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The deformation of single crystals shows two preferential directions for crack formation at 60° to each other. The cracks open very little on crystals lying directly on the Mylar substrate and substantially more on the higher layers of a multilayer crystal. The primary crack direction is parallel to the plane of hydrogen bridges. The microfibrils bridging the cracks are too short for a good dark field electron micrograph. Deformed thin membranes occasionally show a lamellar structure. After annealing at 215°C well oriented single crystal blocks belonging to microfibrils can be observed.
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Sakaoku et al. (1972) studied this question.
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