Browsing by Author "Chiu, Tang-Yao"

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Asymmetries in Porous Membranes: Fabrication of Anodic Aluminum Oxide Membranes with Double-Sized Nanopores and Controlled Surface Properties
(2019-06-13)
Liu, Chih-Ting
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Lin, Yu-Liang
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Chu, Chien-Wei
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Chang, Chun-Wei
;
Chiu, Yu-Jing
Recently, anodic aluminum oxide (AAO) membranes with ordered and monodispersed nanopores have attracted significant attention because the pore sizes and lengths of the AAO membranes can be systematically controlled by changing the anodization parameters. Asymmetries of geometry, wettability, charge, and polarity in nanoporous AAO membranes are now highly desired for applications such as drug delivery, membrane filtration, and catalysis. Although the asymmetries in AAO membranes have been widely studied, AAO membranes whose nanopores simultaneously possess more than two asymmetric properties still need to be developed. In this work, we present a simple method to fabricate asymmetric AAO membranes by combining the post-treatments with the three-step anodization method. The asymmetries of the AAO membranes simultaneously possessing larger nanopores with higher hydrophobicity and smaller nanopores with lower hydrophobicity are characterized by scanning electron microscopy, water contact angle measurements, and energy-dispersive X-ray spectroscopy. Using the asymmetric AAO membranes, nanowires of polystyrene and poly(styreneb/ock-dimethylsiloxane) with double-sized diameters are also fabricated via the melt and solvent wetting methods, exhibiting that the AAO membranes with double-sized diameters can be used as the templates for generating double-sized polymer nanowires.
Block copolymer micelles confined in cylindrical nanopores: Effects of annealing solvents and hybridization
(2020-05-01)
Cheng, Ming-Hsiang
;
Yao, I-Chun
;
Chiu, Tang-Yao
;
Chen, Jiun-Tai
;
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Amphiphilic block copolymer micelles have been intensively investigated and applied into various research fields for decades. One of the most promising characteristics for block copolymer micelles is the selective incorporation of metal precursors in the cores or coronas of the micelles. By combining with nanoporous membranes, aligned polymer nanostructures can be generated, facilitating the applications such as nanolithography and catalysis. The morphology transitions and controllability of block copolymer micelles in confined geometries, however, have seldom been studied. In addition, for hybrid micelles in which polymer segments are selectively incorporated with inorganic metal precursors, the relationship between hybridization and morphologies of polymer nanostructures in the confined states is still under discussion. In this work, we investigate the effects of annealing solvents and hybridization with metal precursors (gold(III) chloride trihydrate (HAuCl4 center dot 3H(2)O)) on the morphologies of polystyrene-block-poly(4-vinylpyridine) (PS-b-P4VP) block copolymer micelles confined in the nanopores of anodic aluminum oxide (AAO) templates. Tuned by the annealing solvent vapors and the selective ion complexation between HAuCl4 and P4VP cores, various morphologies can be effectively controlled, such as the spherical-micelles-in-rod morphology, the parallel-cylinders-in-rod morphology, and the hemispherical-micelles-in-rod morphology. This study not only investigates the effects of annealing solvent vapors and hybridization on the morphologies of block copolymer micelles confined in cylindrical nano-geometries but also offers a viable route for preparing metal nanoparticles embedded in porous templates.
Controlled Assembly of Polymer-Tethered Gold Nanorods via a Rayleigh-Instability-Driven Transformation: Implications for Biomedical Applications
(2019-05-01)
Chiu, Tang-Yao
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Cheng, Ming-Hsiang
;
Chang, Chun-Wei
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Ko, Hao-Wen
;
Chen, Jiun-Tai
We study the assembly and morphology transformation of gold nanorods tethered with polystyrene ligands (AuNRs@PS). The AuNRs@PS nanotubes are first fabricated in the nanopores of anodic aluminum oxide (AAO) templates by the solution wetting method. When the samples are thermally annealed, the Rayleigh-instability-driven transformations of the nanostructures are triggered by the decrease of the interfacial energies between the nanotubes and the inner air cylinders. Four different morphologies are identified: nanotubes (I), undulated structures (II), Rayleigh-instability-induced structures (III), and nanorods (IV). The morphology diagrams of the AuNRs@PS structures using different thermal annealing temperatures and times are also made, showing that the morphology transformation rates are higher at higher annealing temperatures. This work has implications to be applied in different fields such as biomedical applications.
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
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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.
Radial Linear Polymer Patterns Driven by the Marangoni Instability and Lateral Phase Separation for the Formation of Nanoscale Perforation Lines
(2019-05-01)
Wu, Bo-Hao
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Chang, Kai-Chieh
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Hsu, Hsun-Hao
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Chiu, Yu-Jing
;
Chiu, Tang-Yao
Phase separation under convection, related to the Marangoni instability, is critical in the development of advanced polymer processing technologies. The formation mechanisms of polymer patterns driven by the phase separation under convection, however, still require further investigations. In this work, we study the phase separation of polystyrene (PS)/poly(methyl methacrylate) (PMMA) bilayer films during the spin-coating processes. PMMA film-coated glass substrates are dripped by PS solutions in toluene before spinning. The concentration gradients of the PS solutions and the swollen PMMA films cause the surface tension-driven Marangoni instability; lateral phase separations also occur during the spin-coating processes, forming the interesting and uncommon radial linear patterns with nanoscale heights on the PS/PMMA bilayer films. By changing the solution waiting time and spin rates, the surface morphologies of the PS/PMMA bilayer films can be controlled. At longer waiting times, the higher degrees of swelling of the PMMA films by the solvents allow the formation of the polymer patterns; at higher spin-coating rates, the faster solvent evaporation improves the ordering of the polymer patterns. Furthermore, the morphologies of the PS/PMMA bilayer films can be confirmed using the selective removal technique; the PS films with linear-arranged cavities and the PMMA films with bumps can be obtained using acetic acid and cyclohexane, respectively. Finally, a proof of concept on the potentials in applying the cavities-containing PS films for nanoscale perforation lines is also demonstrated.
Sunny-Side-Up Egg-Shaped Structures: Surface Modification To Form Anisotropic Polymer Particles Driven by the Plateau-Rayleigh Instability as Fluorescence Manipulation Platforms
(2019-02-26)
Chiu, Yu-Jing
;
Liu, Chih-Ting
;
Weng, Chang-Ching
;
Chiu, Tang-Yao
;
Li, Jia-Wei
The Plateau-Rayleigh instability is a phenomenon driven by the reduction of the surface energies, in which a liquid cylinder transforms to a series of droplets with distinct spacing. This instability phenomenon is also applied broadly for the transformation of cylindrical materials to spherical particles in homogeneous environments. The demonstration of the instability in heterogeneous environments, however, has been less studied. Here, we study the Plateau-Rayleigh instability of electrospun polystyrene (PS)/poly(methyl methacrylate) (PMMA) core-shell fibers annealed on n-octadecyl-trichlorosilane (ODTS)-modified glass substrates with toluene vapors. After the annealing procedures, the PS/PMMA core-shell fibers transform to anisotropic sunny-side-up egg-shaped polymer structures, driven by the reduction of the total surface and interfacial energies. Quantitative analyses are performed on the sizes of the structures. Fluorescent fibers are also prepared by electrospinning and annealed on the ODTS-modified substrates, demonstrating the potential application as fluorescence manipulation platforms.