Dinitro Compound Research Articles

New Fluorine-Containing Diamine Monomers for Potentially Improved Polyimides.

Two new fluorine-containing diamine monomers were designed with the goal of reducing charge transfer complex (CTC) interactions between neighboring chains in polyimides (i.e., high transparency/low color) while hopefully maintaining the well-known thermal stability and flexibility generally associated with polyimides. The proposed diamines have been prepared through (1) the functionalization of 1,3-bis[(pentafluorobenzyl)oxy]benzene with 4-aminophenol and (2) the addition of 2-chloro-5-nitrobenzotrifluoride to 4,4'-bicyclohexanol followed by reduction of the resulting dinitro compound. The new compounds have been characterized by multinuclear NMR and IR spectroscopy and high-resolution liquid chromatography-mass spectrometry as well as single-crystal X-ray diffraction on the new diamine prepared from 4,4'-bicyclohexanol. Not only was the structure of the proposed new diamine confirmed, but another interesting example of hydrogen bonding between an N-H proton and the π-system of an aromatic ring was observed and documented. Initial polymerizations have been carried out via the two-step imidization process.

Micropacked‐bed Reactor for Continuous Hydrogenation of Aromatic Dinitro Compounds

AbstractDue to the intricacy aromatic dinitro compound hydrogenation processes, it is difficult to attain high conversion and selectivity using merely modified catalysts in batch reactors. The micropacked‐bed reactor (μPBR) offers efficient heat and mass transfer, a precise and controllable reaction process, and a high level of safety. In this work, the hydrogenation of 2,4‐dinitroanisole was selected as the model reaction, and a variety of catalysts were utilized in the continuous flow system based on μPBR for hydrogenation of 2,4‐dinitroanisole. During 960 minutes of operation, the synthesis of 2,4‐diaminoanisole was carried out using a Pd (OH)2/C catalyst and the optimal process condition, yielding 100 % conversion, 99.5 % selectivity, and the favorable durability. For the hydrogenation of relevant aromatic dinitro compounds, the continuous flow system demonstrates exceptional performance.

Electrocatalytic determination of NADH by means of electrodes modified with MWCNTs and nitroaromatic compounds

In this work, we have both synthesized and studied 4-phenylbutyl-3,5-dinitrobenzoate (3,5-DNBPh) as a potential precursor of an electrocatalytic mediator for the oxidation of NADH, with the di-nitro compound immobilized in a three-dimensional network of glassy carbon electrodes modified with MWCNTs. This di-nitro compound is activated electrochemically to selectively generate one nitroso-hydroxylamine redox pair, which ultimately acts as a redox mediator of NADH oxidation. Thus, NADH electrocatalysis displaces the oxidation potential of NADH with the formation of a single voltammetric peak, the displacement occurs from Ep = +0.374 V in GCE/MWCNT to +0.001 V in GCE/MWCNT/3,5-DNBPh (very close to 0 V, ΔEp = 0.373 V). The 4-phenylbutyl-3,5-dinitrobenzoate mediator is sensitive to NADH concentration, and a linear regression between 0.1 and 0.6 mM NADH (r2 = 0.99) was obtained, with a detection limit of 22.3 μM (S/N = 3) and a quantification limit of 74.2 μM (S/N = 10). The developed modified electrode presents low NADH electrocatalytic oxidation potentials, and an interesting and novel advantage is that the preparation of the electrodes is fast, clean and effective, allowing biosensors to be obtained in a few steps.

Novel cardo polyamides with high solubility, thermally stability, and flame retardancy

A new monomeric building block was prepared via three consecutive reactions. 4-(4-Nitrobenzyl)pyridine was catalytically reduced to 4-(4-aminobenzyl)pyridine by converting the nitro to amino group. In second step, the later compound was reacted with 3,5-dinitrobenzoyl chloride to obtain a dinitro compound which finally was converted to a new diamine by reduction of nitro groups. Polycondensation reactions of the diamine with diacidchlorides led to preparation of novel cardo polyamides with high thermal stability and flame retardancy, as well as improved solubility. The structure-property relations were studied by varying the diacidchlorides to investigate the effect of symmetry and aromaticity on the polymers.

