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Hydrogen-bonded bent-core blue phase liquid crystal complexes containing various molar ratios of proton acceptors and donors
(2016-01-01)
Han, Chun-Chieh
;
Chou, Yu-Chaing
;
Chen, San-Yuan
;
Lin, Hong-Cheu
;
材料科學與工程學系
Various hydrogen-bonded (H-bonded) bent-core liquid crystal complexes consisting of pyridyl and benzoic acid derivatives were synthesized and compared with their covalent analogues in this study. The molar ratios of pyridyl and benzoic acid derivatives could be tuned to form various H-bonded liquid crystal (LC) diads (with 1 : 1 molar ratio of H-acceptors T and H-donors D) and complexes (with different molar ratios of T and D). By insertion of H-bonds into different positions of bent-core supramolecules, the mesophasic properties of H-bonded bent-core LC complexes were optimized, which could facilitate the most suitable LC components and compositions to be utilized in H-bonded blue phase (BP) LC complexes. In BPLC complexes, the molar ratios, alkyl chain lengths, the lateral fluoro-substitution and the chiral center of H-bonded bent-core supramolecules would affect the temperature ranges of BPs. Accordingly, H-bonded bent-core complex P(III)C9/A(II)F* (3/7 mol mol(-1)) displayed the widest BPI range of Delta T-BPI = 12.0 degrees C at the correspondent H-acceptor T = PIIIC9 and H-donor D = A(II)F*. Since the covalent-bonded bent-core mixture only had narrow ranges of BPIII, we could summarize that the introduction of H-bonds into the bent-core center effectively stabilizes the BPs and easier induces the BPI.
Novel asymmetrical single- and double-chiral liquid crystal diads with wide blue phase ranges
(2015-01-01)
Wei, Chong-Lun
;
Chen, Te-Cheng
;
Raghunath, Putikam
;
Lin, Ming-Chang
;
Lin, Hong-Cheu
In this study, two series of novel asymmetrical single- and double-chiral liquid crystal diads using a central linker to link two different mesogenic cores were successfully synthesized. The effects of the position of chiral centers and the number of aromatic rings on the mesomorphic and electro-optical properties were investigated. We found that diads III-N (where N = A, B, C and D) have better mesophasic properties than II-N (where N = A, B, C, D and E). Compared with III-C with a chiral center at the terminal alkoxyl chain, diad III-D exhibited the widest temperature range of BPI (ca. 31 degrees C) as the chiral center was introduced to the central linker. Besides III-D, BPs were also observed in diads II-B and III-B with a chiral center at the central spacer. According to our experimental results and molecular modeling, the mesomorphic properties and temperature ranges of BPs will be affected by the values of biaxiality and dipole moment, along with the bent shape of molecular geometry. Therefore, we demonstrated the first example of asymmetrical single- and double-chiral liquid crystal diads involved chiral centers located at the central linker to exhibit BPs, including the mesophases of BPI and BPIII, which might offer new BP single-components to the future applications of eutectic liquid crystal mixtures with wide BP ranges.
Hydrogen-bonded effects on supramolecular blue phase liquid crystal dimeric complexes
(2015-01-01)
Wei, Chong-Lun
;
Chen, Te-Cheng
;
Raghunath, Putikam
;
Lin, Ming-Chang
;
Lin, Hong-Cheu
In this study, a series of novel asymmetric hydrogen-bonded (H-bonded) dimeric complexes D/P and D/P* (proton donors D = A, A*, AF and AF*) were synthesized and self-assembled by appropriate molar ratios of H-donors (A, A*, AF and AF*) and H-acceptors (P and P*). In addition, the influences of the lateral fluoro-substituent of H-donors, the number (along with the position) of chiral centers and the molar ratio of H-donors and H-acceptors on the mesophasic behaviours (e.g., BPs) of asymmetric H-bonded dimeric complexes are investigated. Interestingly, the blue phase (i.e., BPI) was observed in complexes A*/P, A*/P*, AF*/P and AF*/P* containing at least a chiral center in H-donors (A* and AF*), including the widest BPI ranges of complexes AF*/P* (ca. 6 degrees C and 13 degrees C for 1 : 1 and 3 : 1 mol, respectively). For the first time, the hydrogen-bonded effects on supramolecular blue phase LCs are compared with their analogous covalent diads. Based on our theoretical calculation, we discovered that the bend angle plays an important role in manipulating the existence of the blue phase, which is preferred to appear at the bend angle within 132.1-152.9 degrees. Hence, owing to inappropriate bend angles, both H-bonded dimeric complex A/P* and covalent diad A*-P (with bend angles of 162.0 degrees and 126.5 degrees, respectively) did not possess any blue phase.
