Browsing by Author "Yang, Po-Jen"

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Configuration Effects of H-Bonded Sites and Rigid Core Lengths on H-Bonded Banana-Shaped Liquid Crystalline Supramolecules Consisting of Symmetric Trimers and Asymmetric Heterodimers
(2009-11-05)
Wang, Ling-Yung
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Chiang, I-Hung
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Yang, Po-Jen
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Li, Wan-Sheung
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Chao, I-To
Several series of novel banana-shaped H-bonded symmetric trimers (with two H-bonds) and asymmetric heterodimers (with one H-bond) were self-assembled by appropriate molar ratios of proton donors (H-donors) and acceptors (H-acceptors). The influences of H-bonded linking positions and aromatic ring numbers (4-8 aromatic rings in the rigid cores) as well as the chain lengths (n, m = 12 or 16, respectively, in the flexible parts) on the mesomorphism and the switching behavior of the bent-core supramolecules were evaluated and theoretically analyzed. Except for the supramolecular structures with longer rigid cores or shorter flexible chains possessing the rectangular columnar (Col(r) or Bl) phase, the SmC(A)P(A) phase was revealed in most supramolecular asymmetric heterodimers and switched to the SmC(S)P(F) phase by applying electric fields. The polar smectic C phase was dominated for those with H-bonded sites apart from the core center. Interestingly, the SmA and nematic phases were observed in H-bonded asymmetric dimers with H-bonded sites close to the core center, which theoretically proved that the polar smectic C phase was disfavored due to an unfavorable bend angle (smaller than the lower limit of 110 degrees) in the lowest-energy H-bonded conformer. Compared with the fully covalently bonded analogue, lower transition temperatures and lower threshold voltages were developed in the H-bonded asymmetric dimers with the polar smectic C phase. On the basis of the theoretical calculations of molecular modeling, the existence of polar switching behavior in the polar smectic C phase of asymmetric heterodimers; was proven to be associated with their configurations with higher dipole moments and suitable bend angles. Furthermore, the lack of polar switching behavior in supramolecular symmetric trimers, which exhibited the regular SmC phase with weak electrical stabilities, was related to their configurations with smaller dipole moments and confirmed by theoretical calculations.
LC mixture with promoted electro-optical properties for LCD applications by using a highly UV-resistant dopant
(2015-04-01)
Liu, Shih-Hsien
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Yang, Po-Jen
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Lin, Hong-Cheu
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材料科學與工程學系
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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
Novel Reversible Chemosensory Material Based on Conjugated Side-Chain Polymer Containing Fluorescent Pyridyl Receptor Pendants
(2011-07-21)
Chu, Hsuan-Chih
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Lee, Yu-Hsien
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Hsu, Shou-Jen
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Yang, Po-Jen
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Yabushita, Atsushi
A novel light-emitting monomer M1 and its side-chain polymer PI containing three conjugated aromatic pendants, including one pyridyl terminus, were successfully synthesized via Wittig and Pd-catalyzed Heck coupling reactions. The fluorescence of polymer P1 was efficiently quenched upon addition of different metal ions due to the facile energy transfers from the pendent groups of polymer PI to specific metal ions. Among these metal ions, PI exhibited extraordinary sensory selectivities for Ni(2+) and Cu(2+) ions over the other metal ions due to the stronger binding capabilities of Ni(2+) and Cu(2+) ions with polymer P1. From the time-resolved fluorescence (TRF) signals in photoluminescence spectra, the emergences of tau(1) decay components in polymer complexes (P1+Ni(2+)) and (P1-FCu(2+)) clearly indicated that their TRF traces consisted of two contributions, one from the complexes (tau(1)) and the other from free polymer P1 (tau(2)). Upon addition of Ni(2+) and Cu(2+) ions, polymer PI showed faster decay time constants (tau(1)) of metal ion quenching on TRF signals (i.e., better quenching efficiencies on photoluminescence) than its monomer M1. Furthermore, the on-off-on fluorescent switching behavior by adding a tridentate ligand 1,1,4,7,7-pentamethyl-diethylenetriamine (PMDTA) to the polymer complex (P1+Cu(2+)),for several successive cycles demonstrated a superior reusable chemosensor of P1 for further applications.
