Browsing by Author "Chuang, Wei-Tsung"

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Bioinspired assembly of functional block-copolymer nanotemplates
(2013)
Lin, I. -Hong
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Cheng, Chih-Chia
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Chuang, Wei-Tsung
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Chen, Jem-Kun
;
Jeng, U. -Ser
A new concept on bioinspired assembly of functional diblock copolymers, capable of forming different microstructures through nucleobase-induced supramolecular interactions, has been explored. In this paper, a new series of uracil-functionalized poly(epsilon-caprolactone)-b-(4-vinylbenzyl uracil)s (PCL-b-PVBU) have been prepared which exhibit a high self-complementary ability in solution and solid states owing to the formation of uracil-uracil pairs by induced hierarchical self-assembly. The ordered morphologies of PCL-b-PVBU diblock copolymers changed from a lamellar, hexagonally packed cylinder to a sphere with respect to the content of the hydrogen bond segment. Moreover, we further show that the PCL segment could be easily extracted by enzymatic degradation, leading to a cylinder porous structure of long-range order, which gives a facile method for the fabrication of uracil-functionalized nanotemplates. In addition, bio-complementary PCL-b-PVBU/9-hexadecyladenine (AC16) hierarchical supramolecular complexes formed through strong cooperative hydrogen bonding between the uracil group of PVBU and the adenine group of A-C16. When the mixing ratios of PCL-b-PVBU/AC16 differ from the stoichiometric ratio, these complexes self-assemble into well-ordered lamellar and hexagonal structures; the changing morphology at different AC16 loadings reveals that the molecular structures of the PCL-b-PVBU/AC16 complexes are readily tailored.
Broad Ranges and Fast Responses of Single-Component Blue-Phase Liquid Crystals Containing Banana-Shaped 1,3,4-Oxadiazole Cores
(2014-01-08)
Chiang, I-Hung
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Long, Chun-Ji
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Lin, Hsin-Chieh
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Chuang, Wei-Tsung
;
Lee, Jey-Jau
In this study, we synthesized two novel 1,3,4-oxadiazole-based bent-core liquid crystals (OXD7*, OXD5B7F*) containing a chiral tail that display broad ranges of the blue phase III (34 and 7 K, respectively); we characterized them using polarized optical microscopy, differential scanning calorimetry, and circular dichroism. The electro-optical responses of both of these liquid crystals are much faster than those of previously reported single-component blue-phase liquid crystals. To optimize its electro-optical performance, we mixed OXD7* (the blue-phase range of which is broader than that of OXD5B7F*) with its analogue OXD6 (at weight ratios of 6:4 and 4:6). We also performed molecular modeling of single-component BPLCs (OXD7* and OXD5B7F*) to analyze the possible parameters affecting their blue phase ranges.
Directional Solution Coating by the Chinese Brush: A Facile Approach to Improving Molecular Alignment for High-Performance Polymer TFTs
(2017-09-13)
Lin, Fang-Ju
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Guo, Cheng
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Chuang, Wei-Tsung
;
Wang, Chien-Lung
;
Wang, Qianbin
Directional solution coating by the Chinese brush provides a facile approach to fabricate highly oriented polymer thin films by finely controlling the wetting and dewetting processes under directional stress. The biggest advantage of the Chinese brush over the normal western brush is the freshly emergent hairs used, whose unique tapered structure renders a dynamic balance of the liquid within the brush by multiple forces when interacting with the liquid. Consequently, the liquid is steadily held within the brush without any unexpected leakage, making the liquid transfer proceed in a well-controllable manner. It is demonstrated that the Chinese brush coating enables the crystallization of the polymer and the self-assembly of conjugated backbones to proceed in a quasi-steady state via a certain direction, which is attributed to the controllable receding of the three-phase contact line during the dewetting process by the multiple parallel freshly emergent hairs. The as-prepared polymer thin films exhibit over six times higher charge-carrier mobility compared to the spin-coated films, which therefore provides a general approach for high-performance organic thin-film transistors.
