Browsing by Author "Kuo, SW"

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A new strategy for the one-step synthesis of block copolymers through simultaneous free radical and ring opening polymerizations using a dual-functional initiator
(2005-02-14)
Huang, CF
;
Kuo, SW
;
Lee, HF
;
Chang, FC
;
應用化學系
Block copolymers are fascinating and complex materials that have been used in a range of diverse scientific and technological capacities. We demonstrate that a single one-step approach based on dual simultaneous polymerizations is a viable technique for the synthesis of a wide range of block copolymers by combining two dissimilar polymerization systems and using a dual-functional initiator. The main advantage of this methodology is that a simple, one-step, and simultaneous polymerization occurs in the bulk, which makes this process very attractive from both industrial and academic points of view. We plan to study the reaction kinetics and evaluate how well the ring opening catalyst [in this case, Sn(oct)(2)] works under reverse ATRP conditions. (C) 2004 Elsevier Ltd. All rights reserved.
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.
Characterization of poly(vinyl pyrrolidone-co-isobutylstyryl polyhedral oligomeric silsesquioxane) nanocomposites
(2004-02-15)
Xu, HY
;
Kuo, SW
;
Huang, CF
;
Chang, FC
;
應用化學系
Poly(vinyl pyrrolidone-co-isobutyl styryl polyhedral oligomeric silsesquioxane)s (PVP-POSS) were synthesized by one-step polymerization and characterized 13 using FTIR, high-resolution H-1-NMR, solid-state C-13-NMR, Si-29-NMR, GPC, and DSC. The POSS content can be controlled by varying the POSS feed ratio. The T-g of the PVP-FOSS hybrid is influenced by three main factors: (1) a diluent role of the POSS in reducing the self-association of the PVP; (2) a strong interaction between the POSS siloxane and the PVP carbonyl, and (3) physical aggregation of nanosized POSS. At a relatively low FOSS content, the role as diluent dominates, resulting in a decrease in T-g. At a relatively high POSS content, the last two factors dominate and result in T-g increase of the PVP-POSS hybrid. (C) 2003 Wiley Periodicals, Inc.
Crystallization kinetics and morphology of binary phenolic/poly(epsilon-caprolactone) blends
(2004-01-01)
Kuo, SW
;
Chan, SC
;
Chang, FC
;
應用化學系
;
Department of Applied Chemistry
For the first time, quantitative analyses of the crystallization kinetics, surface free energy of chain folding, and morphology in phenolic/poly(epsilon-caprolactone) (PCL) binary blends have been studied. The spherulite growth rate and the overall crystallization rate depend on the crystallization temperature and PCL content in the blend. In addition, the crystallization and melting temperatures of the PCL phase decrease with an increase in the phenolic content. An Avrami analysis shows that the addition of phenolic to PCL results in a decrease in the overall crystallization rate of the PCL phase. The presence of an amorphous phenolic phase results in a reduction in the rate of the spherulite growth of PCL. The surface free energy of folding increases with increasing phenolic content, and the crystal thickness of a phenolic/PCL blend, according to small-angle X-ray scattering (SAXS), is greater than that of pure PCL because of the increase in the surface free energy of chain folding and the decrease in the degree of supercooling. The observed domain size of the crystalline/amorphous phase (5.9 nm) from SAXS is also consistent with that from solid-state NMR (3-20 nm). All these results indicate that the crystallization ability of PCL decreases with increasing phenolic content in the blends. (C) 2003 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 42: 117-128,2004.
