Browsing by Author "Wu, FI"

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Bis(2,2-diphenylvinyl)spirobifluorene: An efficient and stable blue emitter for electroluminescence applications
(2005-08-15)
Wu, FI
;
Shu, CF
;
Wang, TT
;
Diau, EWG
;
Chien, CH
We have synthesized a spirobifluorene-based DPVBi [4,4'-bis(2,2-diphenylvinyl)-1,1'-biphenyl] analogue, DPVSBF [2,7-bis(2,2diphenylvinyl)-9,9'-spirobifluorene], in which the bis(2,2-diphenylvinyl) groups are connected through the 2 and 7 positions of the spirobifluorene framework, and have characterized its thermal properties, electronic properties (viz. absorption and photoluminescence), and electrochemical behavior. The presence of the rigid spirobifluorene linkage imparts significant improvement in the material's glass transition temperature and morphological stability, while preserving most of the photophysical and electronic properties of its non-spiro, biphenyl analogue, DPVBi. Organic electroluminescent devices having the structure ITO/NPB/DPVSBF/AlQ/LiF/Al display bright emissions with a lambda(max) at 474 nm (CIE coordinates: 0.16, 0.24) and exhibit maximum luminescence exceeding 40,000 cd/m(2). At a driving current density of 100 mAcm(2) (6.4 V), a luminance of 4110 cd/m(2) was obtained with external quantum efficiency of 2.54%, luminance efficiency of 4.1 cd/A, and power efficiency of 2.0 lm/W. Moreover, the DPVSBF-based device exhibits a 16-fold enhancement in the operation lifetime relative to that of a similar device based on DPVBi. (C) 2005 Elsevier B.V. All rights reserved.
Color tuning of a light-emitting polymer: Polyfluorene-containing pendant amino-substituted distyrylarylene units
(2005-07-01)
Su, HJ
;
Wu, FI
;
Tseng, YH
;
Shu, CF
;
應用化學系
We have synthesized a novel polyfluorene copolymer polyfluorene-bis[4-(diphenylamino)styryl]fluorene (PF-DPAS) by orthogonally attaching an amino-substituted distyrylarylene dye bis[4-(diphenylamino)styryl]fluorene, onto the C9 position of a fluorene unit. We have investigated this polymer's thermal properties, electronic properties (viz., absorption and photoluminescence), and electrochemical behavior. Photoluminescence studies indicate that color tuning can be achieved through efficient Forster energy transfer from the higher-energy polyfluorene backbone to the lower-energy pendant DPAS units. We have fabricated light-emitting diodes with the structure indium tin oxide (ITO)/poly(3,4-ethylenedioxythiophene) (PEDOT)/ emitting layer/1,3,5-tris(N-phenylbenzimidazol-2-yl)benzene (TPBI)/Mg:Ag. The devices, based on blends of PF-DPAS in polyfluorene-triphenylamine-oxadiazole (PF-TPA-OXD), exhibit significant improvements in device performance relative to that of the pure PF-TPA-OXD device; we attributed this improvement to both a red-shift of the electroluminescence (EL) spectra and an enhancement in quantum efficiency. At a blend ratio of 1:20, the EL spectrum is voltage-independent and stable, and exhibits the characteristic emission of a DPAS moiety: a peak at 461 nm and Commission Internationale de l'Eclairage (CIE) coordinates of (0.1.5, 0.18). The maximum external quantum efficiency is 2.08 % (2.87 cd A(-1)) at a bias of 9 V (86.1 mA cm(-2)) with a brightness of 2467 cd m(-2); the maximum brightness (6916 cd m-2) occurred at an applied voltage of 13 V and a current density of 361 mA cm(-2).