Dynamic supramolecular self-assembly: hydrogen bonding-induced contraction and extension of functional polymers
(2017-06-07)
Cheng, Chih-Chia
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Wang, Jui-Hsu
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Chuang, Wei-Tsung
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Liao, Zhi-Sheng
;
Huang, Jyun-Jie
Simple construction and manipulation of low-molecular-weight supramolecular polymers, based on incorporation of self-complementary multiple hydrogen bonding interactions, with the desired dynamic response characteristics to achieve high-efficiency supramolecular assembly and control the morphological properties of the polymers remain highly challenging. Herein, we developed a new difunctional tele-chelic supramolecular polymer (UrCy-PPG) containing self-complementary quadruple hydrogen-bonded ureido-cytosine (UrCy) moieties, which spontaneously self-assembles to form long-range-ordered lamellar structures in the bulk state. Scattering and rheological studies confirmed that the dynamic behavior of UrCy units induces structural phase transitions from quadruple to dual hydrogen-bonded arrays, leading to well-controlled, self-organized supramolecular nanostructure morphologies. The microstructural features could be easily tuned by altering environmental conditions, making the self-assembly processes highly efficient. Importantly, temperature/shear stress-dependent microstructural analyses indicated that UrCy-PPG has the capacity to manipulate the transition between contractile and fully extended lamellar structures. Given its novelty, simple synthesis, high reliability, and efficient self-assembly processes, this newly developed supramolecular polymer represents a new concept and pathway for controlled arrangement of self-assembled polymeric nanostructures.
Fluorinated heptacyclic carbazole-based ladder-type acceptors with aliphatic side chains for efficient fullerene-free organic solar cells
(2019-05-01)
Chen, Tsung-Wei
;
Hsiao, Yu-Tang
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Lin, You-Wei
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Chang, Chia-Chih
;
Chuang, Wei-Tsung
Molecular engineering of non-fullerene acceptors (NFAs) is a promising strategy to uncover new structure-property relationships and design principles for developing next-generation high performance n-type materials. Two dithienocyclopentacarbazole (DTC)-based NFAs, DTC(4R)-IC and DTC(4R)-4FIC, are synthesized to elucidate the effects of incorporating aliphatic side chains and 2-(5,6-difluoro-3-oxo-2,3-dihydro-1H-inden-1-ylidene)malononitrile (2FIC) end groups on the thermal and optoelectronic properties of these NFAs. An inverted organic solar cell architecture of ITO/ZnO/J71:NFA/MoO3/Ag is employed. By replacing the phenyl-based side chains with aliphatic side chains on the carbon bridges of the carbazole-based core, the device containing DTC(4R)-IC exhibits an enhanced PCE of 9.61%, a V-OC of 0.94 V, a J(SC) of 16.44 mA cm(-2), and a FF of 62.00%, whereas the device containing DTC(4Ph)-IC exhibits a PCE of 7.76%. The incorporation of 2FIC end groups affords DTC(4R)-4FIC featuring better device performance relative to DTC(4R)-IC, a more red-shifted absorption edge, and a broader absorption range upon fluorination. Notably, the device fabricated with DTC(4R)-4FIC affords a V-oc of 0.82 V, a J(sc) of 18.92 mA cm(-2), a FF of 70.22% and a highest PCE of 10.89%, which is by far the highest PCE for NFA containing heptacyclic carbazole cores.
