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Syntheses and specific interactions of poly(epsilon-caprolactone)-block-poly(vinyl phenol) copolymers obtained via a combination of ring-opening and atom-transfer radical polymerizations
(2006-11-01)
Kuo, Shiao-Wei
;
Huang, Chih-Feng
;
Lu, Chu-Hua
;
Lin, Ho-May
;
Jeong, Kwang-Un
A series of PCL-b-PVPh diblock copolymers were prepared through combinations of ring-opening and atom-transfer radical polymerizations of c-caprolactone and 4-acetoxystyrene, and subsequent selective hydrolysis of the acetyl protective group. This PCL-b-PVPh diblock copolymer shows a single glass transition temperature over the entire composition range, indicating that this copolymer is able to form a miscible amorphous phase due to the formation of intermolecular hydrogen bonding between the hydroxyl of PVPh and the carbonyl of PCL. In addition, DSC analyses also indicated that the PCL-b-PVPh diblock copolymers have higher glass transition temperatures than their corresponding PCL/PVPh blends. FT-IR was used to study the hydrogen-bonding interaction between the PVPh hydroxyl group and the PCL carbonyl group at various compositions.
Formation of honeycomb structures and superhydrophobic surfaces by casting a block copolymer from selective solvent mixtures
(2007-02-02)
Tung, Pao-Hsiang
;
Kuo, Shiao-Wei
;
Jeong, Kwang-Un
;
Cheng, Stephen Z. D.
;
Huang, Chih-Feng
Poly(vinyl phE!nol)-block-polystyrene (PVPh-b-PS) diblock copolymers are synthesized by sequential anionic polymerization with sec-butyl lithium as the initiator. The Pvph-b-PS diblock copolymer is cast (on a substrate) from several solvent mixtures that contain tetrahydrofuran/toluene ratios of 1:0.1, 1:1, and 1:2. After solvent evaporation the resulting films are characterized by SEM, TEM, and contact angle measurements. A honeycomb structure is fabricated from the vesicle structure at relatively low toluene contents. On the contrary, at relatively higIier toluene contents, a micelle structure with porous microspheres is formed, which possesses higher surface roughness and results in film surface superhydrophobicity. The simple method described here that uses common/selective mixed solvents may be easily extended to prepare honeycomb structures and superhydrophobic surfaces simultaneously from a wide variety of block copolymers by carefully controlling the weight composition of the block copolymer and the selective solvent con-tent.
Micellization and the surface hydrophobicity of amphiphilic poly(vinylphenol)-block-polystyrene block copolymers
(2007-08-20)
Tung, Pao-Hsaing
;
Kuo, Shiao-Wei
;
Chan, Shih-Chien
;
Hsu, Chih-Hao
;
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.
Supramolecular micellization of diblock copolymer mixtures mediated by hydrogen bonding for the observation of separated coil and chain aggregation in common solvents
(2008-02-01)
Kuo, Shiao-Wei
;
Tung, Pao-Hsaing
;
Lai, Chih-Ling
;
Jeong, Kwang-Un
;
Chang, Feng-Chih
This paper describes a new approach towards preparing self-assembled hydrogen-bonded complexes that have vesicle and patched spherical structures from two species of block copolymer in non-selective solvents. The assembly of vesicles from the intermolecular complex formed after mixing polystyrene-block-poly(4-vinyl phenol) (PS-b-PVPh) with poly(methyl methacrylate)-block-poly(4-vinylpyridine) (PMMA-b-P4VP) in tetrahydrofuran (THF) is driven by strong hydrogen bonding between the complementary binding sites on the PVPh and P4VP blocks. In contrast, well-defined patched spherical micelles form after blending PS-b-PVPh with weaker hydrogen bonds form between the PVPh and P4VP blocks in DMF, relative to those in THF, which results in the formation of spherical micelles that have compartmentalized coronas that consist of PS and PMMA blocks.
Synthesis of Photoisomerizable Block Copolymers by Atom Transfer Radical Polymerization
(2009-09-22)
Huang, Chih-Feng
;
Chen, Wei
;
Russell, Thomas P.
;
Balazs, Anna C.
;
Chang, Feng-Chih
A series of polystyrene-block-poly(n-butyl methacrylate) (PS-b-PnBMA) diblock copolymers (di-BCPs) with an azobenzene moiety [trans-4-methacryloyloxyazobenzene (MOAB)] in the PnBMA segment was prepared by atom transfer radical polymerization (ATRP). P(nBMA-co-MOAB) macroinitiators were prepared by activators regenerated by electron transfer (ARGET) ATRP. The MOAB was slightly more reactive than nBMA, resulting in a weak gradient fashion of copolymer. The macroinitiators were subsequently chain-extended with styrene. Acceleration of the ATRP rate was observed in the presence of a reducing agent. P(nBMA-co-MOAB)-b-PS di-BCPs were obtained with relatively narrow molecular weight distributions ((M) over bar (w)(M) over bar (n) = 1.16-1.49) and the molecular weights were in good agreement with the theoretical values. The efficiency of photoisomerization of the MOAB units was above 80%. DSC traces showed a single T(g) suggesting the block copolymers were miscible before UV irradiation. After UV irradiation, the X-ray reflectivity measurements showed the beating of two frequencies, indicating the formation of island-hole structure.
