Browsing by Author "Jeng, Kai-Sheng"

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Asymmetric Polymer Particles with Anisotropic Curvatures by Annealing Polystyrene Microspheres on Poly(vinyl alcohol) Films
(2016-11)
Tseng, Hsiao-Fan
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Cheng, Ming-Hsiang
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Jeng, Kai-Sheng
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Li, Jia-Wei
;
Chen, Jiun-Tai
Anisotropic polymer particles such as Janus particles have attracted significant attention in recent years because of their unique properties and unusual self-assembly behavior. Most anisotropic polymer particles synthesized so far, however, only have different chemical regions compartmentalized on the particles. It remains a great challenge to fabricate anisotropic polymer particles with different shapes within a single particle. A novel approach is developed to prepare anisotropic polymer particles that contain two hemispheres with different curvatures by annealing polystyrene microspheres on poly(vinyl alcohol) films. During the annealing process, the polymer microspheres gradually sink into the polymer films and transform to asymmetric polymer particles, driven by the surface and interfacial tensions of the polymers. Selective removal techniques are also used to confirm the morphologies of the asymmetric particles.
Confinement Effects on the Optical Properties and Chain Conformations of Poly(9,9-di-n-octylfluorene-alt-benzothiadiazole) Nanotubes
(2016-09)
Chu, Chien-Wei
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Jeng, Kai-Sheng
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Chi, Mu-Huan
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Tsai, Chia-Chan
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Cheng, Ming-Hsiang
Although many fabrication methods of conjugated polymer nanostructures have been developed, the effects of confinement on the morphologies, chain conformations, and optical properties of conjugated polymers are still not well understood. In this work, poly(9,9-di-n-octylfluorene-alt-benzothiadiazole) (F8BT), a light-emitting conjugated polymer, is used to fabricate nanotubes by a solution wetting method using anodic aluminum oxide templates. The property changes under the nanoscale confinement have been investigated. The morphologies of F8BT nanostructures are characterized by scanning electron microscope, transmission electron microscope, and laser scanning confocal microscope. The data show the hollow morphologies and no or low crystallinity of the nanostructures. The optical properties are also measured using UV-vis absorption, photoluminescence, and confocal Raman spectroscopy. The spectroscopy data indicate that F8BT polymer chains have less intermolecular interactions and coplanarity under the confinement effect.
Dewetting of Swollen Poly(3-hexylthiophene) Films during Spin-Coating Processes: Implications for Device Fabrication
(2018-05-01)
Chung, Pei-Yun
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Cheng, Ming-Hsiang
;
Tseng, Hsiao-Fan
;
Liu, Chih-Ting
;
Chiu, Tang-Yao
Poly(3-hexylthiophene) (P3HT) films have been usually prepared by spin-coating for the applications of electronic devices such as organic photovoltaic devices (OPV) and organic field-effect transistors (OFETs). The wetting and dewetting behaviors of the swollen P3HT films during the spin-coating processes, however, are still poorly understood. In this work, we investigate the dewetting behaviors of P3HT thin films and the formation of ring structures during the spin-coating process by controlling the spin rates and the solution temperatures. Quantitative studies of the dewetting phenomena are conducted by measuring the sizes of the ring structures of the dewetting patterns. It is observed that the sizes of the ring structures are larger at lower spin rates because of the longer dewetting times allowed during the spin-coating processes. More importantly, the dewetting behaviors of the P3HT films are discovered to be affected by the formation of the P3HT nanowhiskers (nanowires). This work offers a deeper understanding of the dewetting behaviors of swollen P3HT films during the spin-coating processes, which is crucial for the development of P3HT-based optoelectronic devices.
Effects of Thermal Annealing and Solvent Annealing on the Morphologies and Properties of Poly(3-hexylthiophene) Nanowires
(2015-01-01)
Fu, Chuan-Min
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Jeng, Kai-Sheng
;
Li, Yu-Hsun
;
Hsu, Yuan-Chen
;
Chi, Mu-Huan
In recent years, poly(3-hexylthiophene) (P3HT) nanowires have attracted great interest because of their unique physical and electronic properties. The annealing effects on the properties and morphologies of P3HT nanowires, however, are still not fully understood. In this work, the effects of thermal annealing and solvent annealing on the morphologies and crystallinities of P3HT nanowires prepared by the whisker method are studied. P3HT is first dissolved in heated p-xylene, followed by a cooling process to room temperature, and P3HT nanowires are formed by self-assembly. The crystallinities of the P3HT nanowires are observed to increase by both thermal annealing and solvent annealing, as confirmed by differential scanning calorimetry and X-ray diffraction. The device performances of organic field-effect transistors based on the annealed nanowires are also examined. After annealing, an enhancement of the charge mobility by one order is observed.