Handedness of Twisted Lamella in Banded Spherulite of Chiral Polylactides and Their Blends
(2017-07-25)
Wang, Hsiao-Fang
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Chiang, Chen-Hung
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Hsu, Wen-Chun
;
Wen, Tao
;
Chuang, Wei-Tsung
Banded spherulite resulting from lamellar twisting due to the imbalanced stresses at opposite fold surfaces can be formed by isothermal crystallization of chiral polylactide and its blends with poly(ethylene glycol) (PEG). Using a polarized light microscope, the handedness of the twisted lamella in banded spherulite is determined. With the same growth axis along the radial direction as evidenced by wide-angle X-ray diffraction (WAXD) for isothermally crystallized samples at different temperatures, the twisted lamellae of chiral polylactides (poly(L-lactide) (PLLA) and poly(D-lactide) (PDLA)) display opposite handedness. The split-type Cotton effect on the Co=O stretching motion of vibrational circular dichroism (VCD) spectra helps determine the helix handedness (i.e., conformational chirality). The results indicate that the conformational chirality can be defined by the molecular chirality through intramolecular chiral interactions. Moreover, the preferred sense of the lamellar twist in the banded spherulite corresponds to the twisting direction identified by the C-O-C vibration motion of VCD spectra, reflecting the role of intermolecular chiral interactions in the packing of polylactide helices. Similar results are obtained in the blends of chiral polylactides and poly(ethylene glycol) (PEG, a polymer compatible with polylactide), indicating that the impact of chirality is intrinsic irrespective of the specific crystallization conditions. In contrast to the chiral polylactides, the spectrum of the crystalline stereocomplex that associates PLLA and PDLA shows VCD silence. The spectroscopic results are in line with the morphological observations. No banded spherulites are observed in the stereocomplex crystallites due to the symmetric packing of mirror L and D-chain conformations in the fold surfaces and the crystallites core.
Large-scale production of ureido-cytosine based supramolecular polymers with well-controlled hierarchical nanostructures
(2015-01-01)
Cheng, Chih-Chia
;
Chang, Feng-Chih
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Wang, Jui-Hsu
;
Chu, Yu-Lin
;
Wang, Yeh-Sheng
A novel supramolecular polymer containing urea-cytosine (UrCy) quadruple hydrogen-bonding moieties that possesses a high association constant (K-a > 10(6) M-1) was synthesized at high yield (96%) at kilogram-scale. The synthesized telechelic macromer dissolved in solution can undergo a substantial change in solution viscoelasticity and can self-assemble due to the noncovalent nature of supramolecular polymerization. As the concentration of UrCy in solution was increased, the spherical assemblies gradually transformed to an ordered lamellar phase with an extremely high degree of polymerization. In addition, the dynamic behavior of UrCy units induced a sudden phase transition in the bulk state, revealing an interesting order-disorder transition from a crystalline solid to liquid state. This newly-discovered material has excellent polymer-like features that are distinct to existing systems. A simple path for forming supramolecular polymers is recommended for the design, large-scale production and manipulation of self-assembled materials with distinctive properties.
Luminescence Enhancement of Pyrene/Dispersant Nanoarrays Driven by the Nanoscale Spatial Effect on Mixing
(2013-02-05)
Lo, Kuan-Hsin
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Li, Ming-Chia
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Ho, Rong-Ming
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Zhao, Yuan-Chun
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Massuyeau, Florian
This work presents a simple method to generate ordered chromophore/dispersant nanoarrays through a pore-filling process for a nanoporous polymer template to enhance chromophore luminescence. Fluorescence results combining with the morphological evolution examined by scanning probe microscopy reveal that the enhanced luminescence intensity reaches the maximum intensity as the nanopores of the template are completely filled by the chromophore/dispersant mixture. The variation is attributed to nanoscale spatial effect on the enhanced mixing efficiency of chromophore and dispersant, that is, the alleviation of self-quenching problem, as evidenced by the results of attenuated total reflection Fourier transform IR spectroscopy combining with grazing incident wide-angle X-ray diffraction. The enhanced luminescence of the chromophore/dispersant nanoarrays driven by the nanoscale spatial effect is highly promising for use in designing luminescent nanodevices.
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).
Micro-Layer and Lattice Structure Effects on Impedance of Titanium Oxide Phthalocyanine
(2018-07-01)
Lam, Tu-Ngoc
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Huang, Wei-Jie
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Wang, Chun-Chieh
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Chuang, Wei-Tsung
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Su, Ya-Wen
In this study, the authors employ synchrotron techniques to characterize multi-scale microstructure in elucidating how the modified crystal lattices at angstrom level and molecular stacking at micrometer scale of titanium oxide phthalocyanine (TiOPc) thin film tuning the impedance. The a and c lattice lengths of the TiOPc reveal a positive correlation with the impedance because of the - stacking distances of TiOPc molecules arrangements. Our results suggest a promising dip coating method to tailor the charge storage capability of TiOPc through controlling the crystal lattice sizes of TiOPc.
