Crystal imperfections structural control

Structure Used herein to refer to the molecular-level, crystallographic, three-dimensional arrangement of atoms, as controlled by the chemical bonding. Both long-range and short-range order/disorder, including crystal imperfections and defects, must be considered. 

Perfect crystals do not exist in real life and it has long been known that the physical properties of materials may depend at least as much on some deviations from the perfect periodicity as on the structure itself. Indeed, the structure is always averaged over a large number of unit cells and thus does not show atomic scale defects or disorder. Further, while the introduction of a controlled amount of imperfection in samples tells us very much about the physics of the material, on the contrary, uncontrolled sample imperfections may lead to incorrect or inaccurate deductions. 

In summary, it can be concluded that there are three major regions that characterize a semicrystalline polymer. There are the crystalline, the interfacial, and the interlamellar or liquid-like regions. In each region there is a different chain conformation. Many of the individual chains traverse all three regions. The crystalline region represents the three-dimensional ordered structure with the typical lamellar-like habit. The levels of imperfection within the crystallites are no different in concentration and type from those found in crystals formed by similar low molecular weight compounds. The crystallite, or core, thickness can be related to the nucleation requirements. However, the control by nucleation of the process of... 

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