Can You Explain The Concept Of Cyrstal Growth And Enthalpy Changes?

When a molecule of low molecular weight or an atomic material crystallizes, the change in energy and entropy is the same for every individual molecule. With macromolecules on the other hand, the chain segments deposit themselves on the preferred crystallite sites and when a chain segment changes place it affects its succeeding chain segment through intramolecular and intermolecular binding forces. This changes not only the entropy and internal energy of the depositing chain segments but also those of the free chains that remain near the surface of the crystallite during the amorphous-crystalline transition.

During the nuclei-formation phase, the free enthalpy increases as crystallization begins. The state of maximum free enthalpy is the least stable. With increasing crystal growth, the free enthalpy decreases again and the nuclei become more stable. In the case of nucleus formation from fringed micelles with protruding free chains (solid curve), the free enthalpy decreases strongly just before crystallization of the entire mass. The reason is that the influence of the not-yet-ordered chain segments on the ordered ones decreases the shorter these segments area. In the more common case of crystal formation from folded chain nuclei, the folds become more and more stressed with increasing crystallization so that the free enthalpy goes through a minimum and then rises again.