Browsing by Author "Jeng, U-Ser"

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Anomalous SAXS for the morphology and metal content of a metallothionein in a metal-atom replacement
(2008-01-01)
Jeng, U-Ser
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Li, Meiyi
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Hsu, I-Jui
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Huang, Yu-Shan
;
Wu, YewChung Sermon
Bispentafluorophenyl-Containing Additive: Enhancing Efficiency and Morphological Stability of Polymer Solar Cells via Hand-Grabbing-Like Supramolecular Pentafluorophenyl-Fullerene Interactions
(2017-12-20)
Hung, Kai-En
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Tsai, Che-En
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Chang, Shao-Ling
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Lai, Yu-Ying
;
Jeng, U-Ser
A new class of additive materials bis(pentafluorophenyl) diesters (BFEs) where the two pentafluorophenyl (C6F5) moieties are attached at the both ends of a linear aliphatic chain with tunable tether lengths (BFS, BF7, and BF13) were designed and synthesized. In the presence of BF7 to restrict the migration of fullerehe by hand-grabbing-like supramolecular interactions induced between the C6F5 groups and the surface of fullerene, the P3HT:PC61BM:BF7 device showed stable device characteristiCs after thermal heating at 150 degrees C for 25, 'IL The morphologies Of the active layers were systematically investigated by optical microscopy, grazing-incidence small-angle X-ray scattering (GISAXS), and atomic force microscopy. The tether length between the two C6F5 groups plays a pivotal role in controlling the intermolecular attractions. BF13 with a long and flexible tether might form a BF13-fullerene sandwich complex that fails to prevent fullerene's movement and aggregation, while BF5 with too short tether length decreases the possibility of interactions between the C6F5 groups and the fullerenes. BF7 with the optimal tether length has the best ability to stabilize the morphology. In sharp contrast, the nonfluorinated BP7 analogue without C6F5-C-60 physical interactions does not have the capability of morphological stabilization, unambiguously revealing the necessity of the C6F5 group. Most importantly, the function of BF7 can be also applied to the high-performance PffBT4BT-20D:PC71BM system, which exhibited an original PCE of 8.80%. After thermal heating at 85 degrees C for 200 h, the efficiency of the Pffi3T4BT-20D:PC71BM:BF7 device only decreased slightly to 7.73%, maintaining 88% of its original efficiency. To the best of our knowledge, this is the first time that the thermabdriven morphological evolution of the high-performance PffBT4BT-20D polymer has been investigated, and its morphological stability in the inverted device can be successfully preserved by the incorporation of BF7. This research also demonstrates that BF7 is not only effective with PC61BM but also to PC71BM.
Competition between Fullerene Aggregation and Poly(3-hexylthiophene) Crystallization upon Annealing of Bulk Heterojunction Solar Cells
(2011-08-01)
Wu, Wei-Ru
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Jeng, U-Ser
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Su, Chun-Jen
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Wei, Kung-Hwa
;
Su, Ming-Shin
Concomitant development of [6,6]-phen-C(61)-butyric acid methyl ester (PCBM) aggregation and poly(3-hexylthiophene) (P3HT) crystallization in bulk heterojunction (BHJ) thin-film (ca. 85 nm) solar cells has been revealed using simultaneous grazing incidence small-/wide-angle X-ray scattering (GISAXS/GIWAXS). With enhanced time and spatial resolutions (5 s/frame; minimum q approximate to 0.004 angstrom(-1)), synchrotron GISAXS has captured In detail the fast growth in size of PCBM aggregates from 7 to 18 nm within 100 s of annealing at 150 degrees C. Simultaneously observed is the enhanced crystallization of P3HT Into lamellae oriented mainly perpendicular but also parallel to the substrate. An Avrami analysis of the observed structural evolution indicates that the faster PCBM aggregation follows a diffusion-controlled growth process (confined by P3HT segmental motion), whereas-the slower development of crystalline P3HT nanograins is characterized by constant nucleation rate (determined by the degree. of supercooling and POW demixing). These two competing kinetics result in local phase separation with space filling PCBM and P3HT nanodomains less than 20 nm in size when annealing temperature is kept below 180 degrees C. Accompanying the morphological development is the synchronized Increase In electron and hole mobilities of the BHJ thin-film solar cells, revealing the sensitivity of the carrier transport of the device on the structural features of PCBM and P3HT nanodomains. Optimized structural parameters, including the aggregate size and mean spacing of the PCBM aggregates, are quantitatively correlated to the device performance; a comprehensive network structure of the optimized BHJ thin film is presented.