The synthesis and characterization of fluorinated polyimides derived from 2′-methyl-1,4-bis-(4-amino-2-trifluoromethylphenoxy)benzene and various aromatic dianhydrides

The synthesis and characterization of pendant methyl fluorinated polyimides (5a–f) derived from fluorinated diamine monomer, 2′-methyl-1,4-bis(4-amino-2-trifluoromethylphenoxy)benzene (2) and several aromatic dianhydrides (3a–f) is described. The synthesis of new fluorinated diamine (2) and the precursor fluorinated dinitro compound (1) are also discussed. The presence of trifluoromethyl group in the backbone of the fluorinated polyimide exhibited better optical transparency, organic solubility, dielectric constant, moisture adsorption and maintained mechanical and thermal properties than trifluoromethyl-free analogs (5′a–f). The highly fluorinated polyimides 5f via chemical imidization exhibited the best organic solubility, highest optical properties (b* cutoff wavelength = 367 nm). In addition, the highly fluorinated polyimide via thermal imidization also displayed relative lower dielectric constants (3.06 at 1 MHz) and moisture adsorption (0.16%) than most fluorinated polyimides. The t-butyl and phenyl substituted fluorinate diamine analogs and their fluorinated polyimides were also compared and discussed on thermal and mechanical properties.

Synthesis and characterization of two novel poly(amide-imide)s containing pendent (5-(4,5-diphenyl-1H-imidazol-2-yl)furan-2-yl)phenyl moieties and natural amino acids linkages for adsorption of Cu(II)

Two novel optically active poly(amide-imide)s (PAI)s were prepared by the direct polycondensation of diamine, 3,5-diamino-N-(4-(5-(4,5-diphenyl-1H-imidazol-2-yl)furan-2-yl)phenyl)benzamide with two optically active dicarboxylic acids such as N,N′-(pyromellitoyl)-bis-l-phenylalanine and N,N′-(4,4′-carbonyldiphthaloyl)-bis-l-phenylalanine in molten tetrabutylammonium bromide (TBAB) as a green medium with triphenyl phosphite as condensing agent. The diamine was synthesized via the direct condensation of 2-[5-(4-aminophenyl)furan-2-yl]-4,5-diphenyl-1H-imidazole with 3,5-dinitrobenzoyl chloride and following reduction in the dinitro compound. The resulting PAIs had inherent viscosities of 0.38 and 0.35 dL g−1. The PAIs were dissolved in polar organic solvents, such as NMP, DMAc, DMSO and DMF at room temperature. These polymers were solution-cast from DMAc solution into transparent, flexible and tough films. Wide-angle X-ray measurement exhibited that the PAIs were amorphous. These PAIs had 10% weight loss temperatures of 427 and 440 °C under nitrogen atmosphere. The polymer films had a tensile strength of 102 and 108 MPa and a tensile modulus of 2.2 and 2.3 GPa. The adsorption capability of one of the PAIs for removal Cu2+ from aqueous solutions was tested at pH 5.

Synthesis of functionalized diazocines for application as building blocks in photo- and mechanoresponsive materials.

Seven symmetrically 3,3’-substituted diazocines were synthesized. Functional groups include alcohol, azide, amine and vinyl groups, which are suitable for polymer synthesis. Upon irradiation at 385 and 530 nm the diazocines perform a reversible, pincer-type movement switching the 3,3’-distance between 6.1 Å (cis, stable isomer) and 8.2 Å (trans, metastable isomer). Key reactions in the synthesis are an oxidative C–C coupling of 2-nitrotoluenes (75–82% yield) and a reductive ring closure to form the diazocines (56–60% yield). The cyclization of the dinitro compound to the azo compound was improved in yield and reproducibility, by over-reduction to the hydrazine and reoxidation to the azo unit. In contrast to 3,3’- and 4,4’-diaminodiazocine, which have been implemented in macromolecules for conformation switching, our compounds exhibit improved photophysical properties (photostationary states, separation of absorption bands in the cis and trans configuration). Hence they are promising candidates as molecular switches in photo and mechanoresponsive macromolecules and other smart materials.

