Unit Cells of Polymer Crystals

The packing of polymer chains into the unit cell normally follows two basic rules  

The survey over about 150 polymer crystals shows their distribution among seven crystal series. The number in the cubic crystal series is zero, because the c-axis contains completely different interactions (covalent bonds along the chain axis) from the other two axes (sub-valence interactions). The orthorhombic and the 

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Note 1 Unlike in the case of low-molar-mass substances, the unit cell of polymer crystals usually comprises only parts of the polymer molecules and the regularity of the periodic repetition may be imperfect. 

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