Higher-order structure of as-spun and highly-drawn poly(glycolic acid)(PGA) fibers has been characterized by solid-echo H-1 NMR and WAXD methods. In the observed WAXD patterns, as-spun PGA fiber shows a very broad amorphous peak and highly-drawn PGA fibers show very sharp diffraction peaks at 2 theta = 21.9 degrees from which the crystallinities of highly-drawn fibers with the drawing ratio(lambda(d.r.)) of 2.5, 2.8 and 3.2 are determined to be 0.50, 0.51 and 0.52, respectively. These show that the crystallinities of the PGA fibers with different drawing ratios are very close to each other. On the other hand, the observed solid-echo H-1 NMR free induction decay(FID) signals of as-spun and drawn PGA fibers show a multi-component decay consisting of the short T-2 component and the long T-2 component. From these results, the short T-2 component was assigned to the crystalline region and the immobile amorphous region, and the long T-2 component was assigned to the mobile amorphous region. It was found that the fractions of the short T-2 component and the long T-2 component of highly-drawn fibers largely depend on the drawing ratio lambda(d.r.) and temperature, and that the fractions of the short T, component for drawn PGA fibers with lambda(d.r.). of 2.5 at 120 degrees C and 160 degrees C are 0.85 and 0.56, respectively. Further, it was found that the fractions of the short T, component for the drawn fibers above 160 degrees C are very close to the crystallinities determined by the WAXD patterns, but the fractions of the short T-2 component at 120 degrees C are different from each other. The structural characterization was made to understand mechanical property of the drawn PGA fibers. Then, it was found that the fraction of the corresponding amorphous region is closely related to the ratio of the tensile strength after hydrolytic acceleration test to that before hydrolytic acceleration for PGA fibers.
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