Synthesis and properties of organosoluble and thermal stable polyimides from 3,5-diamino-N-(4-(5-(4,5-diphenyl-1H-imidazol-2-yl)furan-2-yl)phenyl)benzamide

In this investigation, a novel aromatic diamine containing imidazole, furan and benzamide units in the side chain was successfully synthesized via direct condensation of 2-[5-(4-aminophenyl)furan-2-yl]-4,5-diphenyl-1H-imidazole with 3,5-dinitrobenzoyl chloride and following reduction in the dinitro compound. A series of novel polyimides (PI)s with aromatic heterocyclic structure were synthesized by a conventional two-step polymerization process from the reaction of aromatic diamine monomer with tetracarboxylic dianhydrides. These polymers were characterized using Fourier transform infrared spectroscopy (FTIR), proton nuclear magnetic resonance (1H NMR), X-ray diffraction (XRD) and elemental and thermogravimetric analysis techniques. The resulting PIs exhibited good thermal stability and small mass loss before temperature of 400 °C in nitrogen. They showed high solubility in polar organic solvents, such as NMP, DMAc, DMSO and DMF at room temperature. XRD studies exhibited that the obtained polymers exhibit amorphous morphology. In this research, PIs were used as a novel and efficient adsorbent for removal of malachite green dye from aqueous solution. The results showed that prepared PIs are an effective adsorbent for the removal of Cu ions from aqueous solutions.

Polyimide derivatives of 4,4ʹ-bis((4-aminophenoxy)methyl)-1,1ʹ-biphenyl: Synthesis, spectroscopic characterization, single crystal XRD and thermal studies

Novel diamine monomer 4,4′-bis((4-aminophenoxy)methyl)-1,1′-biphenyl (B4AP) was synthesized from precursor dinitro compound 4,4′-bis((4-nitrophenoxy)methyl)-1,1′-biphenyl (B4NP). A new series of polyimides was developed by condensation of B4AP with three dianhydrides (BTDA, ODPA, 6FDA). 4,4ʹ-methylenedianiline (MDA) was incorporated within the backbone of afore-synthesized polyimides for the preparation of copolyimides. Structural elucidations were carried out by FTIR and NMR (1H, 13C) spectroscopic techniques along with single crystal X-ray diffraction analysis, while TGA (dynamic and isothermal) and WAXRD techniques were used for properties evaluations of polymers. The crystal systems of B4NP and B4AP were found to adopt the space group P-1 and P21/c respectively. Polyimides showed substantially high thermal stability as their decomposition started around 400 °C. Execution of copolymerization strategy with MDA further enhanced their thermal stability. The temperature at 5% weight loss (T5) of polyimides under nitrogen atmosphere was in the range of 459–516 °C which increased to 496–538 °C for copolyimides. Air accelerated decomposition above 550 °C. Isothermal TGA disclosed that copolyimides are capable to withstand elevated temperatures for long time.

Preparation and characterization of polyimides containing triaryl imidazole side groups

A novel triaryl imidazole‐containing diamine, 3,5‐diamino‐N‐(4‐(4,5‐diphenyl‐1H‐imidazol)phenyl)benzamide, was successfully synthesized via the condensation of 4‐(4,5‐diphenyl‐1H‐imidazol)benzenamine and 3,5‐dinitrobenzoyl chloride, followed by reduction of the dinitro compound. A series of new aromatic polyimides with pendent triaryl imidazole moieties were prepared from the reaction of this diamine with various tetracarboxylic dianhydrides by a conventional two‐step polymerization process via thermal and chemical imidizations. The polyimides were obtained in quantitative yields with inherent viscosities of 0.21–0.44 dL/g. All the polymers are readily soluble in polar organic solvents. Flexible and strong films of polyimides were obtained by solution casting. The glass transition temperature of these polymers was in the range of 261–264°C. They were fairly stable up to a temperature around 300°C and lost 10% weight at 408°C under nitrogen. The ultraviolet–visible absorption spectra showed that all of the polymers had absorption maxima around 320 nm with a fluorescence emission maxima around 388–407 nm in N‐methyl‐2‐pyrrolidinone solution. Cyclic voltammograms of the polyimides revealed an oxidation wave with a peak around 1.7 V. Copyright © 2016 John Wiley & Sons, Ltd.

Soluble and degradable polyimides with phenyl-2-pyridyl ether structure: Synthesis and characterization

A diamine monomer o-phenylenedioxybis(5-amino-2-pyridine) was synthesized via reduction of a dinitro compound o-phenylenedioxybis(5-nitro-2-pyridine), producing a series of new polyimides from this diamine and various commercially available aromatic dianhydrides via conventional two-stage processes. The resulting polyimides are able to form tough and transparent films, with decomposition temperatures in the range of 529–551 °C, and can be dissolved in organic polar solvents. Meanwhile, these polyimides can be degraded in a hydrazine hydrate medium, a degradation mechanism proposed by analyzing the degradation products suggests that the degradable properties could be attributed to the phenyl-2-pyridyl ether structure in the polymer. In addition, the transformation of the compound structure from dinitro compound to damine monomer in the synthetic process is discussed in respect to X-ray structure.

