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 beta phase when ethanol content was <= 60% (by volume, same hereinafter), instead, alpha and beta 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 alpha 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. (C) 2011 Elsevier B.V. All rights reserved.