Exceptionally low thermal conductivity of poly(3-hexylthiophene) single nanowires
(2015-01-01)
Lee, Yi-Jung
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Jeng, Kai-Sheng
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Chen, Jiun-Tai
;
Sun, Kien Wen
;
應用化學系
Electrical and thermal conductivity measurements were conducted by using microfabricated four-point probe and T-type nanosensors in a vacuum on poly(3-hexylthiophene) (P3HT) single nanowires prepared by the whisker method. The nanowires had a cross-section of only 5 nm x 15 nm and a length of 0.5-10 mu m. The electrical conductance of nanowires was 3.3 x 10(-7) 1/Omega and remained stable even after exposing the wires to ambient conditions for a few days. The thermal conductivity of a nanowire was 0.055 +/- 0.003 Wm(-1) K-1 which was approximately an order of magnitude lower than other previously reported P3HT single nanowires with a diameter of 120 nm and embedded in anodic aluminum oxide matrix. This thermal conductivity was also approximately four times smaller than that of P3HT amorphous thin films (similar to 0.2 W m(-1) K-1). The exceptionally low thermal conductivity was attributed to increased interface-phonon scattering because heat propagation was confined to an extreme narrow spatial dimension.
On-Film Annealing: A Simple Method to Fabricate Heterogeneous Polymer Surfaces, Porous Films, and Hemispheres
(2015-07-01)
Chen, Jiun-Tai
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Lee, Po-Hsi
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Tseng, Hsiao-Fan
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Chiu, Yu-Jing
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Kao, Yi-Huei
Polymer microspheres have been widely investigated because of their applications in areas such as drug delivery, latex diagnostics, and affinity bioseparators. The effect of annealing on polymer microspheres, however, has been rarely studied. In this work, we demonstrate the morphology transformation of polystyrene (PS) microspheres annealed thermally on poly(methyl methacrylate) (PMMA) films. During the annealing process, the PS microspheres gradually sink into the PMMA films and transform into PS hemispheres, driven by the reduction of the surface and interfacial energies. The effect of the film thicknesses on the morphology transformation is also studied. In addition, porous PMMA films or PS hemispheres can be obtained by removing the PS or the PMMA domains of the polymer composites using cyclohexane or acetic acid, respectively.
Orientation Preferences of Interchain Stackings for Poly(3-hexylthiophene) Nanowires Prepared Using Template-Based Wetting Methods
(2018-06-01)
Jeng, Kai-Sheng
;
Chu, Chien-Wei
;
Liu, Chien-Liang
;
Jean, Woan-Mei
;
Chen, Hsin-Lung
Poly(3-hexylthiophene) (P3HT) nanowires have drawn great attention recently because of their unique properties that can be applied to optoelectronic devices such as conjugated polymer solar cells and organic field-effect transistors. There is still an urgent need, however, to study the fabrication and characterization of P3HT nanowires with controllable morphologies and molecular orientations. In this work, feasible routes are presented to fabricate P3HT nanowires using the solution wetting template method and the solvent-annealing-induced nanowetting in template (SAINT) method. The morphologies and chemical compositions of the P3HT nanowires prepared using these two methods are confirmed by scanning electron microscopy, transmission electron microscopy (TEM), and Raman spectroscopy. From the ultraviolet-visible spectroscopy and wide-angle X-ray scattering results, it is concluded that the degrees of the crystallinity and the orientation preferences of interchain stackings along the pore axis for the P3HT nanowires prepared by the SAINT method are higher than those prepared by the solution wetting template method.
Reversible morphology control of three-dimensional block copolymer nanostructures by the solvent-annealing-induced wetting in anodic aluminum oxide templates
(2016)
Chu, Chiang-Jui
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Cheng, Ming-Hsiang
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Chung, Pei-Yun
;
Chi, Mu-Huan
;
Jeng, Kai-Sheng
In this work, the authors study the fabrication of three-dimensional block copolymer nanostructures in which the morphologies can be reversibly controlled. Polystyrene-block-polydimethylsiloxane (PS-b-PDMS), a promising candidate for nanolithography, is introduced into cylindrical nanopores of anodic aluminum oxide (AAO) templates using a solvent annealing-induced nanowetting in templates (SAINT) method. Not only the morphologies of the infiltrated PS-b-PDMS nanostructures can be tuned by the annealing solvents, but also the solvent-vapor-controlled morphologies can be altered reversibly by annealing the samples repeatedly between different solvent vapors.