Macromolecular nucleation

The rate‐determining step of crystallization of macromolecules from melt and solution is shown to be molecular nucleation. Molecular nucleation is described by using classical nucleation theory. Good agreement is found between the molecular nucleus size and the critical length of the rejected species. Molecular nucleation has a higher free‐energy barrier than secondary nucleation; it might thus lead initially to independent patches of each molecule on the crystal surface. A possible reason for secondary nucleation on extended surfaces is suggested.