Synthesis and properties of novel diisocyanate based optically active polyimides

A new optically active diisocyanate was prepared from the reaction of l-leucine and pyromellitic dianhydride (PMDA) and subsequent transformation of intermediate imide-containing diacid to diisocyanate via Weinstock modification of Curtius rearrangement. Solution polycondensation reaction of the prepared diisocyanate with PMDA, 3,3,4,4-benzophenonetetracarboxylic dianhydride, and hexafluoroisopropylidene 2,2-bis(phthalic anhydride) resulted in the preparation of novel optically active polyimides. The optimal conditions for polyimidations (reaction duration and temperature programming) were obtained via study of the model compound. The monomer, model compound and polymers were characterized by FTIR, ¹HNMR, mass spectroscopy and elemental analysis and their optical and physical properties were studied as well.     

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.     

Synthesis and properties of novel organosoluble polyimides derived from bis[3-(4-amino-2-trifluoromethylphenoxy) phenyl] ether

A new aromatic ether diamine, bis[3-(4-amino-2-trifluoromethylphenoxy) phenyl] ether, was successfully synthesized via nucleophilic substitution reaction of 3,3′-oxydiphenol and 2-chloro-5-nitrotrifluoromethylbenzene, followed by a catalytic reduction. A series of new polyimides were synthesized from the diamine with various commercially available aromatic dianhydrides via a conventional two-stage process, i.e. ring-opening polyaddition forming the poly(amic acid)s and further thermal or chemical imidization forming polyimides. The resulting polyimides exhibited good solubility in polar solvents, such as N,N-dimethylacetamide, N,N-dimethylformamide, N-methyl-2-pyrrolidinone and common solvents such as chloroform, tetrahydrofuran upon heating and possessed the inherent viscosities of 0.51-0.68 dL/g. The resulting strong and flexible films exhibited excellent thermal stability with the temperature at 10% weight loss is above 502 °C and the glass transition temperature in the range of 191-232 °C. The polyimides also were found to possess high optical transparency.     

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 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, characterization and H2O2-sensing properties of pyrimidine-based hyperbranched polyimides

A series of hyperbranched polyimides having pyrimidine core in the backbone was prepared by solution polycondensation of pyromellitic dianhydride (A₂ type) and 2,4,6-triaminopyrimidine (B₃ type). The resulting polyimides were characterized by IR, GPC, DTA, DSC, TGA, density and viscosity measurement. The results showed that polyimides were obtained in 82-86% yield, had inherent viscosities of 1.58-1.87 dL/g and highly thermal stability. From the solubility tests, it was found that all the polyimides were soluble in NMP, DMAc and DMSO at room temperature. In addition, because of their interesting film properties, attempts were made to prepare H₂O₂-sensing polyimide material. For this reason, selectivity of film-coated electrodes obtained from the chemically prepared hyperbranched polyimides toward electroactive (ascorbic acid, oxalic acid and hydrogen peroxide) and non-electroactive (lactose, sucrose and urea) species was examined by means of CV, DPV and TB techniques. From the electrochemical data obtained, it has been demonstrated that polyimide (HPI-2) film responded to only hydrogen peroxide among the species examined. In other words, it has been claimed that the mentioned polyimide-coated electrode can be used as H₂O₂-selective membrane in the presence of the electroactive and non-electroactive interferents.     

Synthesis and characterization of heat resistant, pyridine-based polyimides with preformed ether and ester groups

A pyridine-based diamine as a building block for the preparation of heat resistant polyimides was prepared. Reaction of 1,5-dihydroxy naphthalene with 4-nitrobenzoyl chloride resulted in preparation of 5-hydroxy-1-naphthyl-4-nitrobenzoate (HNNB). 5-Hydroxyl-1-naphthyl-4-aminobenzoate (HNAB) was prepared via reduction of nitro group of HNNB. The diamine with built-in ether and ester groups was synthesized by nucleophilic substitution reaction of HNAB with 2,6-dichloropyridine in the presence of K₂CO₃. The obtained diamine was fully characterized and its polycondensation reaction with different aromatic dianhydrides led to preparation of novel heat resistant poly (ether ester imide)s. All the polymers were characterized and their physical and thermal properties were studied.     

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     

Synthesis and properties of novel sulfonated (co)polyimides bearing sulfonated aromatic pendant groups for PEFC applications

Novel sulfonated diamines bearing aromatic pendant groups, namely, 3,5‐diamino‐3′‐sulfo‐4′‐(4‐sulfophenoxy) benzophenone (DASSPB) and 3,5‐diamino‐3′‐sulfo‐4′‐(2,4‐disulfophenoxy) benzophenone (DASDSPB), were successfully synthesized. Novel side‐chain‐type sulfonated (co)polyimides (SPIs) were synthesized from these two diamines, 1,4,5,8‐naphthalene tetracarboxylic dianhydride (NTDA) and nonsulfonated diamines such as 4,4′‐bis(3‐aminophenoxy) phenyl sulfone (BAPPS). Tough and transparent membranes of SPIs with ion exchange capacity of 1.5–2.9 meq g^?1 were prepared. They showed good solubility and high thermal stability up to 300 °C. They showed isotropic membrane swelling in water, which was different from the main‐chain‐type and sulfoalkoxy‐based side‐chain‐type SPIs. The relative humidity (RH) and temperature dependence of proton conductivity were examined. At low RH, the novel SPI membranes showed much higher conductivity than the sulfoalkoxy‐based SPIs. They showed comparable or even higher proton conductivity than Nafion 112 in water at 60 °C (>0.10 S cm^?1). The membrane of NTDA‐DASDSPB/BAPPS (1/1)‐s displayed reasonably high proton conductivities of 0.05 and 0.30 S cm^?1 at 50 and 100% RH, respectively, at 120 °C. © 2006 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 44: 2862–2872, 2006     