Effect of bisphenol A on the miscibility, phase morphology, and specific interaction in immiscible biodegradable poly(epsilon-caprolactone)/poly(L- lactide) blends
(2006-04-15)
Kuo, SW
;
Huang, CF
;
Tung, YC
;
Chang, FC
;
應用化學系
We have investigated the enhancement in miscibility, upon addition of bisphenol A (BPA) of immiscible binary biodegradable blends of poly(epsilon-caprolactone) (PCL) and poly(L-lactide) (PLLA). That BPA is miscible with both PCL and PLLA was proven by the single value of T-g observed by differential scanning calorimetry (DSC) analyses over the entire range of compositions. At various compositions and temperatures, Fourier transform infrared spectroscopy confirmed that intermolecular hydrogen bonding existed between the hydroxyl group of BPA and the carbonyl groups of PCL and PLLA. The addition of BPA enhances the miscibility of the immiscible PCL/PLLA binary blend and transforms it into a miscible blend at room temperature when a sufficient quantity of the BPA is present. In addition, optical microscopy (OM) measurements of the phase morphologies of ternary BPA/PCL/ PLLA blends at different temperatures indicated an upper critical solution temperature (UCST) phase diagram, since the Delta K effect became smaller at higher temperature (200 degrees C) than at room temperature. An analysis of infrared spectra recorded at different temperatures correlated well with the OM analyses. (c) 2006 Wiley Periodicals, Inc.
Effect of copolymer composition on the miscibility of poly(styrene-co-acetoxystyrene) with phenolic resin
(2001-11-01)
Kuo, SW
;
Chang, FC
;
應用化學系
;
Department of Applied Chemistry
The miscibility behavior and specific interaction of phenolic/polystyrene-co-acetoxystyrene, (PS-co-PAS) blends by varying acetoxystyrene contents of the PS-co-PAS copolymer were investigated by differential scanning calorimetry (DSC) and Fourier transform infrared spectroscopy (FT-IR). A miscibility window was found when the acetoxystyrene fraction in the copolymer is higher than 45 mol% in phenolic/PS-co-PAS = 50/50 blend system. Painter-Coleman Association Model (PCAM) is able to predict the miscibility window at 150 degreesC compared with our experimental results based on DSC analyses. (C) 2001 Elsevier Science Ltd. All rights reserved.
Effect of hydrogen bonding strength on the microstructure and crystallization behavior of crystalline polymer blends
(2003-08-26)
Kuo, SW
;
Chan, SC
;
Chang, FC
;
應用化學系
;
Department of Applied Chemistry
Combinations of differential scanning calorimetry, Fourier transform infrared spectroscopy, optical microscopy, and small-angle X-ray scattering were used to investigate the influence of hydrogen bonding strength on the crystallization kinetics and morphologies in poly(epsilon-caprolactone) (PCL) blends with three different well-known hydrogen bond donating polymers, i.e., phenolic, poly(vinylphenol) (PVPh), and phenoxy. The strength of the intercomponent interactions in the blend system depends on the hydrogen bond donor group and occurs, based on the Painter-Coleman association model, in the order phenolic/PCL > PVPh/PCL > phenoxy/PCL. Significantly reduced overall crystallization kinetics and crystal growth rate in PCL crystalline phase were also in the order phenolic/PCL > PVPh/PCL > phenoxy/PCL, which is consistent with the relative strengths of their intermolecular hydrogen bonding. Our experimental findings show that the hydrogen bonding strength has a greater effect on the rate of crystallization than does the influence of the blend's glass transition temperature, which is related to its chain mobility. In addition, values of the surface free energy of chain folding and crystalline thickness in PCL blends depend strongly on the relative ratio of the interassociation equilibrium constant and the self-association equilibrium constant (K-A/K-B). In phenolic/PCL and PVPh/PCL blends, the values of the surface free energies of chain folding in the PCL crystalline phase are increased with an increase in the content of the hydrogen bond donating polymer since the K-A is greater than the K-B in these two blend systems. In contrast, in the phenoxy/PCL blend system, the smaller K-A relative to the K-B induces a smaller value for the surface free energy of chain folding than that of pure PCL. Various miscible crystalline/amorphous binary polymer blends exhibiting either strong hydrogen bonding or weak interactions are also reviewed.
