Molecular dipole orientation controlled variation in nanoscale ferroelectricity and surface potential in P(VDF-TrFE) polymer

Research on nanoscale piezoelectricity and ferroelectricity in polymers has recently generated a great deal of attention due to stress confinement phenomena.^1,2 In this work, we demonstrate how the nanoconfinement driven morphological modification of a model ferroelectric polymer, poly(vinylidenefluoride-trifluoroethylene) (P(VDF-TrFE) into nanoparticles (0D), nanofibers (1D), and thin films (2D) affects molecular dipole orientation on the piezoelectric and ferroelectric capabilities. The molecular dipoles in 0D nanoparticles are found to be parallel to the substrate or face-on orientation, whereas they are perpendicular or in edge-on orientation in 1D and 2D nanostructures.3 The piezoresponse force microscopic (PFM) study reveals that the dipole orientation significantly controls the nanoscale piezo- and ferro-electric functionalities. Further study with Kelvin probe force microscopy (KPFM) revealed that different dipole orientation tunes the surface potential of the nanostructures. The surface potential from 0D, 1D to 2D nanostructures range from ~( -4) mV, ~(-370) mV to ~(-125) mV in 2D nanostructure, respectively. This wide range of surface potential tunability can further be utilized in functional devices such as ferroelectric photovoltaics, triboelectric nanogenerators. This study offers a comprehensive understanding on effect of molecular dipole orientation on the material properties in dimensionally confined nanostructures of P(VDF-TrFE).

References:

1. J. Mater. Chem. C 2013, 1, 2618-2638.

2. Adv. Sci. 2016, 3, 1500358.

3. Langmuir 2012, 28, 10310-10317.