Organic light emitting diodes with an organic acceptor/donor interface involved in hole injection

Organic light emitting diodes with an interface of organic acceptor 3-, 4-, 9-, 10-perylenetetracarboxylic dianhydride (PTCDA) and donor copper phthalocyanine (CuPc) involved in hole injection are fabricated. As compared to the conventional device using a 5 nm CuPc hole injection layer, the device using an interface of 10 nm PTCDA and 5 rim CuPc layers shows much lower operating voltage with an increase of about 46% in the maximum power efficiency. The enhanced device performance is attributed to the efficient hole generation at the PTCDA/CuPc interface. This study provides a new way of designing hole injection.

Tandem organic light-emitting diodes with an effective charge-generation connection structure

The tandem organic light-emitting diodes (OLEDs) with an effective charge-generation connection structure of Mg-doped tris(8-hydroxyquinoline) aluminum (Alq(3))/Molybdenum oxide (MoO3)-doped 3, 4, 9, 10-perylenetetracarboxylic dianhydride (PTCDA) were presented. At a current density of 50 mA/cm(2), the current efficiency of the tandem OLED with two standard NPB/Alq(3) emitting units is 4.2 cd/A, which is 1.7 times greater than that of the single EL device. The tandem OLED with the similar connection structure of Mg-doped PTCDA/MoO3-doped PTCDA was also fabricated and the influences of the different connection units on the current efficiency of the tandem OLED were discussed as well.

Preparation and characterization of polyimide/Al2O3 hybrid films by sol-gel process

A sol-gel process has been developed to prepare polyimide (PI)/Al2O3 hybrid films with different contents of Al2O3 based on pyromellitic dianhydride (PMDA) and 4,4'-oxydianiline (ODA) as monomers. FESEM and TEM images indicated that Al2O3 particles are relatively well dispersed in the polyimide matrix after ultrasonic treatment of the sol from aluminum isopropoxide and thermal imidization of the gel film. The dimensional stability, thermal stability, mechanical properties of hybrid PI films were improved obviously by an addition of adequate Al2O3 content, whereas, dielectric property and the elongation at break decreased with the increase of Al2O3 content. Surprisingly, the corona-resistance property of hybrid film was improved greatly with increasing Al2O3 content within certain range as compared with pure PI film.

Synthesis and properties of sulfonated poly[bis(benzimidazobenzisoquinolinones)] as hydrolytically and thermooxidatively stable proton conducting ionomers

Novel sulfonated poly [bis(benzimidazobenzisoquinolinones)] as hydrolytically and thermooxidatively stable electrolyte for high -temperature fuel cell applications are reported. A series of sulfonated polymers (SPBIBI-x, x refers to molar percentage of sulfonated dianhydride monomer) were synthesized from 6,6'-disulfonic-4,4'-binaphthyl-1,1',8,8'-tetracarboxylic dianhydride (SBTDA), 4,4-binaphthyl-1,1,8,8-tetracarboxylic dianhydride (BTDA), and 3,3'-diaminobenzidine. The chemical structures of those polymers as well as model compounds synthesized from SBTDA and o-phenylenediamine were confirmed by nuclear magnetic resonance (NMR) and Fourier transform infrared (FTIR).

Synthesis of isomeric bis(amine anhydride)s for novel poly(amine imide)s by Pd-catalyzed amination of 4-chlorophthalic anhydride

Two novel bis(amine anhydride) monomers, N,N'-bis(3,4-dicarboxyphenyl)-1,4-phenylenediamine dianhydride I and N,/N'-bis(3,4-dicarboxyphenyl)-1,3-phenylenediamine dianhydride 11, were prepared via palladium-catalyzed amination reaction of 4-chloro-N-methylphthaliniide with 1,4-phenylenediamine or 1,3-phenylenediamine, followed by alkaline hydrolysis of the intermediate bis(amine imide)s and subsequent dehydration of the resulting tetraacids. A series of new poly(amine imide)s were prepared from the synthesized dianhydride monomers with various diamines in NMP via conventional two-step method.

