Hi
I would like to know if is it possible to obtain the crystallinity of a material such as starch from the ratio of the birefringent area to total area using the images obtained from light and polarized light microscopy?
Dear Alejandro,
Please find attached two photomicrographs (width of images 0.5 mm) of potato starch, first: transmitted light digital image in plane polarized light, second: with crossed polars. The second picture clearly shows that the individual starch granules are anisotropic and have the deformed cross of the spherulites. Amorphous parts cannot be seen in the individual grains, since no extinction exists. The degree of quasi-crystallinity can be clearly determined and assessed here.
Best regards,
Guenter Grundmann
I do not know how it is for starch, but it is not possible to say in general that amorphous materials and glasses do not exhibit a signal between crossed polarizers whereas crystallites do. In addition, crystallites have to be large enough to be resolved by the light, otherwise random orientation may prevent a signal. Therefore you really would have to investigate the particular material of interest to be able to say something about crystallinity from the doubly refracting area/volume relative to the total area/volume.
Dear Alejandro,
Please find attached two photomicrographs (width of images 0.5 mm) of potato starch, first: transmitted light digital image in plane polarized light, second: with crossed polars. The second picture clearly shows that the individual starch granules are anisotropic and have the deformed cross of the spherulites. Amorphous parts cannot be seen in the individual grains, since no extinction exists. The degree of quasi-crystallinity can be clearly determined and assessed here.
Best regards,
Guenter Grundmann
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