Browsing by Author "Chu, Chien-Wei"

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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
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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.
Bamboo-like nanostructures prepared using template-based wetting methods: Molecular arrangements of polyimide and carbon tubes in cylindrical nanopores
(2019-12-17)
Tu, Yi-Hsuan
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Liu, Chih-Ting
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Chu, Chien-Wei
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He, Hung-Chieh
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Chang, Chun-Wei
With excellent mechanical and physical properties, polyimides (PIs) possess diverse applications in different fields. PI-based materials can also be converted to carbon materials by high temperature carbonization processes. The fabrication and properties of PI-based nanomaterials and corresponding carbon nanomaterials, however, have been less investigated, especially the packing behaviors of the polymer chains. In this work, we study the fabrication and characterization of PI nanostructures using the solution wetting (SW) method and the solvent-annealing-induced nanowetting in templates (SAINT) method. Poly(amic acid) (PAA) tubes are first prepared using anodic aluminum oxide (AAO) membranes. After thermal imidization and carbonization processes, PI and carbon tubes can be obtained, respectively. Bamboo-like structures are also observed in the tubes, which can be attributed to the Marangoni effect induced by the gradient of the surface tensions during the solvent evaporation process. Moreover, the laser Raman micro-spectroscopy results show that the packing behaviors of the polymer chains in the nanostructures prepared by the SAINT method are better than those prepared by the SW method, indicating that the solvent annealing process can improve the chain packing while assisting the infiltration of polymer chains in the nanopores.
Competition Between Effects of Pore Sizes and Annealing Solvents on the Morphology Manipulation of 3D Block Copolymer Nanostructures Using Anodic Aluminum Oxide Templates
(2016-06)
Chu, Chiang-Jui
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Chung, Pei-Yun
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Chu, Chien-Wei
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Cheng, Ming-Hsiang
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Chi, Mu-Huan
In this work, the morphologies of polystyrene-block-polydimethylsiloxane (PS-b-PDMS) nanostructures using solvent-induced wetting in the nanopores of anodic aluminum oxide (AAO) templates are investigated. AAO templates with three different pore sizes (approximate to 200, approximate to 60, and approximate to 30 nm) are used in this work to differentiate the effect of confinement and annealing solvents. Different from the results by the traditional wetting methods, two major effects are identified in affecting the morphologies. At larger pore sizes, the morphologies of the nanostructures are mainly affected by the annealing solvent. At smaller pore sizes, however, the morphologies are mainly controlled by the confinement effect (pore sizes).
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.
Curved block copolymer nanodiscs: structure transformations in cylindrical nanopores using the nonsolvent-assisted template wetting method
(2019-11-07)
Lin, Yu-Liang
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Cheng, Ming-Hsiang
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Chang, Chun-Wei
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Chu, Chien-Wei
;
Liu, Chih-Ting
In this work, we study the structure transformations of cylinder-forming polystyrene-block-polydimethylsiloxane (PS31k-b-PDMS14.5k) confined in cylindrical nanopores. PS-b-PDMS nanotubes, nanospheres, and curved nanodiscs are ingeniously prepared by a facile template wetting strategy using anodic aluminum oxide (AAO) templates. Quantitative analyses of the structure transformations from nanospheres to curved nanodiscs are also conducted, showing that the lengths of the curved nanodiscs can be controlled by adjusting the annealing temperature and time. Furthermore, the PDMS domains of the nanostructures can be selectively etched using HF solutions, generating porous PS nanostructures. This work not only offers versatile routes to prepare block copolymer nanostructures with controlled shapes but also provides a deeper understanding of the structure transformation of block copolymers in confined geometries.
