Figure 3 shows the XRD patterns and SEM micrographs of the nano-ZnO/P(MMA-co-BA) nanocomposites after hydrothermal treated under various pH for 24 hrs. When increase the pH of the hydrothermal treatment, the intensity of the amorphous halo peakwas gradually decreased while that of the ZnO crystalline peaks was increased. These results indicated the newly growth of ZnO on the surface of nanocomposites. In Fig. 3(a), although the newly grown ZnO crystalline peaks were detected in XRD pattern of the nanocomposites treated at pH=7, the ZnO crystals could not clearly seen in the SEM micrograph due to their tiny sizes. However, the newly grown ZnO could be sharply observed on the nanocomposites treated at pH=8 or higher. At pH=8, the morphology of ZnO crystals was nanorods of approximately 300 nm in length and 250 nm in diameter as shown in Fig. 3(b). The increase of pH to 9 induced the flower-like nanostructure of ZnO as shown in Fig. 3(c).The flower-like nanostructure consisted of ZnO nanorods with shape tip, growing from the center to the edge, in which each nanorod was approximately 200 nm in length and 125 nm in diameter. In Fig. 3(d), almost of the ZnO/P(MMA-co-BA) surface was covered with the clusters of ZnO formed after hydrothermal treatment at pH=10. In addition, the long thin ZnO nanofibers with nanospine on the surface were also observed on the dense clusters of ZnO as shown in the enlarge SEM micrograph in Fig. 4. From these results, the morphologies of ZnO changed with the changing of pH of hydrothermal treatment. The higher the pH of hydrothermal system, the higher amount of Zn(OH)4 2−could formed on the surface of the previous formed ZnO crystals, acting as the nucleation point for multi-direction growth as flower-like nanostructure and nanofibers with nanospine on the surface as concluded in Table 1.