Synthesis and properties of novel optically active polyimides

A facile synthesis of an optically active di‐isocyanate containing alkylene groups and a preformed imide structure is described. Polycondensation reactions of the prepared di‐isocyanate with pyromellitic dianhydride, benzophenone tetracarboxylic dianhydride, and hexafluoroisopropylidene diphthalic anhydride resulted in the preparation of optically active, thermally stable polyimides. The prepared monomer and polymers were characterized by conventional methods. Optical and physical properties of the polymers including thermal stability, thermal behavior, solution viscosity, and solubility behavior were studied. © 2001 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 39: 514–518, 2001     

Novel thermally stable polyimides based on flexible diamine: synthesis, characterization, and properties

A novel diamine with built-in sulfone, ether, and amide structure was prepared via three-step reactions. Nucleophilic reaction of 4-aminophenol with 4-nitrobenzoyl chloride in the presence of propylene oxide led to preparation of N-(4-hydroxy phenyl)-4-nitrobenzamide (HPNB). The nitro group of this compound was reduced with hydrazine and Pd/C to afford 4-amino-N-(4-hydroxy phenyl)benzamide (AHPB). Two moles of AHPB were reacted with bis-(4-chloro phenyl)sulfone to provide a novel sulfone ether amide diamine (SEAD). All the prepared compounds were characterized by common spectroscopic methods. The prepared diamine (SEAD) used to prepare related polyimides by reaction with different aromatic dianhydrides. The obtained poly(sulfone ether amide imide)s were characterized and their properties were studied.     

A novel direct method for preparation of aromatic polyimides via microwave-assisted polycondensation of aromatic dianhydrides and diisocyanates

Possibility of imide structure formation under microwave irradiation of molecules containing anhydride and isocyanate functional groups was investigated. The microwave-assisted polycondensation of aromatic diisocyanates and dianhydrides for preparation of polyimides was studied. The effect of microwave irradiation time and power, solvent nature, solid content of monomers, effect of catalyst, effect of polymerization reactor material and possibility of pressure development during polymerization, on the inherent viscosity of prepared polyimides were discussed. Experimental results showed that polymers obtained via this method had superior inherent viscosity and yield in comparison to the polymers obtained via conventional solution method.     

Synthesis and characterization of soluble polyimides based on trifluoromethylated aromatic dianhydride and substitutional diaminetriphenylmethanes

A series of novel and soluble polyimides containing fluorine were synthesized by the polycondensation of fluorine-containing aromatic dianhydride TFDA with substitutional diaminetriphenylmethanes TDPT, FTDPT and 3FTDPT. The composition, structure and properties of the resulting polyimides were studied by means of FT-IR, DSC, TGA and elemental analysis methods, as well as general characterization methods that test solubility or viscosity. The results show that all the novel polyimides were obtained in quantitative yields with inherent viscosities of 0.70-0.76 dL/g, and showed excellent solubility in common organic solvents, such as NMP, DMAc, DMF, DMSO, THF, m-cresol, chloroform and 4-butyrolactone. Meanwhile, their T_g values from DSC are in the range of 265-293 °C, the temperature of 5 and 10% weight loss from TGA are in the range of 460-465 and 513-524 °C in N₂, respectively.     

Synthesis and properties of thermally stable and optically active novel wholly aromatic polyesters containing a chiral pendent group

5-(2-Phthalimidyl-3-methyl butanoylamino)isophthalic acid (5), as a novel diacid monomer containing phthalimide and flexible chiral groups, was prepared by the reaction of 2-phthalimidyl-3-methyl butyric acid chloride (4) with 5-aminoisophthalic acid (5AIPA) in dry N,N-dimethylacetamide (DMAc). A series of novel polyesters (PE)s containing phthalimide group was prepared by the reaction of diacid monomer 5 with several aromatic diols via direct polyesterification with the tosyl chloride/pyridine/dimethylformamide (DMF) system as a condensing agent. The resulting new polymers were obtained in good yields with inherent viscosities ranging between 0.37 and 0.61 dL g⁻¹ and were characterized with FT-IR, ¹H NMR, elemental and thermogravimetric analysis techniques. These polymers are readily soluble in amide type solvents such as DMAc, DMF, 1-methyl-2-pyrrolidone, hexamethyl triaminophosphine, dimethyl sulfoxide and protic solvents such as sulfuric acid. Thermogravimetric analysis showed that the 10% weight loss temperature in a nitrogen atmosphere was more than 345 °C, which indicates that the resulting PEs have a good thermal stability as well as excellent solubility.     

