Reversible crystallization and melting in polymers

The intramolecular, vibrational, and conformational motion of the condensed state of flexible, linear macromolecules and their contributions to thermal properties can be described quantitatively. The translational and rotational motion of the molecules as a whole is more difficult to assess but contributes only negligibly to the calorimetry, making the condensed state of polymers easier to understand than that of small molecules. A semicrystalline polymer is typically metastable and consists of crystals, amorphous material, and intermediate phases. The micrometer-long macromolecules may extend through several micro- or nanophases, causing a strong coupling throughout the phase structure. The intermediate phases are the keys to understanding the physical properties. Their glass transitions may be in the vicinity of the transition of the bulk-amorphous phase, occur at higher temperature, coincide with the melting temperature of the crystals, or even be located above the melting temperature. Temperature-modulated differential scanning calorimetry has developed into a valuable tool for the study of the various nanophases and will be used to disseminate examples of different behaviors on crystallization and melting via their thermal properties.