Synthesis and first evaluation of [¹⁸F]fluorocyano- and [¹⁸F]fluoronitro-quinoxalinedione as putative AMPA receptor antagonists.

Derivatives of quinoxalinedione (QX) were chosen as chemical lead for the development of new radioligands of the AMPA receptor, since there are several examples of QX-derivatives with high affinity. The radiosyntheses of the new compounds 6-[(18)F]fluoro-7-nitro-QX([(18)F]FNQX) and 7-[(18)F]fluoro-6-cyano-QX ([(18)F]FCQX) with radiochemical yields of 8±2 and 3± 2%, respectively, as well as the evaluation of their binding properties to the AMPA-receptor were performed. A comparison of the Ki-values of the new QX-derivatives FCQX and FNQX with mono-substituted cyanoand nitro-QX shows negligibly small differences of affinity (within the range of 1.4 to 5 µM), but exhibits a tenfold lower affinity than derivatives with two electron withdrawing groups like the 7-cyano-6-nitro-compound CNQX and the 6,7- dinitro compound DNQX. Thus, with respect to the low affinity and a high non-specific binding with in vitro and ex vivo autoradiographic studies, the new compounds do not lend themselves for in vivo imaging.

Synthesis and properties of thermally stable polyimides bearing pendent fluorene moieties

A new diamine monomer containing fluorene unit, 3,5-diamino-N-(9H-fluoren-2-yl)benzamide was successfully synthesized via the condensation of 2-aminofluorene and 3,5-dinitrobenzoyl chloride and subsequent reduction of the dinitro compound. A series of novel aromatic polyimides having pendent fluorenamide moieties were prepared from the reaction of the diamine monomer and various tetracarboxylic dianhydrides by a conventional two-step polymerization process. The polyimides were obtained in quantitative yields with inherent viscosities of 0.33–0.44 dl/g. The resulting polymers dissolved in N-methyl-2-pyrrolidinone, N,N-dimethylacetamide, N,N-dimethylformamide, and dimethyl sulfoxide. The glass transition temperature of these polymers was in the range of 261–289°C. They were fairly stable up to a temperature around 450°C and lost 10% weight in the range of 498–556°C in nitrogen. The UV–vis absorption spectra showed that all of the polymers had absorption maxima around 320 nm. Cyclic voltammograms of the polyimides revealed an oxidation wave with a peak around 1.3 V. Copyright © 2014 John Wiley & Sons, Ltd.

Synthesis and characterisation of novel soluble polyimides for the application as liquid crystal vertical alignment layers

A new triphenylamine-based functional diamine monomer named N, N-bis (4-aminophenyl)-4-(nonyloxy-biphenyl)-4′-aminophenyl ether (N9) was successfully synthesised from cesium fluoride-mediated N,N-diarylation of 4-(nonyloxy-biphenyl)-4′-aminophenyl ether with p-fluoronitrobenzene and subsequent reduction of the resultant dinitro compound. A series of polyimides (PIs) with triphenylamine (TPA) moieties were prepared from the newly synthesised diamine monomer, 3,3′-dimethyl-4,4′-methylene-dianiline and 4,4′-oxydiphthalic anhydride through a conventional two-step procedure that included a ring-opening polyaddition to give polyamic acids, followed by chemical cyclodehydration. The PIs were completely amorphous and exhibited good solubility in organic solvents. PI films attained from a casting method showed high transmittance above 90% in the wave length range of 400–700 nm and could align liquid crystals vertically before and after rubbing treatment. The PIs derived from N9 exhibited much higher thermal stability compared with the corresponding PIs from 4-dodecyloxy-biphenyl-3′,5′-diaminobenzoate (D12). The results demonstrated that the introduction of TPA units into the polymer backbone could largely enhance the thermal stability of PIs while sustaining its solubility.