Effect of hydrolysis on the strength of hydrogen bonds and T-g of poly(vinylphenol-co-acetoxystyrene)
(2003-07-15)
Kuo, SW
;
Liu, WP
;
Chang, FC
;
應用化學系
;
Department of Applied Chemistry
A series of poly(vinylphenol-co-acetoxystyrene) (PVPh-co-PAS) copolymers were prepared by partial hydrolyses of poly(acetoxystyrene) (PAS) in acidic and basic solutions. Higher glass transition temperature, higher fraction of hydrogen-bonded carbonyl group, and higher interassociation equilibrium constant were observed for copolymers with same composition prepared from the acidic hydrolysis than from the basic hydrolysis because the sequence distribution of the former is relatively more random than the latter. Infrared spectra provide positive evidence in terms of sequence distribution, glass transition temperature, and hydrogen-bonding strength in poly(vinylphenol-co-acetoxystyrene) by prepared these two hydrolysis methods.
Effect of inert diluent segment on the miscibility behavior of poly(vinylphenol) with poly(acetoxystyrene) blends
(2002-08-01)
Kuo, SW
;
Chang, FC
;
應用化學系
;
Department of Applied Chemistry
Polymer blends of poly(vinylphenol) (PVPh) and poly(styrene-co-vinylphenol) with poly(p-acetoxystyrene) (PAS) were prepared by solution casting from tetrahydrofuran solution. The thermal properties and hydrogen bonding of the blends were investigated by differential scanning calorimetry (DSC) and Fourier transform infrared spectroscopy. Although hydrogen bonding existed between the PVPh and PAS segments, the experimental results indicated that PVPh is immiscible with PAS as shown by the existence of two glass-transition temperatures over the entire composition range by DSC. This phenomenon is attributed to the strong self-association of PVPh, intramolecular screening, and functional group accessibility effects of the PVPh/PAS blend system. However, the incorporation of an inert diluent moiety such as styrene into the PVPh chain renders the modified polymer to be miscible with PAS. Copolymers containing between 16 and 51 mol % vinylphenol were fully miscible with PAS according to DSC studies. These observed results were caused by the reduction of the strong self-association of PVPh and the increase of the interassociation between PVPh and PAS segments with the incorporation of styrene on the PVPh chain. According to the Painter-Coleman association model, the interassociation equilibrium constant of PVPh/PAS blends was determined by a model compound and polymer blend. Good correlation between these two methods was obtained after considering the intramolecular screening and functional group accessibility effect in the polymer blend. (C) 2002 Wiley Periodicals, Inc.
Effects of copolymer composition and free volume change on the miscibility of poly(styrene-co-vinylphenol) with poly(epsilon-caprolactone)
(2001-10-23)
Kuo, SW
;
Chang, FC
;
應用化學系
;
Department of Applied Chemistry
A series of poly(styrene-co-vinylphenol) (PSOH) copolymers were prepared and characterized. The miscibility and hydrogen bonding between the partially hydroxylated polystyrene with poly(is an element of -caprolactone) (PCL) blend were investigated by differential scanning calorimetry and Fourier transform infrared spectroscopy. The copolymers containing higher than 13 mol % vinylphenol were found to be fully miscible with PCL according to differential scanning calorimetry studies. Quantitative analyses on the fraction of hydrogen-bonded carbonyl groups in the solid state were made by FTIR spectroscopy, and good correlations between thermal behaviors and infrared results were observed. The critical vinylphenol content of 0.1 mol % in PSOH copolymer for the blend to be miscible was predicted from the Painter-Coleman association model and binary interaction model. The discrepancy between the experimental result and theoretical prediction is probably caused by significant free volume increase in this blend system, which is analyzed by the Kovacs' free volume theory. The free volume of the PSOH/PCL is increased which give a positive contribution in the Gibbs free energy. As a result, the polystyrene needs to incorporate more poly(vinylphenol) in PSOH copolymer in order to overcome the free energy increased caused by the free volume increase predicted by the Painter-Coleman association model and the binary interaction model.
