ABSTRACT:Semi-rigid homo-and copoly(ester-imide)s were prepared from bismethyl ester of 3,3 ,4,4 -pterphenyltetracarboxdiimide and bisalcohols of 3,3 ,4,4 -biphenyltetracarboxdiimide by melt polycondensation and their thermotropic liquid-crystalline, photo-(PL) and electroluminescent (EL) properties were investigated. Differential scanning calorimetry (DSC) measurements, polarizing microscope observations of textures and powder X-Ray analyses suggested that homopolymer having hexamethylene chain form monotropic smectic C or A phase and most of copolymers enantiotropic nematic phase. PL spectra showed that the polymers emitt blue light in the chloroform solutions and in the films. EL spectra of polymers in double-layer devices (ITO/poly(3,4-ethylene dioxythiophene) (PE DOT)/polymer/LiF or Ca/Al), with blue emission, were almost identical to the PL spectra, although luminances were very low. The poly(esterimide)s can be used as blue light-emitting and/or electron-transporting materials for organic EL devices.KEY WORDS Semi-Rigid Poly(ester-imide) / Photoluminescent Property / Electroluminescent Property / 3,3 ,4,4 -p-Terphenyltetracarboxdiimide / 3,3 ,4,4 -Biphenyltetracarboxdiimide / Powder X-Ray Analysis / Monotropic Smectic Phase / Blue Emission / Semi-rigid polyimides have been known to form thermotropic liquid-crystalline (LC) phases. [1][2][3][4][5][6][7][8][9][10][11][12][13][14][15][16][17][18] Kricheldorf et al. found that semi-rigid poly(esterimide)s derived from N, N -bisphenol 1 or N, Nbisester 2 derivative of 3,3 ,4,4 -biphenyltetracarboxdiimide with benzene ring next to the imide unit form enantiotropic smectic phases and aliphatic chains having odd numbers favor LC formation of polymers. We have prepared a series of semi-rigid poly(esterimide)s and poly(imide-carbonate)s [5][6][7][8][9][10][11][12][13][14][15][16][17][18] and found that the 3,3 ,4,4 -p-terphenyltetracarboxdiimide has good mesogenic property, but that of 3,3 ,4,4 -biphenyltetracarboxdiimide is low. 8,9,18 Aliphatic chains next to the imide ring play an important role on LC formation of polymers. Among the abovementioned semi-rigid poly(ester-imide)s having the 3,3 ,4,4 -biphenyltetracarboxdiimide, homopolymers containing decamethylene chain and decamethylene chain-rich copolymers formed nematic phase, although its texture was not clear. 18 Introduction of 3,3 ,4,4 -p-terphenyltetracarboxdiimide, which has higher mesogenic character than the 3,3 ,4,4 -biphenyltetracarboxdiimide, 16,17 into the backbones of semi-rigid poly(ester-imide)s would be likely to enhance potential of emergence of LC phases and to promote the formation of clearer LC textures.On the other hand, it has been reported that aromatic polyimides being heat-resistant polymeric materials display photoluminescent (PL) and LC properties, because they are made up of electron-donating and electron-withdrawing well-defined conjugation units. [19][20][21] They have a potential as light-emitting and electron-or hole-transporting materials for electroluminescent (EL) devices. P...

ABSTRACT:Thermotropic liquid crystalline and photoluminescent properties of semi-rigid homo-and copoly(ester imide)s composed of only both 3,3 ,4,4 -biphenyltetracarboxdiimide and aliphatic chains without traditional mesogens, which were prepared by transesterification of N, N -bismethyl ester derivatives and N, N -bisalcohols of 3,3 ,4,4 -biphenyltetracarboxdiimide, were evaluated by differential scanning calorimetry (DSC), polarizing microscope observation, powder X-Ray analyses, UV-vis absorption and PL spectrum measurements. These measurements suggested that polymers having decamethylene chain neighboring the imide ring and decamethylene chain-rich copolymers tend to form nematic phase and that they show maximum absorbances and blue-emission maxima arising from the 3,3 ,4,4 -biphenyltetracarboxdiimide both in solutions and in films.KEY WORDS Liquid Crystalline Property / Photoluminescent Property / Semi-Rigid Poly(ester imide) / 3,3 ,4,4 -Biphenyltetracarboxdiimide / Transesterification / Nematic Phase / Differential Scanning Calorimetry / Blue-Emission / Polyimides have not only excellent thermal, mechanical and chemical properties, but also various interesting physical properties such as nonlinear optical, liquid crystalline (LC) and fluorescent properties. [1][2][3][4]34 Active works about synthesis and LC properties of the polyimides have been done by Kricheldorf and so on. [5][6][7][8][9][10][11][12][13][14][15][16] We have also continued to prepare a series of semi-rigid thermotropic LC poly(ester imide)s and poly(imide carbonate)s and to discuss a relationship between polymer structure and LC property in the semi-rigid polyimides. [17][18][19][20][21][22][23][24][25][26][27][28][29][30] There are basically two different approaches in order to obtain the thermotropic LC polyimides. The first approach is to prepare polymers constituted of symmetric aromatic diimide units such as 3,3 ,4,4 -biphenyltetracarboxdiimide and 3,3 ,4,4 -p-terphenyltetracarboxdiimide, and the seconds is to synthesize polymers having asymmetric aromatic imide structures like N-phenylphthalimide. The former polymer has low or poor mesogenic property compared with the latter. Most of them don't show LC properties without the presence of benzene ring next to the imide ring or conventional biphenyl mesogen in the main chain. The 3,3 ,4,4 -p-terphenyltetracarboxdiimide unit is a better mesogen than the 3,3 ,4,4 -biphenyltetracarboxdiimide. 26,27 In recent years, we developed semi-rigid homo-and copoly(imide carbonate)s made up of only the symmetric diimides (3,3 ,4,4 -biphenyltetracarboxdiimide and/or 3,3 ,4,4 -p-terphenyltetracarboxdiimide) and aliphatic chains without coexistence of the biphenyl moiety in the main chain and showed that the 3,3 ,4,4 -p-terphenyltetracarboxdiimide-rich polymers form thermotropic LC phases in spite of absence of the conventional mesogens. 28,29 The aliphatic chains next to the imide ring play an important role in the LC formation of the semi-rigid poly(imide carbonate)s. Kricheldorf et al. found that...

No abstract