Competition between PCBM Aggregation and P3HT crystallization in thin films upon annealing
(2011-01-01)
Jeng, U-Ser
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Wu, Wei-Ru
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Su, Chun-Jen
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Wei, Kung-Hwa
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Su, Ming-Shin
Complementary solvent additives tune the orientation of polymer lamellae, reduce the sizes of aggregated fullerene domains, and enhance the performance of bulk heterojunction solar cells
(2014-01-01)
Liu, Chih-Ming
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Su, Yu-Wei
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Jiang, Jian-Ming
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Chen, Hsiu-Cheng
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Lin, Shu-Wei
In this study we employed 1-chloronaphthalene (CN) and 1,8-diiodooctane (DIO) as binary additives exhibiting complementarily preferential solubility for processing the crystalline conjugated polymer poly[bis(dodecyl)thiophene-dodecyl-thieno[3,4-c]pyrrole-4,6-dione] (PBTC12TPD) and the fullerene [6,6]-phenyl-C-71-butyric acid methyl ester (PC71BM) in chloroform. Using synchrotron grazing-incidence small-/wide-angle X-ray scattering and transmission electron microscopy to analyse the structure of the PBTC12TPD-PC71BM blend films, we found that the binary additives with different volume ratios in the processing solvent allow us to tune the relative population of face-on to edge-on PBTC12TPD lamellae and the size of PC71BM clusters in the blend films; the sizes of the fractal-like PC71BM clusters and the aggregated domains of PC71BM clusters increased and decreased, respectively, upon increasing the amount of DIO, whereas the relative ratio of face-on to edge-on PBTC12TPD lamellae increased upon increasing the amount of CN. When fabricating the photovoltaic devices, the short-circuit current density of the devices with the PBTC12TPD-PC71BM active layer having been processed with the binary additives is higher than that of the device incorporating an active layer processed without any additive. As a result, the power conversion efficiency of a device incorporating an active layer of PBTC12TPD-PC71BM (1 : 1.5, w/w) processed with binary additives of 0.5% DIO and 1% CN in chloroform increased to 6.8% from a value of 4.9%, a relative increase of 40%, for the corresponding device containing the same active layer but processed without any additive.
Effect of Curing on the Porogen Size in the Low-k MSQ/SBS Hybrid Films
(2011)
Chen, Yu-Han
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Jeng, U-Ser
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Leu, Jihperng
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材料科學與工程學系
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Department of Materials Science and Engineering
The interaction between a polystyrene-b-polybutadiene-b-polystyrene (SBS) porogen and a low-k methylsilsesquioxane (MSQ) matrix under different curing profiles and their impact on porogen size were studied by grazing incidence small-angle X-ray scattering, viscosity measurement, and Fourier transform infrared analysis. For slow curing, significant porogen diffusion and aggregation occurred between 100 and 170 degrees C, at which the porogen size increased from 12 to 32 nm. The interaction mechanism between porogen and the MSQ matrix and its correlation with porogen size during the thermal cure process were elucidated. The aggregation of the SBS porogen was greatly influenced by the microstructure of the MSQ matrix at three controlling temperatures; namely, (1) glass transition temperature, T(g) (similar to 100 degrees C), (2) onset temperature (160 degrees C) for transforming cage to network structure, and (3) immobilization temperature (170 degrees C). In contrast, a rapid curing rate enabled the formation of small porogen size (similar to 12 nm) in the hybrid films and yielded better mechanical strength. (C) 2011 The Electrochemical Society. [DOI: 10.1149/1.3529246] All rights reserved.