The Self-Assembled Structure of the Diblock Copolymer PCL-b-P4VP Transforms Upon Competitive Interactions with Octaphenol Polyhedral Oligomeric Silsesquioxane
(2009-12-16)
Lu, Chu-Hua
;
Kuo, Shiao-Wei
;
Chang, Wen-Teng
;
Chang, Feng-Chih
;
應用化學系
This paper describes the miscibility and self-assembly, mediated by hydrogen-bonding interactions, of new block copolymer/nanoparticle blends. The morphologies adopted by the immiscible poly[(epsilon-caprolactone)-block-(4-vinyl pyridine)] (PCL-b-P4VP) diblock copolymer changes upon increasing the number of competitive hydrogen-bonding interactions after adding increasing amounts of octaphenol polyhedral oligomeric silsesquioxane (OP-POSS). Transmission electron microscopy reveals morphologies that exhibit high degrees of long-range order, such as cylindrical and spherical structures, at relatively low OP-POSS contents, and short-range order or disordered structures at higher OP-POSS contents. Analyses performed using differential scanning calorimetry, wide-angle X-ray diffraction, and FT-IR spectroscopy provide positive evidence that the pyridyl units of the P4VP block are significantly stronger hydrogen-bond acceptors toward the OH group of OP-POSS than are the C=O groups of the PCL block, thereby resulting in excluded and confined PCL phases.
Thin-Film Composite Materials as a Dielectric Layer for Flexible Metal-Insulator-Metal Capacitors
(2010)
Tiwari, Jitendra N.
;
Meena, Jagan Singh
;
Wu, Chung-Shu
;
Tiwari, Rajanish N.
;
Chu, Min-Ching
A new organic-organic nanoscale composite thin-film (NCTF) dielectric has been synthesized by solution deposition of 1-bromoadamantane and triblock copolymer (Pluronic P123, BASF, EO(20)-PO(70)-EO(20)), in which the precursor solution has been achieved with organic additives. We have used a sol-gel process to make a metal-insulator-metal capacitor (MIM) comprising a nanoscale (10 nm-thick) thin-film on a flexible polyimide (PI) substrate at room temperature. Scanning electron microscope and atomic force microscope revealed that the deposited NCTFs were crack-free, uniform, highly resistant to moisture absorption, and well adhered on the Au-Cr/PI. The electrical properties of 1-bromoadamantane-P123 NCTF were characterized by dielectric constant, capacitance, and leakage current measurements. The 1-bromoadamantane-P123 NCTF on the PI substrate showed a low leakage current density of 5.5 x 10(-11) A cm(-2) and good capacitance of 2.4 fF at 1 MHz. In addition, the calculated dielectric constant of 1-bromoadamantane-P123 NCTF was 1.9, making them suitable candidates for use in future flexible electronic devices as a stable intermetal dielectric. The electrical insulating properties of 1-bromoadamantane-P123 NCTF have been improved due to the optimized dipole moments of the van der Waals interactions.
Star Block Copolymers Through Nitroxide-Mediated Radical Polymerization From Polyhedral Oligomeric Silsesquioxane (POSS) Core
(2010-06-15)
Lu, Chu-Hua
;
Wang, Jui-Hsu
;
Chang, Feng-Chih
;
Kuo, Shiao-Wei
;
應用化學系
A series of star block copolymers were prepared through nitroxide-mediated radical polymerization (NMRP) from polyhedral oligomeric silsesquioxanes (POSS) nanoparticle by core-first polymerization. Eight N-alkoxyamine groups were incorporated onto the eight corners of a POSS cube through quantitative hydrosilylation through addition of octakis(dimethylsiloxy)silsesquioxane (O(8)M(8)(H) POSS) with 1-(2-(allyloxy)-1-phenylethoxy)-2,2,6,6-tetramethyl-piperidine (allyl-TEMPO) and Karstedt's agent (a platinum divinylsiloxane complex) was used as a catalyst. Octa-N-alkoxyamines POSS (OT-POSS) were used as platform to synthesize star polystyrene-POSS ((PS)(8)-POSS) homopolymer and diblock copolymers of poly(styrene-block-4-vinyl-pyridine)-POSS ((PS-b-P4VP)(8)-POSS) and poly(styrene-block-acetoxystyrene) ((PS-b-PAS)(8)-POSS) through NMRP. In addition, subsequent selective hydrolysis of the acetyl protective group of (PS-b-PAS)(8)-POSS, the poly(styrene-block-vinyl phenol) ((PS-b-PVPh)(8)-POSS) with strong hydrogen bonding group was obtained. The detailed chemical structure and self-assembled structures of these star block copolymers based on POSS were characterized by (1)H NMR, FTIR, SEC, TEM, and SAXS analyses.

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