LC mixture with promoted electro-optical properties for LCD applications by using a highly UV-resistant dopant
(2015-04-01)
Liu, Shih-Hsien
;
Yang, Po-Jen
;
Lin, Hong-Cheu
;
材料科學與工程學系
;
Department of Materials Science and Engineering
A highly ultraviolet (UV)-resistant dopant 3HBBTfV consisting of an alpha-trifluomethyl vinylbenzene (TfV) moiety was synthesized and mixed with a commercial LC host (A) to promote its dielectric anisotropy in LC mixture C (A:3HBBTfV = 9:1 w/w). Their electric-optical properties were studied and compared with those of an analogous commercial LC mixture B composed of LC mixture A (as a commercial host) mixed with the same weight ratio (10% wt.) of a commercial component 3HBEBTf containing a 3,4,5-trifluorobenzene (BTf) moiety. The electro-optical properties of voltage holding ratio (VHR) values and voltage-transmission (V-T) curves of LC mixture C were sustained after the UV irradiation. These results showed that dopant 3HBBTfV (acting as an UV stabilizer) demonstrated a higher stability under UV exposure in contrast to commercial component 3HBEBTf. Therefore, LC mixture C (containing UV-resistant dopant 3HBBTfV) exhibited good UV resistance, high dielectric anisotropy, and excellent electro-optical properties. (C) 2015 Optical Society of America
Lateral fluoro-substitution and chiral effects on supramolecular liquid crystals containing rod-like and H-bonded bent-core mesogens
(2016-01-01)
Han, Chun-Chieh
;
Yang, Li-Han
;
Raghunath, Putikam
;
Lin, Ming-Chang
;
Kumar, Rohit
The first series of liquid crystalline supramolecular diads C/D containing asymmetric rod-like and H-bonded bent-core mesogens were designed and synthesised, among which supramolecular diad P*(III)/A*(II) with two chiral centers on both the H-acceptor/H-donor and non-lateral fluoride substitution possessed a wide blue phase (BPI) range of 13.7 degrees C. According to the molecular modeling, a large biaxial parameter (>= 3.2) and an appropriate HTP value (4.2-4.8 mu m(-1)) are the most important factors to stabilize the double twisted cylinder structure (i.e., BPI) in supramolecular diads. Moreover, the bent angles, biaxial parameters and dipole moments of supramolecular diads are mainly affected by the locations and numbers of H-bonds and chiral centers. Not only larger bent angles and biaxial parameters but also smaller dipole moments and HTP values were obtained by removing the lateral fluoride substitution on supramolecular diads to achieve the blue phase of P*(III)/A*(II) (without lateral fluoride substitution). Finally, the special optimal 1 : 1 molar ratio of supramolecular diad P*(III)/A*(II) (i.e., H-donor = 50 mol%) with the widest blue phase range is mainly attributed to its rod-like and H-bonded bent-core mesogens, rather than H-donor = 75 mol% in most supramolecular complexes containing linear H-bonded rod-like mesogens.
Facile rhodamine-based colorimetric sensors for sequential detections of Cu(II) ions and pyrophosphate (P2O74-) anions
(2016-01-01)
Arumugaperumal, Reguram
;
Srinivasadesikan, Venkatesan
;
Lin, Ming-Chang
;
Shellaiah, Muthaiah
;
Shukla, Tarun
Two rhodamine hydrazine derivatives Rh1 and Rh2 with catechol and ether functionalities have been synthesized and utilized towards sequential colorimetric detections of Cu(II) and pyrophosphate (PPi) ions in CH3CN-H2O (v/v = 9 : 1, 5 mM Tris-HCl, pH 7.4) semi-aqueous medium. Notably, Rh1 and Rh2 are the first example of colorimetric rhodamine-based probes for the sequential detections of Cu2+ ion and PPi anion. Based on the significant colorimetric responses (from colorless to pink) of Rh1 and Rh2 to Cu2+ ions, the detection limits were estimated as low as 1.22 x 10(-8) M and 8.0 x 10(-7) M, respectively, which signified the utilities of designed probes towards facile detections of Cu2+ ions. Furthermore, upon the successive addition of PPi ion to Rh1-Cu2+ and Rh2-Cu2+ complexes, it has been altered and restored to its origin of Rh1 and Rh2 via re-coordination of PPi to Cu2+ ion, which was confirmed by color changes from pink to colorless. Moreover, computational DFT calculations provided more insights into HOMO-LUMO structures of rhodamine derivatives and their copper complexes. Additionally, the solid state strip-based colorimetric detections of Cu2+ ion were supplemented as a real time application.
