Formation Mechanism of β-Phase in PVDF/CNT Composite Prepared by the Sonication Method

ABSTRACT: Two poly(vinylidene fluoride)(PVDF)/carbon nanotube (CNT) composites are prepared by solution sonication andmechanical mixture approaches. It is found that R-phase coexists with β-phase in the composite prepared by sonicating the PVDF/CNTmixture solution, while no β-phase can be observed in the composite prepared from the mechanical mixture route. With the help of the density functional theory calculations, it is explained that a large amount of energy is required for transforming trans-gauche-trans-gauche0 (TGTG0) into trans-trans (TT) conformations and the TT molecular chain can be bound on the CNT surface tightly. The emergence of β-phases is independent of zigzag carbon atoms on the CNT surface. The formation mechanism of β-phase is proposed based on the theoretical calculations and experimental results