Synthesis of soluble and thermally stable polyimides from unsymmetrical diamine containing 2,4,5-triaryl imidazole pendent group

A novel unsymmetrical diamine monomer containing triaryl imidazole pendant group, 4-[4-(4,5-diphenyl-1H-imidazol-2-yl)phenoxy] benzene-1,3-diamine (DAI), was successfully synthesized via aromatic substitution reaction of 1-chloro-2,4-dinitrobenzene with 4-(4,5-diphenyl-1H-imidazol-2-yl)phenol, followed by palladium-catalyzed hydrazine reduction. The diamine monomer DAI polymerized with commercial available dianhydrides such as benzophenone tetracarboxylic dianhydride (BTDA), pyromellitic dianhydride (PMDA) and bicyclo[2.2.2]-oct-7-ene-2,3,5,6-tetracarboxylic dianhydride (BCDA) by using two step synthetic methods to obtain corresponding polyimides (PIs). PIs had inherent viscosity of 0.42-0.51 dL/g and exhibited excellent solubility in aprotic polar solvents such as N,N-dimethylacetamide (DMAc), N-methyl-2-pyrrolidone (NMP), N,N-dimethylformamide (DMF), pyridine and methyl sulfoxide (DMSO). PIs showed high glass transition temperatures between 230 and 320 °C, and they were fairly stable up to a temperature above 300 and 450 °C depending on the dianhydride monomer used for the PIs preparation.     

Synthesis and characterization of polyimides based on novel isomeric perfluorinated naphthylenediamines

Novel highly fluorinated polyimides containing hexafluoronaphthylene fragment in the main chain were prepared by the two-stage polymerization of 2,7- and 2,6-diaminohexafluoronaphthalenes with 4,4′-oxydiphthalic anhydride: polycondensation in a solution at 80 °C followed by high-temperature solid-state chain extension. The influence of hexafluoronaphthylene fragment isomerism on the key polyimide features - molecular weight, thermal stability, solubility, optical properties - was characterized. Polyimides based on 2,7-diaminohexafluoronaphthalene or easily accessible mixture of isomeric diamines formed the flexible, transparent, and thermostable films.     

Synthesis and properties of optically active aromatic polyimides derived from optically pure 1,1′-bi-2-naphthol

A series of new optically active aromatic polyimides containing axially dissymmetric 1,1′-binaphthalene-2,2-diyl units were prepared from optically pure (R)-(+)- or(S)-(−)-2,2′-bis(3,4-dicarboxyphenoxy)-1,1′-binaphthalene dianhydrides and various aromatic diamines via a conventional two-step procedure that included ring-opening polycondensation and chemical cyclodehydration. The optically pure isomer of dianhydride was prepared by a nucleophilic substitution of optically pure (R)-(+)- or(S)-(−)-1,1′-bi-2-naphthol with 4-nitrophthalonitrile in aprotic polar solvent and subsequent hydrolysis of the resultant tetranitrile derivatives, followed by the dehydration of the corresponding tetracarboxylic acids to obtain the dianhydrides. These polymers were readily soluble in common organic solvents such as N,N-dimethylacetamide, N-methyl-2-pyrrolidone, and m-cresol, etc., and have glass transition temperatures of 251–296°C, and 5% weight loss occurs not lower than 480°C. The specific rotations of the optically active polyimides ranged from +196° to +263°, and the optical stability and chiroptical properties of them were also studied. © 1997 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 35: 3287–3297, 1997     

Soluble polyimides from a semi-aliphatic diamine containing ester,amide and ether groups

A diamine was synthesized by two successive reactions.Nucleophilic reaction of 4-hydroxybenzoic acid with terephthaloyl chloride yielded terephthaloyl bis(4-oxybenzoic) acid.Then reaction of this compound with 1,8-diamino-3,6- dioxaoctane via Yamazaki method resulted in preparation of diamine named terephthalic acid bis(4-{2-[2-(2-amino ethoxy)ethoxy]ethyl carbamoyl}phenyl) ester.After fully characterization it was used to prepare new polyimides through polycondensation with different dianhydrides using trimethylchlorosilane.Characterization of polymers was achieved by common methods and their physical properties including inherent viscosity,thermal behavior,thermal stability,crystallinity and solubility were studied.Prepared polyimides showed improved solubility and good thermal stability.     

Synthesis and properties of organosoluble polyimides based on novel perfluorinated monomer hexafluoro-2,4-toluenediamine

New highly fluorinated aromatic polyimides based on hexafluoro-2,4-toluenediamine and commercially available dianhydrides (6FDA and ODPA) were synthesized by one-pot high temperature polycondensation in benzoic acid melt. Owing to the CF₃ group and fluorine atoms in the meta-linked phenylenediamine fragment, these polyimides combine good solubility in organic solvents including such a low boiling point solvent as chloroform with high glass transition temperatures (330-345 °C), thermal and thermooxidative stability (T₅ is >500 °C). The highly fluorinated polyimide films (hydrogen content is ≤1%) exhibit good dielectric properties and low water absorption as well as excellent optical transparency in the UV-vis region (cut-off wavelength is 311 nm for 6FDA-based and 357 nm for ODPA-based polyimides), which is very important for optoelectronic materials.     