Polymeric Dopant Effects of Bent-Core Covalent-Bonded and Hydrogen-Bonded Structures on Banana-Shaped Liquid Crystalline Complexes
(2010-02-15)
Yang, Po-Jen
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Wang, Ling-Yung
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Tang, Chieh-Yin
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Lin, Hong-Cheu
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材料科學與工程學系
Two series of banana-shaped liquid crystalline (LC) H-bonded complexes HP(m)/CB(n) (i.e., bent-core H-bonded side-chain homopolymer HP mixed with bent-core covalent-bonded small molecule CB) and CP(m)/HB(n) (i.e., bent-core covalent-bonded side-chain homopolymer CP mixed with bent-core H-bonded small molecular complex HB) with various m/n molar ratios were developed. The bent-core covalent- and H-bonded structural moieties were homopolymerized in the banana-shaped LC H-bonded complexes HP(m)/CB(n) and CP(m)/HB(n), respectively. The influences of m/n molar ratios (polymeric moieties vs. small molecular moieties) on the mesomorphic and electro-optical properties of both banana-shaped LC H-bonded complexes HP(m)/CB(n) and CP(m)/HB(n) were investigated. The polar smectic phases could be achieved and stabilized by smaller contents of polymeric dopants in banana-shaped LC H-bonded complexes, such as HP1/CB10, HP1/CB15, CP1/HB10, and CP1/HB15, which possessed tunable spontaneous polarization (Ps) values according to the molar ratios of m/n, that is, lower Ps values obtained in H-bonded complexes HP(m)/CB(n), and CP(m)/HB(n) with higher ratios of H-bonded moieties (larger m/n molar ratios), respectively. (C) 2010 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 48: 764-774, 2010
Quenching effects of gold nanoparticles in nanocomposites formed in water-soluble conjugated polymer nanoreactors
(2012-02-17)
Yang, Po-Jen
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Chu, Hsuan-Chih
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Lee, Yu-Hsien
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Kobayashi, Takayoshi
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Chen, Te-Cheng
In this paper we describe the first example of the in situ synthesis of gold nanoparticles (AuNPs) in the presence of a water-soluble conjugated polyfluorene (NPF) presenting pendent ammonium groups, with the polymer acting as an aqueous surfactant and providing fluorescent nanoreactors. Using this approach, we produced well-dispersed NPF-AuNP nanocomposites without the need for any additional reducing agents. The photoluminescence emission intensity of NPF-AuNP nanocomposite solution was quenched to a greater extent upon increasing the concentration of AuNPs, presumably through energy transfer or electron transfer from the fluorescent polymer to the metal nanoparticles. Through variations in the degrees of protonation and deprotonation of the amino groups of NPF at different values of pH, we found that the extent of quenching of AuNPs in NPF-AuNP nanocomposite solutions was directly related to the adsorption and desorption behavior of NPF on the metal surfaces. Transmission electron microscopy revealed that the greatest aggregation of AuNPs in the nanocomposite solution occurred at pH 3. suggesting that the ammonium groups (RNMe2 at pH 8.5; RNMe2H+ at pH 3) of the polymer side chains adsorbed onto the AuNP surfaces under these conditions. Distinct time-resolved fluorescence signals of the AuNP-quenched NPF polymers at different values of pH confirmed the interactions between these species. (C) 2012 Elsevier Ltd. All rights reserved.
Recoverable fluorescence chemosensors for Ni2+ ions based on hydrogen-bonded side-chain copolymers presenting pendent benzoic acid and pyridyl receptor units
(2012)
Yang, Po-Jen
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Chu, Hsuan-Chih
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Chen, Te-Cheng
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Lin, Hong-Cheu
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材料科學與工程學系
In this study we synthesized the novel fluorescent conjugated homopolymers P1 and P4 and the copolymers P2 and P3 containing proton-acceptor (pyridyl receptor) M1 monomer units and proton-donor (benzoic acid) M2 monomer units and investigated them as recoverable chemosensors for Ni2+ ions (based on adjusting the fluorescence energy transfer between the M1 and M2 moieties through varying the degree of hydrogen bonding). The levels of available (i.e., non-hydrogen-bonded) pyridyl receptors in the copolymers P2 and P3 were modified using different molar ratios of the pyridyl monomer M1 and the benzoic acid monomer M2. Significant chelation of the Ni2+ ions by the fluorescent homopolymers P1 and P4 and the copolymers P2 and P3 was evident by their distinct fluorescence quenching behaviors; the specific quenching constants (K-SV) decreased in the order P1 > P2 > P3 > P4, following the trend of the molar ratios of pyridyl receptors. When we added a third component, cyclodextrin (CD), to cap the benzoic acid moieties and, thereby, disrupt the hydrogen bonding between the M1 and M2 moieties in the copolymers P2 and P3, the levels of available pyridyl receptors in the recoverable chemosensor copolymers increased, resulting in relatively higher quenching constants for the P2 + CD, P3 + CD and blend (P1/P4) + CD systems. Fluorescence decay experiments revealed that the addition of CD also increased the fluorescence quenching efficiencies of the copolymers P2 and P3 towards Ni2+ ions. Such supramolecular (hydrogen-bonded) side-chain fluorescent copolymers might have practical applicability as recoverable and/or adjustable chemosensors.