Effects of inert diluent segment and hydrogen bonding in poly(styrene-co-methacrylamide) copolymers
(2003)
Kao, HC
;
Kuo, SW
;
Chang, FC
;
應用化學系
;
Department of Applied Chemistry
A series of random poly(styrene-co-methacrylacmide) (PS-co-PMAAM) copolymers were prepared by free radical polymerization of styrene and methacrylamide monomers. The PS and PMAAM units of the copolymer do not have any specific interaction based on the Kwei equation and the infrared spectroscopy result, indicating that the styrene plays strictly as an inert diluent segment on the PMAAM main chain. This result offers an opportunity to enhance the miscibility and specific interaction between the amide group of PMAAM and the functional group of second polymer by reducing the strong self-association of the PMAAM.
Enhanced thermal properties of PS nanocomposites formed from inorganic POSS-treated montmorillonite
(2004-04-13)
Yei, DR
;
Kuo, SW
;
Su, YC
;
Chang, FC
;
應用化學系
We have prepared polystyrene/clay nanocomposites using an emulsion polymerization technique. The nanocomposites were exfoliated at up to a 3 wt% content of pristine clay relative to the amount of polystyrene (PS). We used two different surfactants for the montmorillonite: the aminopropylisobutyl polyhedral oligomeric silsesquioxane (POSS) and the ammonium salt of cetylpyridinium chloride (CPC). Both surfactants can intercalate into the layers of the pristine clay dispersed in water prior to polymerization. Although the d spacing of the POSS-intercalated clay is relatively smaller than that of the CPC-intercalated clay, PS more easily intercalates and exfoliates the POSS-treated clay than the CPC-treated clay. IR spectroscopic analysis further confirms the intercalation of POSS within the clay layers. We used X-ray diffraction (XRD) and transmission electron microscopy (TEM) to characterize the structures of the nanocomposites. The nanocomposite prepared from the clay treated with the POSS containing surfactant is exfoliated, while an intercalated clay was obtained from the CPC-treated surfactant. The molecular weights of polystyrene (PS) obtained from the nanocomposite is slightly lower than the virgin PS formed under similar polymerization conditions. The value of T, of the PS component in the nanocomposite is 8 degreesC higher than the virgin PS and its thermal decomposition temperature (21 degreesC) is also higher significantly. The presence of the POSS unit in the MMT enhances the thermal stability of the polystyrene. (C) 2004 Elsevier Ltd. All rights reserved.
Enhanced thermal properties of PS nanocomposites formed from montmorillonite treated with a surfactant/cyclodextrin inclusion complex
(2005-01-26)
Yei, DR
;
Kuo, SW
;
Fu, HK
;
Chang, FC
;
應用化學系
We have prepared polystyrene/clay nanocomposites using an emulsion polymerization technique. The nanocomposites were exfoliated at 3 wt% content of pristine clay relative to the amount of polystyrene (PS). We employed two surfactants for the montmorillonite: cetylpyridinium chloride (CPC) and the CPC/alpha-CD inclusion complex. Prior to polymerization, each surfactant intercalates into the layers of the pristine clay dispersed in water. The inclusion complex was characterized by X-ray diffraction, C-13 CP/MAS NMR spectra, and H-1 NMR spectroscopy, and TGA. X-ray powder patterns of the CPC/alpha-CD complex indicate that the alpha-CDs units form channels. The C-13 CP/MAS NMR spectrum of the complex suggests that a CPC chain is included in the channel formed by the alpha-CDs. The H-1 NMR spectra of the complexes indicate that the stoichiometry of the complexes is 1:2 (i.e. one CPC molecule and two alpha-CD units). The TGA reveals that the inclusion complex has higher thermal stability relative to the virgin CPC. We employed both X-ray diffraction (XRD) and transmission electron microscopy (TEM) to characterize the structures of the nanocomposites. The value of T-g of the PS component in the nanocomposite is 6degreesC higher than that of the virgin PS and its thermal decomposition temperature is 33degreesC higher. The CPC/alpha-CD-treated clay is more effective than is virgin CPC-treated clay at enhancing the thermal stability of polystyrene. (C) 2004 Published by Elsevier Ltd.
