Crystallization behaviors and related dielectric properties of semicrystalline matrix in polymer-ceramic nanocomposites

Crystallization behaviors and related dielectric properties of semicrystalline matrix in polymer-ceramic nanocomposites have been systemically investigated by using P(VDF-TrFE) 70/30 mol.% as matrix and Ba_0.5Sr_0.5TiO₃ nanoparticles as filler. It is found that due to the presence of ceramic nanofiller, there are two types of crystals formed in the matrix: one formed on the surface of the ceramic nanoparticles and the other formed in the polymer. The former favors the all-trans β phase due to the interaction between matrix chains and ceramic surface. The later has defects that result in two low-temperature phases: the well-ordered β phase and less-ordered β phase (i.e. β′ phase). The conformation defects of the β′ phase result in it a lower dielectric permittivity than β phase. The proportion of β’ phase decreases with increasing ceramic content and only β phase can be observed in the nanocomposites with a ceramic content higher than 35 vol%. These results were reflected in and confirmed by the DSC analyses and the dielectric properties.