Browsing by Author "Wang, Chih-Feng"

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Effect of intermolecular hydrogen bonding on low-surface-energy material of poly(vinylphenol)
(2007-04-07)
Lin, Han-Ching
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Wang, Chih-Feng
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Kuo, Shiao-Wei
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Tung, Pao-Hsiang
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Huang, Chih-Feng
We discovered that poly(vinylphenol) (PVPh) possesses an extremely low surface energy (15.7 mJ/m(2)) after a simple thermal treatment procedure, even lower than that of poly(tetrafluoroethylene) ( 2.0 mJ/m(2)) calculated on the basis of the two-liquid geometric method. Infrared analyses indicate that the intermolecular hydrogen bonding of PVPh decreases by converting the hydroxyl group into a free hydroxyl and increasing intramolecular hydrogen bonding after thermal treatment. PVPh results in a lower surface energy because of the decrease of intermolecular hydrogen bonding between hydroxyl groups. In addition, we also compared surface energies of PVPh-co-PS (polystyrene) copolymers (random and block) and their corresponding blends. Again, these random copolymers possess a lower fraction of intermolecular hydrogen bonding and surface energy than the corresponding block copolymers or blends after similar thermal treatment. This finding provides a unique and easy method to prepare a low-surface-energy material through a simple thermal treatment procedure without using fluoro polymers or silicones.
Fabrication of Patterned Superhydrophobic Polybenzoxazine Hybrid Surfaces
(2009-03-17)
Liao, Chun-Syong
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Wang, Chih-Feng
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Lin, Han-Ching
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Chou, Hsin-Yi
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Chang, Feng-Chih
The hydrophilicity of bis(3-allyl-3,4-dihydro-2H-1,3-benzoxazinyl)isopropane(B-ala) polybenzoxazine film and superhydrophobic polybenzoxazine-hybrid surface can be controlled through UV exposure to change the ratio of intra to intermolecular hydrogen bonds. A fraction of the intramolecular hydrogen bonding of the as-cured sample will convert into intermolecular hydrogen bonding upon UV exposure and thus results in an increase of hydrophilicity. This simple method allows for manipulating the hydrophilicity at selected regions on a superhydrophobic polybenzoxazine hybrid surface to create a patterned surface with superhydrophobic and superhydrophilic regions. Additionally, we have found that the superhydrophobic polybenzoxazine-silica hybrid surface exhibits good adhesion of water droplets after UV exposure, which can be served as a "mechanical hand" to transfer water droplets from a superhydrophobic surface to a hydrophilic one.
Fabrication of superhydrophobic and superoleophilic polystyrene surfaces by a facile one-step method
(2007-12-03)
Tu, Cheng-Wei
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Tsai, Chia-Hua
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Wang, Chih-Feng
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Kuo, Shiao-Wei
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Chang, Feng-Chih
A facile one-step method has been developed to prepare both superhydrophobic and superoleophilic surfaces of polystyrene (PS) without any chemical modification. A rough film consisting of micro-bead and nano-fiber mixed structures is formed by spraying a PS solution onto a large area and any type of substrate. The mixed structures with such unique wettability properties can be used in oil/water separation and as oil sorbents.
Hydrogen-bonding interactions mediate the phase behavior of an A-B/C block copolymer/homopolymer blend comprising poly(methyl methacrylate-b-vinylpyrrolidone) and poly(vinylphenol)
(2006-08-08)
Lee, Hsin-Fang
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Kuo, Shiao-Wei
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Huang, Chih-Feng
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Lu, Jiann-Shing
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Chan, Shih-Chi
We have investigated a new type of A-B/C blend, formed between poly(methyl methacrylate-b-vinylpyrrolidone) and poly(vinylphenol) (PMMA-b-PVP/PVPh), that displays unusual phase behavior. In this blend, the PMMA (A) and PVP (B) blocks within the PMMA-b-PVP (A-B) copolymer are miscible; although PVPh (C) experiences attractive interactions (xi <= 0) through hydrogen bonding, with both the PVP and PMMA blocks, its interaction with the former block is significantly stronger than that with the latter (xi(BC) >> xi(AC)). We investigated the miscibility and phase behavior of this novel A-B/C blend through the use of FTIR spectroscopy, DSC, C-13 CP/MAS solid-state NMR spectroscopy, and TEM. The proton spin-lattice relaxation time in the rotating frame (T-1 rho(H)), which we determined using 13C NMR spectroscopy, indicates that phase separation occurs for blends containing ca. 20-60 wt % PVPh. TEM images indicated clearly that the morphology of phase separation consists of a matrix of homogeneous mixed PVP/PVPh and micellar domains of excluded PMMA. This special phase behavior and miscibility is due mainly to the diversity of interactions that exist between the PMMA/PVPh and PVP/PVPh units.
