Molecular Mobility and Higher-Order Structural Analysis of Polyoxymethylene under Heating and Fuel Swelling

and fuel swelling on the molecular mobility and higher-order structure of POM. In this study, the molecular mobility and higher-order structural changes of POM under heating and fuel swelling were analyzed using solid-state NMR, wide-angle X-ray diffraction (WAXD), and small-angle X-ray scattering (SAXS). Solid-state NMR measurements showed that the molecular mobility of all regions including crystalline to amorphous phases was enhanced under heating, while selective enhancement of molecular mobility was observed only in the amorphous and intermediate phases under fuel swelling. The results of solid-state NMR, WAXD, and SAXS measurements also confirmed that higher-order structural changes, such as increased crystallinity and increased volume of amorphous portions which occurred simultaneously due to fuel swelling.