Transitions in Pure Polymers

Depending on the temperature, the dynamics and conformations of polymer molecules—taken again for simplicity as long, regular chain consisting of a succession of single bonds—can be very different. Three states that are well recognized are as follows  

The melt state. At relatively high temperatures, free rotation around each bond allows the chain to assume an infinite number of conformations in space and the molecules are continuously changing their conformation and are able to translate (diffuse) in space. The higher the temperature, the more intense is the molecular motion. 

The crystalline state. As described in Section 3.1, the chemical composition and configuration of a polymer may allow it to pack in a regular lattice and achieve a long-range order as the polymer is cooled from the melt state. Rotations around bonds are prevented by intermolecular interactions that lead to the formation of stable crystalline domains. 

Factors that affect the physical state of a polymer or the temperature at which transitions occur are as follows  

The polymer chain may contain double or triple bonds or rings, which do not permit rotation at any temperature without actual bond breaking. 

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