809285-98-1Relevant academic research and scientific papers
Chirality and macroscopic polar order in a ferroelectric smectic liquid-crystalline phase formed by achiral polyphilic bent-core molecules
Dantlgraber, Gert,Eremin, Alexei,Diele, Siegmar,Hauser, Anton,Kresse, Horst,Pelzl, Gerhard,Tschierske, Carsten
, p. 2408 - 2412 (2002)
In conventional fluids the molecular dipole moments of the individual molecules cancel out, which leads to a macroscopic apolar structure. Directed molecular design using microsegregation and tailoring the molecular shape of compounds such as 1, can lead
Biphenyl based non-symmetrical bent-core mesogens containing a chiral moiety and an olefinic end group
Ocak, Hale,Bilgin-Eran, Belkiz
, p. 19 - 30 (2015/04/22)
New nonsymmetrical bent-core compounds consisting of a biphenyl-3,4'-diol central unit, a chiral terminal chain and an olefinic end group at the other terminus have been synthesized and characterized to study the influence of a chiral moiety, the length of terminal alkenyl chain, and the number of aromatic rings in the rod-like wings which are substituted at the 3- and 4-position of central biphenyl core on mesophase properties of bent-core mesogens. The liquid crystalline properties of the compounds were investigated by differential scanning calorimetry, optical polarizing microscopy, and electro-optic methods. Depending on the length of the olefinic chain and the number of aromatic rings in the rod-like wings, the bent-core compounds with a chiral moiety show B1 type mesophase, polar smectic C phase (SmCP) or nonmesomorphic behavior.
Bent-core compounds with two branched chains: Evidence of a new dark conglomerate mesophase
Ocak, Hale,Bilgin-Eran, Belkiz,Prehm, Marko,Tschierske, Carsten
, p. 4590 - 4597 (2013/07/26)
Biphenyl-3,4′-diol derived bent-core compounds with branched side chains have been synthesized and characterized to study the influence of terminal branched groups on mesophase properties and transition temperatures of bent-core mesogens. The liquid crystalline properties of the compounds were investigated by differential scanning calorimetry, optical polarizing microscopy and X-ray scattering. Depending on the length of the chain, the size of molecular branches and the position of branched chains, either enantiotropic or monotropic rectangular columnar phases were observed. For one of the compounds combining two different branched side chains, a new type of optically isotropic dark conglomerate phase (MIso[*]) was found. It is proposed to be a distorted version of a non-tilted or only slightly tilted B6-like intercalated smectic phase with additional in plane order.
New SmCG phases in a hydrogen-bonded bent-core liquid crystal featuring a branched siloxane terminal group
Chen, Wei-Hong,Chuang, Wei-Tsung,Jeng, U-Ser,Sheu, Hwo-Shuenn,Lin, Hong-Cheu
, p. 15674 - 15685 (2011/11/28)
In this study, we synthesized three analogous bent-core molecules, a hydrogen-bonded complex and a covalent-bonded compound with branched siloxane units (H-SiO and C-SiO, respectively) and a hydrogen-bonded complex with an alkyl unit (H-Alk), and investigated the effects of the hydrogen bonding and branched siloxane terminal units on their mesomorphic properties. The covalent-bonded compound C-SiO and the hydrogen-bonded complex H-Alk exhibited typical SmCP phases; in contrast, the hydrogen-bonded complex H-SiO exhibited a series of general tilt smectic (SmCG) phases with highly ordered layer structures (i.e., SmCG2PF-USmCG2P A-SmCG2PF-SmCGPF upon cooling). During the SmCG-type phase transition process, a 2D-modulated ribbon structure transferred into highly ordered layers via undulated layers, as the hydrogen-bonding strength increased with reduced temperatures. As the SmCG domains were aligned under dc electric fields, a gradual decrease in the leaning angle from ca. 60° to 50° (while the tilt angle kept at ca. 31°) could be determined by in situ wide-angle X-ray scattering (WAXS). Combined with Fourier transform infrared and Raman spectroscopic data, our results suggest that the change in the leaning angle was governed by the competition of the hydrogen bonds and microsegregation of siloxane units within the bilayer structure of the hydrogen-bonded complex H-SiO. In addition, the ferroelectric-(antiferroelectric)-ferroelectric transitions proven by the switching current responses in the SmCG-type phases of H-SiO reveal that the polar switching occurred through collective rotations around the long axis of H-SiO. Therefore, novel SmCG phases with a series of highly ordered 2D-structures were induced by the effects of the hydrogen bonding and branched terminal siloxane unit in the bent-core hydrogen-bonded LC complex H-SiO.
Smectic-layer alignments of surface-modified gold nanoparticles in the nanocomposite induced by a hydrogen-bonded bent-core liquid crystalline host under electric fields
Chen, Wei-Hong,Chang, Yi-Ting,Lee, Jey-Jau,Chuang, Wei-Tsung,Lin, Hong-Cheu
, p. 13182 - 13187 (2012/02/02)
Packing tips: The layer spacing of 5.5 nm (see TEM image) of the nanocomposite VPy-SiA/AuNPs-S (5 wt %) under DC/AC electric fields perfectly matches the d spacing of 5.5 nm obtained by in situ XRD measurements under a DC electric field. TEM images revealed that the well-organized packing of layers of surface-modified gold NPs could be induced in the nanocomposite under electric fields. Copyright
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
scheme or table, 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.
TTF-based bent-core liquid crystals
Pintre, Inmaculada C.,Serrano, Jose Luis,Ros, M. Blanca,Ortega, Josu,Alonso, Ibon,Martinez-Perdiguero, Josu,Folcia, Cesar L.,Etxebarria, Jesus,Goc, Faustyna,Amabilino, David B.,Puigmarti-Luis, Josep,Gomar-Nadal, Elba
supporting information; scheme or table, p. 2523 - 2525 (2009/02/04)
The synthesis and characterization of bent-core liquid crystals which incorporate TTF groups is reported; different bent-core mesophases are induced depending on the molecular structure and properties derived from their compact packing have been studied.
Silicon-containing polyphilic bent-core molecules: The importance of nanosegregation for the development of chirality and polar order in liquid crystalline phases formed by Achiral molecules
Keith, Christina,Reddy, R. Amaranatha,Hauser, Anton,Baumeister, Ute,Tschierske, Carsten
, p. 3051 - 3066 (2007/10/03)
Polyphilic molecules composed of a bent aromatic core, oligo(siloxane) units, and alkyl segments were synthesized, and the self-organization of these molecules was investigated. Most materials organize into polar smectic liquid crystalline phases. The swi
Hydrogen-bonded banana liquid crystals
Gimeno, Nelida,Ros, Maria Blanca,Serrano, Jose Luis,De La Fuente, Maria Rosario
, p. 5235 - 5238 (2007/10/03)
Top banana! Hydrogen-bonded bent complexes of benzoic acids (H donor) and nonmesomorphic V-shaped 4′-stilbazoles (H acceptor) give rise to polar smectic C (SmCP, see graphic) mesophases. The multifunctional character of these noncovalent materials is conf
