Elastic flexibility of ferroelectric supramolecular co-crystals

In recent years, great efforts are paying to design and understand the origins of elastic flexibility of molecular crystals. In this work, we investigate the elastic flexibility of two ferroelectric supramolecular co-crystals, phenazine-chloranilic acid (Phz-H₂ca) and phenazine-bromanilic acid (Phz-H₂ba) for the first time. Both of them show good elastic flexibility while the flexibility of the Phz-H₂ca co-crystal is better. The measurements of mechanical properties show that the Phz-H₂ca co-crystal has larger elastic modulus and smaller hardness value than the Phz-H₂ba co-crystal. The bent co-crystal still keeps the ferroelectric properties. The Raman spectra reveal that the weak hydrogen-bond, halogen-bond and π···π stacking interactions contribute to the observed elastic flexibility of the co-crystals.