Effect of Porogen Incorporation on Pore Morphology of Low-k SiCxNy Films Prepared Using PECVD
(2015-01-01)
Tu, Hung-En
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Su, Chun-Jen
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Jeng, U-Ser
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Leu, Jihperng
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材料科學與工程學系
Low-k porous SiCxNy films were prepared through plasma-enhanced chemical vapor deposition, using 1,3,5-trimethyl-1,3,5-trivinylcyclotrisilazane (VSZ) as the matrix precursor and epoxycyclohexane (ECH) as a porogen. The effects of porogen loading and deposition temperature on porogen incorporation, pore morphology, and the properties of porous SiCxNy films were examined. In addition, the impact of film shrinkage and the corresponding nanopore structures after annealing were studied. The porosity of films deposited at 100 degrees C increased from 1.8% to 19.8% when ECH loading increased to 30%, above which the porosity remained nearly constant because of high film shrinkage. The pore size decreased slightly from 4.1 to 3.7 nm when ECH loading increased to 30%, above which the pores became larger and were broadly distributed. By contrast, increasing deposition temperature at 20% ECH loading decreased porogen incorporation and increased film density. The porosities and pore size of films decreased, respectively, when the deposition temperature increased. A short-range ordering of pores was observed only at low deposition temperatures because the N-Si-C cross-linked structures and organic phase were present. Optimized processing parameters facilitated the fabrication of low-k porous SiCxNy films exhibiting 19.8% porosity, 3.7-nm pores, a k value of 3.18, and an elastic modulus of 7.7 GPa. (C) The Author(s) 2014. Published by ECS. All rights reserved.
Envelope Structure of Human eNOS Protein Revealed by Small-Angle X-ray Scattering
(2012-04-01)
Chen, Chun-Yu
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Chen, Pei-Feng
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Hwu, Yeukuang
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Jeng, U-Ser
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Wu, Kun-Yu
We investigate the solution structure of human eNOS protein by using synchrotron small-angle X-ray scattering (SAXS). The pair-correlation analysis of the profile shows the radius of gyration (R-g) and maxima dimension (D-max) of 6.87 +/- 0.03 nm and 22 nm, respectively. The ratio of D-max and R-g revealed that the protein was an extended conformation. The ab initio shape determination and rigid-body calculations were performed to reconstruct the real-space structure of eNOS in solution. The result shows that human eNOS form homodimer form in solution with the closed contact of two oxygenase domains.
Global and Local Structural Changes of Protein Unfolding
(2009)
Shiu, Ying-Jen
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Jeng, U-Ser
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Lin, Sheng-Hsien
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應用化學系
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應用化學系分子科學碩博班
In the mean-field Ising model, the folding-unfolding behavior of a protein is regarded as an ensemble of units reduced from, presumably, peptide bonds or amino acid residues. Units of similar thermodynamic properties are further classified into groups that are related to, for instance, alpha-helices or beta-sheets. Units of the same group are assumed to unfold collectively, whereas those of different groups may undergo either sequential or coupled unfolding. The introduction of unfolding groups facilitates the description of non-collective local structural changes experimentally observed via a multi-group unfolding. We incorporate denaturants and temperature effects into the free energy expression of the protein upon dissolution in a specific environment at thermal equilibrium, and a model protein, cytochrome c, was examined. Results indicate that there are at least four unfolding groups induced unfolding of cytochrome c: two are related to the prosthetic heme group, whereas another two groups are a-helices and global nearly group, which largely account for global changes in protein morphology. The extracted thermodynamic parameters, on the basis of the Ising model, can closely predict unfolding behaviors of the proteins in compounded denaturing environments.
