Formation of Exciplexes in Films of Polyimides,Polyamides, and Polyquinazolones Derived from Aromatic and Heteroaromatic Diamines

The emission bands exchibited by films of polyimides derived from 1,3-bis(3,4-dicarboxyphenoxy)benzene dianhydride, hexafluoroisopropylidenedibenzene-3,3′,4,4′-tetracarboxylic dianhydride, and aromatic and heteroaromatic diamines, and also of polyamides and polyquinazolones derived from the same amines are exciplex bahnds. With polyamides, complexes in the ground state are formed. The fluorescence of the photoconductivity sensitizer Rhodamine 6G is quenched in films of these polymers by the exciplex mechanism.     

Synthesis and photophysical properties of soluble polyimides and polyquinazolones containing side-chain chalcones or azo chromophores

Soluble aromatic and carboxyl- and hydroxyl-containing polyimides, mixed polyimides, and polyquinazolones of various chemical structures, as well as a series of new dicyanoazobenzene chromophores, are synthesized. From 20 to 80 mol % of chromophore groups are incorporated into side chains of the polymers. The thermal, photosensitive, and nonlinear optical properties (second-harmonic generation) of the chromophore-containing polymers are investigated. The polymers with covalently attached groups of the dye DR-13 or azo-derivatives of 4-phthalonitrile demonstrate the highest nonlinearity. The T _g values of the polyimides vary from 165 to 215°C; their temperatures corresponding to 5% weight loss lie in the range 290–350°C; and the measured coefficients of second-harmonic generation, d ₃₃, for a number of polarized films based on chromophore-containing polymers attain several tens of picometers per volt. The incorporation of chromophore groups into the side chains of the polymers causes an increase in the photosensitivity of polyimides by an order of magnitude relative to that of the parent polymers (S _0.1 = (3?4) × 10⁵ cm²/J in the range of dye absorption).     

光致发光聚酰亚胺研究进展

聚酰亚胺是一类重要的高性能高分子材料,具有优异的热性能、机械性能、电学性能和尺寸稳定性等,同时具有良好的结构可设计性,已逐渐成为有机光电领域的研究热点.然而,传统聚酰亚胺材料一般不发光,文献中有关发光聚酰亚胺的研究并不多.同时,所报道的荧光量子产率普遍较低,极大地限制了其作为发光功能层在有机光电器件领域的应用.为了更好地了解聚酰亚胺发光的规律,拓展高性能聚酰亚胺材料在有机发光器件中的应用领域,本文介绍了聚酰亚胺光致发光的机理,综述了国内外有关光致发光聚酰亚胺的研究进展,总结了提高聚酰亚胺荧光量子产率的方法,并对未来高性能高效发光聚酰亚胺材料的研究方向做了展望.     

Fluorescence of perylene- and naphthalene-containing polyimides: Evidence of molecular aggregation and chain coiling in chloroform solution

Fluorescence of several new polyimides in which neighboring imides are linked by a N-N bond was examined in chloroform solutions. For the naphthalene-containing polyimide 1 , analysis of the emission, excitation, and absorption spectra at different concentrations showed the existence of a ground-state intermolecular charge transfer (CT) complex due to chain association and aggregation. For the perylene-containing polyimides 3-6 , the fluorescence was characterized by a low energy band superimposed on the normal perylenediimide bands. This was interpreted as arising from a CT interaction between electron donor-acceptor pairs on the polymers backbone of the same chain, revealing certain degrees of chain coiling of these polymers in solution. © 1995 John Wiley & Sons, Inc.     

