Abstract
Agarose hydrogels which showed optical anisotropy were obtained by the directional freezing of starting isotropic gels under a temperature gradient. The directional freezing caused a crystallization of many isolated ice crystal phases, leaving a honeycomb-like gel phase with a higher polymer content. The crystallographic c-axis of the ice crystals was directed to the temperature gradient. X-ray and optical analyses showed that agarose chains had a strong planar orientation along the walls'side surfaces, which were parallel to the equatorial planes of the ice crystals.
Scanning electron microscopy showed that the wall consisted of a large number of sheets stacked along the wall thickness; in each sheet, agarose fibrillar structures were found to be densely aligned. With the application of repeated freezing and thawing, the anisotropy of the segregated gel phases increased.
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Yokoyama, F., Achife, E.C., Momoda, J. et al. Morphology of optically anisotropic agarose hydrogel prepared by directional freezing. Colloid & Polymer Sci 268, 552–558 (1990). https://doi.org/10.1007/BF01410297
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DOI: https://doi.org/10.1007/BF01410297