Influence of process conditions and effect of functionalization in inducing time dependent polymorphic states in single walled carbon nanotube incorporated poly(vinylidene fluoride)

Abstract

Poly(vinylidene fluoride) (PVDF) based composites were prepared using the compatibilizing properties of optimally functionalized single walled carbon nanotubes (SWCNTs). Our previous studies revealed that acid treatment of SWCNTs for 4 h (FSWCNT-4) incorporates maximum concentration of –COOH functional groups on nanotube surface with least defects. Therefore, PVDF-SWCNT composites were prepared by dispersing FSWCNT-4 in PVDF through ultrasonication. Here time of ultrasonication controls the crystallization of the polymer either in the electroactive γ phase or in the non-electroactive α phase. γ polymorphic state is easily obtained with very low concentration of FSWCNT-4 followed by ultrasonication for just 5 min. The chemical composition of the composites is studied using X-ray photoelectron spectroscopy confirming the inclusion of nanotubes in PVDF. Computational analysis explained the role of ultrasonication in providing the required energy for the transformation from α phase to γ phase apart from establishing the favourable site of interaction of PVDF with FSWCNT-4. The micrographs of the composite showed scrolled lamellar features of γ phase morphology. PVDF-FSWCNT-4 composites showed 54% higher capacitance compared to its unfilled counterpart with significant improvement in mechanical properties due to stronger interactions between H atom with positive charge in PVDF and “O” atom with π orbital in FSWCNT-4.