Synergistic Enhancement of β-Phase Crystallization in Poly(vinylidene fluoride) by Adding Organo-Modified Montmorillonite and Cellulose Nanofiber

The synergistic effects of adding organo-modified montmorillonite (OMMT) and cellulose nanofiber (CNF) to poly-(vinylidene fluoride) (PVDF) on its crystallization behavior were systematically investigated, with particular focus on the formation of the ferroelectric β-phase in the resulting composite films. The composite films were fabricated using a solvent-casting method using <i>N</i>,<i>N</i>-dimethylformamide as the solvent and varying filler compositions, and the films were characterized by using wide-angle X-ray diffraction, Fourier-transform infrared spectroscopy, differential scanning calorimetry, and transmission electron microscopy. The results demonstrated that OMMT acts as an epitaxial nucleating agent for β-phase crystallization, and CNF promotes nucleation. A slight increase in crystallization temperature (≈2 °C) was observed with CNF alone, compared with a considerable increase (≈12 °C) with the addition of OMMT. Among the PVDF/OMMT, PVDF/CNF, and PVDF/OMMT/CNF composites, the PVDF/OMMT/CNF composite exhibited the highest β-phase crystal fraction due to the enhanced dispersibility of OMMT and CNF when combined. This study highlights the potential of synergistic filler efficiency in developing advanced ferroelectric and piezoelectric PVDF for high-performance applications.