Study of Supramolecular Side-Chain Copolymers Containing Light-Emitting H-Acceptors and Electron-Transporting Dendritic H-Donors
(2008-12-23)
Yang, Po-Jen
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Wu, Chung-Wen
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Sahu, Duryodhan
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Lin, Hong-Cheu
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材料科學與工程學系
A novel light-emitting hydrogen-bonded (H-) acceptor PBB (M1) containing three conjugated aromatic rings, including one pyridyl terminus and two lateral methoxyl groups (on the middle ring), was successfully synthesized via Horner-Wadsworth-Emmons (HWE) olefination and Sonogashira coupling reaction. Moreover, different molar ratios of light-emitting H-acceptor monomer PBB (MI) and hole-transporting monomer CAZ (M2) bearing a carbazole unit were copolymerized through free radical polymerization to obtain light-emitting and hole-transporting H-acceptor copolymers (P1-P5). H-acceptor copolymers P3 and P4 were complexed with different generations of dendritic H-donors (G1COOH-G3COOH) bearing 1,3,4-oxadiazole (OXD) dendrons and terminal benzoic acids via H-bonded self-assembly to form supramolecular side-chain copolymers (i.e., H-bonded dendritic complexes). In contrast to H-acceptor homopolymer P1(HPBB), H-acceptor copolymers P2-P4 incorporated with carbazole (CAZ) moieties effectively enhance the glass transition temperatures (T(g)s) and minimize the interchain interations of the light-emitting H-acceptor units, and similar effects occur in their H-bonded dendritic complexes. In addition, red shifts of photoluminescence (PL) emissions in H-bonded dendritic complexes can be tuned up to 61 nm. Furthermore, H-bonded dendritic complexes excited at 305 nm of OXD absorption can create a stronger fluorescence than that excited at 397 nm of PBB absorption, indicating that the intensity of the sensitized emission of PBB (by energy transfer from OXD absorption at 305 nm) is even stronger than that of a direct emission of PBB (by merely PBB absorption at 397 nm). The OXD dendritic wedges in H-bonded dendritic complexes can lower the LUMO energy levels and provide a better electron injection property. H-acceptor polymer P4 and its H-bonded dendritic complexes showed electroluminescence (EL) emissions in the range of 464-519 nm from blue to green. In addition, a PLED device containing H-bonded dendritic complex P4/G1COOH showed an EL emission of 519 nm under a turn-on voltage of 6.5 V. with a maximum luminance of 408 cd/m(2) at 18 V and a luminance efficiency of 0.39 cd/A at 100 mA/cm(2), respectively.
Substrate Noise Suppression Technique for Power Integrity of TSV 3D Integration
(2012)
Yang, Po-Jen
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Huang, Po-Tsang
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Hwang, Wei
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電子工程學系及電子研究所
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Department of Electronics Engineering and Institute of Electronics
In this paper, a substrate noise suppression technique is proposed for the power integrity of TSV 3D integrations. This substrate noise suppression technique reduces both substrate and TSV coupling noises using active substrate decouplers (ASDs) to absorb the substrate noise current. Additionally, the ASD placing is also presented to suppress noises effectively for different 3D structures. For a processor-memory stacking integration, the ground bouncing noises can be reduced by 44.1% via the noise suppression technique. The proposed substrate noise suppression technique can enhance the power integrity of TSV 3D-ICs by reducing the coupling substrate noises.
