Browsing by Author "Chan, Shih-Chi"

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Hydrogen-bonding interactions mediate the phase behavior of an A-B/C block copolymer/homopolymer blend comprising poly(methyl methacrylate-b-vinylpyrrolidone) and poly(vinylphenol)
(2006-08-08)
Lee, Hsin-Fang
;
Kuo, Shiao-Wei
;
Huang, Chih-Feng
;
Lu, Jiann-Shing
;
Chan, Shih-Chi
We have investigated a new type of A-B/C blend, formed between poly(methyl methacrylate-b-vinylpyrrolidone) and poly(vinylphenol) (PMMA-b-PVP/PVPh), that displays unusual phase behavior. In this blend, the PMMA (A) and PVP (B) blocks within the PMMA-b-PVP (A-B) copolymer are miscible; although PVPh (C) experiences attractive interactions (xi <= 0) through hydrogen bonding, with both the PVP and PMMA blocks, its interaction with the former block is significantly stronger than that with the latter (xi(BC) >> xi(AC)). We investigated the miscibility and phase behavior of this novel A-B/C blend through the use of FTIR spectroscopy, DSC, C-13 CP/MAS solid-state NMR spectroscopy, and TEM. The proton spin-lattice relaxation time in the rotating frame (T-1 rho(H)), which we determined using 13C NMR spectroscopy, indicates that phase separation occurs for blends containing ca. 20-60 wt % PVPh. TEM images indicated clearly that the morphology of phase separation consists of a matrix of homogeneous mixed PVP/PVPh and micellar domains of excluded PMMA. This special phase behavior and miscibility is due mainly to the diversity of interactions that exist between the PMMA/PVPh and PVP/PVPh units.
Supramolecular aggregations through the inclusion complexation of cyclodextrins and polymers with bulky end groups
(2007-01-01)
Chan, Shih-Chi
;
Kuo, Shiao-Wei
;
She, Hwo-Shuenn
;
Lin, Ho-May
;
Lee, Hsin-Fang
Mono-polyhedral oligomeric sillsesquioxane-end capped poly(epsilon-caprolactone) (mPPCL) can form inclusion complexes (ICs) with alpha- and gamma-cyclodextrins (CDs) but not with beta-CD. These CD ICs have been characterized with X-ray diffraction, solid-state C-13 cross-polarization/magic-angle-spinning NMR spectroscopy, H-1 NMR spectroscopy, Fourier transform infrared spectroscopy, differential scanning calorimetry, thermogravimetric analysis, and scanning electron microscopy. The poly(epsilon-caprolactone) (PCL) chain of mPPCL is included within the channel provided by the CDs to form a columnar, crystalline structure. The PCL/CD ratios determined by H-1 NMR spectroscopy for the ICs with alpha- or gamma-CDs are higher than the stoichiometries because of the steric hindrance of the bulky polyhedral oligomeric silsesquioxane chain end and result in a fraction of the e-caprolactone units free from complexation with the CDs. On the basis of these analyses, we propose some possible structures for these CD/mPPCL ICs. (c) 2006 Wiley Periodicals, Inc.
Syntheses and characterizations of the multiple morphologies formed by the self-assembly of the sernicrystalline P4VP-b-PCL diblock copolymers
(2007-08-10)
Chan, Shih-Chi
;
Kuo, Shiao-Wei
;
Lu, Chu-Hua
;
Lee, Hsin-Fang
;
Chang, Feng-Chih
A series of semicrystalline diblock copolymers of poly(4-vinylpyridine-b-epsilon-caprolactone) (P4VP-b-PCL) have been synthesized by the living ROP of CL followed by the TEMPO polymerization of 4-VP. Depending on the relative block length and different solvent compositions, these copolymers self-assemble into different supramolecular structures in toluene/dichloromethane (DCM) solution, including spherical micelles, bowl-shaped vesicles, multilayer vesicles, porous spheres, and large compound micelles. In methanol/DCM solution system, the crystalline PCL core disturbs the balance of free energy, thus results in a series of morphological changes including spherical micelles, worm-like rods, vesicles, coexisted vesicles and lamella, and finally platelet lamella. (c) 2007 Elsevier Ltd. All rights reserved.