Dewetting of polymer thin films on modified curved surfaces: preparation of polymer nanoparticles with asymmetric shapes by anodic aluminum oxide templates
(2018-04-21)
Liu, Chih-Ting
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Tsai, Chia-Chan
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Chu, Chien-Wei
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Chi, Mu-Huan
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Chung, Pei-Yun
We study the dewetting behaviors of poly(methyl methacrylate) (PMMA) thin films coated in the cylindrical nanopores of anodic aluminum oxide (AAO) templates by thermal annealing. Self-assembled monolayers (SAMs) of n-octadecyltrichlorosilane (ODTS) are introduced to modify the pore surfaces of the AAO templates to induce the dewetting process. By using scanning electron microscopy (SEM), the dewetting-induced morphology transformation from the PMMA thin films to PMMA nanoparticles with asymmetric shapes can be observed. The sizes of the PMMA nanoparticles can be controlled by the original PMMA solution concentrations. The dewetting phenomena on the modified nanopores are explained by taking into account the excess intermolecular interaction free energy (AG). This work opens a new possibility for creating polymer nanoparticles with asymmetric shapes in confined geometries.
Fabrication of Core-Shell Polymer Nanospheres in the Nanopores of Anodic Aluminum Oxide Templates Using Polymer Blend Solutions
(2015-07-01)
Ko, Hao-Wen
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Chi, Mu-Huan
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Chang, Chun-Wei
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Chu, Chien-Wei
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Luo, Ke-Hsuan
Spherical core-shell structures have been widely investigated in recent years, and they can be used for various applications, such as drug delivery, biological labeling, and batteries. Although many methods have been developed to prepare core-shell structures, it is still a great challenge to fabricate core-shell structures in the nanoscale with well-controlled morphologies and sizes. In this work, we present a simple method to fabricate core-shell polymer nanospheres consisting of polystyrene (PS) cores and poly(methyl methacrylate) (PMMA) shells. The nanostructures are prepared by a solution-based template wetting method. After the nanopores of anodic aluminum oxide (AAO) templates are wetted sequentially by PS/PMMA blend solutions and water, the core-shell nanostructures can be formed. The formation process is related to the Rayleigh-instability-type transformation. Selective removal techniques are also used to confirm the morphologies of the core-shell nanostructures.
Fabrication of Electrospun Polymer Fibers with Nonspherical Cross-Sections Using a Nanopressing Technique
(2016-02)
Chen, Jiun-Tai
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Kao, Yi-Huei
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Kuo, Tyng-Yow
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Liu, Chih-Ting
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Chiu, Yu-Jing
The fabrication of electrospun polymer fibers is demonstrated with anisotropic cross-sections by applying a simple pressing method. Electrospun polystyrene or poly(methyl methacrylate) fibers are pressed by flat or patterned substrates while the samples are annealed at elevated temperatures. The shapes and morphologies of the pressed polymer fibers are controlled by the experimental conditions such as the pressing force, the pressing temperature, the pressing time, and the surface pattern of the substrate. At the same pressing force, the shape changes of the polymer fibers can be controlled by the pressing time. For shorter pressing times, the deformation process is dominated by the effect of pressing and fibers with barrel-shaped cross-sections can be generated. For longer pressing times, the effect of wetting becomes more important and fibers with dumbbell-shaped cross-sections can be obtained. Hierarchical polymer fibers with nanorods are fabricated by pressing the fibers with porous anodic aluminum oxide templates.