Electrochromic Property of Cured Epoxy Resins Containing Triphenylamine Moiety

4-Phenoxy-4', 4''-diaminotriphenylamine was synthesized from N, N-diarylation of 4-amino diphenyl ether and 4-fluoro nitrobenzene, and subsequent reduction of the resultant dinitro compound. The prepared triphenylamine and 4-methoxy-4', 4''-diaminotriphenylamine were dissolved in acetone respectively as the curing agents with epoxy resins to obtain a homogeneous mixture of the reactants. The cross-linked polymer film, which was well adhered to the ITO glass were cured by gradually increasing the temperature under N2 atmosphere. The cured epoxy resins films exhibited good thermal stability and electroactive properties. CV of the films revealed two pairs of reversible redox peaks, with coloration change from the colorless neutral state to the blue oxidized state.

Synthesis and characterization of poly(pyridine–imide)s with tert-butyl substituents

The aromatic diamine monomer containing a pyridine heterocyclic group and a tert-butyl substituent, 4-[(4′- tert-butyl)phenyl]-2,6-bis(4-aminophenyl)pyridine (BPAP), was successfully synthesized by a modified Chichibabin reaction of 4-nitro-acetophenone and 4- tert-butyl benzaldehyde, followed by a reduction of the resulting dinitro compound 4-[(4′- tert-butyl)phenyl]-2,6-bis(4-nitrophenyl)pyridine with palladium/carbon and hydrazine monohydrate, successively. A series of poly(pyridine–imide)s were prepared from the diamine BPAP with the alicyclic anhydride 1,2,3,4-cyclobutanetetracarboxylic dianhydride, aromatic anhydride pyromelitic dianhydride, 3,3′,4,4′-biphenyl tetracarboxylic dianhydride, and 4,4′-oxydiphthalic anhydride in N, N-dimethylformamide (DMF) via the conventional two-step method and further chemical imidization to obtain poly(pyridine-imide) powders. Due to the introduction of tert-butyl group, the polyimides (PIs) derived from BPAP were amorphous and displayed good solubility in amine-type polar solvents, such as DMF, dimethyl sulfoxide, N, N-dimethylacetamide, and N-methyl-2-pyrrolidone. Because of the presence of rigid triphenylpyridine units and bulky substituents, the final PIs held a good thermal stability with 10% weight loss temperatures above 504°C and left more than 55% residue even at 700°C under nitrogen atmosphere. The effect of tert-butyl substituents on the properties of the PIs was studied by comparing with 4-phenyl-2,6-bis(4-nitrophenyl)pyridine. These PIs exhibited some fluorescent properties because of the triphenylpyridine units, and the chemical structure of dianhydrides took an effect on the fluorescent property of these PIs.

Silarylene-containing poly(ether-amide)s obtained by Yamazaki–Higashi phosphorylation technique: use of bis(4-(4-aminophenoxy)phenyl)ethylmethyl silane

Aromatic poly(ether-amide)s (PEAs) based on -(R1,R2)diphenylsilane- and oxyether units were synthesized by direct polycondensation of a diamine and two dicarboxylic acids. For this, the diamine bis(4-(4-aminophenoxy)phenyl)ethylmethylsilane was obtained by reduction of the respective dinitro compound, which was synthesized by nucleophilic aromatic halogen displacement from 1-fluoro-4-nitrobenzene with bis(4-hydroxyphenyl)ethylmethylsilane in basic medium. New silicon-containing aromatic diamine and the PEAs were characterized by elemental analysis, FT-IR, 1H, 13C and 29Si NMR spectroscopy and the results were in agreement with the proposed structures. The incorporation of aliphatic units such as methyl and/or ethyl groups on the silicon atoms affected positively the solubility of the PEAs in organic polar solvents. When their thermal and optical properties were compared with two PEAs of similar structure, containing phenyl groups bonded to the silicon atoms, it was observed a decrease of the glass transition temperature and transmittance values, maintaining a high thermal resistance.

Synthesis and characterization of highly soluble and thermally stable new polyimides based on 3,5-diamino benzoyl amino phenyl-14H-dibenzo[a,j]xanthene

A new xanthene-containing diamine monomer was successfully synthesized in four steps by the condensation of β-naphthol and 4-nitrobenzaldehyde in the presence of p-toluenesulfonic acid catalyst, reduction of the nitro intermediate, the nucleophilic substitution reaction of amine compound and 3,5-dinitrobenzoyl chloride, and subsequent reduction of the dinitro compound. The diamine monomer could be obtained in quantitative yield. A series of novel organosoluble aromatic polyimides were prepared by direct polycondensation of synthesized diamine with four tetracarboxylic dianhydrides via a conventional two-step polymerization process. The polymers were obtained in quantitative yields with inherent viscosities of 0.20–0.74 dL/g. Most of the polymers dissolved in N-methyl-2-pyrrolidone, N,N-dimethylacetamide, N,N-dimethylformamide and dimethyl sulfoxide. The resulting polyimides exhibited good thermal stability; no weight loss was detected before a temperature of 450 °C in nitrogen. Wide-angle X-ray diffraction measurements showed that these polyimides were predominantly amorphous.