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.
Novel conjugated polymers based on bis-dithieno [3,2-b;2 ',3 '-d] pyrrole vinylene donor and diketopyrrolopyrrole acceptor: side chain engineering in organic field effect transistors
(2018-01-07)
Lin, Fang-Ju
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Lin, Song-Di
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Chin, Chih-Hao
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Chuang, Wei-Tsung
;
Hsu, Chain-Shu
Two new donor-acceptor conjugated polymers, i.e. PB(C12DTP) V-DTDPP-C-12 and PB(C12DTP) V-DTDPP-C12C8, were prepared by the Stille coupling of (E)-1,2-bis(4-dodecyl-6-(trimethylstannyl)-4H-dithieno[ 3,2-b: 2', 3'-d] pyrrol-2-yl) ethene (Sn-B(C12DTP)V) with 3,6-bis(5-bromothiophen-2-yl)-2,5-didodecylpyrrolo[ 3,4-c] pyrrole-1,4-dione (Br-DTDPP-C-12) and 3,6-bis(5-bromo-thiophen-2-yl)-2,5-bis(2octyldodecyl) pyrrolo[ 3,4-c] pyrrole-1,4-dione (Br-DTDPP-C8C12), respectively. The molecular weight and thermal properties of the obtained polymers were characterized by gel permeation chromatography (GPC), differential scanning calorimetry (DSC) and thermogravimetry (TG). Their optical and electrochemical properties were analyzed by UV-vis-NIR spectroscopy and cyclic voltammetry (CV). The morphological and molecular-packing features of the polymers were characterized by optical microscopy and atomic force microscopy (AFM), UV polarization spectroscopy and grazing incidence X-ray diffraction (GIXD) to determine the relationship between the structural morphology and the performance. PB (C12DTP) V-DTDPP-C12C8 with branched C12C8 side chains on DPP units shows much higher hole mobility (1.2 cm(2) V-1 s(-1)) than 0.69 cm(2) V-1 s(-1) of PB(C12DTP) V-DTDPP-C-12.
Packing Principles for Donor-Acceptor Oligomers from Analysis of Single Crystals
(2016-08-09)
Huang, Chi-Feng
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Wu, San-Lien
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Huang, Yi-Fan
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Chen, Ying-Chen
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Chang, Shu-Ting
D-A conjugated molecules are complicated in both their molecular and their packing structures. In this perspective, we summarize more than 40 crystal lattices of conjugated oligomers to identify the morphological influence of each building block on the D-A molecules. These lattice structures reveal not only the packing preferences of the conjugated oligomers but also the conformational disorder in the lattices. The presence of this disorder in slowly grown crystals implies that attaining total long-range conformational order is challenging for D-A oligomers, which are structurally complicated and readily distorted and which have building blocks of incommensurate packing dimensions. In optoelectronic applications, a decreased duration of processing can prevent ordering and trap the thin films of D-A oligomers from becoming crystalline phases. Although D-A oligomers conform to packing principles in the formation of a single crystal, their phase behaviors in the formation of active thin films are much more difficult to comprehend. Continuous advances in methods of characterization are still strongly required for the steps of attaining a true structure property relation of D-A oligomers in active films for optoelectronic applications.