Improving Device Efficiency of Polymer/Fullerene Bulk Heterojunction Solar Cells Through Enhanced Crystallinity and Reduced Grain Boundaries Induced by Solvent Additives
(2011-08-02)
Su, Ming-Shin
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Kuo, Chih-Yin
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Yuan, Mao-Chuan
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Jeng, U-Ser
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Su, Chun-Jen
The power conversion efficiency of a device incorporating a crystalline polymer/fullerene thin film improves from 5% to 7.3% - a relative increase of 45% - when an additive, diiodohexane (DIH), is present during processing. The DIH-processed active layer exhibits substantially enhanced polymer crystallinity and smaller fractal-like fullerene clusters.
Intrinsic coordination for revealing local structural changes in protein folding-unfolding
(2016-01-28)
Shiu, Ying-Jen
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Hayashi, Michitoshi
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Shih, Orion
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Su, Charlene
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Tsai, Min-Yeh
With a deformed object of a rigid rod inside, the local dislocations may be tracked relatively easily with respect to the internal rigid rod. We apply this concept on protein folding-unfolding to track the internal structural changes of an unfolded protein in solution. Proposed here is a protein internal coordination based on the major axis X of an ellipsoidal protein and the stable intrinsic transition dipole moment mu of the protein during unfolding. In this methodology, small-angle X-ray scattering (SAXS) is used to provide the protein global morphologies in the native and unfolded states. Furthermore, time-resolved fluorescence anisotropy (TRFA) provides the relative orientation between X and mu of Trp59 of the model protein cytochrome c. Hence observed in the protein unfolding with denaturants, acid, urea, or GuHCl, is the elongation of the native protein conformation along a reoriented protein major axis; accompanied are the different extents of relocations of the terminal a helices and loop structures of the protein in the corresponding unfolding.
Mesostructured Arrays of Nanometer-spaced Gold Nanoparticles for Ultrahigh Number Density of SERS Hot Spots
(2014-05-01)
Lai, Ying-Huang
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Chen, Shiaw-Woei
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Hayashi, Michitoshi
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Shiu, Ying-Jen
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Huang, Chiao-Cheng
A novel one-trough synthesis via an air-water interface is demonstrated to provide hexagonally packed arrays of densely spaced metallic nanoparticles (NPs). In the synthesis, a mesostructured polyoxometalate (POM)-silicatropic template (PSS) is first self-assembled at the air-water interface; upon UV irradiation, anion exchange cycles enable the free-floating PSS film to continuously uptake gold precursors from the solution subphase for diffusion-controlled and POM-site-directed photoreduction inside the silica channels. NPs approximate to 2 nm can hence be homogeneously formed inside the silica-surfactant channels until saturation. As revealed via X-ray diffraction, small-angle X-ray scattering (SAXS), grazing incidence SAXS, and transmission electron microscopy, the Au NPs directed by the PSS template are arrayed into a 2D hexagonal lattice with inter-channel spacing of 3.2 nm and a mean along-channel NP spacing of 2.8 nm. This corresponds to an ultra-high number density (approximate to 10(19) NPs cm(-3)) of narrowly spaced Au NPs in the Au-NP@PSS composite, leading to 3D densely deployed hot-spots along and across the mesostructured POM-silica channels for surface-enhanced Raman scattering (SERS). Consequently, the Au-NP@PSS composite exhibits prominent SERS with 4-mercaptobenzoic acid (4-MBA) adsorbed onto Au NPs. The best 4-MBA detection limit is 5 nm, with corresponding SERS enhancement factors above 10(8).
