Molecular Mechanism Responsible for Reentrance toIa3dGyroid Phase in Cubic Mesogen BABH(n)

Reassessment of structure of smectic phases: Nano-segregation in smectic E phase in 4-n-alkyl-4′-isothiocyanato-1,1′-biphenyls

“…Essentially the same results were obtained through the maximum entropy analysis, which worked effectively to reveal molecular aggregation/arrangement in nano-segregated cubic LCs. 12,42 Calculated electron densities are shown in Fig. 9.…”

“…The present authors have previously revealed that alkyl chain(s) attached to mesogenic core are molten in any liquid crystalline phases, including the SmE phase. [7][8][9][10] The molten chains stabilize LC phases through a large contribution in entropy term in Gibbs energy, and brings nano-segregated LC phases [such as SmA phase in nCB 11 and a) Electronic mail: kazuya@chem.tsukuba.ac.jp cubic phases in ANBC(n) and BABH(n) 12 ] by serving as an intramolecular solvent (self-solvent).…”

“…12,[33][34][35][36][37][38] Indeed, the phase problem for a bicontinuous Gyroid phase was solved while taking into account the systematic variation of reflection intensities with the alkyl chain length. 12,37 In this paper, we attempt to establish the validity of the model proposed in a previous paper 29 for SmE phase through the analysis of systematics against chain-length n in the X-ray diffraction intensity of neat nTCB. Implications of the aggregation struc- ture are discussed in relation to the intrinsic lyotropic nature of thermotropic smectics.…”

Chemical Programming of the Domain of Existence of Liquid Crystals

“…They depend on the nature of the material and contribute to the stabilization of the different states of matter . For instance, the large and variable entropic contributions of the molten flexible chains to the Gibbs free energy have been exploited for the stabilization of the nanosegregated liquid‐crystalline phases found in alkylcyanobiphenyls (smectic A mesophase), bis‐alkyloxybenzoylhydrazines (cubic mesophase), and alkylisothiocyanatibiphenyls (smectic E mesophase) …”

“…However,c on-trary to Trouton's rule for the vaporization of liquids, the entropy changes, DS tr ,a ccompanying the melting process that transforms as olid into al iquid or al iquid crystal,o rt he isotropization process that transforms al iquid crystal into an isotropic liquid, are not constant.T hey depend on the nature of the materiala nd contribute to the stabilization of the different states of matter. [13] For instance, the large and variable entropic contributions of the moltenf lexible chains to the Gibbs free energy have been exploited for the stabilization of the nanosegregatedl iquid-crystalline phases found in alkylcyanobiphenyls (smectic Am esophase), [14] bis-alkyloxybenzoylhydrazines (cubic mesophase), [15] and alkylisothiocyanatibiphenyls (smectic E mesophase). [16] Consequently,the square of the Hildebrands olubility parameter, d 2 ,p ertinent to the vaporizationo fl iquids, has been replaced by the concept of cohesive free energy density,C FED = ÀDG ref tr /V mol in liquid crystals, in which DG ref tr = DH tr ÀT ref DS tr measures the intermolecular cohesion free energy in the solid or in the liquid-crystalline phase estimated at af ixed reference temperature, T ref (DH tr and DS tr are the enthalpy ande ntropy changes of the incriminated phase transition, respectively).…”