Synthesis and pharmacological evaluation of 5-carboxamide-substituted tetrahydrochromeno[7,8-d]imidazoles

A fast access to novel 5-carboxamide-substituted tetrahydrochromeno[7,8-d]imidazoles 4 was developed using the readily available preclinical candidate BYK 405879 (1) as starting material. The 5-amino function was installed by the Curtius rearrangement of carboxylic acid 2 or by the Hofmann rearrangement of carboxamide 8 furnishing benzimidazole 3 as key intermediate. In the Ghosh Schild rat, some of the target compounds 10-14 showed noteworthy activity as potassium-competitive acid blockers.     

Synthesis, chiroptical properties and photoinduced birefringence of optically active methacrylic copolymers bearing side-chain bisazoaromatic moieties

Three series of optically active photochromic copolymers, deriving from methyl methacrylate (MMA) and the chiral bisazoaromatic monomers (S)-3-methacryloyloxy-1-[4′-phenylazo-(4-azobenzene)]-pyrrolidine [(S)-MPAAP], (S)-3-methacryloyloxy-1-[4′-cyanophenylazo-(4-azobenzene)]-pyrrolidine [(S)-MPAAP-C] and (S)-3-methacryloyloxy-1-[4′-nitrophenylazo-(4-azobenzene)]-pyrrolidine [(S)-MPAAP-N], have been prepared and characterized in solution and in the solid state with the aim to evaluate the effect on their chiroptical and thermal properties originated by the insertion of inactive MMA groups along the main chain. The optical activity displayed by the bisazo polymers is discussed in terms of extent of chiral conformation assumed by the macromolecules as a consequence of dipole-dipole interactions between the bisazoaromatic chromophores.The photoinduction of birefringence has been assessed on thin films of the investigated copolymers in order to evaluate their behaviour as materials for optical data storage. The results are interpreted in terms of copolymer composition and conformational stiffness of the bisazoaromatic chromophoric co-units, which are responsible for the optical response rates, and are compared to those of the similar derivatives containing only one azo bond. The observed enhanced thermal properties and the temporal stability appear of interest for a potential use of these materials in nano technologies for all-optical data manipulation and in optoelectronics.     

Synthesis and electrochromic properties of polyimides with pendent benzimidazole and triphenylamine units

Five novel near-infrared electrochromic aromatic polyimides(PIs) with pendent benzimidazole group were synthesized from 4,4'-diamino-4'-(1-benzylbenzimidazol-2-yl)triphenylamine(named as DBBT) with five different dianhydrides via two-step polymerization process, respectively. The maximum UV-Vis absorption bands of these PIs locate at about 335 nm for solid films due to the π-π* transitions. A reversible pair of distinct redox peaks, that were associated with a noticeable color change from original yellow to blue, was observed in the cyclic voltammetry(CV) test. A new absorption peak emerged at 847 nm in near-infrared(NIR) region with increasing voltage in UV-Vis-NIR spectrum, which indicates that PI can be used as NIR electrochromic material. These novel PIs have good electrochemical stability, appropriate energy levels for the highest occupied molecular orbital(HOMO) and the lowest unoccupied molecular orbital(LUMO), in the range of-5.17 e V to-5.20 e V and-2.14 e V to-2.26 e V(versus the vacuum level) determined by cyclic voltammetry method. These values basically consisted with the results of quantum chemical calculation. These polyimides can be used as novel electrochromic and hole transportation materials.     

Synthesis and properties of novel triptycene‐based polyimides

Two new triptycene‐containing bis(ether amine)s, 1,4‐bis(4‐aminophenoxy)triptycene ( 4 ) and 1,4‐bis(4‐amino‐2‐trifluoromethylphenoxy)triptycene ( 6 ), were synthesized, respectively, from the nucleophilic chloro‐displacement reactions of p‐chloronitrobenzene and 2‐chloro‐5‐nitrobenzotrifluoride with 1,4‐dihydroxytriptycene in the presence of potassium carbonate, followed by palladium‐catalyzed hydrazine reduction of the dinitro intermediates. The bis(ether amine)s were polymerized with six commercially available aromatic tetracarboxylic dianhydrides to obtain two series of novel triptycene‐based polyimides 8a – f and 9a – f by using a conventional two‐step synthetic method via thermal and chemical imidizations. All the resulting polyimides exhibited high enough molecular weights to permit the casting of flexible and strong films with good mechanical properties. Incorporation of trifluoromethyl groups in the polyimide backbones improves their solubility and decreases their dielectric constants. The fluorinated polyimides 9d and 9f derived from diamine 6 with 4,4′‐oxydiphthalic anhydride and 2,2‐bis(3,4‐dicarboxyphenyl)hexafluoropropane dianhydride (6FDA), respectively, could afford almost colorless thin films. © 2011 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2011     

