Browsing by Author "Wu, HD"

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An unusual, completely miscible, ternary hydrogen-bonded polymer blend of phenoxy, phenolic, and PCL
(2005-05-31)
Kuo, SW
;
Chan, SC
;
Wu, HD
;
Chang, FC
;
應用化學系
We have investigated the miscibility and hydrogen-bonding behavior of ternary blends of phenoxy, phenolic, and poly(e-caprolactone) (PCL) by using differential scanning calorimetry (DSC) and Fourier transform infrared spectroscopy. On the basis of DSC analyses, we observed a rare totally miscible ternary hydrogen-bonded polymer blend in the amorphous phase: all compositions of this ternary blend display a single glass transition temperature. In addition, these single glass transition temperatures can be predicted well by extending the Kwei equation from the binary polymer blend to this ternary polymer blend. The infrared spectra indicate that the intermolecular hydrogen bonding of each pair of binary components still exists in the ternary polymer blend. We used the ternary totally miscible blend to determine the interassociation equilibrium constant between the hydroxyl groups of phenolic and the hydroxyl groups of phenoxy indirectly from the fraction of hydrogen-bonded carbonyl groups of PCL. Quantitative analyses suggest that interassociation between the hydroxyl groups of phenolic and the hydroxyl groups of phenoxy is more favorable than the hydroxyl-carbonyl interassociations of either phenolic/PCL or phenoxy/PCL and the hydroxyl-hydroxyl self-association of the pure phenolic and phenoxy homopolymers at room temperature.
Chain conformation and crystallization behavior of the syndiotactic polystyrene nanocomposites studied using Fourier transform infrared analysis
(2001-04-24)
Wu, HD
;
Tseng, CR
;
Chang, FC
;
應用化學系
;
Department of Applied Chemistry
Analyses of the effects of montmorillonite (clay) on the chain conformation and crystallization of syndiotactic polystyrene (s-PS) thin films are investigated using FTIR spectroscopy, X-ray diffraction, and TEM. The clay is dispersed into the s-PS matrix using a solution blending with scale in 1-2 nm or in a few tenths to 100 nm, depending on whether a surfactant is added or not. Upon adding clay, the chain conformation of s-PS tends to convert to TTTT from rTTGG after drying because the highly dispersed clay overcomes the energy barrier of chain conformation transformation. This phenomenon leads to a change in a conventional mechanism of molecular packing for s-PS in the drying stage. During melt-crystallization, clay plays a vital role in facilitating the formation of the thermodynamically favored all-trans p form crystal, particularly on the s-PS thin film. When the s-PS is melt-crystallized at a cooling rate of 1 degreesC/min from 320 degreesC, the highest absolute crystallinity of beta form up to 0.56 occurs in the clay dispersibility of few tenths to 100 nm in the s-PS matrix; then dispersibility is of 1-2 nm (0.49), and the final one is of pure s-PS (0.42). Evidently, clay significantly affects the chain conformation and crystallization of s-PS.
Characterization of crystallization in syndiotactic polystyrene thin film samples
(2000-11-28)
Wu, HD
;
Wu, ID
;
Chang, FC
;
應用化學系
;
Department of Applied Chemistry
Compatibilization and elastomer toughening of polyamide-6 (PA6)/poly(phenylene ether) (PPE) blends
(1999-10-03)
Chiou, KC
;
Wu, SC
;
Wu, HD
;
Chang, FC
;
應用化學系
In the elastomer-modified (polyamide-6/poly(phenylene ether) (PA6/PPE) = 50/50 blends, poly(styrene-co-maleic anhydride) (SMA) was demonstrated to be an efficient reactive compatibilizer. The G1651 elastomer was shown to be an effective impact modifier to result in superior toughness and heat-deflection temperature (HDT) than is the 1901X elastomer for the SMA-compatibilized blends because G1651 particles exclusively reside within the dispersed PPE phase but 1901X particles tend to distribute in the PA6 matrix and/or along the interface. The apparent average diameter of the dispersed PPE phase is insignificantly dependent on the elastomer content in the G1651-modified blend, whereas it increases with increase of the elastomer content in the 1901X-modified blend. Moreover, there exists a critical elastomer content, 15 phr, for the ductile-brittle transition of the G1651-modified SMA-modified PA6/PPE blends. (C) 1999 John Wiley & Sons, Inc.