Enhancing the thermal and spectral stabilities of polyfluorene-based bluelight-emitting materials by incorporating pendent spiro-cycloalkyl groups
(2004-05-20)
Wu, FI
;
Dodda, R
;
Jakka, K
;
Huang, JH
;
Hsu, CS
We have synthesized polyfluorene-based copolymers containing spiro-cycloalkyl groups functionalized on the C-9 position of alternate fluorene units using the Suzuki coupling reaction. The presence of the rigid spiro-cycloalkyl pendent groups not only hinders the close packing and intermolecular interactions between polymer chains, but also preserves the molecular rigidity of the polymer, leading to polyfluorenes with high glass transition temperatures and improved thermal and spectral stabilities. The results of photoluminescence measurements of the isothermally heated spiro-polyfluorene thin films (150degreesC for 20h) show that the commonly observed aggregate/excimer formation is suppressed effectively in these polymers. Blue electroluminescence was demonstrated in a double-layer LED device using the spiro-derivatized polyfluorene as the emitting layer. (C) 2004 Elsevier Ltd. All rights reserved.
Fluorene-based oxadiazoles: thermally stable electron-transporting materials for light-emitting devices
(2005-01-31)
Wu, FI
;
Shu, CF
;
Chien, CH
;
Tao, YT
;
應用化學系
We have synthesized and characterized a series of fluorene-based oxadiazole derivatives, in each of which two identical oxadiazole moieties are linked to a fluorene unit via an sp(3)-hybridized carbon atom (C-9) to form a rigid, nonplanar structure. This structural feature leads to a reduction in the tendency to crystallize and an increase in the glass transition temperature. Electrochemical studies revealed that these materials undergo reversible reductions and have high electron affinities. Each fluorene-based oxadiazole exhibited reasonably good performance when it was used as the electron-transporting layer in a multi-layer organic EL device. (C) 2004 Elsevier B.V. All rights reserved.
Highly efficient blue-light-emitting diodes from polyfluorene containing bipolar pendant groups
(2003-09-09)
Shu, CF
;
Dodda, R
;
Wu, FI
;
Liu, MS
;
Jen, AKY
A highly efficient blue-light-emitting copolymer with bulky hole-transporting triphenylamine (TPA) and electron-transporting oxadiazole (OXD) pendant groups at the C-9 position of fluorene was synthesized. The results from photoluminescence and electrochemical measurements reveal that both the side chains and the polyfluorene main chain retain their own electronic characteristics in the copolymer. It shows a pure blue emission with no aggregates or excimers formed even after being annealed at 150 degreesC under nitrogen for 20 h. In addition, it also demonstrates improved charge injection and balanced charge transport in electroluminescence. The maximum external quantum efficiency of a single-layer device using this copolymer as the emitting layer is 1.21% (at a brightness of 354 cd/m(2) with driving voltage of 7.6 V). The maximum luminance of the device reaches 4080 cd/m(2) at a bias of 12.0 V and a current density of 640 mA/cm(2).
Highly efficient light-emitting diodes based on fluorene copolymer consisting of triarylamine units in the main chain and oxadiazole pendent groups
(2005-11-01)
Wu, FI
;
Shih, PI
;
Shu, CF
;
Tung, YL
;
Chi, Y
We have synthesized a fluorene-based copolymer, PFA-OXD, which possesses bipolar charge-transporting functionalities, through the incorporation of electron-rich triphenylamine moieties and electron-deficient oxadiazole pendent groups into the polymer backbone and onto the C9 position of each fluorene repeating unit, respectively. The propeller-shaped triphenylamine units in the main chain and the rigid cardo-type OXD side chains endow this polymer with a very high glass transition temperature (306 degrees C) and good thermal stability, without sacrificing its good solution processability. Both in dilute solution and as a thin film, PFA-OXD exhibits a bright blue emission upon excitation of either the main chain or oxadiazole side chains; this phenomenon indicates that efficient energy transfer occurs from the photoexcited pendent groups to the polymer backbone. An organic light-emitting device incorporating this copolymer as the emitting layer exhibits a voltage-independent and stable blue emission having color coordinates (0.14, 0.15) at 9 V; the maximum brightness was 7128 cd m(-2) and the maximum luminance efficiency was 2.07 cd A(-1). In addition, doping PFA-OXD as a host material with 2.6 wt % of a red-emitting phosphorescent dye, Os(fppz), led to a high-brightness, highly efficient red electroluminescent device having CIE coordinates of (0.65, 0.34), a maximum brightness of 28 440 cd m(-2), and a maximum external efficiency of 9.30%.
