Browsing by Author "Chen, Shih-Chien"

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Micellar morphologies of self-associated diblock copolymers in acetone solution
(2007-05-21)
Tung, Pao-Hsiang
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Kuo, Shiao-Wei
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Chen, Shih-Chien
;
Lin, Chen-Lung
;
Chang, Feng-Chih
We describe the synthesis and solution morphologies of poly(vinyl phenol-b-styrene) (PVPh-b-PS) micelles and the effects that changing the copolymer composition and concentration have on self-assembly structures of PVPh-b-PS in acetone (a good solvent for PVPh). These PVPh-b-PS copolymers aggregated into spherical, rod-like, and vesicular morphologies. The transformations of the PVPh-b-PS block copolymer micelles in acetone depended on a number of parameters, including the relative block lengths, their concentrations, and the degree of self-association through hydrogen bonding of the coronal PVPh chains. We also investigated the morphologies of the micelles formed from acetone solutions of poly (4-tert-butoxystyrene-b-styrene) (PtBOS-b-PS) copolymers having the same degree of polymerization as the precursor of PVPh-b-PS copolymer before hydrolysis reaction. Our results indicate that the micelles formed from PVPh-b-PS copolymers in acetone were more complicated than those prepared from PtBOS-b-PS copolymers in acetone because hydrogen bonding occurs in the micelle corona of the PVPh block. Finally, we also discussed the morphology transition when the self-association hydrogen bonding of PVPh block was destroyed by adding proton acceptor poly(4-vinylpyridine) (P4vp). (c) 2007 Elsevier Ltd. All rights reserved.
On Modulating the Phase Behavior of Block Copolymer/Homopolymer Blends via Hydrogen Bonding
(2010-01-26)
Chen, Shih-Chien
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Kuo, Shiao-Wei
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Jeng, U-Ser
;
Su, Chun-Jen
;
Chang, Feng-Chih
We have investigated the phase behavior or poly(4-vinylphenol-b-styrene) (PVPh-b-PS) when respectively blended with poly(4-vinylpyridine) (NVP), poly(methyl methacrylate) (PMMA), and PVPh homopolymers by mediated hydrogen bonding strengths with the PVPh block of the copolymer. The Fourier transform infrared spectroscopic result indicates that the PVPh-b-PS/P4VP blend has a much higher fraction (f(H)) of hydrogen-bonded PVPh blocks for it significantly higher miscibility compared with the blends with PMMA and PVPh homopolymers. Consequently, the PVPh-b-PS/P4VP blend, behaving as a neat diblock copolymer, exhibited a series of order-order phase transitions from the lamellar, gyroid, hexagonally packed cylinder to body-centered cubic structures when the P4VP content increases from 6 to 71% (volume fraction), as evidenced consistently by transmission electron microscopy and small-angle X-ray scattering. In contrast, both file PVPh-b-PS/PMMA and PVPh-b-PS/PVPh blends maintained essentially the lamellar structure upon a similar volume fraction increase in the homopolymers; the lamellar structure, however, was distorted to different extents at higher volume fractions of the additives, depending on the hydrogen bonding strength. On the basis of the results, the ratio of interassociation equilibrium constant (KA) over self-association equilibrium constant (K(B)), K(A)/K(B), is introduced as a convenient guide in estimating the phase behavior of similar polymer blends featuring hydrogen bonding interactions between file homopolymer additive and copolymer: with a K(A)/K(B) ratio much larger than unity, the blend system tends to behave as a neat copolymer; with a K(A)/K(B) ratio significantly smaller than unity, phase separation instead of order-order phase transitions call be expected for the blend above certain volume fraction of homopolymer additive.
On Modulating the Self-Assembly Behaviors of Poly(styrene-b-4-vinylpyridine)/Octyl Gallate Blends in Solution State via Hydrogen Bonding from Different Common Solvents
(2011-08-16)
Chen, Shih-Chien
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Kuo, Shiao-Wei
;
Chang, Feng-Chih
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應用化學系
;
Department of Applied Chemistry
We have investigated the complexation-induced phase behavior of the mixtures of poly(styrene-b-4-vinylpyridine) (PS-b-P4VP) and octyl gallate (OG) due to hydrogen bonding in different solvents. The Fourier transform infrared spectroscopic result indicates that the hydrogen-bonding was formed between the P4VP blocks and OG in both THF and DMF, implying the P4VP blocks can bind to OG. For PS-b-P4VP/OG mixture in chloroform, the morphological transitions were induced from the unimer configuration to swollen aggregate and complex-micelles by adding OG. Interestingly, the complex-micelles can lead the formation of the honeycomb structure from chloroform solution. The PS-b-P4VP/OG mixture in THF, behaving an amphiphilic diblock copolymer in solution state, exhibited a series of morphological transitions from sphere, pearl-necklace-liked rod, worm-liked rod, vesicle, to core shell-corona aggregates by increasing the OG content. In contrast, the PS-b-P4VP/OG mixture in DMF maintained the unimer configuration upon adding OG. Therefore, the complexation-induced morphology of the mixtures of PS-b-P4VP and OG can be mediated by adopting different common solvents to affect the self-assembly behavior.
Regular honeycomb porous polymer films based on amphiphilic block copolymer
(2006-11-20)
Tung, Pao-Hsaing
;
Huang, Chih-Feng
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Chen, Shih-Chien
;
Hsu, Chih-Hao
;
Chang, Feng-Chih
Syntheses, Specific Interactions, and pH-Sensitive Micellization Behavior of Poly [vinylphenol-b-2-(dimethylamino)ethyl methacrylate] Diblock Copolymers
(2008-11-25)
Chen, Shih-Chien
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Kuo, Shiao-Wei
;
Liao, Chun-Syong
;
Chang, Feng-Chih
;
應用化學系
We have used anionic polymerization to prepare a series of poly [vinylphenol-b-2(dimethylamino)ethyl methacrylate] (PVPh-b-PDMAEMA) block copolymers. These block copolymers are miscible, with strong specific interactions occurring between the OH groups of the PVPh segments and the tertiary ammonium groups of the PDMAEMA segments. These PVPh-b-PDMAEMA diblock copolymers exhibit higher glass transition temperatures than do the corresponding PVPh/partially protonated PDMAEMA blends obtained from DMSO solution, which we suspect exist in the form of separate coils. The blocks of the PVPh-b-PDMAEMA diblock copolymers interact strongly, resulting in polymer complex aggregation similar to the behavior of PVPh/partially protonated PDMAEMA blend complexes obtained from methanol solution. The spin-lattice relaxation times in the rotating frame, determined through solid state NMR spectroscopic analysis, provided clear evidence that the polymer complex aggregates formed from the diblock copolymers have shorter values of TV, than do the corresponding separated coils in the miscible blends. In addition, these PVPh-b-PDMAEMA diblock copolymers exhibit a novel type of pH sensitivity: at low pH, compact spherical micelles are formed possessing PDMAEMA coronas and PVPh cores; at medium pH, vesicles are observed, consisting of partially protonated hydrophilic PDMAEMA shells and hydrophobic PVPh cores; at high pH, the spherical micelles that formed comprised ionized PVPh coronas and deprotonated hydrated-PDMAEMA cores, i.e., phase inversion of the micelles formed at pH 2.