Browsing by Author "Kuo, Tyng-Yow"

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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.
Morphology transformations of electrospun polymer fibers annealed on polymer films with thickness-controlled growth rates of undulation
(2018-01-03)
Kuo, Tyng-Yow
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Tseng, Hsiao-Fan
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Chiu, Yu-Jing
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Chen, Jiun-Tai
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應用化學系
Electrospun polymer fibers have attracted great attention in recent years because of their unique properties and applications in various areas such as tissue engineering and drug delivery. It remains a great challenge, however, to understand the morphology and property changes of electrospun polymer fibers induced by post-treatment, especially thermal annealing. In this work, we investigate the morphology evolution of electrospun polystyrene (PS) fibers thermally annealed on poly(vinyl alcohol) (PVA) films. Driven by the surface and interfacial tensions, the PS fibers transform to a series of regularly aligned anisotropic particles embedded in the PVA films via a Rayleigh instability-type transformation. From the in-situ observed optical microscopy (OM) images, higher growth rates of undulated amplitude can be obtained for thinner PVA films, revealing the effect of the underlying glass substrates. (C) 2017 Elsevier Ltd. All rights reserved.
Rayleigh-instability-driven morphology transformation of electrospun polymer fibers imaged by in situ optical microscopy and stimulated Raman scattering microscopy
(2014-01-01)
Lee, Ting-Hsien
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Chiu, Yu-Jing
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Lai, Yu-Cheng
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Fan, Ping-Wen
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Kuo, Tyng-Yow
Electrospinning is one of the most common methods to prepare polymer fibers with sizes ranging from several nanometers to hundreds of micrometers. In most studies of electrospun polymer fibers, the properties and morphologies of polymer fibers are controlled by changing the electrospinning conditions. Few studies focus on the post-treatments of polymer fibers, which are critical for many fiber-based applications. In this work, we investigate the morphology transformation of electrospun polystyrene (PS) fibers annealed on top of poly(methyl methacrylate) (PMMA) film-coated glass substrates. In situ optical microscopy and stimulated Raman scattering (SRS) microscopy are used to observe the transformation process, which is driven by the Rayleigh instability, the surface tensions, and the interfacial tensions of polymers. Depending on the thickness of the underlying PMMA films, the electrospun PS fibers may transform into hemispheres or disks. The growth rates of the undulating amplitude are also affected by the film thickness.
Three-dimensional thermal annealing: An unconventional method to fabricate monodisperse polymer nanoparticles from polymer films
(2016-12)
Chiu, Yu-Jing
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Kuo, Tyng-Yow
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Cheng, Ming-Hsiang
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Tseng, Hsiao-Fan
;
Lo, Yu-Ching
We develop a simple and feasible method to fabricate polymer nanoparticles by annealing polymer films in a uniform environment. Different from the conventional methods, no extra additive or emulsifier is needed in the preparation processes. Poly(methyl methacrylate) (PMMA) films are used as a model system and annealed at elevated temperatures in ethylene glycol, which provides a uniform three-dimensional annealing environment and acts as stabilizers once the nanoparticles are formed. After the annealing process, PMMA nanoparticles with monodisperse diameters are formed. By examining the remaining films after the annealing process, the formation mechanism, which involves surface undulation and detachment of polymer nanoparticles, is proposed. (c) 2016 Wiley Periodicals, Inc. J. Polym. Sci., Part B: Polym. Phys. 2016, 54, 2471-2475