Synthesis and study of hybrid hydrogen-bonded bent-core liquid crystal complexes containing C-60- and Si-based proton donors
(2015-01-01)
Liu, Shih-Hsien
;
Yang, Po-Jen
;
Wei, Chong-Lun
;
Chiang, I. -Hung
;
Liao, Chun-Yen
Novel hydrogen-bonded (H-bonded) C-60- and Si-based bent-core liquid crystal (LC) complexes containing a bent-shaped proton acceptor and C-60- and Si-based single/double armed proton donors were synthesized and mixed to produce hybrid H-bonded LC complexes. The SmCP phases could be introduced in the hybrid LC complexes with a very high C-60-based moiety up to 90 mol%. Among our H-bonded LC complexes, the hybrid LC complexes with low amounts of the C-60-based moiety (<= 24 mol%) possessed the highest spontaneous polarization value (ca. 494 nC cm(-2)), the widest mesophasic range (40.8 degrees C) and the lowest saturated electric field (8.8 V-pp mu m(-1)). Under electric fields of modified triangle waveforms, both series of hybrid H-bonded LC complexes displayed an anti-ferroelectric (AF) to a ferroelectric (FE) polar switching as the C-60-based moiety increased up to 24-50 mol%. Therefore, the hybrid H-bonded LC complexes containing a broad molar ratio (0-90 mol%) of C-60-based moiety revealed a tunable route for the electro-optical applications of C-60-based H-bonded liquid crystals.
A plug-and-measure diagnostic tool for flux, resolution and beam size of a soft X-ray beamline
(2015-09-01)
Wei, Ching-Hsuan
;
Lin, Hong-Cheu
;
Lin, Shang-Wei
;
Yuh, Jih-Young
;
材料科學與工程學系
A compact multi-functional diagnostic tool has been installed for commissioning beamlines at the Taiwan Light Source. For a photon beam, the instrument can measure the photon flux, energy resolution and beam size, consecutively with a photodiode or gold mesh, a windowless gas cell and a movable fluorescence screen viewport. Two gratings with ruling densities of 350 and 1000 lines mm(-1) and dispersing photons of energies from 80 to 1200 eV were calibrated with a photon flux of 10(11) photon s(-1) at slit openings of 50 mu m x 50 mu m; a maximum resolving power of greater than 10000 was certified with an absorption spectra of gaseous samples. Pressure differences over four orders of magnitude were achieved between the ion chamber and the flux measurement chamber with a single capillary differential pumping stage. A sequence of beam profiles was measured by moving continuously in the vicinity of the nominal focal positions. This tool is useful in commissioning or trouble-shooting at most beamlines in a synchrotron facility.
Synthesis and mesomorphic behaviours of a homologous series of 2-(4-alkyloxybenzylidenamino)benzothiazoles
(2014-11-02)
Foo, Kok-Leei
;
Ha, Sie-Tiong
;
Win, Yip-Foo
;
Yeap, Guan-Yeow
;
Lin, Hong-Cheu
The synthesis and characterisation of a series of new rod-shaped liquid crystal (LC), 2-(4-alkyloxybenzylidenamino)benzothiazoles possessing even number of carbon atoms at the alkyloxy chain (CnH2n + 1O-, n=2, 4, 6, 8, 10, 12, 14, 16, 18) are reported. The molecular structures of title compounds were elucidated using FTIR and nuclear magnetic resonance spectroscopic techniques. The phase behaviour of these new compounds was characterised and studied by differential scanning calorimetry and polarising optical microscopy. Lower members (n=2, 4 and 6) did not exhibit mesophase. Octyloxy derivative was monotropic LC. Enantiotropic smectic A phase was observed from n-decyloxy derivatives onward to the last homologous synthesised.
Toward Optimization of Oligothiophene Antennas: New Ruthenium Sensitizers with Excellent Performance for Dye-Sensitized Solar Cells
(2010-08-10)
Yin, Jen-Fu
;
Chen, Jian-Ging
;
Lu, Zong-Zhan
;
Ho, Kuo-Chuan
;
Lin, Hong-Cheu
This paper reports on the design and synthesis of three new ruthenium sensitizers, as well as the optimization of their linear or dendritic light-harvesting oligothiophene antennas to achieve superior device performance. The three new ruthenium sensitizers, [Ru(dcbpy)(obtip)(NCS)(2)] (JF-5, dcbpy = 4,4'-dicarboxylic obtip = 2-(5-octyl-(2,2'-bithiophen)-5'-yl)-1H-imidazo[4,51][1,10]-phenanthroline), [Ru(dcbpy)(ottip)(NCS)(2)] (JF-6, ottip = 2-(5-octyl-2,2',5',2 ''-terthiophen)-5 ''-yl)-1H-imidazo[4,5-f][1,10]-phenanthroline), and [Ru(dcbpy)(dottip)(NCS)(2)] (JF-7, dottip = di-(5-octylthiophen-2-ypthiophen-5-yl)-1H-imidazo[4,5-f][1,10]phenanthroline), were synthesized in a typical one-pot reaction. The ruthenium sensitizer JF-5 incorporating a linear and planar 2,2'-bithiophene antenna showed the best DSCs performance (9.5%; compared to N3, 8.8%). The difference in the performance of these sensitizers demonstrates that elongating the linear and planar light-harvesting antenna result in an enhancement in MLCT intensity, but a reduction in the quantity of dye-loading. This finding not only permitted the power-conversion efficiency in ruthenium sensitizers containing oligothiophene antennas to be optimized, but also points to a promising direction for molecule engineering in DSCs.

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