Infrared proximity sensor using organic light-emitting diode with quantum dots converter
(2012-11-01)
Chen, En-Chen
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Yeh, Han-Cheng
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Chao, Yu-Chiang
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Meng, Hsin-Fei
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Zan, Hsiao-Wen
An efficient visible-to-infrared conversion film is made by blending CdTe quantum dots (CdTe QDs) of 12 nm diameter in a polyvinylpyrrolidone 360 (PVP 360) polymer matrix cast by water solution. The solid-state photoluminescence quantum efficiency exceeds 10% with emission peak at 810 nm. Strong 810 emission is obtained by combining the quantum dot film and a green polyfluorene light-emitting diode. Color filter is used to remove residual light below 780 nm to make it entirely invisible. Infrared photo-detector is made by blending poly[5-(5-(2,5-bis(decyloxy)-4-methylphenyl)thiophen-2-yl)-2,3-bis(4-(2-ethylhexyloxy)phenyl)-7-(5-methylthiophen-2-yl)thieno[3,4-b]pyrazine] (PBDOTTP) with band-gap 1.2 eV and (6,6)-phenyl-C61-butyric acid methyl ester (PCBM). The pixel contains one PD surrounded by four PLED on its four sides. The active areas of the five devices are all I cm by 1 cm and they are on the same plane. Infrared proximity sensor with photo-current over 300 nA at 10 cm object distance is achieved by detecting the reflected infrared signal. (C) 2012 Elsevier B.V. All rights reserved.
Micellization and the surface hydrophobicity of amphiphilic poly(vinylphenol)-block-polystyrene block copolymers
(2007-08-20)
Tung, Pao-Hsaing
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Kuo, Shiao-Wei
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Chan, Shih-Chien
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Hsu, Chih-Hao
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Wang, Chih-Feng
The self-assembly of PVPh-b-PS in different solvents was studied. Upon replacing toluene by THF as the solvent, the morphology of the resulting aggregates change from core-shell spheres, rod-like micelles and vesicles to onion-like aggregates. With increasing block copolymer concentration, morphologies such as honeycomb-like films, surfaces of aggregated large porous spheres, or pincushion-like spheres with protruding tubular vesicle aggregates are observed. These surface-patterned films show significantly enhanced hydrophobicity. The results suggest that a superhydrophobic . behavior can be achieved, with a maximum contact angle of 158 degrees, by using the pincushion-like micellar structure.
Modification of polymer substrates with low surface free energy material by low-temperature cured polybenzoxazine
(2008-01-02)
Liao, Chun-Syong
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Wu, Jiann-Shing
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Wang, Chih-Feng
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Chang, Feng-Chih
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應用化學系
The B-ala/AIBN PBZ system has a high extent of ring-opening of oxazine because phenol-containing oligomers are formed at the early stage of the curing process. As a result, the B-ala/AIBN PBZ system possesses a relatively stronger intramolecular hydrogen bonding and lower surface energy than the pure B-ala system at low temperature curing. In this context, poly(4-vinyl pyridine), poly(4-vinyl phenol) thin films and polycarbonate substrates, which lack liquid resistance, possess low surface free energy after modification with B-ala/AIBN = 5/1 PBZ.