Morphologies of Self-Organizing Regioregular Conjugated Polymer/Fullerene Aggregates in Thin Film Solar Cells
(2010-01-12)
Chiu, Mao-Yuan
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Jeng, U-Ser
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Su, Ming-Shin
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Wei, Kung-Hwa
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材料科學與工程學系
In this study, We used simultaneous synchrotron grazing incidence X-ray scattering and diffraction to elucidate the overall morphologies of bulk heterojunction (BHJ) thin film (ca. 100 nm) solar cells containing phase-separated poly(3-hexylthiophene) (P3HT) and [6,6]-phertyl-C(61)-butyric acid methyl ester (PCBM) domains. Specifically, the dimensions and orientation of the P3HT crystallites and the sizes of the PCBM aggregates in BHJ thin films were determined. The appropriate PCBM aggregate size and density required for all optimum performance of the film in the photovoltaics device resulted in deteriorated ordering in the out-of-plane direction, but improved the in-plane packing of the P3HT lamellae. When the P3HT crystallites and PCBM aggregates had comparable domain sizes and number densities, the interpercolated networks for electron- and hole-transport were optimized in the film. This new understanding of the underlying mechanism of carrier mobility in BHJ thin films might be crucial in improving the efficiency of future solar cells.
New SmCG Phases in a Hydrogen-Bonded Bent-Core Liquid Crystal Featuring a Branched Siloxane Terminal Group
(2011-10-05)
Chen, Wei-Hong
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Chuang, Wei-Tsung
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Jeng, U-Ser
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Sheu, Hwo-Shuenn
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Lin, Hong-Cheu
In this study, we synthesized three analogous bentcore 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., SmCG(2)P(F)-USmCG(2)P(A)-SmCG(2)P(F)-SmCGP(F) 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 degrees to 50 degrees (while the tilt angle kept at ca. 31 degrees) 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.
Non-volatile organic field-effect transistor memory comprising sequestered metal nanoparticles in a diblock copolymer film
(2012-01-14)
Chen, Chia-Min
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Liu, Chih-Ming
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Wei, Kung-Hwa
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Jeng, U-Ser
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Su, Chiu-Hun
In this study, we fabricated p-channel-type non-volatile organic field-effect transistor (OFET) memory devices featuring an asymmetric PS-b-P4VP diblock copolymer layer incorporating high- and low-work-function metal nanoparticles (NPs) in the hydrophilic and hydrophobic blocks, respectively. We chose the highly asymmetric diblock copolymer PS(56k)-b-P4VP(8k) as the polymer electret to create the memory windows, and used the different work functions of the ex situ-synthesized metal NPs to tune the memory window for either p- or n-channel applications. The transfer curves of non-volatile OFET memory devices incorporating an asymmetric PS(56k)-b-P4VP8k layer embedded with high-work-function Pt NPs (5.65 eV) in the P4VP block exhibited a positive threshold voltage shift and a large memory window (ca. 27 V). In contrast, the transfer curves of the corresponding non-volatile OFET memory devices featuring embedded low-work-function (4.26 eV) Ag NPs exhibited a negative threshold voltage shift and a smaller memory window (ca. 19 V). This approach provides a versatile way to fabricate p- or possibly n-channel-type non-volatile organic field-effect transistor (OFET) memory devices with the same processing procedure.
