Organic piezoelectric
materials have recently garnered significant
attention as potential alternatives to ceramics. However, there are
only a handful of reports on single-component molecular crystals exhibiting
piezoelectric properties. Introducing homochirality is one of the
simplest approaches to achieving piezoelectricity in molecular crystals.
Herein, we present an enantiomeric pair of 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 noncentrosymmetric P212121 space group making
them suitable for piezoelectric studies In contrast, the racemic mixture
of these compounds, Rac-2-(((1-(p-tolyl)ethyl)imino)methyl)phenol (
Rac
PTIMP), crystallizes in the centrosymmetric P21/n space group. The noncentrosymmetry
of both
R
PTIMP and
S
PTIMP was confirmed through second harmonic
generation (SHG) measurements, showing the SHG efficiencies of 0.11
and 0.12, respectively, relative to standard potassium dihydrogen
phosphate (KDP). Piezoelectric coefficient (d
33) measurements on a powder-pressed pellet of
S
PTIMP resulted in a d
33 value of 4.7 pC N–1. The piezoelectric energy
harvesting experiments performed on the poled thermoplastic polyurethane
(TPU) composite films of
S
PTIMP resulted in a maximum voltage output of 7.04 V for the 15 wt %
S
PTIMP-TPU composite device. The
energy storage efficacy was also tested by successfully charging a
10 μF capacitor within 100 s using the best-performing 15 wt
%
S
PTIMP-TPU device.