A Highly Electrostrictive Salt Cocrystal and the Piezoelectric Nanogenerator Application of Its 3D-Printed Polymer Composite

Abstract

Ionic cocrystals with hydrogen bonding can form exciting materials with enhanced optical and electronic properties. We present a highly moisture-stable ammonium salt cocrystal) crystallizing in the polar monoclinic C2 space group. The asymmetry in (p-TEA)(p-TEAH)•PF 6 was induced by its chiral substituents, while the polar order and structural stability were achieved by using the octahedral PF 6 − anion and the consequent formation of salt cocrystal. The ferroelectric properties of (p-TEA)(p-TEAH)•PF 6 were confirmed through P−E loop measurements. Piezoresponse force microscopy (PFM) enabled the visualization of its domain structure with characteristic "butterfly" and hysteresis loops associated with ferroand piezoelectric properties. Notably, (p-TEA)(p-TEAH)•PF 6 exhibits a large electrostrictive coefficient (Q 33 ) value of 2.02 m 4 C −2 , higher than those found for ceramic-based materials and comparable to that of polyvinylidene difluoride. Furthermore, the composite films of (p-TEA)(p-TEAH)•PF 6 with polycaprolactone (PCL) polymer and its gyroid-shaped 3D-printed composite scaled-up device, 3DP-Gy, were prepared and evaluated for piezoelectric energy-harvesting functionality. A high output voltage of 22.8 V and a power density of 118.5 μW cm −3 have been recorded for the 3DP-Gy device. Remarkably, no loss in voltage outputs was observed for the (p-TEA)(p-TEAH)•PF 6 devices even after exposure to 99% relative humidity, showcasing their utility under extremely humid conditions.

Homochirality-Induced Piezoelectricity in a Single-Component Molecular System

“…Piezoelectric energy harvesting from all-organic piezoelectric materials is still in its initial stages of investigation due to the abovementioned difficulties researchers face in crystallizing organic materials in suitable noncentrosymmetric space groups. − Herein, we present an enantiomeric pair of single-molecule organic Schiff base compounds ( R )-2-(((1-( p -tolyl)ethyl)imino)methyl)phenol ( R PTIMP ) and ( S )-2-(((1-( p -tolyl)ethyl)imino)methyl)phenol ( S PTIMP ) crystallizing in the piezoelectrically active P 2 1 2 1 2 1 space group. Their racemic analogue Rac -2-(((1-( p -tolyl)ethyl)imino)methyl)phenol ( Rac PTIMP ) crystallizes in the centrosymmetric P 2 1 / n space group, emphasizing the role of homochirality in realizing the desired functionality.…”