Highly efficient red phosphorescent osmium(II) complexes for OLED applications
(2004-07-19)
Tung, YL
;
Wu, PC
;
Liu, CS
;
Chi, Y
;
Yu, JK
The nonionic, red-emitting complexes [Os(fppz)(2)L-2] (L = PPh2Me (1), PPhMe2 (2)) and [Os(bptz)(2)L-2] (L = PPh2Me (3)) were synthesized, showing highly intense red phosphorescent emission in CH2Cl2 solution at lambda(max) 617, 632, and 649 nm, respectively. The electroluminescent properties of these compounds on OLEDs showed promising device efficiencies required for future OLED applications.
Highly efficient red-electrophosphorescent devices based on polyfluorene copolymers containing charge-transporting pendant units
(2005-07-28)
Wu, FI
;
Shih, PI
;
Tseng, YH
;
Chen, GY
;
Chien, CH
We have systematically examined the photoluminescence (PL) and electroluminescence (EL) behavior of blends comprising two efficient red phosphors doped, respectively, into the blue-emitting polyfluorene derivatives PF-TPA-OXD and PF-OXD. The host polymers, which contain both hole- and electron-transporting or merely electron-tran sporting side chains, are capable of facilitating charge injection and transport. After determining the HOMO and LUMO energy levels of these materials, we were able to match the dopant with its most suitable host to achieve the direct formation and confinement of an exciton at the dopant. This configuration also leads to a reduction in the electrical excitation of the host polymer, which in turn decreases the degree of exciton loss arising from nonradiative decay of the host triplet. Using this approach, we were able to realize the production of high-performance red-electrophosphorescent devices. For Os(fppz)-doped devices, we obtain a balanced charge recombination in conjunction with higher current and luminance when using PF-TPA-OXD as the host matrix; this device reached a maximum external quantum efficiency of 8.37% with a peak brightness of 16 720 cd/m(2). The absence of charge-transporting pendant units, i.e., the device fabricated from poly [9,9-dioctylfluorene-2,7-diyl] (POF), led, however, to relatively poor electroluminescence characteristics (5.81% and 2144 cd/m(2)).
Hyperbranched aromatic poly(ether imide)s: Synthesis, characterization, and modification
(2001-07-15)
Wu, FI
;
Shu, CF
;
應用化學系
;
Department of Applied Chemistry
The synthesis and characterization of hyperbranched aromatic poly(ether imide)s are described. An AB, monomer, which contained a pair of phenolic groups and an aryl fluoro moiety activated toward displacement by the attached imide heterocyclic ring, was prepared. The nucleophilic substitution of the fluoride with the phenolate groups led to the formation of an ether linkage and, subsequently, to the hyperbranched poly(ether imide), which contained terminal phenolic groups. A similar one-step polymerization involving a monomer that contained silyl-protected phenols yielded a hyperbranched poly(ether imide) with terminal silylated phenols. The degree of branching of these hyperbranched polymers was approximately 55%, as determined by a combination of model compound studies and H-1 NMR integration experiments. End-capping reactions of the terminal phenolic groups were readily accomplished with a variety of acid chlorides and acid anhydrides. The nature of the chain-end groups significantly influenced physical properties, such as the glass-transition temperature and the solubility of the hyperbranched poly(ether imide)s. As the length of the acyl chain of the terminal ester groups increased, the glass-transition temperature value for the polymer decreased, and the solubility of the polymer in polar solvents was reduced, becoming more soluble in nonpolar solvents. (C) 2001 John Wiley & Sons, Inc.
