Cholesterol Cocrystal Ferroelectrics Modulated by Solvent Effect.

Cholesterol (CHOL) is an inherently biodegradable material with multiple chiral centers, being an essential component for cell membranes. Considering the close relationship between chirality and ferroelectric feature, this compound with chiral-polar structure is an intrinsic polar material. However, the ferroelectricity of CHOL crystals has never been found to date. Herein, a series of ferroelectric cocrystals of CHOL methanol (CHOL-MeOH) and CHOL ethanol (CHOL-EtOH) have been constructed through the solvent effect. It is found that the introduction of some solvent molecules containing hydroxyls such as methanol and ethanol can reduce the acceptor···donor length and thus form a 1D electroactive channel and further induce ferroelectricity in CHOL. Based on the density functional theory (DFT) calculation analyses represented by CHOL-EtOH, the largely decreased maximum energy barrier for the polarization reversal of ≈50% suggests that the electric polarization of the cocrystal is much easier to be reoriented under the external electric field through the solvent effect. These ferroelectric materials show good biocompatibility and biodegradability through in vitro and in vivo evaluation. These attributes make these CHOL cocrystals good candidates for the application of next-generation smart implantable electronic devices. This work sheds light on the chemical design of biodegradable ferroelectrics in biomaterials.