Browsing by Author "Huang, Cheng-Jyun"

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Fabrication of vesicle-like dual-responsive click capsules by direct covalent layer-by-layer assembly
(2011)
Huang, Cheng-Jyun
;
Hong, Chia-Wei
;
Ko, Fu-Hsiang
;
Chang, Feng-Chih
;
應用化學系
We report a click chemistry approach for the consecutive layer-by-layer assembly of thermo-and pH-sensitive clickable copolymers on silica particles and the subsequent formation of vesicle-like dual-responsive click capsules. These click capsules exhibit both thermo- and pH-responsive behaviors by elevating the solution temperature and incubating in acidic or basic solutions respectively. We also demonstrate the in situ preparation of silver nanoparticles within the multilayer of the click capsules. These stimuli-responsive behaviors were examined by using confocal laser scanning microscopy (CLSM), transmission electron microscopy (TEM), and atomic force microscopy (AFM). This approach provides potential applications in preparing well-defined vesicle-like capsules with covalent stabilization and flexibility in introducing a range of new materials including different functional polymers.
Polypeptide diblock copolymers: Syntheses and properties of poly(N-isopropylacrylamide)-b-polylysine
(2008-10-14)
Huang, Cheng-Jyun
;
Chang, Feng-Chih
;
應用化學系
;
Department of Applied Chemistry
A hydrolysis-resistant amide-linkage heterofunctional initiator was synthesized and used successfully for polymerization of well-defined rod-coil block copolymers poly(N-isopropylacrylamide)-b-poly(Z-L-lysine) (PNIPAm-b-PZLys) by combination of atom transfer radical polymerization (ATRP) and amine hydrochloride mediated ring-opening polymerization (ROP). The ATRP of NIPAm was carried out at 0 degrees C using CuBr/Me6TREN complex in 2-propanol and resulted in narrow polydispersity and high monomer conversion. The amine hydrochlorides have replaced the primary amine in the PNIPAm macroinitiator resulting in a well-controlled ROP of N-epsilon-(carbobenzoxy)-L-lysine N-carboxyanhydride in DMF at 20 degrees C. These amphiphilic block copolymers are able to form universal micelle morphologies of spherical micelles, wormlike micelles, and vesicles by varying the polymer compositions and the helicogenic common solvents. From synchrotron SAXS, WAXS, and TEM results, the PNIPAm-b-PZLys microphase self-assembly morphology in solid state is a hierarchical lamellar-in-hexagonal structure. After the protective epsilon-benzyloxycarbonyl group is removed, the dual stimuli-responsive behaviors of the PNIPAm-b-PLys investigated by nuclear magnetic resonance spectroscopy in aqueous solution resulted in either coil-to-helix or coil-globule transition by changing the environmental condition of elevating the temperature or increasing the pH value.
Using Click Chemistry To Fabricate Ultrathin Thermoresponsive Microcapsules through Direct Covalent Layer-by-Layer Assembly
(2009-07-28)
Huang, Cheng-Jyun
;
Chang, Feng-Chih
;
應用化學系
;
Department of Applied Chemistry
We report the syntheses of azido- and acetylene-functionalized poly(N-isopropylacrylamide) (PNIPAm) copolymers and their use in the fabrication of ultrathin thermoresponsive microcapsules through direct covalent layer-by-layer (LbL) assembly using click chemistry. The clickable copolymers poly[N-isopropylacrylamide-co-(trimethylsilyl)propargylacrylamide] and poly(N-isoropylacrylamide-co-3-azideo-propylacrylamide) were prepared through atom transfer radical polymerization (ATRP) at 0 degrees C using a synthesized dansyl-labeled initiator and the CuBr/Me(6)TREN (hexamethylated tris[2-(dimethylamino)ethyl]amine) catalyst complex in 2-propanol. After removing the protective trimethylsilyl groups, these clickable PNIPAm copolymers assemble alternately onto azido-modified silica particles in aqueous media through click reactions catalyzed by copper sulfate and sodium ascorbate. After removing the template, the microcapsules remained stable because of the presence of the covalently bonded triazole units; the microcapsules exhibited thermoresponsive and thermoreversible swelling/deswelling behaviors upon changing the temperature of the medium. Adjusting the number of clickable functionalities resulted in changes to the degree of cross-linking, thereby allowing control over the surface morphology and thickness of the covalently stabilized PNIPAm multilayer thin films. The microcapsules fabricated close to the lower critical solution temperature of PNIPAm exhibited extremely low surface roughnesses and thick multilayer films as a result of their compact chain conformation in aqueous solution, leading to tighter packing of the PNIPAm structure. We further postfunctionalized the surface of the multilayer thin film through click reactions with an azido-modified lissamine rhodamin dye to demonstrate the feasibility of further modification with potentially useful functionalities. Finally, preliminary study on the permeability of microcapsules was presented by using different molecular weigh tetramethylrhodamine isothiocyanate (TRITC)-labeled dextran and rhodamine 6G as probe molecules, and the results revealed that the microcapsules with tighter packing wall are selectively permeable to molecules and show potential applications for the encapsulation of a variety of materials.