Hyperbranched poly(aryl ether oxazole)s: Synthesis, characterization, and modification
(2000-11-14)
Gong, ZH
;
Leu, CM
;
Wu, FI
;
Shu, CF
;
應用化學系
In this paper the synthesis and characterization of a hyperbranched poly(aryl ether oxazoIe) with terminal phenolic groups are described. An ABB' monomer containing a pair of phenolic groups and an aryl fluoride which is activated toward displacement by the attached oxazole ring was prepared. The nucleophilic substitution of the fluoride with the phenolic group leads to the formation of ether linkage and subsequently the hyperbranched poly(aryl ether oxazole) P1. As determined by a combination of model compound studies and H-1 NMR integration experiments, the degree of branching of PI is approximately 50%. The polymer P1 is thermally stable and readily soluble in polar organic solvents. The terminal phenolic groups in P1 were easily functionalized, yielding hyperbranched polymers with a variety of functional chain ends. Physical properties, such as the glass transition temperature and the solubility of the hyperbranched poly(aryl ether oxazole)s, depended significantly on the nature of the chain ends.
Interplay between intra- and interligand charge transfer with variation of the axial N-heterocyclic ligand in osmium(II) pyridylpyrazolate complexes: Extensive color tuning by phosphorescent solvatochromism
(2005-10-21)
Li, SW
;
Cheng, YM
;
Yeh, YS
;
Hsu, CC
;
Chou, PT
The rational design and syntheses of a new series of Os-II complexes with formula [Os(fppz)(2)(CO)(L)] (1: L=4-dimethylaminopyridine; 2: L=pyridine; 3: L = 4,4'bipyridine; 4: L=pyridazine; 5: L = 4-cyanopyridine), bearing two (2-pyridyl)pyrazolate ligands (fppz) together with one carbonyl and one N-heterocyclic ligand at the axial positions are reported. Single-crystal X-ray diffraction studies of, for example, 2 reveal a distorted octahedral geometry in which both fppz ligands reside in the equatorial plane with a trans configuration and adopt a bent arrangement at the metal center with a dihedral angle of similar to 23 degrees, while the carbonyl and pyridine ligands are located at the axial positions. Variation of the axial N-heterocyclic ligand leads to remarkable changes in the photophysical properties as the energy gap and hence the phosphorescence peak wavelength can be tuned. For complexes 1 and 2 the solvent-polarity-independent phosphorescence originates from a combination of intraligand (3)pi-pi* ((ILCT)-I-3) and metal-to-ligand charge transfer transitions ((MLCT)-M-3). In sharp contrast, as supported by cyclic voltammetry measurements and theoretical calculations, complexes 3-5 exhibit mainly ligand-to-lilgand charge transfer (LLCT) transitions, resulting in a large dipolar change. The phosphorescence of complexes 3-5 thus exhibits a strong dependence on the polarity of the solvent, being shifted for example, from 560 (in C6H12) to 665 nm (in CH3CN) and from 603 (in C6H12) to 710 nm (in CH3CN) for complexes 3 and 5, respectively. The results clearly demonstrate that a simple, straightforward derivatization of the axial N-heterocyclic ligand drastically alters the excitation properties per se from intraligand charge transfer (ILCT) to LLCT transitions. The latter exhibit remarkable LLCT phosphorescence solvatochromism so that a broad range of color tunability can be achieved.
