Physical Degrees of Order

Completely statistical (random) arrangements of the macromolecules without a regular order or orientation, i.e., without constant distances, are known as amorphous states. There is no long-range order whatsoever. The valid model for such states is the statistical coil. This is the dominating secondary structure in synthetic polymers and polymeric solutions. Its determinant parameter is coil density. 

This spatial coil structure represents the most favorable state from the point of view of entropy the macromolecule tends toward this state to the extent allowed by external conditions (mobility). Under conditions of rising temperature or diffusion of solvents into the material, the mobility of the chain segments and side chains increases. Rotations and shifts are more frequent (molecular microbrownian motion). 

According to the second law of thermodynamics, a macromolecule strives to attain the state of greatest possible entropy and will therefore tend to coil. 

Besides the state of greatest disorder, ordered states within a macromolecule are also possible, particularly in semicrystalline thermoplastics. These short-range orders presumed to exist in the amorphous state develop in the melt of semicrystalline thermoplastics, then act as crystallization nuclei in the subsequent cooling process. 

Linear macromolecules, either without substituents or with small ones regularly arranged, can juxtapose themselves at a microscopic level in uniform parallel aereas and form crystals. Plastics with crystalline regions always also contain more or less amorphous, unordered regions, for which reason they are termed semicrystalline. This macromolecular arrangement can be altered by a number of influences. 

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