Glass transition temperatures of poly(hydroxystyrene-co-vinylpyrrolidone-co-isobutylstyry1 polyhedral oligosilsesquioxanes)
(2002-09-01)
Xu, HY
;
Kuo, SW
;
Lee, JS
;
Chang, FC
;
應用化學系
A series of poly(hydroxystyrene-co-vinylpyffolidone-co-isobutylstyryl polyhedral oligosilsesquioxanes) (PHS-PVP-POSS) hybrid polymers with various POSS contents was prepared by free radical copolymerization of acetoxystyrene, vinylpyrrolidone with styrylisobutylpolyhedral oligosilsesquioxanes (POSS), followed by selective removal of the acetyl protective group. The POSS content of a hybrid polymer can be effectively controlled by varying the feed ratios of reactants. The T-g of the POSS hybrid increases with the POSS content of PHS-PVP-POSS hybrids. The mechanism of T-g enhancement in these PHS-PVP-POSS hybrids was investigated using DSC, FTIR and GPC. The formation of the physically cross-linked POSS in these hybrid polymers trends to restrict polymer chain motion and results in significant T-g increase. (C) 2002 Published by Elsevier Science Ltd.
Homopolymerization and copolymerization of tert-butyl methacrylate and norbornene with nickel-based methylaluminoxane catalysts
(2004-05-05)
Huang, CF
;
Wang, SK
;
Kuo, SW
;
Huang, WJ
;
Chang, FC
The homopolymerization and copolymerization of tert-butyl methacrylate (tBMA) and norbornene (NB) with nickel(II) acetylacetonate in combination with methylaluminoxane were systematically investigated. This catalytic system showed high activity toward the homopolymerization of both NB and tBMA. For these copolymerizations, activity was gradually lost with an addition of tBMA to NB or of NB to tBMA. This result was qualitatively explained with the trigger coordination mechanism. Furthermore, the determination of the reactivity ratios indicated a significantly whigher reactivity for NB than for tBMA (r(NB) = 4.14 and r(tBMA) = 0.097), and this was interpreted by the coordination mechanism. The synthesized acrylate/NB copolymers exhibited glass-transition temperatures of 100-250degreesC. The absence of crystallinity and the homogeneous repartition of the monomer units along the main chain yielded products with high transparency and high stability. (C) 2004 Wiley Periodicals, Inc.
Hydrogen bonding interactions and miscibility between phenolic resin and octa(acetoxystyryl) polyhedral oligomeric silsesquioxane (AS-POSS) nanocomposites
(2006-02-15)
Kuo, SW
;
Lin, HC
;
Huang, WJ
;
Huang, CF
;
Chang, FC
We have synthesized a polyhedral oligomeric silisesquioxane (POSS) derivative containing eight acetoxystyryl functional groups [octa(acetoxystyryl)octasilsesquioxane (AS-POSS)] and then blended it with phenolic resin to form nanocomposites stabilized through hydrogen bonding interactions between the phenolic resin's hydroxyl group and the AS-POSS derivative's carbonyl and siloxane groups. One-and two-dimensional infrared spectroscopy analyses provided positive evidence for these types of hydrogen bonding interactions. In addition, we calculated the interassociation equilibrium constant, based on the Painter-Coleman association model (PCAM), between phenolic resin and POSS indirectly from the fraction of hydrogen-bonded carbonyl groups; quantitative analyses indicate that the hydroxyl-siloxane interassociation from the PCAM is entirely consistent with the classical Coggesthall and Saier (C and S) methodology. From a thermal analysis, we observed that the miscibility between phenolic and AS-POSS occurs at a relatively low AS-POSS content, which characterizes this mixture as a polymer nanocomposite system. (c) 2006 Wiley Periodicals, Inc.
