Abstract
Differential scanning calorimetry (DSC), X-ray diffraction and probe microscopy were used to study the annealing behavior of an aromatic copolyester with bulky side group. A transition from one crystalline state to another was observed in the thermal analyses. However, no transition was found in the X-ray diffraction patterns. The phenomenon was explained by the model based on the molecular structure. The material used in this study has a cylindrical projection due to the conformational freedom in a repeat unit which contains phenylene groups and a couple of ester linkages. Such molecules are likely to aggregate in the manner of the closed packing and generate comformationally disordered crystals. The thermal treatment promotes the molecular segments to settle in the most stable conformation which is free of steric hindrance, and hence the shrinkage of the unit cell takes place. The diameter of the crystal is as small as 10-20nm. The morphological change due to the thermal treatment was observed as the generation of constricted part in the cylindrical crystals.
