Crystallization behavior of PVDF/PMMA blends prepared by in situ polymerization from DMF and ethanol

The crystallization behavior of poly(vinylidene fluoride)/poly(methyl methacrylate) (PVDF/PMMA) blends was investigated at different PMMA content and from two solvents N,N-dimethylformamide (DMF) and ethanol. The PVDF/PMMA blends were obtained by in situ polymerization of methyl methacrylate (MMA) in the solution of PVDF in DMF. The crystalline phases of PVDF were dependent on crystalline solvents and independent on PMMA content. For the in situ PVDF/PMMA blends, β phase of PVDF was predominant when they were crystallized from their good solvent DMF, while PVDF exhibited well-defined α and β phases from non-solvent ethanol. However, the relative fraction of β phase of PVDF in blends crystallized from ethanol varied with PMMA content. The crystallization morphology was related to crystallization solvent and PMMA content. The in situ blends crystallized from DMF and ethanol presented spherulites morphology and numerous minute particle structures, respectively. The addition of PMMA could reduce the spherulite size of PVDF. Thermal properties of in situ blends were also dominated by crystallization solvent and PMMA content. For the blends crystallized from DMF, their peak melting temperatures and lamellar thickness calculated by WAXD showed a first increasing and then decreasing tendency. At the same PMMA content, the blends crystallized from ethanol had a higher degree of crystallinity (X c) of PVDF compared with those from DMF. In addition, the X c calculated by DSC increased noticeably at PMMA content of 1.0 wt% and afterward it decreased with PMMA content, regardless of the kind of crystallization solvent. Besides, the hydrophilicity of the PVDF/PMMA blends was improved with PMMA content based on contact angle measurements.