Crystallization of poly(ethylene oxide) from solutions of different solvents

The kinetics and crystalline morphology for isothermal crystallization of poly(ethylene oxide) (PEO) from solutions in three different solvents, N, N-dimethylacetamide (DMAc), toluene, and tripropionin (TP), were investigated. The energy barrier A' of primary nucleation was highest for PEO/TP, and that of radial growth C' was highest for PEO/toluene. Crystallites grew from both the DMAc and toluene solutions as aggregates of small layers of lamellae with branching and splitting. In addition, the crystallites from PEO/DMAc were found to have polygonal-like contours outside the lamella aggregates. This finding suggests that liquid-liquid phase separation occurred before or during the crystallization for PEO/DMAc. Relatively large spherulites were obtained from PEO/TP solutions due to the relatively low primary nucleation rate. The number density of the crystallites from PEO/TP was much lower than those from PEO/DMAc and PEO/toluene.