Novel distyrylcarbazole derivatives as hole-transporting blue emitters for electroluminescent devices
(2005)
Wu, FI
;
Shih, PI
;
Yuan, MC
;
Dixit, AK
;
Shu, CF
We have synthesized three novel distyrylcarbazole derivatives for use as simultaneously hole- transporting and light- emitting layers in blue light- emitting diodes. Each compound, which contains a rigid carbazole core and two 2,2- diphenylvinyl end groups substituted through either the 3,6- or the 2,7- position, forms films satisfactorily and exhibits a blue emission with its PL maximum in the range 459 - 470 nm. Photophysical measurements indicate that twisting of the adjacent C - C bonds in the 3,6- position of the carbazole core in dilute solutions causes an efficient nonradiative relaxation to occur, yielding a much smaller quantum yield for fluorescence in 3,6- linked carbazoles. As intense emissions of 2,7- linked carbazoles are observed, such deactivation from an excited- state is inefficient therein. Electrochemical studies revealed that incorporation of the carbazole core increased the HOMO energy effectively; this feature facilitates hole injection. These distyrylcarbazole derivatives are promising bifunctional, blue- emitting, holetransporting molecules for use in simple double- layer devices of a general structure ITO/ emitting layer/ TPBI/ Mg : Ag, in which TPBI - 1,3,5- tris( N- phenylbenzimidazol- 2- yl) benzene - serves as a hole- blocking and electron- transporting material. The devices prepared using 2,7-distyrylcarbazole as the emitter produced bright blue emissions having activating voltages below 3.0 V. A DPVTCz- based device attained a luminance efficiency of 3.11 cd A(-1) at 5V, a brightness of 3062 cd m(-2), and CIE color coordinates of ( 0.14, 0.22).
Novel oxadiazole-containing polyfluorene with efficient blue electroluminescence
(2003-01-14)
Wu, FI
;
Reddy, DS
;
Shu, CF
;
Liu, MS
;
Jen, AKY
A novel oxdiazole-containing polyfluorene copolymer (PF-OXD) was synthesized by attaching two electron-deficient, 4-tent-butylphenyl-1,3,4-oxadiazole groups onto the C-9 position of the alternating fluorene unit to form a 3-D cardo-structure. This polymer possesses a very high glass transition temperature (T-g: 213 degreesC) and very good thermal stability due to its rigid cardo-linkage. The results from the photoluminescence measurements of the isothermally heated PF-OXD thin film (150 degreesC for 20 h) show that the commonly observed aggregate/excimer formation in polyfluorenes is very effectively suppressed in this polymer due to its 3-D structure and high T-g. A double-layer LED device using this polymer as the emitting layer shows a bright blue emission with a low turn-on voltage at 5.3 V and a high brightness of 2770 cd/m(2) at a drive voltage of 10.8 V. The maximum external quantum efficiency is 0.52% at 537 cd/m(2) with a bias of 7.4 V. The improved device performance over that of poly(9,9-dioctylfluorene) (POF) may be due to better electron injection and transport in PF-OXD and the efficient energy transfer from the OXD side chain to the polyfluorene main chains.
Poly(p-phenylenevinylene) presenting pendent pentaphenylene dendron groups for light-emitting diodes
(2005-11-01)
Tseng, YH
;
Wu, FI
;
Shih, PI
;
Shu, CF
;
應用化學系
We have synthesized, using the Gilch method, a novel poly(p-phenylenevinylene) derivative (PPV-PP) containing two pendent pentaphenylene dendritic wedges, and have characterized its structure and properties. The incorporated side chain pentaphenylene dendrons serve as solubilizing groups, prevent pi-stacking interactions from occurring between the polymer main chains, and suppress the formation of excimers in the solid state. Photoluminescence studies indicate that efficient intramolecular energy transfer occurred from the photoexcited pentaphenylene groups to the poly(p-phenylenevinylene) backbone. The polymer film exhibits a maximum emission at 510 nm and had a photoluminescence efficiency of 46%, which is similar to that measured in dilute solution. The photoluminescence spectra remained almost unchanged after thermal annealing at 150 degrees]C for 20 h, and displayed inhibited excimer formation. Polymer light-emitting diodes that we fabricated in the configuration ITO/PEDOT/PPV-PP/Mg:Ag/Ag exhibited a maximum emission peak at 513 nm, corresponding to the green region [x = 0.30 and y = 0.62 in the Commission Internationale de L'Eclairage (CIE) chromaticity coordinates]. The maximum brightness and maximum luminance efficiency were 1562 cd/m(2) and 1.93 cd/A, respectively. (c) 2005 Wiley Periodicals, Inc.
