Polymorphism in poly(3,3‐dimethyloxetane)

Abstract

Abstract A detailed study of the polymorphism of poly(3,3‐dimethyloxetane) was carried out by differential scanning calorimetry and X‐ray diffraction. From the relaxed melt state, two modifications, Form II (monoclinic) and Form III (orthorhombic), are separately obtained depending on crystallization temperature. When the crystallization is accomplished for a given modification, this one is stable at any temperature below its melting temperature. However, if the crystallization of a given modification is not complete, the other modification can be crystallized from the amorphous phase. Thus, a possibility of obtaining both forms exists. The kinetic and thermodynamic factors which govern this process are analyzed. The free energies were calculated and the conclusion is that modification II is thermodynamically the most stable one at all temperatures below its melting point.