On Modulating the Phase Behavior of Block Copolymer/Homopolymer Blends via Hydrogen Bonding
(2010-01-26)
Chen, Shih-Chien
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Kuo, Shiao-Wei
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Jeng, U-Ser
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Su, Chun-Jen
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Chang, Feng-Chih
We have investigated the phase behavior or poly(4-vinylphenol-b-styrene) (PVPh-b-PS) when respectively blended with poly(4-vinylpyridine) (NVP), poly(methyl methacrylate) (PMMA), and PVPh homopolymers by mediated hydrogen bonding strengths with the PVPh block of the copolymer. The Fourier transform infrared spectroscopic result indicates that the PVPh-b-PS/P4VP blend has a much higher fraction (f(H)) of hydrogen-bonded PVPh blocks for it significantly higher miscibility compared with the blends with PMMA and PVPh homopolymers. Consequently, the PVPh-b-PS/P4VP blend, behaving as a neat diblock copolymer, exhibited a series of order-order phase transitions from the lamellar, gyroid, hexagonally packed cylinder to body-centered cubic structures when the P4VP content increases from 6 to 71% (volume fraction), as evidenced consistently by transmission electron microscopy and small-angle X-ray scattering. In contrast, both file PVPh-b-PS/PMMA and PVPh-b-PS/PVPh blends maintained essentially the lamellar structure upon a similar volume fraction increase in the homopolymers; the lamellar structure, however, was distorted to different extents at higher volume fractions of the additives, depending on the hydrogen bonding strength. On the basis of the results, the ratio of interassociation equilibrium constant (KA) over self-association equilibrium constant (K(B)), K(A)/K(B), is introduced as a convenient guide in estimating the phase behavior of similar polymer blends featuring hydrogen bonding interactions between file homopolymer additive and copolymer: with a K(A)/K(B) ratio much larger than unity, the blend system tends to behave as a neat copolymer; with a K(A)/K(B) ratio significantly smaller than unity, phase separation instead of order-order phase transitions call be expected for the blend above certain volume fraction of homopolymer additive.
Pore morphology of low-k SiCxNy films prepared with a cyclic silazane precursor using plasma-enhanced chemical vapor deposition
(2015-09-01)
Tu, Hung-En
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Su, Chun-Jen
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Jeng, U-Ser
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Leu, Jihperng
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材料科學與工程學系
Low-k SiCxNy films were prepared using radio-frequency plasma-enhanced chemical vapor deposition (PECVD), with only 1,3,5-trimethyl-1,3,5-trivinylcyclotrisilazane (VSZ) as the precursor; VSZ has cyclic Si-N-Si linkages and three pendent vinyl groups. At lower PECVD temperatures, SiCxNy films possess relatively low film densities, indicating the existence of a loose structure or voidswithin the cross-linked matrix structure. The poremorphology of SiCxNy films deposited at distinct temperatures were examined using grazing-incidence small-angle X-ray scattering, while the chemical bondings and structural information were analyzed using Fourier-transform infrared spectroscopy. At 100 degrees C, SiCxNy films without porogen displaying 4.9 nm pores and a mean pore spacing of 30.1nmgenerated low-density films because Si-(CH2)(n)-Si and/or Si-(CH2)(n)-CH3 could be incorporated free volume into the N-Si-C cross-linked structure under plasma deposition. At 300 degrees C, the N-Si-C cross-linked structure and the some organic phase were disrupted and transformed into a denser structure, reducing pore size (3.5 nm) and losing pore correlation. Thus, low deposition temperatures facilitate the formation of large pores and the ordering of the pores. Post annealing converted the 100 and 300 degrees C as-deposited SiCxNy films into loose and dense structures, respectively, and maintained slightly reduced pore size and pore correlation in the annealed films. (C) 2015 Elsevier B.V. All rights reserved.
Quantitative Characterization and Mechanism of Formation of Multilength-scale Bulk Heterojunction Structures in Highly Efficient Solution-Processed Small-Molecule Organic Solar Cells
(2015-07-23)
Huang, Yu-Ching
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Tsao, Cheng-Si
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Huang, Tzu-Yen
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Cha, Hou-Chin
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Patra, Dhananjaya
In this study we used simultaneous grazing-incidence small- and wide-angle X-ray scattering (GISAXS and GIWAXS, respectively) to probe the multilength-scale structures of thin active layers comprising the linear A-D-A-type pi-conjugated donor molecule TBDTCNR and the fullerene acceptor molecule PC61BM for use in solution-processed small-molecule-based organic solar cells (SMOSCs). We found that the pseudo-two-dimensional fractal-like networks in the bulk heterojunction (BHJ) structure were determined by mutual interactions between the small-molecule (SM) crystallites and the nanoscale PC61BM clusters during their formation and phase separation, and deduced quantitatively, at multiple length scales, the BHJ structures comprising these SM crystallites and PC61BM clusters. We also conducted in situ GIWAXS measurements to study the temporal behavior and kinetics of SM crystallization from solution to the solid film state. Our GISAXS/GIWAXS study revealed that the multilength-scale BHJ structures in the thin films could be tuned effectively by varying the amount of incorporated PC61BM and the annealing temperature. This study provides fundamental information relating to the mechanism of formation of hierarchical BHJ structures through relatively rapid crystallization of a highly crystalline SM, as well as the relationships among the hierarchical structure, the photovoltaic performance, and the mechanism of formation, thereby allowing greater control over BHJ structures in SMOSCs with optimized fabrication and performance.