Polyfluorene containing diphenylquinoline pendants and their applications in organic light emitting diodes
(2005-02-15)
Su, HJ
;
Wu, FI
;
Shu, CF
;
Tung, YL
;
Yun, C
We present a short, efficient synthetic route for the preparation of a novel polyfluorene copolymer (PF-Q) containing two electron-deficient, 2,4-diphenylquinoline groups functionalized at the C-9 positions of alternate fluorene units that form a three-dimensional cardostructure. The presence of the rigid bulky pendent groups leads to a polyfluorene possessing a high glass-transition temperature (207 degreesC) and very good thermal stability (5% weight loss observed at 460 degreesC). A photoluminescence study revealed that the Forster energy transfer from the excited quinoline groups to the polyfluorene backbone is Very efficient; it also demonstrated that, the commonly observed aggregate/excimer formation in polyfluorenes is suppressed very effectively, in this polymer, even after it has been annealed at 150 degreesC for 20 h. A light emitting diode (LED) device prepared with PF-Q as the emitting layer exhibits a stable blue emission with a maximum brightness of 1121 cd/m(2) at 12 V and a maximum external quantum efficiency of 0.80% at 250 cd/m(2). We also used PF-Q, which contains diphenylquinoline units that behave as electron-transporting side chains, as a host. material and doped it with 2.4 wt % of a red-emitting phosphorescent dye, Os(fppz). to realize a red electrolumineseence with CIE color coordinates of (0.66, 0.34). The doped device exhibits a maximum external quantum efficiency of 6.63% (corresponding a luminance efficiency of 8.71 cd/A) at a current density of 47.8 mV/cm(2) together with a maximum brightness of 10457 cd/m(2). (C) 2005 Wiley Periodicals, Inc.
Relaxation dynamics of 2,7-and 3,6-distyrylcarbazoles in solutions and in solid films: Mechanism for efficient nonradiative deactivation in the 3,6-linked carbazole
(2005-12-22)
Wang, TT
;
Chung, SM
;
Wu, FI
;
Shu, CF
;
Diau, EWG
We performed time-resolved spectral investigations of two distyrylcarbazole derivatives, 2,7- and 3,6-distyrylcarbazole (2,7-DPVTCz and 3,6-DPVTCz, respectively), in dilute toluene solution and in solid films mixed with poly(methyl methacrylate) (PMMA). The lifetime of 2,7-DPVTCz in its excited state in solution is similar to 100 times as great as that of 3,6-DPVTCz, consistent with their photophysical nature. The former shows intense emission, but the latter is nearly nonfluorescent in a free environment. Moreover, the lifetime of 3,6-DPVTCz in its excited state increased also similar to 100 times when the molecule was encapsulated in a 3,6-DPVTCz/PMMA solid film, indicating that intramolecular motion of the molecule significantly affects the observed relaxation dynamics in a confined environment. Calculations on the excited states indicate that ail efficient intersystern crossing is activated upon twisting of the bridged C-C single bond in a free 3,6-linked carbazole; such efficient deactivation is impractical in 2,7-linked carbazole or for 3,6-linked carbazole in a PMMA matrix. Information obtained from experiments on femtosecond fluorescence enables LIS to distinguish crucial relaxation processes in the excited state for a profound understanding of the details of vibrational and electronic relaxations of 3,6-DPVTCz in Solution.
Spirobifluorene-based pyrazoloquinolines: efficient blue electroluminescent materials
(2004)
Chen, CH
;
Wu, FI
;
Shu, CF
;
Chien, CH
;
Tao, YT
We report the synthesis of spirobifluorene-based pyrazoloquinolines, spiro-PAQ-Me and spiro-PAQ-Ph, in which two identical luminophores are connected through an sp(3)-hybridized carbon atom (a spiro center) and are orthogonally arranged. The incorporation of the rigid spirobifluorene linkage results in significant increases in the glass transition temperatures, which are in the range 246-280degreesC. These new materials display the characteristic absorptions of the mono-pyrazoloquinoline (i.e. non-spiro) derivatives, each with a broad, low-energy absorption at ca. 420 nm, and emit photoluminescence efficiently in the blue region. Electrochemical studies reveal that these compounds exhibit reversible reductions and low-lying LUMO energy levels that originate from the electron-deficient nature of the pyrazoloquinoline ring. Multilayer organic electroluminescent devices constructed using spiro-PAQ-Ph as a dopant in the emitting layer produced bright blue emissions with maximum luminescence exceeding 20 000 cd m(-2). For the 2.0%-doped device, a high external quantum efficiency of 3.6% (4.5 cd A(-1), 2.02 lm W-1) was achieved at 20 mA cm(-2) and 7.0 V with color coordinates of (0.14, 0.17).
