Polymer crystallization mechanism through a mesomorphic state

The isothermal crystallization from the molten state of poly(butylene terephthalate) is studied by differential scanning calorimetry and small-angle x-ray scattering. The relations among the crystallization temperature, lamella thickness, and melting temperature give two equilibrium transition temperatures. We propose a model of crystalline lamella formation through a mesomorphic state at the growth front by which these equilibrium transition temperatures are interpreted as the transition temperature between the mesophase and the crystal, and the one between the melt and the crystal of infinitely thick lamellae. These results show that the mesomorphic state plays a key role in the ordering process of polymers.