Influence of PMMA-chain-end tethered polyhedral oligomeric silsesquioxanes on the miscibility and specific interaction with phenolic blends
(2006-01-10)
Huang, CF
;
Kuo, SW
;
Lin, FJ
;
Huang, WJ
;
Wang, CF
Two different molecular weights of poly(methyl methacrylate) (PMMA) and PMMA containing polyhedral oligomeric silsesquioxane (PMMA-POSS) homopolymers have been prepared via the atom transfer radical polymerization (ATRP) technique. The miscibility and specific interaction behaviors of PMMA-POSS and PMMA with phenolic resin were investigated by differential scanning calorimetry and Fourier transform infrared spectroscopy (FTIR). FTIR results reveal that at least three competing equilibriums are present in the phenolic/PMMA-POSS blend: self-association of phenolic (hydroxyl-hydroxyl), hydroxyl-siloxane interassociation between phenolic and POSS, and hydroxyl-carbonyl interassociation between phenolic and PMMA. Among these blends, single and higher T(g)s of these phenolic/PMMA-POSS blends were observed than the corresponding phenolic/PMMA blends at same composition, revealing that a stronger interassociation interaction of hydroxyl-siloxane than the hydroxyl-carbonyl interaction. Furthermore, we also found the screening effect in phenolic/LPMMA-POSS blends that tends to significantly decrease the hydrogen bond formation of the hydroxyl-carbonyl interassociation.
Investigating the effect of miscibility on the ionic conductivity of LiClO4/PEO/PCL ternary blends
(2004-11-02)
Chiu, CY
;
Chen, HW
;
Kuo, SW
;
Huang, CF
;
Chang, FC
We demonstrate that miscibility affects the ionic conductivity of ternary polymer blends of lithium perchlorate (LiClO4), poly(ethylene oxide) (PEO), and poly(E-caprolactone) (PCL). Although individually these three binary blends are fully miscible, a closed immiscibility loop exists in the ternary blend phase diagram as a result of the complicated interactions among LiClO4, PEO, and PCL. The addition of PCL suppresses the crystallization of PEO and results in higher ionic conductivity. FTIR spectroscopy studies indicate that an excess PCL content causes immiscibility, which results in PCL being excluded from the ternary blends. Consequently, the maximum ionic conductivity (6.3 x 10(-7) S cm(-1)) at ambient temperature of ternary blends having a fixed LiClO4 content (25 wt %) is at a composition of 25/60/15 (LiClO4:PEO:PCL).
Low-dielectric, nanoporous polyimide films prepared from PEO-POSS nanoparticles
(2005-11-14)
Lee, YJ
;
Huang, JM
;
Kuo, SW
;
Chang, FC
;
應用化學系
Dielectric insulator materials that have low dielectric constants (k < 2.5) are required as inter-level dielectrics to replace silicon dioxide (SiO2) in future semiconductor devices. In this paper, we describe a novel method for preparing nanoporous polyimide films through the use of a hybrid PEO-POSS template. We generated these nanoporous foams are generated by blending polyimide as the major phase with a minor phase consisting of the thermally labile PEO-POSS nanoparticles. The labile PEO-POSS nanoparticles would undergoes oxidative thermolysis to releases small molecules as byproducts that diffuse out of the matrix to leave voids into the polymer matrix. We achieved significant reductions in dielectric constant (from k = 3.25 to 2.25) for the porous PI hybrid films, which had pore sizes in the range of 1040 nm. (c) 2005 Elsevier Ltd. All rights reserved.
Low-surface-free-energy materials based on polybenzoxazines
(2006)
Wang, CF
;
Su, YC
;
Kuo, SW
;
Huang, CF
;
Sheen, YC