Fabrication of Polymer Nanopeapods in the Nanopores of Anodic Aluminum Oxide Templates Using a Double-Solution Wetting Method
(2014-08-12)
Chen, Jiun-Tai
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Wei, Tzu-Hui
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Chang, Chun-Wei
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Ko, Hao-Wen
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Chu, Chien-Wei
Although one-dimensional polymer nanomaterials can be prepared by approaches such as the template method, the control over the morphologies of one-dimensional polymer nanomaterials containing multiple components is still a great challenge. In this work, we investigate the formation of polymer nanopeapods using a novel double-solution wetting method in the nanopores of anodic aluminum oxide (AAO) templates. A polystyrene (PS) solution in dimethylformamide (DMF) is first introduced into the nanopores of the AAO templates. Then a second polymer solution of poly(methyl methacrylate) (PMMA) in acetic acid is infiltrated into the nanopores. Because of the stronger interaction between acetic acid and aluminum oxide than that between DMF and aluminum oxide, the PMMA solution preferentially wets the pore walls of the templates and the PS solution is isolated in the center of the nanopores. After the evaporation of the solvent, peapod-like PS/PMMA nanostructures are obtained, where the shell and the core are composed of PMMA and PS, respectively. The compositions of the polymer nanopeapods are confirmed by removing PS or PMMA selectively. The formation mechanism of the nanostructures is related to the Rayleigh-instability-type transformation and further studied by changing experimental parameters such as the polymer concentration or the polymer molecular weight. This work not only provides a simple approach to prepare multicomponent polymer nanomaterials with controlled morphologies and sizes, but also contributes to a deeper understanding of polymer solvent-interactions in confined geometries.
Hierarchical hybrid nanostructures: controlled assembly of polymer-encapsulated gold nanoparticles via a Rayleigh-instability-driven transformation under cylindrical confinement
(2016-01-01)
Ko, Hao-Wen
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Chang, Chun-Wei
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Chi, Mu-Huan
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Chu, Chien-Wei
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Cheng, Ming-Hsiang
We develop a novel route based on the solution wetting method using anodic aluminum oxide (AAO) templates to fabricate hierarchical hybrid nanostructures assembled from polystyrene-encapsulated gold nanoparticles (Au@PS NPs). Hybrid nanostructures including nanotubes and nanospheres can be reliably prepared, in which the spatial arrangement of the Au@PS NPs is determined by the pore diameters of the templates and the molecular weights of the thiol-ended polystyrene (PS-SH) ligands. In particular, the Rayleigh-instability-driven transformation plays a key role in the formation of the hybrid nanospheres.
Hierarchical Polymer Structures Using Templates and the Modified Breath Figure Method
(2018-06-26)
Lee, Lin-Ruei
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Liu, Chih-Ting
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Tseng, Hsiao-Fan
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Lin, Kuan-Ting
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Chu, Chien-Wei
Hierarchical structures are commonly observed in nature and possess unique properties. The fabrication of hierarchical structures with well-controlled sizes in different length scales, however, is still a great challenge. To further understand the morphologies and properties of the hierarchical structures, here we present a novel strategy to prepare hierarchical polymer structures by combining the modified breath figure method and the template method. Poly(methyl methacrylate) (PMMA) honeycomb films with regular micropores are first prepared using the modified breath figure method by dipping PMMA films into mixtures of chloroform and methanol. The polymer chains on the honeycomb films are then annealed and wetted into the nanopores of anodic aluminum oxide templates via capillary forces, resulting in the formation of hierarchical polymer structures. The morphologies of the polymer structures, which can be controlled by the molecular weights of the polymers and the concentrations of the polymer solutions, are characterized by scanning electron microscopy. The surface wettabilities of the polymer structures are also examined by water contact angle measurements, and the hierarchical structures are observed to be more hydrophobic than the flat films and honeycomb films. This work not only provides a feasible approach to fabricate hierarchical polymer structures with controlled sizes but also gives a better understanding of the relationship between surface morphologies and properties.
Microwave-annealing-induced nanowetting of block copolymers in cylindrical nanopores
(2018-01-07)
Chang, Chun-Wei
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Cheng, Ming-Hsiang
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Ko, Hao-Wen
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Chu, Chien-Wei
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Tu, Yi-Hsuan
Block copolymers have attracted great attention because of their abilities to self-assemble into well-ordered microphase-separated structures. To generate nanopatterns of block copolymers with long-range ordering and low-defect densities in shorter time scales, microwave annealing has recently been applied. Microwave annealing, however, has so far only been used for block copolymer bulks and thin films. In this work, we discover that microwave annealing can be successfully applied to three-dimensional block copolymer nanostructures by studying the infiltration and microphase separation of block copolymers in cylindrical nanopores upon microwave irradiation. Cylinder-forming and lamella-forming poly(styrene-block-dimethylsiloxane) (PS-b-PDMS) are introduced into the nanopores of anodic aluminum oxide (AAO) templates. In addition, AAO templates with different pore sizes are used to study the effect of the commensurabilities between the pore diameters and the repeating periods of the block copolymers on the morphologies of the block copolymer nanostructures.