Synthesis of novel polyimides with (tert-butyldimethylsiloxy)biphenyloxy groups and the effect of side-chains content on their properties

A novel aromatic diamine 4′-(tert-butyldimethylsiloxy)biphenyl-4-yl 3,5-diaminobenzoate (DPA) was synthesized through three steps including monoesterification, silylation and hydrogenation. DPA with different ratios was copolymerized with 4,4′-diaminodiphenyl ether (ODA) and 3,3′,4,4′-biphenyl dianhydride (BPDA) to give poly(amic acid)s which were converted into polyimides (PIs) by thermal imidization. The effect of side-chain content on the thermal stability, optical transparency and surface energies was investigated by DSC, TGA, UV-vis spectra and contact angle measurement. With the content of side-chains increasing, the PIs revealed lower thermal stability, higher optical transparency and lower surface energies. The pretilt angles of 4-pentyl-4′-cyanobiphenyl (5CB) on the PI films were measured by a crystal rotation method. For the same rubbing strength, the pretilt angles increased with the increasing of the content of side-chains. When the content of side-chains rose from 5% to 20%, the pretilt angles increased from 2.8° to 15.0° under 28.5 mm of rubbing strength. When the content of side-chains increased to 70%, 80%, 90%, and 100%, the pretilt angles was 75.0°, 82.9°, 87.0°, and 87.7°, respectively, under 28.5 mm rubbing strength.     

Synthesis of novel aromatic polyimides containing bulky side chain for vertical alignment liquid crystals

In this study, a novel 4-（4-octyloxybenzoyloxy）biphenyl-3′,5′-diaminobenzoate and polyimides based on it were synthesized. The polyimide with mesogenic unit side chain exhibited excellent vertical alignment for nematic liquid crystal （LC）. The pretilt angles of LCs above 89° were kept after the rubbing process with 220 mm rubbing strength. The polyimide films as the alignment layer were baked at 120℃ for 12 h, the vertical alignment of LCs was still uniform and stable. Meanwhile, the UV-vis spectra of the noyel polyimide films showed the high transparency in a visible wave length.     

Synthesis and properties of optically active ferrocenylethylindazoles

The stereochemistry of two processes, viz., -ferrocenylalkylation of indazole with optically active S-(+)-1-ferrocenylethanol and the thermal rearrangement of S-(+)-2-N-(ferrocenylethyl)indazole into S-(+)-1-N-(ferrocenylethyl)indazole, was studied. Both reactions proceed stereoselectively.     

Synthesis of optically active alicyclic polyimides from a chiral,nonracemic dianhydride

Optically active alicyclic polyimides were prepared for the first time from (?)‐[1S*,5R*,6S*]‐3‐oxabicyclo[3.2.1]octane‐2,4‐dione‐6‐spiro‐3′‐(tetrahydrofuran‐ 2′,5′‐dione) [(?)‐DAn] via polycondensation with diamines and subsequent chemical or thermal imidization. The dianhydride (?)‐DAn was synthesized by an asymmetric Diels–Alder reaction of a chiral itaconic acid derivative as a key step. Colorless or slightly yellow flexible films were obtained for the (?)‐DAn‐derived polyimides {PI[(?)‐DAn]s}. PI[(?)‐DAn]s showed good solubility toward dipolar aprotic solvents and pyridine. For 1,4‐dioxane and chloroform, the optically active polyimides showed slightly better solubility than the corresponding polyimides prepared from rac‐DAn [PI(rac‐DAn)s]. PI[(?)‐DAn]s showed glass‐transition temperatures of 267–268 °C and 10% weight‐loss temperatures of 416–424 °C in nitrogen. These values were almost identical to those of PI(rac‐DAn)s. The circular dichroism spectra of PI[(?)‐DAn]s showed exciton coupling patterns indicating that to some extent these polyimides had a higher order structure in solution. © 2002 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 40: 4038–4044, 2002     

Synthesis and mechanical properties of novel photosensitive polyimides

This paper surveys novel photoimageable polyimides (PHIMPI), with emphasis on synthesis. Details of the chemistry and synthesis techniques on PHIMPI are discussed. A number of associated issues such as swelling, storage stability, shrinkage, photospeed, solvent developability, moisture absorption, thermal expansion and mechanical properties are presented. Most of the photoimageable polyimides that are commercially suitable to date are negative-acting, although recent developments in positive-acting PHIMPI are included.