1225283-79-3Relevant articles and documents
Achiral bent-core molecules with a series of linear or branched carbosilane termini: Dark conglomerate phases, supramolecular chirality and macroscopic polar order
Zhang, Yongqiang,Baumeister, Ute,Tschierske, Carsten,O'Callaghan, Michael J.,Walker, Christopher
, p. 2869 - 2884 (2011/11/14)
New organic-inorganic hybrid materials that combine a bent π-conjugated aromatic core with one linear or branched carbosilane unit have been synthesized and investigated, with respect to their self-assembly in liquid crystalline (LC) phases, by means of polarizing microscopy, differential scanning calorimetry (DSC), X-ray diffraction (XRD), and electro-optical techniques. Most of these achiral compounds show spontaneous symmetry breaking into chiral superstructures that represent conglomerates with macroscopic domains of opposite handedness. These fluid chiral superstructures can be frozen into the glassy state and, for one of the compounds, chirality was switched under the application of a special waveform of an applied external electric field between two enantiomeric states. This flipping of supramolecular chirality occurs between oppositely tilted structures, which represents a new mode of chirality switching. Besides spontaneous chirality, these materials show polar order, leading to ferroelectric (FE) and antiferroelectric (AF) switching modes. For one compound with a highly branched carbosilane unit, a temperature-, voltage-, and frequency-dependent reversible transition from AF switching with inversion of chirality to FE switching with retention of chirality was observed. Models were developed to explain the experimental observations, based on enthalpic and entropic contributions of distinct supermolecular arrangements in these soft matter systems.