Supramolecular Assembly of H-Bonded Side-Chain Polymers Containing Conjugated Pyridyl H-Acceptor Pendants and Various Low-Band-Gap H-Donor Dyes Bearing Cyanoacrylic Acid Groups for Organic Solar Cell Applications
(2009-11-15)
Liang, Tzung-Chi
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Chiang, I-Hung
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Yang, Po-Jen
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Kekuda, Dhananjay
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Chu, Chih-Wei
Novel supramolecular side-chain polymers were constructed by complexation of proton acceptor (H-acceptor) polymers, i.e., side-chain conjugated polymers P1-P2 containing pyridyl pendants, with low-band-gap proton donor (H-donor) dyes S1-S4 (bearing terminal cyanoacrylic acids) in a proper molar ratio. Besides unique mesomorphic properties confirmed by DSC and XPD results, the H-bonds of supramolecular side-chain structures formed by pyridyl H-acceptors and cyanoacrylic acid H-donors were also confirmed by FTIR measurements. H-donor dyes S1-S4 in solid films exhibited broad absorption peaks located in the range of 471-490 nm with optical band-gaps of 1.99-2.14 eV. Furthermore, H-bonded polymer complexes P1/S1-P1/S4 and P2/S1-P2/S4 exhibited broad absorption peaks in the range of 440-462 nm with optical band-gaps of 2.11-2.25 eV. Under 100 mW/cm(2) of AM 1.5 white-light illumination, the bulk heterojunction polymer solar cell (PSC) devices containing an active layer of H-bonded polymer complexes P1/S1-P1/S4 and P2/S1-P2/S4 (as electron donors) mixed with [6,6]-phenyl C(61) butyric acid methyl ester (i.e., PCBM, as an electron acceptor) in the weight ratio of 1:1 were investigated. The PSC device containing H-bonded polymer complex P1/S3 mixed with PCBM (1:1 w/w) gave the best preliminary result with an overall power conversion efficiency (PCE) of 0.50%, a short-circuit current of 3.17 mA/cm(2), an open-circuit voltage of 0.47 V, and a fill factor of 34%. (C) 2009 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 47: 5998-6013, 2009
Surface Modification of Gold Nanorods by Grafting Fluorene-Based Conjugated Copolymers Containing Thiol-Pendants
(1970-01-01)
Sahu, Duryodhan
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Chu, Hsuan-Chih
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Yang, Po-Jen
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Lin, Hong-Cheu
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材料科學與工程學系
"Two conjugated surfactants of monomer TF and polymer PTF with pendant thiol groups are synthesized for surface modifications of gold nanorods (GNRs). Cetyltrimethylammonium bromide (CTAB)-GNRs (without surface-modification) in aqueous solutions are prepared, and the original CTAB surfactant is replaced with TF and PTF due to their thiol-gold grafting reactions. Surface-modified TF-GNRs and PTF-GNRs in THF are obtained. UV-visible spectra provide the grafting evidence of TF and PTF. Compared with TF-GNRs, the PTF-GNRs show better solubility and stability against aggregations of nanorods in THF. TEM and XPS confirm the existence of binding bonds between the sulfur groups of PTF and the gold surface in PTF-GNRs. Compared with polymer surfactant (PTF), the faster PL emission decay in PTF-GNRs match well with the PL quenching of PTF-GNRs. Surface modifications are verified by UV-visible, TEM, XPS, PL and lifetime measurements."
Synthesis and characterization of achiral banana-shaped liquid crystalline molecules containing bisnaphthyl moieties
(2006-05-01)
Yang, Po-Jen
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Lin, Hong-Cheu
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材料科學與工程學系
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Department of Materials Science and Engineering
Three analogous series of symmetric banana-shaped liquid crystalline molecules containing bisnaphthyl units were synthesized and characterized. The effects of linking groups (on the side wings) and lateral meta-fluoro substitutions (on the middle outer rings) on the mesogenic properties were examined. The type of mesophase depends on the lengths of terminal alkoxy chains. Thus, achiral molecules with shorter flexible chains (n = 8) exhibit a rectangular columnar (B-1) phase, while analogous derivatives with longer flexible chains (n = 12) display the B-2 phase. All lateral meta-fluoro substituted analogues (series II) possess the lowest isotropization temperatures and the narrowest mesophasic ranges of the B-1 and B-2 phases. The B-1 and B-2 phases were confirmed by X-ray diffraction, polarizing optical microscopy (POM) and electro-optical (EO) switching experiments. An electric field-induced transition from an antiferroelectric (tristable) state to a ferroelectric (bistable) state was observed in the EO measurements. Spontaneous polarization (by switching current response), tilt angle of chiral domains (by POM), and transmittance -voltage measurements of the B-2 phase in related compounds have been surveyed in this study.
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
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Yang, Po-Jen
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Wei, Chong-Lun
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Chiang, I. -Hung
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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.