Polymorphisms and morphological studies of a difluorobenzothiadiazole conjugated copolymer with 7.8% polymer solar cell efficiency
(2015-01-01)
Huang, Chi-Feng
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Chang, Jen-Yun
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Huang, Sin-Hong
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Wu, Kuan-Yi
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Jheng, Jyun-Fong
This study presents the structural characterization of a 5,6-difluorobenzo- 2,1,3-thiadiazole (FBT)-quaterthiophene (Th-4) alternating copolymer (PTh4FBT) and how the crystalline nature of PTh4FBT affects the PTh4FBT-PC71BM morphology and the device performances. The single crystal structure of 5,6-difluoro-4,7-di(thiophen-2-yl) benzothiadiazole (Th2FBT) first confirms the low conformational preference of the FBT containing molecule. Since the crystallization process does not assist in unifying the conformation of Th2FBT, both intrachain conformation and interchain c-shifts in the crystalline state of PTh4FBT have to be scrutinized. By comparing the 2D WAXS pattern of PTh4FBT and the simulated patterns generated from Cerius(2) molecular modeling, it was found that the diffraction pattern generated from the lattice containing PTh4FBT with anti-conformation and limited interchain c-shift matches best with the experimental one. The face-to-face interchain stacking of PTh4FBT rendered strong crystalline nature to the polymer and caused large segregation in the PTh4FBT-PC71BM blend system, which was indicated by the TEM and GI WAXS morphological studies. The aggregation size was reduced via the use of the 1-chloronaphthalene additive. The optimized morphology led to improved J(sc) and FF. The single-junction PTh4FBT-PC71BM based polymer solar cells deliver a high PCE of 7.75% with a V-oc of 0.76 V, a J(sc) of 14.36 mA cm(-2), and a FF of 71.0%.
Shape and confinement effects of various terminal siloxane groups and C60 on supramolecular interactions of hydrogen-bonded bent-core liquid crystals
(2015-01-01)
Lin, Hong-Cheu
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Chiang, I-Hung
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Chuang, Wei-Tsung
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Lu, Chia-Lin
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Liao, Chun-Yen
Shape and Confinement Effects of Various Terminal Siloxane Groups on Supramolecular Interactions of Hydrogen-Bonded Bent-Core Liquid Crystals
(2015-07-14)
Chiang, I-Hung
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Chuang, Wei-Tsung
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Lu, Chia-Lin
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Lee, Ming-Tao
;
Lin, Hong-Cheu
To investigate the shape and confinement effects of the terminal siloxane groups on the self-assembled behavior of molecular arrangements in hydrogen-bonded (H-bonded) bent-core complexes, four H-bonded bent-core complexes Si, P1, C4, and P8 with string-, ring-, and cagelike siloxane termini (i.e., linear siloxane unit -Si-O-Si-O-Si, cyclic siloxane unit (Si-O)(4), and silsesquioxane unit PUSS, respectively) were synthesized and investigated. By X-ray diffraction measurements, different types of SmCG (B8) phases and leaning angles were controlled by the shape effect of the string- and cage-like siloxane termini for Si and P1 (with only one arm of H-bonded bent-core), respectively. In addition, the confinement effect of Pi, C4, and P8 (accompanied by increasing the numbers of attached H-bonded bent-core arms) resulted in higher transition temperatures and the diminishing of mesophasic ranges (even the disappearance of mesophase in P8). Moreover, AFM images showed the bilayer smectic CG phases of Si and P1 were aligned to reveal highly ordered thread-like structures by a DC field. By spontaneous polarization measurements within the mesophasic ranges, Si and P1 showed ferroelectric transitions but C4 displayed antiferroelectricity. Finally, the electro-optical performance of B8 phases could be optimized through binary mixtures of Si and P1, and a well aligned modulated ribbon phase could be formed via specific molar ratios of the binary mixtures.