Effects of molecular structure of modifiers on the thermodynamics of phenolic blends: An entropic factor complementing PCAM
(1999-05-04)
Wu, HD
;
Chu, PP
;
Ma, CCM
;
Chang, FC
;
應用化學系
Different thermodynamics in phenolic blends with different polymeric modifiers, i.e., phenoxy, poly(decamethylene adipate), poly(ethylene oxide), and poly(vinyl alcohol), calculated by the Painter and Coleman association model (PCAM) are examined. The thermodynamics is calculated based upon the equilibrium constants derived experimentally from infrared spectroscopies of low molecular weight analogues with similar hydrogen-bonding formation. The discrepancies between the PCAM predictions and the experimentally observed T-g and free volume variation with blending composition are attributed to the additional entropic effects introduced by the long repeated units of modifiers. The structural characteristics and hydrogen-bonding heterogeneity as derived from solid-state NMR and IR spectra support the notion that the length and size of the modifier repeated unit are responsible for such discrepancies. These observed nonidealities can be interpreted as competition between inter- and intraassociations (Delta H-m favored), which depend on the entropy rise associated with the amount of increase of the breaking off of the self-association in phenolic and modifiers within blends. While PCAM is based on "true" miscibility, however, minor modification is required to better describe the thermodynamics for "real" blends where microdomain heterogeneity with size greater than that defined by thermodynamic criteria may be present.
Hydrogen bonding effect on the poly(ethylene oxide), phenolic resin, and lithium perchlorate-based solid-state electrolyte
(2004-01-15)
Chen, HW
;
Jiang, CH
;
Wu, HD
;
Chang, FC
;
應用化學系
The interaction behavior of solid-state polymer electrolytes composed of poly(ethylene oxide) (PEO)/novolac-type phenolic resin and lithium perchlorate (Li-ClO4) was investigated in detail by DSC, FTIR, ac impedance, DEA, solid-state NMR, and TGA. The hydrogen bonding between the hydroxyl group of phenolic and ether oxygen of the PEO results in higher basicity of the PEO. The higher basicity of the ether group can dissolve the lithium salts more easily and results in a greater fraction of "free" anions and thus higher ionic conductivity. DEA results demonstrated that addition of the phenolic increases the dielectric constant because of the partially negative charge on the ether group induced by the hydrogen bonding interaction between ether oxygen and the hydroxyl group. The study showed that the blend of PEO(100)/LiClO4(25)/phenolic(15) possesses the highest ionic conductivity (1.5 X 10(-5) S cm(-1)) with dimensional stability. (C) 2003 Wiley Periodicals, Inc.
Miscibility and hydrogen bonding in blends of poly(vinyl acetate) with phenolic resin
(2002-04-01)
Huang, MW
;
Kuo, SW
;
Wu, HD
;
Chang, FC
;
Fang, SY
The miscibility of phenolic resin and poly(vinyl acetate) (PVAc) blends was investigated by differential scanning calorimeter (DSC), Fourier transform infrared spectroscopy (FT-IR) and solid state C-13 nuclear magnetic resonance (NMR). This blend displays single glass transition temperature (T-g) over entire compositions indicating that this blend system is miscible in the amorphous phase due to the formation of hydrogen bonding between hydroxyl groups of phenolic resin and carbonyl groups of PVAc. Quantitative measurements on fraction of hydrogen-bonded carbonyl group using both C-13 solid-state NMR and FT-IR analyses result in good agreement between these two spectroscopic techniques. According to the proton spin-lattice relaxation time in the rotating frame (T-lp(H)), the phenolic/PVAc blend is intimately mixed on a scale less than 2-3 nm. Furthermore, the inter-association equilibrium constant and its related enthalpy of phenolic/PVAc blends were determined as a function of temperatures by infrared spectra based on the Painter-Coleman association model. (C) 2002 Elsevier Science Ltd. All rights reserved.
Molecular dynamics and mechanical properties correlations of PA6/PPO blends compatibilized with SMA
(1999-06-01)
Chu, PP
;
Huang, JM
;
Wu, HD
;
Chiang, CR
;
Chang, FC
The effects of the compatibilizer, styrene maleic anhydride (SMA-8% MA) upon the change of morphology and molecular dynamics of polyamide-6 (PA6) and poly (2,6-dimethyl-1,4-phenylene oxide) (PPO) blends were investigated by means of solid-state NMR techniques. With increasing amounts of SMA, the domains correspond to PA6 and PPO are reduced and the polymer segmental mobility increased. The correlation between NMR relaxation time, T-1p(H), and the bulk mechanical properties provide a molecular level understanding of the modification of molecular dynamics by the compatibilizer (SMA). The correlation shows that the tensile strength is governed mainly by the morphology, but modulated by the PA6 crystallinity, while the tensile elongation and impact strength are closely affected by both the molecular mobility and morphology. The annealing process improved only the tensile strength, but deteriorated tensile elongation and impact strength due to the increase of PA6 crystallinity, which induced phase separation after annealing. This study raised an important point that the polymer mechanical properties are most sensitive to the molecular structure and dynamics take place within the range of 20 Angstrom to few hundred Angstrom. (C) 1999 John Wiley & Sons, Inc.
