Effect of Elongational Deformation on the Β‐Phase Formation of Poly(vinylidene Fluoride)/Multiwalled Carbon Nanotube Composites and Their Piezoelectric Properties

Abstract

SummaryPoly(vinylidene fluoride) (PVDF), a polymorphic material, has useful electro active properties such as piezo‐, pyro‐, and ferroelectric properties. The piezoelectric crystallization polymorph is the β‐phase which has an all‐trans (TTTT) conformation, i.e., all of its dipoles aligned in the same direction normal to the chain axis. Elongational deformation was applied to poly(vinylidene fluoride)/multiwalled carbon nanotube (MWCNT) nanocomposites. Its effect on the conversion of the α‐phase crystals into the β‐phase crystals and on the piezoelectric properties was investigated. Elongational deformation of PVDF molecules made it easier for the CF2 groups to arrange themselves in the same conformation by reducing the steric hindrance. However, macro‐deformation was dominant in the drawn films, though the interfacial interaction between the functional groups on the MWCNTs and the CF2 dipole of PVDF chains helped the conversion of α‐phase. Uniform distribution of MWCNT in the electrospun films helps efficient charge accumulation at the interface between the MWCNTs and the matrix PVDF molecules. Depolarization effect occurred in the pressed film due to the excessive charge accumulation was not observed, resulting in the high conversion of α‐phase into β‐phase as well as the enhancement of remanent polarization and the mechanical displacement. Added MWCNT helps the film to be extended without rupturing.