Crystallization of PVDF in the PVDF/PMMA blends precipitated from their non-solvents: Special orientation behavior, morphology, and thermal properties

The poly(vinylidene fluoride) (PVDF)/poly(methyl methacrylate) (PMMA) blends were prepared by precipitation (or solution casting) in non-solvent ethanol, good solvent N,N-dimethylformamide (DMF), or DMF/ethanol mixed solvents. Fourier transform infrared (FTIR) spectroscopy and X-ray diffraction (XRD) analyses revealed that the crystalline phases of PVDF in the blends depended on the ethanol content in mixed solvents. PVDF crystallized into β phase when ethanol content was ≤60% (by volume, same hereinafter), instead, α and β phases existed together at ethanol content ≥70%. Correspondingly, different crystallization morphology of PVDF was observed from scanning electron microscopy (SEM) images, due to the transition from good solvent to non-solvent as ethanol content increased. Interestingly, special orientation behavior of PVDF was observed by XRD measurements for the (0 0 2) reflection of the α phase precipitated in the non-solvent DMF/ethanol=3/7 [DE37]. The PVDF in the blend precipitated in the non-solvent [DE37] also had a relatively high degree of crystallinity of 74.8%, according to DSC measurement. The investigation into the crystallization of polymer in non-solvent may attract certain interest, due to the interesting phenomena that occurred in the special solvent environment.