Novel aromatic polyamides and polyimides functionalized with 4‐tert‐butyltriphenylamine groups

A new triphenylamine‐containing diamine monomer, 4,4′‐diamino‐4″‐tert‐butyltriphenylamine, was successfully synthesized by the cesium fluoride‐mediated N,N‐diarylation of 4‐tert‐butylaniline with 4‐fluoronitrobenzene, followed by the reduction of the nitro group. The obtained diamine monomer was reacted with various aromatic dicarboxylic acids and tetracarboxylic dianhydrides to produce two series of novel triphenylamine‐based polyamides and polyimides with pendent tert‐butyl substituents. Most of the polymers were readily soluble in polar organic solvents, such as N‐methyl‐2‐pyrrolidone and N,N‐dimethylacetamide (DMAc), and could be solution cast into tough and flexible polymer films. These polymers showed high glass transition temperatures between 282 and 320 °C, and they were fairly stable up to a temperature above 450 °C (for polyamides) or 500 °C (for polyimides). These polymers exhibited UV absorption maxima around 308 to 361 nm. The photoluminescence spectra of the polyamides in DMAc exhibited a peak emission wavelength in the blue at 421–433 nm. Cyclic voltammograms of polyamides and polyimides showed an oxidation wave at 1.0–1.1 V versus Ag/AgCl in an acetonitrile solution. All the polyamides and polyimides exhibited excellent reversibility of electrochromic characteristics by continuous several cyclic scans between 0.0 and 1.1–1.3 V, with a color change from the original pale yellowish neutral form to the green or blue oxidized forms. © 2006 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 44: 4579–4592, 2006     

Preparation and properties of novel soluble aromatic polyimides from 4,4′-diaminotriphenylamine and aromatic tetracarboxylic dianhydrides

New aromatic polyimides containing triphenylamine unit were prepared by two different methods, i.e., a conventional two-step method starting from 4,4′-diaminotriphenylamine and aromatic tetracarboxylic dianhydrides and the one-step thioanhydride method starting from the aromatic diamine and aromatic tetracarboxylic dithioanhydrides. Both procedures yielded high-molecular-weight polyimides with inherent viscosities of 0.47–1.17 dL/g. Some of these polymers were soluble in organic solvents such as N,N-dimethylacetamide, N-methyl-2-pyrrolidone, m-cresol, and pyridine. All the polyimides afforded transparent, flexible, and tough films, and the color varied from pale yellow to dark red, depending markedly on the tetracarboxylic acid components. The glass transition temperatures (T_gs) of these polyimides were in the range of 287–331°C and the 10% weight loss temperatures were above 520°C in air. The polyimides prepared by the one-step method exhibited better solubility in organic solvents and had somewhat lower T_gs than the polymers prepared by a conventional two-step method.     

Note New Organic Polymers. 5. Synthesis of Poly(2-Vinyl-3-Substituted-4-Quinazolone)s

Heterocyclic polymers are well known for their outstanding thermal stability [I]. Sillion et al. [2, 31 reported that polyquinazolones prepared from 6,6′-bi(3,1-benzoxazin-4-one) substituted in the 2-position by a methyl or phenyl group and aromatic diamines are soluble in m-cresol and possess good thermal stability. The present paper deals with the synthesis of polyquinazolones from poly [l-(2-carboxyanilinocarbonyl)ethylene]. See Figs. 1 and 2.     

Designing aromatic polyamides and polyimides for gas separation membranes

Aromatic polyamides and polyimides with improved gas permselectivity, can be designed and prepared by systematically changing structural elements that affect these properties. Indeed, a conscientious choosing of the chemical changes may still provide a promising approach to get better and better polymers for selective filtration of gases. The results of this work, in which novel monomers have been used, have confirmed that gas permeability through aromatic polyamides and polyimides much higher than that of conventional polyamides and polyimides can be achieved. It has been done by introducing bulky side groups, using non-planar monomers, and combining these elements on both monomers: diamines and dianhydrides or diamines and diacids. A theoretical study has also been made to explain the behaviour of some individual polymers, comparing experimental and calculated values of density and free volume.     

