Browsing by Author "Kung, LR"

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Induced twisting in the self-assembly of chiral Schiff-based rod-coil amphiphiles
(2006-01-24)
Sung, CH
;
Kung, LR
;
Hsu, CS
;
Lin, TF
;
Ho, RM
A series of novel organic superstructures exhibiting diverse aggregate morphologies with liquid-crystalline-like properties were prepared by a simple precipitation method. Here, a chiral sugar moiety was simply introduced at the Schiff-based rod end of rod-coil molecules. In contrast to coil-coil molecules, the self-assembled rod-coil molecules exhibit a high segregation strength for phase separation because of their liquid-crystalline-like behavior. The morphological transformation of self-assembled chiral Schiff-based rod-coil amphiphiles, from a platelet-like morphology to helical twists, was obtained by increasing the length of the hydrophobic tail. Consistent with theoretical predictions, the bending force from the chiral entity depends on the size of the adjacent hydrophobic tail. That is, the size of hydrophobic chain determines the threshold of bending for the formation of a helical morphology. Moreover, by introducing an additional tethered hydrophobic chain self-assembled spherical vesicles can be obtained through the collapse of the twisted shape.
Polarized white emission from fluorene-based polymer blends
(2005-10-01)
Yao, YH
;
Kung, LR
;
Hsu, CS
;
應用化學系
;
Department of Applied Chemistry
Three alternating co-polyfluorenes emitting primary red, green and blue (RGB) colors have been synthesized via a palladium-catalyzed Suzuki coupling reaction. All copolymers reveal good thermal stability and nematic liquid crystalline behavior. The polymers were fabricated to form a polarized electroluminescent device using poly(ethylene dioxythiophene)-poly(styrene sulfonicacid) (PEDOT-PSS) as an alignment layer. For the case of primary colors, a host-guest approach that utilized a blue light emission P1 as a host with a green light P2 or a red light P3 as a guest led to approximately two- to fourfold enhancement in luminescence in comparison with that of a neat film in polymer light emitting diodes (PLEDs), 1039 versus 2205cd/m(2) and 284 versus 1146cd/m(2). In the case of white light, as a consequence of blending, polarized emission peak ratio of up to 4.4 and a pure white luminance brightness of up to 1895cd/m(2) have been attained.
Stereoselective synthesis of 2-isocyanoallopupukeanane
(1999-10-07)
Ho, TL
;
Kung, LR
;
應用化學系
;
Department of Applied Chemistry
[GRAPHICS] A stereoselective synthesis of 2-isocyanoaliopupukeanane (3) in ca, 5% overall yield features an intramolecular Diels-Alder reaction to establish a bridged cydopentane ring to the existing bicyclo[3.2.1]octane unit.
Synthesis of UV-curable liquid crystalline diacrylates for the application of polarized electroluminescence
(2006-01-01)
Yao, YH
;
Kung, LR
;
Chang, SW
;
Hsu, CS
;
應用化學系
Two series of UV-curable rod-like diacrylates containing bis-tolane (M1 - M5) and bis-stilbene (M6 - M10) mesogens were synthesized. All of the diacrylates were prepared through convergent syntheses involving palladium-catalysed coupling reactions. The thermal transitions and mesomorphic properties of the diacrylates were characterized by differential scanning calorimetry and optical microscopy. All the bis-tolane-based monomers reveal nematic phases, except M5 which shows no mesomorphic behaviour. For the bis-stilbene based monomers, most show no mesomorphic behavior and only M7 and M9 exhibit a SmA phase.
Total synthesis of (+/-)-2-isocyanoallopupukeanane
(2000-09-08)
Ho, TL
;
Kung, LR
;
Chein, RJ
;
應用化學系
;
Department of Applied Chemistry
2-Isocyanoallopupukeanane (4) has been obtained in racemic form from methyl 2-exo-methylbicyclo-[2.2.1]hept-5-ene-2-endo-carboxylate via dibromocarbene addition, S(N)2' displacement, chain extension, and elaboration of the unsaturated ketone 12c which underwent an intramolecular hetero-Diels-Alder reaction to afford 13 containing all the skeletal carbon atoms. The dihydropyran unit was cleaved by ozonolysis to give the tricarbocyclic intermediate which required seven more steps to complete the synthesis.