Single-Junction Organic Solar Cell Containing a Fluorinated Heptacyclic Carbazole-Based Ladder-Type Acceptor Affords over 13% Efficiency with Solution-Processed Cross-Linkable Fullerene as an Interfacial Layer
(2019-08-28)
Chen, Tsung-Wei
;
Chang, Chia-Chih
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Hsiao, Yu-Tang
;
Chan, ChoonKee
;
Hong, Ling
In this article, a fluorinated heptacyclic dithienocyclopentacarbazole (DTC)-based non-fullerene acceptor (NFA), DTC(4Ph)-4FIC, is synthesized and blended with J71, PBDB-T, and PBDB-TF, featuring complementary absorption and well-matched energy levels. The DTC(4Ph)-4FIC neat film exhibits face-on preference, whereas the nonfluorinated counterpart, DTC(4Ph)-IC, exhibits edge-on preference; this unique feature owing to fluorination in DTC-based NFAs is observed for the first time. More importantly, DTC(4Ph)-4FIC exhibits improved power conversion efficiencies (PCEs) of 10.92 and 10.41% in J71- and PBDB-T-containing devices, while the devices that employed DTC(4Ph)-IC afford PCEs of 7.76 and 9.48%, respectively. Because PBDB-TF is known to exhibit lower energy levels than J71 and PBDB-T, the corresponding device affords a V-OC of 0.95 V, a J(SC) of 18.29 mA cm(-2), a FF of 75.70%, and a PCE of 13.15%, which is 20 and 26% higher than J71- and PBDB-T-containing devices. Furthermore, the inverted device containing the PBDB-TF:DTC(4Ph)-4FIC blend is fabricated using cross-linkable fullerene (C-PCBSD) as the cathode interlayer, affording a decent PCE of 13.36%, with a V-OC of 0.94 V, a J(SC) of 20.20 mA cm(-2), and a FF of 70.42%.
Smectic-Layer Alignments of Surface-Modified Gold Nanoparticles in the Nanocomposite Induced by a Hydrogen-Bonded Bent-Core Liquid Crystalline Host under Electric Fields
(2011-11-01)
Chen, Wei-Hong
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Chang, Yi-Ting
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Lee, Jey-Jau
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Chuang, Wei-Tsung
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Lin, Hong-Cheu
Stepwise Structural Evolution of a DTS-F2BT Oligomer and Influence of Structural Disorder on Organic Field Effect Transistors and Organic Photovoltaic Performance
(2016-12-27)
Huang, Chi-Feng
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Huang, Sin-Hong
;
Hsieh, Chou-Ting
;
Chao, Yi-Hsiang
;
Li, Chia-Hua
An A-D-A oligomer, DTS(F2BT)(2), was synthesized; its structural evolution was studied with DSC, POM, 2D-WAXD, and in-situ GI-XRD. The structural evolution of DTS(F2BT)(2) is stepwise and kinetically slow. Both rapid drying and the presence of PC71BM trapped DTS(F2BT)(2) in a less ordered nematic (N) phase. PDMS-assisted crystallization enabled a pristine DTS(F2BT)(2) thin film to attain a more ordered equilibrium phase, and enhanced the OFET mobility of DTS(F2BT)(2). In OPV devices, DIO additive drove the DTS(F2BT)(2) domains in the DTS(F2BT)(2):PC71BM blended film from the N phase toward the equilibrium phase, and resulted in enhanced OPV performances. These results reveal the slow ordering process of the A-D-A oligomer, and the importance of monitoring the degree of structural evolution of the active thin films in organic optoelectronics.
Superhelices with tunable twisting power directed from supramolecular pairing of focal asymmetry in achiral dendron-jacketed block copolymers
(2020-02-14)
Lin, I-Ming
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Chou, Che-Min
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Li, Ming-Chia
;
Guo, Rong-Hao
;
Lee, Cheng-Kuang
The formation of helical assemblies from achiral supramacromolecules has been a highly mysterious process, but is of interest for the generation of a variety of structures and properties. Herein, novel hierarchical superhelices are developed from self-assembly of achiral dendron-jacketed block copolymers (DJBCPs). The presence of focal asymmetry in both the stereochemistry of the dendrons (donors) and interactive binding sites of the copolymer chains (acceptors) plays a pivotal role in generating a spontaneous symmetry breaking through tailored donor-acceptor matching via hydrogen bonding. The focal asymmetry, on a scale of several nanometers, propagates to helical twists of the achiral DJBCP hierarchical assemblies over hundreds of nanometers, such that the primary molecular asymmetry sequentially triggers a secondary helical conformation of the dendron-jacketed blocks, then tertiary supramolecular helical assemblies and eventually quaternary superhelices. The helical twisting power of the superhelices is tunable using the dendron grafting ratio, indicating that the magnitude of helical twisting can be quantitatively adjusted from local to entire structures.