Multi-triphenylamine-substituted porphyrin-fullerene conjugates as charge stabilizing "antenna-reaction center" mimics

A new concept of charge stabilization via delocalization of the pi-cation radical species over the donor macrocycle substituents in a relatively simple donor-acceptor bearing multimodular conjugates is reported. The newly synthesized multimodular systems were composed of three covalently linked triphenylamine entities at the meso position of the porphyrin ring and one fulleropyrrolidine at the fourth meso position. The triphenylamine entities were expected to act as energy transferring antenna units and to enhance the electron donating ability of both free-base and zinc(II) porphyrin derivatives of these pentads. Appreciable electronic interactions between the meso-substituted triphenylamine entities and the porphyrin pi-system were observed, and as a consequence, these moieties acted together as an electron-donor while the fullerene moiety acted as an electron-acceptor in the multimodular conjugates. In agreement with the spectral and electrochemical results, the computational studies performed by the DFT B3LYP/3-21G(*) method revealed delocalization of the frontier highest occupied molecular orbital (HOMO) over the triphenylamine entities in addition to the porphyrin macrocycle. Free-energy calculations suggested that the light-induced processes from the singlet excited state of porphyrins are exothermic in the investigated multimodular conjugates. The occurrence of photoinduced charge-separation and charge-recombination processes was confirmed by the combination of time-resolved fluorescence and nanosecond transient absorption spectral measurements. Charge-separated states, on the order of a few microseconds, were observed as a result of the delocalization of the pi-cation radical species over the porphyrin macrocycle and the meso-substituted triphenylamine entities. The present study successfully demonstrates a novel approach of charge-stabilization in donor-acceptor multimodular conjugates.     

Recent development of polyimides: Synthesis,processing, and application in gas separation

High-performance polymers have been concomitant with advanced technology for half a century. With the advancement of synthetic chemistry, the recent development of high-performance polymers has provided superior properties and enabled wide applications. This article reviews recent research progress in aromatic high-performance polymers. Particularly, we focus on the synthesis and processing of polyimides, as well as the application in gas separation membranes. We begin with a brief introduction to highlight important history and physiochemical characteristics of polyimides. Then, we review the various synthesis methods, followed by recent advances for improving processability. Finally, we evaluate the use of high-performance polymers in gas separation membranes with focus given to the key issues of plasticization and aging. Overall, the information presented herein provides an up-to-date overview of high-performance polymers, polyimides particularly, and serves as a guide for further research involving the applications in membrane technologies.     

Exciplex emission from electroluminescent ladder-type pentaphenylene oligomers bearing both electron- and hole-accepting substituents

We examine the photophysical properties of ladder-type pentaphenylenes, which have been prepared as prototypical "all-in-one" emissive materials bearing both electron-accepting (diaryloxadiazole) and electron-donating (triphenylamine) units. We find that donor-acceptor interactions are very dependent on the nature of the connectivity of these groups to the main pentaphenylene chain. When the oxadiazole and triphenylamine units were substituted on opposite sides of the pi-conjugated pentaphenylene chromophore, photoluminescence with long lifetimes typical of exciplex-like species was observed, while being significantly quenched by intermolecular charge separation between the substituents. By contrast, when the triphenylamine units were attached at the ends of the chromophore, no such effects were observed and a blue/green photoluminescence was obtained with very high quantum efficiency. In this latter configuration, evidence of ambipolar charge transport and a blue/green electroluminescence were additionally observed.     