Novel determination of the crystallinity of syndiotactic polystyrene using FTIR spectrum
(2001-05-01)
Wu, HD
;
Wu, SC
;
Wu, ID
;
Chang, FC
;
應用化學系
The crystallinity and crystallization behavior of syndiotactic polystyrene (s-PS) alpha- and beta -crystals have been thoroughly examined using the Fourier Transform Infrared (FTIR). It is shown that absorptivity ratio of respective absorbances of "alpha -crystal/amorphous, a(alpha)" and "beta -crystal/amorphous, a(beta)" can be quantitatively determined using FTIR spectra ranging from 865 to 820 cm(-1). Results from curve fitting show that both absorptivity ratios of a(alpha) and a(beta) are 0.178 +/- 0.005 and 0.272 +/- 0.005 for alpha- and beta -crystal absorbances, respectively. The crystallization rate and crystallinity of alpha -crystal calculated from the absorptivity ratios art: higher than that of beta -crystal crystallized at 240 degreesC for the same isothermal duration in thin film sample. The formation of beta -crystal is thermodynamically more favorable while of alpha -crystal is kinetically more favorable from FTIR spectra. (C) 2001 Elsevier Science Ltd. All rights reserved.
Solid-state electrolyte nanocomposites based on poly(ethylene oxide), poly(oxypropylene) diamine, mineral clay and lithium perchlorate
(2002-08-01)
Chen, HW
;
Chiu, CY
;
Wu, HD
;
Shen, IW
;
Chang, FC
This work has demonstrated that the addition of specific amount of poly(oxypropylene) diamine (d2000) and mineral clay in the PEO-based electrolyte system can form the high conductivity film at room temperature. Specific interactions among silicate layer, d2000, ether oxygen, and lithium cation have been investigated using differential scanning calorimetry (DSC), alternating current impedance (AC impedance) and Fourier-transform infrared (FT-IR). The DSC characterization confirms that the addition of 25 w1% d2000 is able to produce low T-g and fully amorphous (PEO)(8)LiClO4/d2000 electrolyte system which produce the good environment for ionic transfer. Additionally, the incorporation of the mineral clay into the (PEO)(8)LiClO4/d2000 electrolyte system can sustain the polymeric mechanical property by its huge surface area and enhance the conductivity due to the specific interaction between silicate layers and lithium cation. FT-IR spectra confirm that the incorporation of the clay is able to dissolve the lithium salts more effectively and resulting to the higher fraction of free anions due to the strong interaction between negative charges of the silicate layers and lithium cations of the lithium salt. (C) 2002 Elsevier Science Ltd. All rights reserved.
The solid state C-13 NMR studies of intermolecular hydrogen bonding formation in a blend of phenolic resin and poly(hydroxyl ether) of bisphenol A
(2000-07-31)
Wu, HD
;
Ma, CCM
;
Chang, FC
;
應用化學系
;
Department of Applied Chemistry
Full Paper: The formation of intermolecular hydrogen bonds in blends of novolac type phenolic and poly(hydroxyl ether) of bisphenol A was investigated by studying its T-g behavior, excess volume, and solid state C-13 NMR spectra. The T-g and parameters of solid state C-13 NMR, such as the T-CH and spin-lattice relaxation time in the rotating frame T-1p(H), indicate that the London dispersion force (entropically favored) significantly affects the intermolecular hydrogen bonding of the blend. The phenoxy chain forces opening of the intra-association of phenolic and thus creates more free OHs. This strong entropic effect reduces the total hydrogen bonding of the system especially when one of the polymer is the minor component. This also results in the reduction of T-g and free volume expansion, reflecting in the increase of cross-polarization (C-H) time and molecular mobility within the phenolic/phenoxy blend.
Thermal property and hydrogen bonding in blends of poly(vinylphenol) and poly(hydroxylether of bisphenol A)
(2003)
Kuo, SW
;
Lin, CL
;
Wu, HD
;
Chang, FC
;
應用化學系
The thermal property and hydrogen bonding in polymer blends of poly(vinylphenol) (PVPh) and poly(hydroxylether of bisphenol A) (phenoxy) were investigated by differential scanning calorimetry (DSC), Fourier transform infrared spectroscopy (FTIR) and solid-state nuclear magnetic resonance (NMR). This PVPh/phenoxy blend shows single composition-dependent glass transition temperature over the entire compositions, indicating that the hydrogen bonding exists between the hydroxyl of PVPh and hydroxyl of phenoxy. The negative T-g deviation of the PVPh/phenoxy blend indicates the strong intermolecular hydrogen-bonding interaction. The inter-association constant for the PVPh/phenoxy blend is significantly higher than self-association constants of PVPh and phenoxy, revealing that the tendency toward hydrogen bonding between PVPh and phenoxy is more favorable than the intra-hydrogen bonding of the PVPh and phenoxy in the blend.