Resonant X-Ray Scattering and Absorption for the Global and Local Structures of Cu-modified Metallothioneins in Solution
(2009-07-22)
Li, Meiyi
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Huang, Yu-Shan
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Jeng, U-Ser
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Hsu, I-Jui
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Wu, YewChung Sermon
With Cd and Zn metal ions removed from the native rabbit-liver metallothionein upon unfolding, Cu-modified metallothioneins (Cu-MTs) were obtained during refolding in solutions containing Cu(I) or Cu(II) ions. X-ray absorption near-edge spectroscopic results confirm the respectively assigned oxidation states of the copper ions in Cu(I)-MT and Cu(II)-MT. Global and local structures of the Cu-MTs were subsequently characterized by anomalous small-angle x-ray scattering (ASAXS) and extended x-ray absorption fine structure. Energy-dependent ASAXS results indicate that the morphology of Cu(II)-MT resembles that of the native MT, whereas Cu(I)-MT forms oligomers with a higher copper content. Both dummy-residue simulation and model-shape fitting of the ASAXS data reveal consistently rodlike morphology for Cu(II)-MT. Clearly identified Cu-S, Cu-O, and Cu-Cu contributions in the extended x-ray absorption fine structure analysis indicate that both Cu(I) and Cu(II) ions are bonded with O and S atoms of nearby amino acids in a four-coordination environment, forming metal clusters smaller than metal thiolate clusters in the native MT. It is demonstrated that a combination of resonant x-ray scattering and x-ray absorption can be particularly useful in revealing complementary global and local structures of metalloproteins due to the atom specific characteristics of the two techniques.
Self-Assembly Structures through Competitive Interactions of Crystalline-Amorphous Diblock Copolymer/Homopolymer Blends: Poly(epsilon-caprolactone-b-4-vinyl pyridine)/Poly(vinyl phenol)
(2009-05-26)
Chen, Wan-Chun
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Kuo, Shiao-Wei
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Lu, Chu-Hua
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Jeng, U-Ser
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Chang, Feng-Chih
A series of immiscible crystalline-amorphous diblock copolymers, poly(epsilon-caprolactone)-b-(4-vinyl pyridine) (PCL-b-P4VP), were synthesized through combination of sequential ring-opening and controlled living free radical (nitroxide-mediated) polymerizations and then blended with poly(vinyl phenol) (PVPh) homopolymer. Miscibility and self-assembly morphologies mediated by hydrogen-bonding interactions of this new A-B/C type polymer blend are discussed in detail. Self-assembly morphologies of these immiscible PCL-b-P4VP diblock copolymers change through competitive hydrogen-bonding interactions with the increase of PVPh contents The SAXS profiles also reveal a sharp primary peak and highly long-range order reflections such as cylinder or sphere structure at relatively lower PVPh content, which is consistent with TEM images. DSC, WAXD, and FT-IR analyses provide positive evidence that the pyridine group of P4VP is a significantly stronger hydrogen-bond acceptor than the carbonyl group of PCL with the hydroxyl group of PVPh and results in the excluded and confined PCL phase.