Polybenzoxazine as a mold-release agent for nanoimprint lithography
(2007-05-22)
Wang, Chih-Feng
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Chiou, Shih-Feng
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Ko, Fu-Hsiang
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Chen, Jem-Kun
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Chou, Cheng-Tung
One of the most important tasks remaining to be resolved in nanoimprint lithography is the elimination of the resist sticking to the mold during demolding. Previously, the main approach was to apply a thin layer of fluorinated alkyl silane mold-release agent on the surface on the mold; however, this involves complicated steps and high costs. The low surface free energy material polybenzoxazine provides an efficient mold-release agent for silicon molds that is easier to process, costs less, and has no side reactions.
Polymer infrared photo-detector with high sensitivity up to 1100 nm
(2011-08-01)
Chen, En-Chen
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Tseng, Shin-Rong
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Chao, Yu-Chiang
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Meng, Hsin-Fei
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Wang, Chih-Feng
We reported a low band-gap conjugated polymer, poly[2,3-bis(4-(2-ethylhexyloxy)phenyl)-5,7-di(thiophen-2-yl)thienol[3,4-b]pyrazine] (PDTTP), was studied for the near infrared (NIR) photo-detector application. PDTTP shows intense absorption in NIR wavelength (to 1000 nm) and the estimated optical and electrochemical band-gaps of PDTTP are quite small around 1.15 eV and 1.08 eV, respectively. The low band-gap and the extended long wavelength absorption originates from the introduction of alternating TP units when its parent polythieno[3,4-b]pyrazine shows excellent narrow band-gap properties. Therefore, the relatively low band-gap and intense absorption in long wavelength of PDTTP make itself a promising candidate for near-infrared photo-detector. The hole mobility of the PDTTP measured from the bottom contact field effect transistor is around 1.40 x 10(-3) cm(2)/V s with a on/off ratio of 2100. The photo-detector based on bulk hetero-junction PDTTP and (6,6)-phenyl-C61-butyric acid methyl ester blend (PCBM) has the incident photon-to-electron conversion efficiency 28.9% at 1000 nm (-5 V) and 6.2% at 1100 nm (-5 V). This photo-detector can be operated at a high-speed of 1 MHz. The experimental result suggests the potential applications of low band-gap conjugated polymers on near-infrared photo-detectors. (C) 2011 Elsevier B.V. All rights reserved.
Stable superhydrophobic polybenzoxazine surfaces over a wide pH range
(2006-09-26)
Wang, Chih-Feng
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Wang, Yi-Ting
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Tung, Pao-Hsiang
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Kuo, Shiao-Wei
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Lin, Chun-Hung
In this study, we report on a simple two-step casting process designed to create a stable superhydrophobic surface. This method possesses the advantages of being both simple and inexpensive as well as utilizing non-fluorine-containing compounds. Most interestingly, we found that the as-prepared surface possesses superhydrophobic properties not only for pure water but also for corrosive water under both acidic and basic conditions. Furthermore, the superhydrophobic polybenzoxazine surfaces had excellent environmental stability with regard to both heating and organic solvent treatment in terms of the contact angle to water.
Syntheses and specific interactions of poly (hydroxyethyl methacrylate-b-vinyl pyrrolidone) diblock copolymers and comparisons with their corresponding miscible blend systems
(2006-09-20)
Huang, Chih-Feng
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Kuo, Shiao-Wei
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Lin, Fang-Ju
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Wang, Chih-Feng
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Hung, Chen-Jui
Combination of atom transfer radical and conventional free radical polymerizations has been successfully used to prepare poly(hydroxyethyl methacrylate-b-vinyl pyrrolidone) (PHEMA-b-PVP) copolymers with controlled molecular weight and low polydispersity (< 1.4). The thermal behavior and specific interaction of PHEMA-b-PVP diblock copolymers and their corresponding PHEMA/PVP blends were characterized. The result shows that glass transition temperatures of diblock copolymers analysed by differential scanning calorimetry (DSC) are higher than those of the blends. Infrared and solid-state NMR spectroscopic analyses show that hydrogen-bonding interaction of hydroxyl-carbonyl groups of diblock copolymers was also greater than that of the blends. Measurement of the proton spin-lattice relaxation time in the rotating frame, (T-1P(H)), reveals that all diblock copolymers and blends possess one composition-dependent T H, indicating that both diblock copolymers and blends are homogeneous, which is consistent with the DSC analysis. (c) 2006 Elsevier Ltd. All rights reserved.