Novel acid-base polyimides synthesized from binaphthalene dianhydrie and triphenylamine-containing diamine as proton exchange membranes

The synthesis and characterization of novel acid-base polyimide membranes for the use in polymer electrolyte membrane fuel cell is presented in this paper. The sulfonated polyimides (SPIs) bearing basic triphenylamine groups were easily synthesized using 4,4'-binaphthyl-1,1',8,8'-tetracarboxylic dianhydride (BTDA), sulfonated diamine of 4,4'-diaminodiphenyl ether-2,2'-disulfonic acid (ODADS), and nonsulfonated diamines of 4,4'-diaminotriphenylamine (DATPA). The effects of the structure of the dianhydride and diamines on the properties of SPI membranes were evaluated through the study of membrane parameters including water sorption, proton conductivity, water stability, dimensional changes, and methanol permeability.

Novel Sulfonated Polyimide Ionomers by Incorporating Pyridine Functional Group in the Polymer Backbone

A series of sulfonated polyimides (SPIs) containing pyridine ring in the polymer backbone were synthesized by the polycondensation of 1,4,5,8-naphthalene-tetracarboxylic dianhydride (NTDA), 5-(2,6-bis(4-arninophenyl)pyridin-4-yl)-2-methoxy benzene sulfonic acid (SDAM), and 4,4'-diaminodiphenyl ether (ODA). Flexible, transparent, and tough membranes were obtained. Property study revealed that all the membranes displayed high thermal stability with the desulfonation and decomposition temperature higher than 290 and 540 degrees C, respectively, as well as good mechanical property with Young's modulus larger than 1.0 GPa, maximum strength (MS) on a scale of 60-80 MPa, and elongation at break (EB) ranged from 41.79 to 75.17%.

Novel hydrophilic-hydrophobic multiblock copolyimides as proton exchange membranes: Enhancing the proton conductivity

A series of novel multiblock copolymers based on sulfonated copolyimides were developed and evaluated for use as proton exchange membranes (PEMs). In these multiblock copolyimides, the hydrophilic blocks were composed of the sulfonated dianhydride and the sulfonated diamine, with sulfonic acid groups on every aromatic ring (i.e., fully sulfonated). This molecular design was implemented to effectively enhance the proton conductivity. The properties of the multiblock copolyimides with varying IEC values or block lengths were investigated to obtain a better understanding of the relationship between molecular structure and properties of proton exchange membranes. The water uptake and proton conductivity were found to be highly dependent upon their structure. The block copolymers displayed significantly higher proton conductivities, especially at low relative humidity than the random copolymers with a similar IEC.

Synthesis and properties of water stable poly[bis(benzimidazobenzisoquinolinone)] ionomers for proton exchange membranes fuel cells

A novel sulfonated tetraamine, di(triethylammonium)-4,4'-bis(3,4-diaminophenoxy)biphenyl-3,3'-disulfonate (BAPBDS), was successfully synthesized by nucleophilic aromatic substitution of 4,4'-dihydroxybiphenyl with 5-chloro-2-nitroaniline, followed by sulfonation and reduction. A high-temperature polycondensation of sulfonated tetraamine, non-sulfonated tetraamine (4,4 -bis(3,4-aminophenoxy)biphenyl) and 1,4,5,8-naphthalenetetracarboxylic dianhydride (a) or 4,4'-binaphthyl-1,1',8,8'-tetracarboxylic dianydride (b) gave the poly[bis(benzimidazobenzisoquinolinones)] ionomers SPBIBI-a(x) or SPBIBI-b(x), where x refers to the molar percentage of the sulfonated tetraamine monomer. Flexible and tough membranes of high mechanical strength were obtained by solution casting and the electrolyte properties of the polymers were intensively investigated. The ionomer membranes displayed excellent dimensional and hydrolytic stabilities.

