ORDER IN POLY(ETHYLENE-TEREPHTHALATE) IN THE GLASSY STATE BY 2-DIMENSIONAL SOLID-STATE C-13 SPIN-DIFFUSION NUCLEAR-MAGNETIC-RESONANCE SPECTROSCOPY

The locally ordered structure for poly(ethylene terephthalate) in the glassy state, quenched from the melt, has been investigated by two-dim ensional solid-state C-13 spin diffusion nuclear magnetic resonance sp ectroscopy. The orientational correlation is found to be successfully examined for different mixing times, which correspond to C-13 spin dif fusion times, through the C-13 spin diffusion for carbonyl carbon C-13 -labeled poly(ethylene terephthalate). For mixing times shorter than 0 .8 s, the broadening of the diagonal peak occurs and its intensity dec reases in the region from sigma(11) to sigma(22) with increasing mixin g time. From a comparison with the simulated spectrum, it is suggested that such changes are due to the existence of the well ordered region even in the glassy state. For mixing times longer than 0.4 s, the int ensities of the off-diagonal peaks are also found to increase with inc reasing mixing time. Detailed analyses of the off-diagonal peaks sugge st that there is a stacked component for mixing times of around 1 s, i n which the planes composed of the phenylene ring and two adjacent car bonyl groups are stacked with each other. The spectra for mixing times over 3.2 s, which reach the quasiequilibrium state, are in good accor d with the spectrum simulated by assuming no long-range orientational correlation. From the calculation of the C-13 spin diffusion rate, the radius of the region having the orientational correlation is estimate d to be 0.5-1.4 nm. (C) 1998 American Institute of Physics.