Segmental dynamics and rheology of miscible poly(vinylidene fluoride)/poly(methyl methacrylate) (70/30 by weight) blend filled with titania or poly(methyl methacrylate)-grafted titania

Titania (TiO2) or poly (methyl methacrylate) (PMMA)-grafted titania (TiO2-g-PMMA) were incorporated into miscible poly (vinylidene fluoride) (PVDF)/PMMA (70/30 by weight) blend by melt mixing. TiO2 particles exhibited aggregation in the composites as displayed by scanning electron microscopy observations and the storage modulus (G′) plateau in the low frequency (ω) region. This is accompanied with the restriction of molecular mobility and the elevation of glass transition temperature (Tg). Conversely, TiO2-g-PMMA nanoparticles with well-defined cross-linked PMMA shells of 5 nm in thickness are well-distributed in the matrix, without the influence on Tg and the appearance of low-ω plateau. The dispersion of TiO2 is not stable during the thermal annealing of the composite in the melt while the TiO2-g-PMMA nanoparticles demonstrate excellent dispersion stability. Broadband dielectric spectroscopies indicate that TiO2 influenced the molecular relaxations of αa and αc, while the effect of TiO2-g-PMMA was negligible. Furthermore, the core-shell structured TiO2-g-PMMA nanoparticles produced considerable smaller interfacial polarization than TiO2 in the composites.