Microwave-annealing-induced nanowetting: a rapid and facile method for fabrication of one-dimensional polymer nanomaterials
(2015-01-01)
Chang, Chun-Wei
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Chi, Mu-Huan
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Chu, Chien-Wei
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Ko, Hao-Wen
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Tu, Yi-Hsuan
Template wetting methods have been broadly applied to fabricate diverse one-dimensional polymer nanomaterials. The currently used template wetting methods, however, have shortcomings and disadvantages such as long processing times, thermal degradation, and difficulties in controlling the lengths. In this work, we develop a novel microwave-annealing-induced nanowetting (MAIN) method to fabricate one-dimensional polymer nanomaterials using porous anodic aluminum oxide (AAO) templates. Upon microwave annealing, the polymer chains are infiltrated into the nanopores of the AAO templates, and the morphologies of the polymer nanomaterials can be controlled by the annealing conditions. The growth rates of the polymer nanomaterials using the MAIN method are faster than those using the traditional thermal annealing method. This work not only provides a time-saving method to fabricate one-dimensional polymer nanomaterials with controlled morphologies, but also offers a better understanding of the effect of microwave annealing on the wetting behaviors of polymer melts.
Orientation Preferences of Interchain Stackings for Poly(3-hexylthiophene) Nanowires Prepared Using Template-Based Wetting Methods
(2018-06-01)
Jeng, Kai-Sheng
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Chu, Chien-Wei
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Liu, Chien-Liang
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Jean, Woan-Mei
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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.
Rayleigh-Instability-Induced Transformation for Confined Polystyrene Nanotubes Prepared Using the Solvent-Vapor-Induced Wetting Method
(1970-01-01)
Fang, Zhi-Xuan
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Chu, Chien-Wei
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Tsai, Chia-Chan
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Chang, Chun-Wei
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Cheng, Ming-Hsiang
Polystyrene (PS) nanotubes prepared using the solvent-vapor-induced wetting method with anodic aluminum oxide templates are for the first time applied to study the thermal stabilities of polymer nanotubes confined in cylindrical geometries. The morphologies of the PS nanotubes and the corresponding transformed PS nanostructures driven by the Rayleigh instabilities after thermal annealing treatments are characterized by scanning electron microscopy. Morphology diagrams of the Rayleigh-instability-induced nanostructures for PS nanotubes prepared via the solvent-vapor-induced wetting method and the solution wetting method are constructed to study the differences in kinetics for samples using different wetting methods. Slower transformation kinetics for the PS samples prepared by the solvent-vapor-induced wetting method than those prepared by the solution wetting method are observed, indicating the better thermal stabilities and the relatively denser packings of the polymer chains in the nanopores for the PS samples prepared using the solvent-vapor-induced wetting method.
Selective solvent-induced reconstruction in confined space: one-dimensional mesoporous block copolymer structures in cylindrical nanopores
(2017-06-14)
Chang, Chun-Wei
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Chi, Mu-Huan
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Ko, Hao-Wen
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Chu, Chien-Wei
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Fang, Zhi-Xuan
We investigate the formation of polystyrene-block-poly(methyl methacrylate) (PS-b-PMMA) nanostructures confined in cylindrical nanopores via a novel selective solvent-induced reconstruction process. The key factors of the morphologies of the nanostructures are determined, including the choice of solvents, the molecular weights of the polymers, and the pore diameters of the templates.
