Ferroelectric materials are characterized by spontaneous electric polarization that can be reversed by inverting an external electric field. Owing to their unique properties, ferroelectric materials have found broad applications in microelectronics, computers, and transducers. Water molecules are dipolar and thus ferroelectric alignment of water molecules is conceivable when water freezes into special forms of ice. Although the ferroelectric ice XI has been proposed to exist on Uranus, Neptune, or Pluto, evidence of a fully protonordered ferroelectric ice is still elusive. To date, existence of ferroelectric ice with partial ferroelectric alignment has been demonstrated only in thin films of ice grown on platinum surfaces or within microdomains of alkali-hydroxide doped ice I. Here we report a unique structure of quasi-one-dimensional ðH 2 OÞ 12n wire confined to a 3D supramolecular architecture of ½Cu I 2 Cu II ðCDTAÞð4,4 0 -bpyÞ 2 n H 4 CDTA, trans-1,2-diaminocyclohexane-N,N,N′,N′-tetraacetic acid; 4,4′-bpy, 4,4′-bipyridine). In stark contrast to the bulk, this 1D water wire not only exhibits enormous dielectric anomalies at approximately 175 and 277 K, respectively, but also undergoes a spontaneous transition between "1D liquid" and "1D ferroelectric ice" at approximately 277 K. Hitherto unrevealed properties of the 1D water wire will be valuable to the understanding of anomalous properties of water and synthesis of novel ferroelectric materials.ab initio molecular dynamics | phase transition | supramolecular nanochannel A n understanding of the properties of water wire and quasi-1D ice confined to a nanoscale channel has important implications for the biological sciences, geoscience, and nanoscience (1-5). The nanoscale channel can endow the water wire and 1D ice with unusual properties that differ from 3D water and ice. Hence, insights into these properties on the molecular level not only can offer explanation of intriguing phenomena such as proton and water transport in cell membranes (2) and the formation of a 1D ice tube with a water chain at the center (5), but can also assist synthesis of new nanochannels to influence the properties of water wire and 1D ice by changing the environment. In this article, our attention will be placed on the spontaneous formation of a 1D ferroelectric ice in a newly synthesized nanochannel.Does standalone single-phase ferroelectric ice exist in nature? This question has fascinated scientists for decades (6)(7)(8)(9)(10)(11)(12)(13)(14). If the single-phase ferroelectric ice does exist, it would have a net polarization toward one direction (15) because of the ordered alignment of the water molecules. However, achieving a standalone and pure 3D ferroelectric ice seems to be a formidable task in the laboratory because the full phase-transformation time required for a bulk 3D ferroelectric ice is estimated to be on the order of 10 5 y (8, 9) without any assistance of dopants as catalysts. To date, all ferroelectric ices produced in the laboratory are low dimensional and in mix...