Synthesis and characterization of novel polyimides with bulky pendant groups

New dianhydrides containing t‐butyl and phenyl pendant groups have been synthesized and used as monomers, together with commercial diamines, to prepare novel polyimides. The influence of the chemical structure of the monomers on their reactivity has been studied by quantum semiempirical methods. The polyimides have been characterized by FTIR and by NMR in the case of soluble polymers. The presence of pendant groups and the method used to imidize polyimide precursors greatly affected polymer properties such as solubility, glass transition temperature, thermal stability, and mechanical properties. As a rule, the novel polyimides showed better solubility in organic solvents than the parent polyimides. Glass transition temperatures in the range 250–270°C and decomposition temperatures over 520°C were observed for the set of current polymers. Tensile strengths up to 135 MPa and mechanical moduli up to 3.0 GPa were measured on films of the current polyimides. © 1999 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 37: 805–814, 1999     

Cycloaliphatic-aromatic polyimides based on diamines with azobenzene unit

A new family of functionalized semiaromatic polyimides has been developed. Cycloaliphatic-aromatic polyimides, derived from the polycondensation of 1,2,3,4-cyclopentanetetracarboxylic dianhydride (CPDA) with various diamines bearing azobenzene group, have been prepared and characterized. Molecular structural characterization for the resulting polymers has been achieved by ¹³C NMR, ¹H NMR, FTIR and UV-visible spectroscopies. Light-induced optical anisotropy, in novel azobenzene functionalized polyimides, has been studied by holographic polarization grating recording performed at 514.5 nm line of Ar⁺ laser. Two-wave mixing technique has been employed to inscribe the gratings in these polymers. Formation of gratings has been investigated with two s-s and s-p polarized writing beams. The kinetics of grating recording observed within the studied polymers is discussed in relation to their structure.     

Substituent effects on electrochemical and electrochromic properties of aromatic polyimides with 4‐(carbazol‐9‐yl)triphenylamine moieties

Three series of aromatic polyimides with 4‐(carbazol‐9‐yl)triphenylamine moieties were prepared from the polycondensation reactions of 4,4′‐diamino‐4″‐(carbazol‐9‐yl) triphenylamine (1), 4,4′‐diamino‐4″‐(3,6‐di‐tert‐butylcarbazol‐9‐yl)triphenylamine (t‐Bu‐1), and 4,4′‐diamino‐4″‐(3,6‐dimethoxycarbazol‐9‐yl)triphenylamine (MeO‐1), respectively, with various commercially available tetracarboxylic dianhydrides. In addition to high thermal stability and good film‐forming ability, the resulting polyimides exhibited an ambipolar electrochromic behavior. The polyimides based on t‐Bu‐1 and MeO‐1 revealed higher redox‐stability and enhanced electrochromic performance than the corresponding ones based on 1 because the active sites of their carbazole units are blocked with bulky t‐butyl or electron‐donating methoxy groups. © 2014 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2014 , 52, 1172–1184     

Synthesis and characterization of novel electroactive polyamides and polyimides with bulky 4‐(1‐adamantoxy)triphenylamine moieties

A novel adamantoxytriphenylamine‐containing diamine monomer, 4‐(1‐adamantoxy)‐4′,4″‐diaminotriphenylamine, was synthesized from readily available reagents. Two series of novel electroactive aromatic polyamides and polyimides with bulky 4‐(1‐adamantoxy)triphenylamine moieties were prepared from the newly synthesized diamine monomer with various aromatic dicarboxylic acids and tetracarboxylic dianhydrides, respectively. All the resulting polyamides and most of the polyimides were readily soluble in polar organic solvents and could be solution cast into tough and flexible films. These polymers showed moderate to high glass transition temperatures in the range of 263–311 °C, and they were fairly stable up to a temperature above 480 °C (for polyamides) or 500 °C (for polyimides). Cyclic voltammograms of the polyamides and polyimides showed one pair of reversible redox waves with oxidation half‐wave potentials (E_1/2) in the range of 0.78–0.81 and 0.97–1.05 V, respectively, versus Ag/AgCl in an acetonitrile solution. In addition, the polymers were found to display stable electrochromic properties by repeated cyclic scans between 0.0 and 1.1–1.2 V, with coloration change from a colorless or pale yellowish neutral form to a dark blue or bluish green oxidized form. © 2009 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 47: 1740–1755, 2009     

Study on dynamical behaviour of semi-stiff chain polymers. Fluorescence depolarization of proflavine aromatic polyimides

The fluorescence depolarization of proflavine groups incorporated into the backbone of aromatic polyimides has been measured in various solvents. The mean rotational relaxation times of the main chain depend on the structures of aromatic polyimides as planar semi-stiff chain polymers and differ from that of a low molecular analogue.     