Spirobifluorene-linked bisanthracene: An efficient blue emitter with pronounced thermal stability
(2004-03-09)
Shen, WJ
;
Dodda, R
;
Wu, CC
;
Wu, FI
;
Liu, TH
Spiro-FPA, a novel blue emitter, in which two identical anthracene luminophores are linked orthogonally around a spirobifluorene core, has been synthesized and characterized. The introduction of a spiro linkage into the structure of spiro-FPA leads to a reduction in crystallization tendency and an increase in glass transition temperature relative to the monomeric units. In addition, the tetrahedral nature of the carbon atom at the spiro center preserves the optical and electrochemical characteristics of the pristine anthracene units. As demonstrated by AFM measurements, high-quality amorphous films of spiro-FPA with good morphological stability can be prepared by vapor deposition. Organic EL devices constructed using a 1.0-wt % TBP-doped spiro-FPA emitting layer produce bright blue emissions with a high luminescence efficiency of 4.9 cd/A (2.07 lm/W).
Synthesis and characterization of new hyperbranched poly(aryl ether oxadiazole)s
(2001-11-15)
Wu, FI
;
Shu, CF
;
應用化學系
;
Department of Applied Chemistry
A new AB(2) monomer was synthesized for use in the preparation of a hyperbranched poly(aryl ether oxadiazole) with terminal phenol functionality. The AB2 monomer contains two phenolic groups and a single aryl fluoride group that is activated toward nucleophilic displacement by the attached oxadiazole ring. The nucleophilic substitution of the fluoride with the phenolate groups led to the formation of an ether linkage. Subsequently, a hyperbranched poly(aryl ether oxadiazole) having approximately a 44% degree of branching, as determined by a combination of model compound studies and H-1 NMR, was obtained. The terminal phenolic groups underwent facile functionalization, furnishing hyperbranched polymers with a variety of functional chain ends. The nature of the chain-end groups had a significant influence on the physical properties of the polymers, such as the glass-transition temperature and their solubility. (C) 2001 John Wiley & Sons, Inc.
Synthesis and characterization of soluble polyimides derived from 2,2 '-bis(3,4-dicarboxyphenoxy)-9,9 '-spirobifluorene dianhydride
(2002-01-15)
Reddy, DS
;
Shu, CF
;
Wu, FI
;
應用化學系
;
Department of Applied Chemistry
The synthesis of aromatic poly(ether imide)s containing spirobifluorene units in the polymer backbone is described. 2,2'-Bis(3,4-dicarboxyphenoxy)-9,9'-spirobifluorene dianhydride, which was used as a new monomer, was synthesized with 2,2'-dihydroxy-9,9'-spirobifluorene as the starting material. In the spiro-segment, the rings of the connected bifluorene were orthogonally arranged. This bis(ether anhydride) monomer was employed in reactions with a variety of aromatic diamines to furnish poly(ether imide)s, involving an initial ring-opening polycondensation and subsequent chemically induced cyclodehydration. Excellent solubility in common organic solvents at room temperature, good optical transparency, and high thermal stability are the prominent characteristic features of these new polymers, which can be attributed to the presence of spiro-fused orthogonal bifluorene segments along the polymer chain. The glass-transition temperatures of the polyimides were 240-293 degreesC, and the 5% weight-loss temperatures were greater than 500 degreesC. (C) 2001 John Wiley & Sons, Inc.