Browsing by Author "Tung, PH"

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Synthesis of rod-coil diblock copolymers by ATRP and their honeycomb morphologies formed by the 'breath figures' method
(2005-10-24)
Lin, CL
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Tung, PH
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Chang, FC
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應用化學系
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Department of Applied Chemistry
We have synthesized rod-coil diblock PPQ-b-PMMA copolymers by using the versatile atom-transfer radical polymerization method and have characterized them by differential scanning calorimetry (DSC), Fourier transform infrared spectroscopy (FTIR), and thermogravimetric analysis (TGA). The methyl ketone-terminated rod-coil diblock PMMA copolymer has a higher value of T-g because of its syndiotactic-like structure, and a higher decomposition temperature than does the PMMA homopolymer. The presence of the PPQ block tends to retard the early decomposition of the PMMA chain. A regularly porous, honeycomb-structured film was prepared from the dichloromethane solution of the diblock copolymers under a flow of moist air. The diameters of the spherical pores can be controlled in the range from 0.8 to 3 mu m by modifying both the rod-coil copolymers' relative molecular weights and the casting conditions. The wall thickness of the film is varied linearly with the relative molecular mass (M-r). (c) 2005 Elsevier Ltd. All rights reserved.
Synthesis, thermal properties, and specific interactions of high T-g increase in poly(2,6-dimethyl-1,4-phenylene oxide)-block-polystyrene copolymers
(2005-10-24)
Kuo, SW
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Huang, CF
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Tung, PH
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Huang, WJ
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Huang, JM
We have synthesized a series of block copolymers of poly(2,6-dimethyl- 1,4-phenylene oxide) and polystyrene (PPO-b-PS copolymer) by atom transfer radical polymerization. The PS content in these copolymer systems was determined by using infrared spectroscopy, thermal gravimetric analysis, and solution and solid-state NMR spectroscopy; good correlations exist between these characterization methods. DSC analyses indicated that the PPO-b-PS copolymers have higher glass transition temperatures than do their corresponding PPO/PS blends. Our FTIR and solid-state NMR spectroscopic analyses suggest that the PPO-b-PS copolymers possess stronger specific interactions that are responsible for the observed relatively higher values of T-g. We found one single dynamic relaxation from the dynamic mechanical analysis, which implies dynamic homogeneity exists in the PPO-b-PS copolymer; this result is consistent with the one single proton spin-lattice relaxation time observed in the rotating frame [T-1 rho(H)] during solid state NMR spectroscopic analysis. In addition, the 2D FTIR spectroscopy reveals evidence for the stronger interactions between segments of PPO and PS through the formation of pi-cation complexes. (c) 2005 Elsevier Ltd. All rights reserved.
Thermal and dielectric properties and curing kinetics of nanomaterials formed from poss-epoxy and meta-phenylenediamine
(2004-09-16)
Chen, WY
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Wang, YZ
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Kuo, SW
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Huang, CF
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Tung, PH
A nanoporous polyhedral oligomeric silisesquioxane (POSS) containing eight epoxy functional groups [octakis(dimethylsiloxypropylglycidyl ether)silsesquioxane, OG] reacts with meta-phenylenediamine (mPDA) to form epoxy resin network with nanostructures. The glass transition temperature (T-g) of the cured OG/mPDA product is significantly higher than that of the diglycidyl ether of bisphenol A (DGEBA) cured with mPDA (DGEBA/mPDA) material due to the presence of the POSS cages that is able to effectively hinder the motion of the network junctions. The cured OG/mPDA product inherently possesses higher thermal stability than the cured DGEBA/mPDA product based on higher maximum decomposition rate temperature, and higher char yield of the former. However, the existence of large fraction of the unreacted amine groups causes lower initial decomposition temperature of the OG/mPDA because it tends to decompose or volatilize on heating at relatively low temperature. The dielectric constant of the OG/mPDA material (2.31) is substantially lower than that of the DGEBA/mPDA (3.51) as a consequence the presence of nanoporous POSS cubes in the epoxy matrix. (C) 2004 Elsevier Ltd. All rights reserved.