| Budget Amount *help |
¥1,600,000 (Direct Cost: ¥1,600,000)
Fiscal Year 1992: ¥600,000 (Direct Cost: ¥600,000)
Fiscal Year 1991: ¥1,000,000 (Direct Cost: ¥1,000,000)
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| Research Abstract |
Macroscopically molecular-oriented gels of alginate with the shape of cylinder were prepared by extruding an aqueous semi-dilute solution of sodium alginate into various divalent metal ion solutions such as Pb, Cu, Ca, and Zn. Effects of flow, gelation and metal ions on the molecular orientation were examined by polarized optical microscopy, scanning electron micropscopy, wide-angle X-ray diffraction and mechanical measurement.
With increasing flow rate in tube, coil-stretch transi-of the chains increased ; however they underwent a planar orientation along tube wall, in the shear rate range below 3800 sec-1 which was the upper limit in this experiment. During gelation, the die swell and the longitudinal shrinkage occurred, the magnitude of which depended on the metal ions used, with the order, Pb<Cu<Ca<Zn. The chain orientation was characterized by a planar orientation of the chains along the gel wall surface, within which the mean chain orientation was rather directed normal to the flow direction. The gel fibers rapidly dried under vacuum showed sheet-like structures developed cylindrically ; those of Cu alginate was very distinct. The optical anisotropy was in the order, Pb>Cu>Ca>Zn. This was ascribed to the differences in the binding nature of metal ions with the sugar residues. The Pb and Cu alginate gels exhibited higher modulus and tenacity with lower elongation at break. The reverse tendency was found in the Ca and Zn alginate gels. X-ray diffraction patterns of the gel fibers of guluronate and mannuronate showed the existence of the 2_1 helical form ; this was consistent with the results of the hardsphere maps.
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