Synthesis and properties of novel alicyclic‐functionalized polyimides prepared from natural—(D)‐camphor

AbstractIn this article, a new alicyclic‐functionalized diamine, 1,3‐bis(4‐aminophenoxymethylene)‐1,2,2‐trimethylclopentane (BAMT) was successfully synthesized starting from natural —(D)‐camphor through four reaction steps of oxidation to offer a dicaboxylic acid, reduction to offer a diol, nucleophilic substitution to give a dinitro compound and then reduction to give the final diamine. Two alicyclic‐containing polyimides were prepared by polycondensing BAMT with 3,3′,4,4′‐biphenyltetracarboxylic dianhydride (BPDA) and 4,4′‐oxydiphthalicanhydride (ODPA), respectively. For the studies of the structure–property relationships of the polyimides, one aromatic polyimide of 4, 4′‐oxydianiline (ODA) polycondensed with ODPA was prepared in comparison. The alicyclic‐containinig polyimides PI (BPDA‐BAMT) and PI (ODPA‐BAMT) maintain good thermal properties with glass transition temperatures (Tg) of 257°C and 240°C, and temperatures at 5% weight loss (T5) of 443°C and 436°C in nitrogen, respectively. The alicyclic polyimides exhibit tensile strengths of 91.9–133 MPa, Young's moduli of 2.75—3.24 GPa, and elongations at break of 5.6–18%. Compared with the aromatic polyimide PI (ODPA‐ODA), PI (ODPA‐BAMT) shows improved transparency with the UV‐Vis transmittance at 500 nm over 80%. In addition, PI (ODPA‐BAMT) displays better solubility than PI (ODPA‐ODA), which has been confirmed by the bigger d‐spacing value of PI (ODPA‐BAMT) than that of PI (ODPA‐ODA) calculated from the Wide‐angle X‐ray Diffraction spectra. This study indicates that the renewable forestry compound, such as natural —(D)‐camphor, could be a good origin for the structural designing and preparation of alicyclic‐containing polyimides with outstanding combined features suitable for advanced microelectronic and optoelectronic applications. © 2013 Wiley Periodicals, Inc. J. Appl. Polym. Sci., 2013

Design and preparation of novel fluorescent polyimides containing ortho-linked units and pyridine moieties

A novel pyridine-containing aromatic diamine monomer, 4-[4-hydroxyphenyl]-2,6-bis[4-(2-aminophenoxy)phenyl]pyridine (p,o-HAPP), was synthesized by a modified Chichibabin reaction of p-Hydroxybenzaldehyde and a substituted acetophenone, 4-(2-nitrophenoxy)acetophenone (p,o-NPAP), followed by a reduction of the resulting dinitro compound 4-[4-hydroxyphenyl]-2,6-bis[4-(2-nitrophenoxy)phenyl]pyridine with Pd/C and hydrazine monohydrate. The aromatic diamine was employed to prepare a series of pyridine-containing polyimides (PIs) by polycondensation with various aromatic dianhydrides in N,N-dimethylformamide (DMF) via the conventional two-step method. The inherent viscosities of the resulting poly(amic acids) and PIs were in range of 0.62–0.76 and 0.52–0.64 dL/g, respectively. The obtained novel PIs exhibited high solubility in common organic solvents, such as m-Cresol, DMF, N,N-dimethylacetamide, dimethylsulfoxide, N-methylpyrrolidone (NMP), tetrahydrofuran, and chloroform. Meanwhile, flexible PI films were obtained, which had excellent thermal stability, with the glass transition temperature (T g) of 259.8–323.4 °C and the temperature at 10% weight loss of 485.5–576.4 °C in nitrogen atmosphere. The protonated polymer showed UV–vis absorption in the region 200–400 nm and displayed strong fluorescence intensity (470 nm) in NMP solution.