Novel proton exchange membranes based on water resistant sulfonated poly[bis(benzimidazobenzisoquinolinones)]

Novel water resistant sulfonated poly[bis(benzimidazobenzisoquinolinones)] (SPBIBIs) were synthesized from 6,6'-disulfonic-4,4'-binaphthy]-1,1',8,8'-tetracarboxylic dianhydride (SBTDA) and various aromatic ether tetraamines. The resulting polymers with IEC in the range of 2.17-2.87 mequiv g(-1) have a combination of desired properties such as high solubility in common organic solvents, film-forming ability, and excellent thermal and mechanical properties. Flexible and tough membranes, obtained by casting from m-cresol solution, had tensile strength, elongation at break, and tensile modulus values in the range of 87.6-98.4 MPa, 35.8-52.8%, and 0.94-1.07 GPa. SPBIBI membranes with a high degree of sulfonation displayed high proton conductivity and a good resistance to water swelling as well. SPBIBI-b with IEC of 2.80 mequiv g(-1) displayed the conductivity of 1.74 x 10(-1) S cm(-1) at 100 degrees C, which was comparable to that of Nafion (R) 117 (1.78 x 10(-1) S cm(-1), at 100 degrees C).

Synthesis of bis(amine anhydride)s for novel high T(g)s and organosoluble poly(amine imide)s by palladium-catalyzed amination of 4-chlorophthalide anhydride

Two novel bis(amine anhydride)s, NN-bis(3,4-dicarboxyphenyl)aniline dianhydride (I) and N,N-bis(3,4-dicarboxyphenyl)-p-tert-butylaniline (II), were synthesized from the palladium-catalyzed amination reaction of N-methyl-protected 4-chlorophthalic anhydride with arylamines, followed by alkaline hydrolysis of the intermediate bis(amine-phthalimide)s and subsequent dehydration of the resulting tetraacids. The X-ray structures of anhydride I and II were determined. The obtained dianhydride monomers were reacted with various aromatic diamines to produce a series of novel polyimides. Because of the incorporation of bulky, propeller-shaped triphenylamine units along the polymer backbone, all polyimides exhibited good solubility in many aprotic solvents while maintaining their high thermal properties. These polymers had glass transition temperatures in the range of 298-408 degrees C. Thermogravimetric analysis showed that all polymers were stable, with 10% weight loss recorded above 525 degrees C in nitrogen.The tough polymer films, obtained by casting from solution, had tensile strength, elongation at break, and tensile modulus values in the range of 95-164 MPa, 8.8-15.7%, and 1.3-2.2 GPa, respectively.

Synthesis and characterization of rigid-rod sulfonated polyimides bearing sulfobenzoyl side groups as proton exchange membranes

A novel wholly aromatic diamine, 2,2 '-bis(3-sulfobenzoyl)benzidine (2,2 '-BSBB), was successfully prepared by the reaction of 2,2 '-dibenzoylbenzidine (2,2 '-DBB) with fuming sulfuric acid. Copolymerization of 1,4,5,8-naphathlenetetracarboxylic dianhydride with 2,2 '-BSBB and 2,2 '-DBB generated a series of rigid-rod sulfonated polyimides. The synthesized copolymers with the -SO3H group on the side chain of polymers possessed high molecular weights revealed by their high viscosity and the formation of tough and flexible membranes. The copolymer membranes exhibited excellent oxidative stability and mechanical properties due to their fully aromatic structure extending through the backbone and pendent groups. They displayed clear anisotropic membrane swelling in water with negligibly small dimensional changes in the plane direction of the membrane. The proton conductivities of copolymer membranes increased with increasing IEC and temperature, reaching value above 1.25 x 10(-1) S/cm at 20 degrees C, which is higher than that of Nafion (R) 117 at the same measurement condition. They displayed reasonably high proton conductivity due to the higher acidity of benzoyl sulfonic acid group, the larger interchain spacing, which is available for water to occupy, taking their lower water uptake (WU) into account. Consequently, these materials proved to be promising as proton exchange membrane.

