Morphological characterization of the novel fine structure of the PMMA/PVDF blend

Poly(methyl methacrylate) (PMMA)/Poly(vinylidene fluoride) (PVDF) blends are well known as polymer pairs with unique and complex properties. Using low voltage scanning transmission electron microscopy (LV-STEM), we found that there were previously unseen nanoscale structures inside them. The heterogeneous structures in the blends were formed on the same scale that did not deviate from the size of a single molecular chain, regardless of the solution casting, melt mixing, mixing ratios, and even amorphous or crystalline state of PVDF. The characteristics of these structures were discussed in accordance with thermophysical properties and intermolecular interaction properties, which provides the following new findings for the first time. First, the mixing ratio-dependent melting point depression exhibited by PMMA/PVDF blends is due to the size of their interface region. Second, the complex thermophysical behavior of the solution-casting blends is caused by the presence of ultrafine PVDF crystals. Finally, LV-STEM visualized the molecular miscibility of PMMA and PVDF in the melt-mixing samples.