Browsing by Author "Lee, HF"

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A new strategy for the one-step synthesis of block copolymers through simultaneous free radical and ring opening polymerizations using a dual-functional initiator
(2005-02-14)
Huang, CF
;
Kuo, SW
;
Lee, HF
;
Chang, FC
;
應用化學系
Block copolymers are fascinating and complex materials that have been used in a range of diverse scientific and technological capacities. We demonstrate that a single one-step approach based on dual simultaneous polymerizations is a viable technique for the synthesis of a wide range of block copolymers by combining two dissimilar polymerization systems and using a dual-functional initiator. The main advantage of this methodology is that a simple, one-step, and simultaneous polymerization occurs in the bulk, which makes this process very attractive from both industrial and academic points of view. We plan to study the reaction kinetics and evaluate how well the ring opening catalyst [in this case, Sn(oct)(2)] works under reverse ATRP conditions. (C) 2004 Elsevier Ltd. All rights reserved.
Preparation and supramolecular self-assembly of a polypeptide-block-polypseudorotaxane
(2005-07-26)
Lee, HF
;
Sheu, HS
;
Jeng, US
;
Huang, CF
;
Chang, FC
We have successfully prepared a new class of self-assembled biomaterial: a polypeptide-block-polypseudorotaxane diblock copolymer. This diblock copolymer is comprised of an a-helical polypeptide rod, based on gamma-benzyl-L-glutamate, and an originally coiled segment P(EO19-r-PO3); it forms inclusion complexes with a-cyclodextrins (alpha-CDs) to give crystalline polypseudorotaxanes. Formation of the polypseudorotaxane converts the conformation of P(EO19-r-PO3) from a flexible chain into a rodlike structure, which results in a novel block copolymer exhibiting a rod-rod conformation. Intrinsic interactions (e.g., the polypseudorotaxane's channel-type crystallization, the polypeptide's secondary structure, and microphase separation) within and between these rod-rod diblock copolymers contribute to their hierarchical self-assembly behavior, which we characterized using DSC, H-1 NMR spectroscopy, C-13 CP/MAS NMR spectroscopy, WAXS, and SAXS. The data obtained from the WAXS and SAXS studies clearly indicate the formation of juxtaposed bilayer-like nanostructure featuring hexagonally packed PBLG stacks and channel-type polypseudorotaxane moieties.
Star polymers via atom transfer radical polymerization from adamantane-based cores
(2004-03-29)
Huang, CF
;
Lee, HF
;
Kuo, SW
;
Xu, HY
;
Chang, FC
A series of novel multifunctional initiators derived from adamantane-based derivatives have been used in the syntheses of various styrenic and (meth)acrylic star polymers by atom transfer radical polymerization (ATRP). Conditions were identified in each system to produce star polymers with nearly monomodal molecular distributions. These synthesized star polymers have glass transition temperatures similar to those known for high-molecular-weight linear polymers. We obtained a series of adamantane-contained star polymers covering a wide range of molecular weights by adjusting the monomer-to-initiator ratio and the solvent polarity. Because of reaction heterogeneity and inevitable termination processes, the occurrence of star-star coupling led to a lower than predicted molecular weight polydispersity. When hydrolyzed from their cores by NaOH, the values of Mw of the arms of the PMMA star polymer did not change with reaction time, at least for the first 48 h of the reaction, which implies that no significant PMMA hydrolysis occurs within this interval of time. (C) 2004 Elsevier Ltd. All rights reserved.