The influences of H-2 plasma pretreatment on the growth of vertically aligned carbon nanotubes by microwave plasma chemical vapor deposition
(2008-06-01)
Jian, Sheng-Rui
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Chen, Yuan-Tsung
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Wang, Chih-Feng
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Wen, Hua-Chiang
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Chiu, Wei-Ming
The effects of H-2 flow rate during plasma pretreatment on synthesizing the multiwalled carbon nanotubes (MWCNTs) by using the microwave plasma chemical vapor deposition are investigated in this study. A H-2 and CH4 gas mixture with a 9:1 ratio was used as a precursor for the synthesis of MWCNT on Ni-coated TaN/Si(100) substrates. The structure and composition of Ni catalyst nanoparticles were investigated using scanning electron microscopy (SEM) and transmission electron microscopy (TEM). The present findings showed that denser Ni catalyst nanoparticles and more vertically aligned MWCNTs could be effectively achieved at higher flow rates. From Raman results, we found that the intensity ratio of G and D bands (I-D/I-G) decreases with an increasing flow rate. In addition, TEM results suggest that H-2 plasma pretreatment can effectively reduce the amorphous carbon and carbonaceous particles. As a result, the pretreatment plays a crucial role in modifying the obtained MWCNTs structures.
Thermal properties and surface energy characteristics of interpenetrating polyacrylate and polybenzoxazine networks
(2008-10-17)
Lu, Chu-Hua
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Su, Yi-Che
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Wang, Chih-Feng
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Huang, Chih-Feng
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Sheen, Yuung-Ching
We have prepared semi-interpenetrating polyacrylate networks (PA/BA-m s-IPNs) through rapid photo-polymerization of a triacrylate monomer (TMPTA) in the presence of a photomitiator (1184), a tetramercaptane transfer agent (4SH), and N-methyl-bisbenzoxazine (BA-m). Next, we prepared novel fully interpenetrating polyacrylate (PA) and polybenzoxazine (PBZ) networks (PA/PBZ f-IPNs) through thermal polymerization of the BA-m monomer at 180 degrees C for 4 h. For the PA/BA-m s-IPNs, the BA-m monomers can be frozen and dispersed in the UV-cured PA network within 5 min to inhibit macrophase separation. After thermal polymerization, the phenol units of the ring-opened PBZ segments can form a hydrogen-bonding interface with the carbonyl groups to improve the compatibility between the PBZ microdomains and the PA networks. From an analysis using Kissinger's method, the non-isothermal kinetics of the thermal polymerization for the PA/BA-m s-IPNs indicate that an increase in the PA content increased the steric hindrance of PBZ polymerization. We used DSC, TGA, and contact angle analyses to determine the glass transition temperature, thermal stability, and surface free energy, respectively, of the PA/PBZ f-IPNs. The thermal stability and surface free energy of these PA/PBZ f-IPNs display linear relationships with respect to the PBZ content. Crown Copyright (C) 2008 Published by Elsevier Ltd. All rights reserved.
Tuning the Surface Free Energy of Polybenzoxazine Thin Films
(2008-10-01)
Liao, Chun-Syong
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Wang, Chih-Feng
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Lin, Han-Ching
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Chou, Hsin-Yi
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Chang, Feng-Chih
A novel approach to manipulate the surface free energy and wettability on polybenzoxazine thin films can be achieved simply by varying the time of thermal treatment or UV exposure. A fraction of the intramolecular hydrogen bonding of the as-cured sample will convert into intermolecular hydrogen bonding upon thermal treatment or UV exposure and, thus, results in an increase in the hydrophilicity and wettability. This UV approach provides a simple method to generate wettability patterns or wettability gradients on the surface of a polybenzoxazine film. In addition, we have applied this technique to the preparation of a large-area periodic array of CdTe colloidal nanocrystals on polybenzoxazine thin films.