Preparation and evaluation of a proton exchange membrane based on oxidation and water stable sulfonated polyimides

A series of novel oxidation and water stable sulfonated polyimides (SPIs) were synthesized from 4,4'-binaphthyl-1,1',8,8'-tetracarboxylic dianhydride (BTDA), and wholly aromatic diamine 2,2'-bis(3-sulfobenzoyl) benzidine (2,2'-BSBB) for proton exchange membrane fuel cells. These polyimides could be cast into flexible and tough membranes from m-cresol solutions. The copolymer membranes exhibited excellent oxidative stability and mechanical properties due to their fully aromatic structure extending through the backbone and pendant groups. Moreover, all BTDA-based SPI membranes exhibited much better water stability than those based on the conventional 1,4,5,8-naphthalenecarboxylic dianhydride. The improved water stability of BTDA-based polyimides was attributed to its unique binaphthalimide structure. The SPI membranes with ion exchange capacity (IEC) of 1.36-1.90 mequiv g(-1) had proton conductivity in the range of 0.41 x 10(-1) to 1. 12 x 10(-1) S cm(-1) at 20 degrees C. The membrane with IEC value of 1.90 mequiv g(-1) displayed reasonably higher proton conductivity than Nafion((R)) 117 (0.9 x 10(-1) S cm(-1)) under the same test condition and the high conductivity of 0.184 S cm(-1) was obtained at 80 degrees C. Microscopic analyses revealed that well-dispersed hydrophilic domains contribute to better proton conducting properties. These results showed that the synthesized materials might have the potential to be applied as the proton exchange membranes for PEMFCs.

A new class of high T-g and organosoluble polynaphthalimides

A new class of soluble six-membered ring polynaphthalimides (PNIs) was synthesized from asymmetrical fluorinated naphthalenesubstituted monomers. All the resulting PNIs were easily soluble in many organic solvents, such as N-methyl-2-pyrrolidinone (NMP), N,N-dimethylacetamide (DMAc), dimethyl sulfoxide (DMSO). and chloroform. They also showed good thermal stability with glass transition temperature of 340-386 degrees C, 10% weight loss temperature in excess of 529 degrees C. Polyimide 3c could be solution-cast into tough and flexible film. The film had a tensile strength, elongation at break, and Young's modulus of about 117.6 Wa, 23.6%, and 1.77 GPa, respectively. The gas permeation property of the film of 3c was investigated with oxygen permeability coefficient (PO2 = 3.99) and permeability selectivity coefficient of oxygen to nitrogen (P-O2/P-N2 = 5.27). Therefore, these materials are expected to be a good alternative to PIs based on five-membered rings with applications in gas separation membranes.

Sulfonated polyimides bearing benzimidazole groups for proton exchange membranes

A series of sulfonated polymides containing benzimidazole groups were synthesized using 4,4'-binaphthyl-1,1',8,8'-tetracarboxylic dianhydride (BTDA), 4,4'-diaminodiphenyl ether-2,2'-disulfonic acid (ODADS) as the sulfonated diamine, and 2-(3',5-diaminophenyl)benzimidazole (a) or 6,4'-diamino-2-phenylbenzimidazole (b) as the nonsulfortated diamine. The electrolyte properties of the synthesized polyimides Ia-x, Ib-x, x refers to molar percentage of the sulfonated diamine) were investigated and compared with those of polyimides (Ic-x) from BTDA, ODADS, and m-phenylenediamine (c). All synthesized polyimides possessed high molecular weights revealed by their high viscosity, and formation of tough and flexible membranes. Polyintides with benzimidazole groups exhibited much better swelling capacity than those without benzimiclazole groups. This was attributed to the strong interchain interaction through basic benzimidazole functions and sulfonic acid groups. The sulfortated polyimides that are incorporated with 1, 1',8,8'-binaphthalimide exhibited better hydrolytic stability than that with 1,4,5,8-naphthalimide. Polyimide membranes with good water stability as well as high proton conductivity were developed. Polyimide membrane (Ia - 90), for example, did not lose mechanical properties after being soaked in boiling water for tOOO h, while its proton conductivity was still at a high level (compared to that of Nafion 117).