Hydrolytic degradation and thermooxidative stability of polyimides based on 3,5-diaminodiphenyl oxide and 2-methyl-3,5-diaminodiphenyl sulfide

For a number of new polyimides prepared from 3,5-diaminodiphenyl oxide, 2-methyl-3,5-diaminodiphenyl sulfide, and various dianhydrides of aromatic tetracarboxylic acids, the hydrolytic stability in DMF and 96% H₂SO₄ and the thermooxidative stability in the bulk have been studied. Hydrodynamic techniques have been employed to determine the molecular parameters of these polymers at various stages of degradation. It has been shown that the polymers under study form stable solutions in DMF but turn out to be unstable in 96% H₂SO₄ even at room temperature. Degradation accompanies dissolution of the polymer. The correlation between the chemical structure of polymer molecules and their hydrolytic stability in both solvents has been established. It has been demonstrated that the majority of the said polyimides are stable in the solid state at temperatures up to 400°C and marked degradation begins only above 500°C.     

含氧膦结构的可溶性感光聚酰亚胺合成与表征

聚酰亚胺(PI)是一类综合性能优异的功能性材料,广泛应用于航天、航空及电子工业等领域[1].感光聚酰亚胺可以采用光刻工艺,大大简化了其应用加工程序[2,3],因而备受人们所青睐.含查尔酮结构的聚合物对UV辐射敏感度高和化学稳定性好,最近被广泛的研究和应用[4～7].主链含查尔酮结     

Synthesis of new photosensitive silicon-containing poly(salicylideneazomethynes)

Photosensitive silicon-containing poly(salicylideneazomethynes) have been synthesized. It has been shown that these polymers are characterized by the presence of intramolecular donor-acceptor interactions between valence shells of silicon and nitrogen atoms; as a result, polyconjugation appears according to the nonclassical mechanism. The photo-and electrophysical properties of the polymers have been examined. The introduction of an oxygen spacer into a polymer facilitates an increase in the photosensitivity and quantum yield of free charge carrier photogeneration, and it has almost no effect on the conductive behavior of the polymers.     

New thermally stable and organosoluble heterocyclic poly(naphthaleneimide)s

As majority of polyheteroarylenes based on bis(naphthalic anhydrides), are difficult to process due to their infusiblity and insolubility in common organic solvents and solubility only in strong acids, this study is concerned with the synthesis and properties of new, easily processable polyimides and copolyimides containing naphthalene and oxadiazole rings. These polymers have been synthesized and their properties have been compared with regard to the influence of oxadiazole and naphthalene units on their physical properties. The polyimides were prepared by polycondensation reaction in solution of the aromatic diamines containing preformed oxadiazole ring with two dianhydrides having naphthalene units, at high temperature. Also, copolyimides were prepared by using a mixture of each naphthalene‐containing dianhydride, with hexafluoroisopropylidene‐dianhydride in the polycondensation reaction with the same diamino‐oxadiazoles. Most of the resulting polyimides and copolyimides were soluble in polar amidic solvents and in less polar solvents, and their solutions gave flexible films when spread onto glass plates. The thermal stability and glass transition temperature of these polyimides and copolyimides were measured and compared. The quality and the roughness of the spin‐coated films of these polymers were investigated by atomic force microscopy. The photoluminescence properties of the polymers in solution were studied to determine the color of emission. The UV absorption was also studied to determine the Stokes shift, and hence the possible reabsorption effects. The properties of the present polyimides make them attractive for applications in advanced optoelectronics and other related fields. Copyright © 2009 John Wiley & Sons, Ltd.