Wide-angle X-ray diffraction (WAXD) experiments were used to further study the morphology of the SMPU-OOBAm composites. As shown in Figure 3a, only two weak, broad peaks are observed in the pure SMPU at 19.5° and 23.8°, assigned to the (120) and (132) crystal faces, represents the crystal of polyethylene glycol, which indicates that the pure SMPU contains only a semi-crystalline soft phase and an amorphous hard phase. In addition, the pure OOBA shows many sharp peaks in the range of 10°~35°, which indicates a complete crystalline structure of OOBA . When the OOBA is incorporated into the SMPU, nearly all crystalline peaks of OOBA remain detected, e.g., P2 and P5 (see Figure 3a), and the intensity of these crystalline peaks increases when the OOBA content increases (see Figure 3b). The crystalline peaks of the PEG soft phase are also intensified with the increase in OOBA content. This result indicates that OOBA promotes the crystallinity of the soft phase of SMPU. However, the intensity of the crystalline peaks in SMPU-OOBAm is not as strong as that of pure OOBA, which implies a reduced crystallinity of OOBA. Moreover, a new peak at 16.2° is observed; which also intensifies with an increase of OOBA-content. According to the literature , we know that pure OOBA can form two different crystals (α and β crystalline phases) at low temperature. Therefore, this new peak may be ascribed to the second crystal type (β phase) of OOBA. Thus, the crystallizability of the first crystal type (α phase) of OOBA is restrained, and OOBA subsequently tends to form a second β phase when the OOBA content increases. This phenomenon can also be reflected in the thermal properties and phase transitions.