Browsing by Author "Chen, Kai-Chi"

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Catalyst-Controlled Regioselective Synthesis of Benzotriazlolodiazepin-7-ones and Benzotriazolodiazocin-8-ones
(2020-01-17)
Chen, Kai-Chi
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Barve, Indrajeet J.
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Sun, Chung-Ming
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應用化學系
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Department of Applied Chemistry
A catalyst-controlled highly chemoselective and regioselective intramolecular cycloamidation of triazol-1-ylbenzamides toward the synthesis of scarcely known heterocycles is reported. In the presence of a palladium catalyst, this cycloisomerization reaction afforded substituted benzotriazlolodiazepin-7-ones via intramolecular insertion of a palladium into C-C triple bond in a 7-exo-dig way. Alternatively, the use of a silver catalyst in the reaction produced substituted benzotriazolodiazocin-8-ones in a highly regioselective manner through 8-endo-dig intramolecular ring closure.
Effect of crosslinking agents on the dispersive behaviour of polymer particles in seed swelling polymerisation
(2017-07-25)
Kao, Yu-Chen
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Whang, Wha-Tzong
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Chen, Yi-Chun
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Chen, Kai-Chi
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材料科學與工程學系
This study focused on the effect of crosslinker structure between PMMA on the dispersity of crosslinked particles in seed swelling polymerisation. We used five different crosslinking agents in an assessment of the dispersity of crosslinking monodisperse particles using PMMA seed particles in seed swelling polymerisation. These results show that the structure of the crosslinking agent affects the dispersity during the swelling stage. According to the solubility parameter theory of computation, the departure of similar solubility parameter causes the swollen particles to segregate into more dispersity. (C) 2017 The Korean Society of Industrial and Engineering Chemistry. Published by Elsevier B.V. All rights reserved.
Novel Siloxane-Modified Epoxy Resins as Promising Encapsulant for LEDs
(2020-01-01)
Lin, Chih-Hao
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Whang, Wha-Tzong
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Chen, Chun-Hua
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Huang, Shu-Chen
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Chen, Kai-Chi
This study investigated a new category of transparent encapsulant materials for light-emitting diodes (LEDs). It comprised a phenyl group that contained siloxane-modified epoxy (SEP-Ph) hybridized with a cyclic tetrafunctional siloxane-modified epoxy (SEP-D4) with methylhexahydrophthalic anhydride (MHHPA) as a curing agent. The SEP-Ph/SEP-D4 = 0.5/0.5 (sample 3) and SEP-D4 (sample 4) could provide notably high optical transmittance (over 90% in the visible region), high-temperature discoloration resistance, low stress, and more crucially, noteworthy sulfurization resistance. The lumen flux retention of the SEP encapsulated surface mounted device LEDs remained between approximately 97% and 99% after a sulfurization test for 240 h. The obtained comprehensive optical, mechanical, and sulfurization resistance proved the validity and uniqueness of the present design concept with complementary physical and chemical characteristics.
Poly(vinyl alcohol)-controlled synthesis of monodispersed crosslinked poly(methyl methacrylate) microparticles with significantly improved mechanical properties
(2019-07-01)
Kao, Yu-Chen
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Chen, Chun-Hua
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Whang, Wha-Tzong
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Chen, Yi-Chun
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Chen, Kai-Chi
A facile synthesis concept focusing on the poly(vinyl alcohol) (PVA) concentration induced interfacial energy effects in seed swelling polymerization was realized for the successful fabrication of a series of monodispersed poly(methyl methacrylate) (PMMA) microparticles with four crosslinking agents, 2,2-bis[(methacryloyloxy)methyl]butyl methacrylate, 1,2-ethanediyl bis(2-methylacrylate), 1,3-divinylbenzene and 1,2-ethanediyl diacetate. We revealed a special role of PVA in regulating the diffusion of crosslinking agents as well as the swelling degree of latex seeds and, more noticeably, the consequent improved mechanical properties of the crosslinked PMMA microparticles formed. The highest recovery rate obtained from the PMMA microparticles with 0.6 wt% PVA approached 67%, which is higher than or comparable to reported values. This work not only developed a new facile synthesis approach for producing highly uniform tough crosslinked PMMA microparticles for more potential applications but also provided valuable insights into fundamental aspects of seed swelling polymerization. (c) 2019 Society of Chemical Industry
Synthesis and characterization of a novel siloxane-imide-containing polybenzoxazine
(2011-03-01)
Chen, Kai-Chi
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Li, Hsun-Tien
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Chen, Wen-Bin
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Liao, Chun-Hsiung
;
Sun, Kien-Wen
A novel siloxane-imide-containing polybenzoxazine based on N,N'-bis(N-phenyl-3,4-dihydro-2H-benzo[1,3]oxazine)-5, 5'-bis(1,1',3,3'-tetramethyldisiloxane-1,3-diyl)-bis(norborane-2,3-dicarboximide) (BZ-A1) was successfully synthesized. The thermal properties of BZ-A1 are superior to those of conventional polybenzoxazines lacking siloxane groups. Polymerized BZ-A1 possesses extremely low surface free energy (gamma(s) = 15.1 mJ m(-2)) after curing at 230 degrees C for 1 h. Moreover, the surface free energy of polymerized BZ-A1 is more stable than conventional bisphenol A-type polybenzoxazine during thermal curing and annealing processes, indicating that polymerized BZ-A1 is more suitable for applications requiring low surface free energy materials for high temperatures over long periods of time. (C) 2010 Society of Chemical Industry
Synthesis and performance enhancement of novel polybenzoxazines with low surface free energy
(2011-07-01)
Chen, Kai-Chi
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Li, Hsun-Tien
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Huang, Shu-Chen
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Chen, Wen-Bin
;
Sun, Kien-Wen
A new siloxane-imide-containing benzoxazine, BZ-A6, has been successfully synthesized. The thermal properties of the polybenzoxazine (PBZ) prepared from BZ-A6 (PBZ-A6) are superior to those of conventional PBZs lacking siloxane groups. The normally brittle PBZs are toughened significantly as a result of adding siloxane-imide moieties. Moreover, the thermal and UV stabilities of the surface free energy of PBZ-A6 are dramatically improved over the conventional bisphenol-A-type PBZ. Siloxane-imide PBZs are more suitable for application as low-surface-free-energy materials that are highly resistant to temperature and UV radiation. PBZ-A6 may also be useful in weather-resistant and self-cleaning coating materials because of its low surface free energy and good thermal and UV resistance. (C) 2011 Society of Chemical Industry