Transformation of Polymer Nanofibers to Nanospheres Driven by the Rayleigh Instability
(2013-04-24)
Huang, Yu-Chieh
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Fan, Ping-Wen
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Lee, Chih-Wei
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Chu, Chien-Wei
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Tsai, Chia-Chan
We study the thermal annealing effect of poly(methyl methacrylate) (PMMA) nanofibers made from anodic aluminum oxide (AAO) templates and their transformation to PMMA nanospheres. The PMMA nanofibers are prepared by wetting an AAO template with a 30 wt % PMMA solution, followed by the evaporation of the solvent, After the AAO template is removed by a weak base, the PMMA nanofibers are thermally annealed in ethylene glycol, a nonsolvent for PMMA. The surfaces of the nanofibers undulate and transform into nanospheres, driven by the Rayleigh instability. The driving force for the transformation process is the minimization of the interfacial energy between PMMA nanofibers and ethylene glycol. The transformation times at higher annealing temperatures are shorter than those at lower annealing temperatures. This study provides a facile route to prepare polymer nanospheres which are not accessible by other traditional methods.
Wetting in nanopores of cylindrical anodic aluminum oxide templates: Production of gradient polymer nanorod arrays on large-area curved surfaces
(2015-02-01)
Chu, Chien-Wei
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Huang, Yu-Chieh
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Tsai, Chia-Chan
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Chen, Jiun-Tai
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應用化學系
Although the fabrication of nanostructures has been investigated extensively, it is still a challenge to prepare nanostructures or nanostructure arrays on curved surfaces. In this work, we develop a simple and novel method to fabricate polymer nanorod arrays on large-area curved polymer surfaces with controlled curvatures. This method is based on the wetting of polymer melts in the nanopores of cylindrical anodic aluminum oxide templates, which are prepared by electrochemical anodization of aluminum wires. Polymers such as poly(methyl methacrylate) (PMMA) melts can wet the nanopores of the templates via capillary force after thermal annealing, resulting in the formation of PMMA nanorod arrays with gradient heights on curved PMMA surfaces. This work not only opens up new possibilities for creating non-planar surfaces with desired nanostructures, but also contributes to a deeper understanding of wetting behavior in confined geometries. (C) 2014 Elsevier Ltd. All rights reserved.
Zwitterionic polymer brush grafting on anodic aluminum oxide membranes by surface-initiated atom transfer radical polymerization
(2017-04-21)
Chu, Chien-Wei
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Higaki, Yuji
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Cheng, Chao-Hung
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Cheng, Ming-Hsiang
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Chang, Chun-Wei
A feasible processing of zwitterionic polymer-grafted anodic aluminum oxide (AAO) membranes by surface-initiated atom transfer radical polymerization (SI-ATRP) and the geometric effect on the polymer chain growth in the confined nanopores were investigated. A zwitterionic poly(3-(N-2-methacryloyloxyethyl-N,N-dimethyl)ammonatopropanesulfonate) (PMAPS) brush was produced on an AAO membrane via introduction of an initiator with a phosphonate group and subsequent SI-ATRP. The PMAPS-grafted AAO membranes were characterized by water droplet contact angle measurement, size exclusion chromatography (SEC), scanning electron microscopy (SEM), X-ray photoelectron spectroscopy (XPS), thermo-gravimetric analysis (TGA), and laser Raman micro-spectroscopy. The linear relationship between the grafting yield (Y) of the PMAPS brush and number-average molecular weight (M-n) of the unbound PMAPS indicates that there is no significant geometric effect on the chain growth under the spatial confinement inside the nanopores with diameters of similar to 200 nm. The PMAPS brushes were diminished near the center section along the nanopores because the monomer supply was retarded. The capability of the PMAPS-grafted AAO membranes for inorganic nanoparticle immobilization was also demonstrated using gold nanoparticles (AuNPs) through ion-exchange and reduction processes.