172160-93-9Relevant academic research and scientific papers
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)
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.
Topological ferroelectric bistability in a polarization-modulated orthogonal smectic liquid crystal
Zhu, Chenhui,Shao, Renfan,Reddy, R. Amaranatha,Chen, Dong,Shen, Yongqiang,Gong, Tao,Glaser, Matthew A.,Korblova, Eva,Rudquist, Per,MacLennan, Joseph E.,Walba, David M.,Clark, Noel A.
supporting information; experimental part, p. 9681 - 9687 (2012/07/14)
We report a bent-core liquid crystal (LC) compound exhibiting two fluid smectic phases in which two-dimensional, polar, orthorhombic layers order into three-dimensional ferroelectric states. The lower-temperature phase has a uniform polarization field which responds in an analog fashion to applied electric field. The higher-temperature phase is a new smectic state with periodic undulation of the polarization, structurally modulated layers, and a bistable response to applied electric field which originates in the periodically splay-modulated bulk of the LC rather than by surface stabilization at the cell boundaries.
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
supporting information; experimental part, 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
Low-temperature and wide ferroelectric phase in mixtures of chiral and non-chiral tilted smectic C-type liquid crystals
Liao, Chien-Tung,Wu, Zheng-Long,Wu, Nien-Chieh,Liu, Jung-Yo,Jiang, Ming-Hui,Zou, Sing-Fang,Lee, Jiunn-Yih
experimental part, p. 3 - 15 (2011/09/13)
A new liquid crystal of siloxane dimer with an achiral swallow-tail, C11Si3C11, was synthesized and mixed with a chiral material of 4′-(1-butoxy-1-oxopropan-2-yloxy)biphenyl-4-yl 3-bromo-4-[9-(1,1,2,2,3,3, 3-hepta-methyltrisiloxanyl)nonyloxy) benzoate, C9
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.
Bent-core mesogens with branched carbosilane termini: Flipping suprastructural chirality without reversing polarity
Zhang, Yongqiang,O'Callaghan, Michael J.,Baumeister, Ute,Tschierske, Carsten
supporting information; experimental part, p. 6892 - 6896 (2009/04/06)
(Figure Presented) Back flip: Field-induced transformations between the two homogeneously chiral enantiomers of a bent-core mesogen (see picture) take place by two different mechanisms (A and B). Their combination leads to an unexpected field-induced chirality flipping (C) between the oppositely tilted structures without polarity reversal.