Adhesive and dielectric properties of novel polyimides with bis(3,3′-aminophenyl)-2,3,5,6-tetrafluoro-4-trifluoromethyl phenyl phosphine oxide (mDA7FPPO)

Polyimides with a low dielectric constant and excellent adhesion were prepared from a diamine containing phosphine oxide and fluorine groups, bis(3,3′-aminophenyl-2,3,5,6-tetrafluoro-4-trifluoromethyl phenyl phosphine oxide (mDA7FPPO), and rigid-rod type dianhydride containing fluorine groups, such as 3,6-di(3′,5′-bis(trifluoromethyl)-phenyl)pyromellitic dianhydride (12FPMDA). The polyimides were synthesized via the known two-step process, preparation of poly(amic-acid) followed by solution imidization, and characterized by FT-IR, NMR, DSC, TGA and TMA. In addition, their solubility, intrinsic viscosity, dielectric constant and adhesive property were also evaluated. For comparison, 3,6-di(4′-trifluoromethylphenyl) pyromellitic dianhydride (6FPMDA) and 3,6-diphenylpyromellitic dianhydride (DPPMDA) were also utilized. The prepared polyimides exhibited high T_g (276-314 °C), excellent thermal stability (>500 °C in air), good adhesive property (104.7-126.3 g/mm), good solubility, and very low dielectric constant (2.34-2.89).     

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.     

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     

Synthesis and characterization of novel polyimides containing stilbene unit in the side chain and their controllability of nematic liquid crystal alignment on the rubbed surfaces

Four polyimides containing hexylene spacer and a fluorostilbene unit in the side chains were prepared in thin‐film form by two‐step condensation of 3,3′‐bis[(4′‐fluoro‐4‐stilbenyl)oxyhexyloxy]‐4,4′‐biphenyldiamine (FS6B) with pyromellitic dianhydride (PMDA), benzophenone‐3,3′,4,4′‐tetracarboxylic dianydride (BTDA), 4,4′‐oxydi(phthalic anhydride) (ODPA), and 4,4′‐hexafluoroisopropylidenedi(phthalic anhydride) (6FDA), respectively, and their controllability of liquid crystal (LC) alignment on rubbed surfaces was investigated. Pretilt angles of LCs were achieved in the 2–9° range, depending on the rubbing density and backbone structures. The effect of the mesogenic stilbene group on the pretilting of LCs was distinctive in FS6B‐PMDA. Contact‐angle measurements on thin films annealed at 120 °C revealed that FS6B‐PMDA potentially had the better alignment stability than FS6B‐6FDA. © 2001 John Wiley & Sons, Inc. J Polym Sci Part A: Polym Chem 39: 3622–3632, 2001     

Polyimides with main-chain photosensitive groups: Synthesis, characterization and their properties as liquid crystal alignment layers

In this work, a series of polyimides containing main-chain chalcone groups and side-chain cinnamate or acetate groups were synthesized. In the synthetic route, three dianhydride monomers were prepared by the reactions of 1,3-dihydro-1,3-dioxoisobenzofuran-5-carbonyl chloride with 1,3-bis(4-hydroxylphenyl)prop-2-en-1-one, 1,3-bis(4-(2-hydroxyethyl)phenyl)prop-2-en-1-one, and 1,3-bis(4-hydroxyphenyl)-pent-1-en-3-one-4-en, respectively. The precursor polyimides were obtained by the polycondensation of the dianhydride monomers with 2,2-bis(3-amino-4-hydroxyphenyl)hexafluoropropane and the in situ imidization. After the polymerization, the final products were obtained by introducing the side groups through the reactions of the polyimide precursors with cinnamoyl chloride or acetic anhydride. The chemical structures and properties of the polyimides were characterized by elemental analysis, ¹H NMR, ¹³C NMR, FTIR, GPC, and thermal analysis. The polyimides show high thermal stability and good solubility in aprotic polar organic solvents. The polyimides can undergo sensitive [2+2] photocycloaddition reaction upon the UV light irradiation. After irradiation with linearly polarized UV light, the polyimide thin films can induce 5CB liquid crystal molecules to homogeneously align in the liquid crystal cells. Both the alignment ability and pretilt angles of the molecular orientation depend on the chemical structures of the polyimides.     

Synthesis and characterization of novel polyimides derived from 4-phenyl-2, 6-bis [3-(4-aminophenoxy)-phenyl]-pyridine diamine and aromatic dianhydrides

A new kind of pyridine-containing aromatic diamine monomer, 4-phenyl-2, 6-bis [3-(4-aminophenoxy)phenyl]-pyridine(m-PAPP),was synthesized by a modified Chichibabin reaction of benzaldehyde and a substituted acetophenone, 3-(4-nitrophenoxy)-acetophenone(m-NPAP), and a reduction of the resulting dinitro compound 4-phenyl-2, 6-bis[3-(4-nitrophenoxy)phenyl]-pyridine (m-PNPP) with Pd/C and hydrazine monohydrate, successively. A series of novel aromatic polyimides were prepared from the diamine with various aromatic dianhydrides via a conventional two-step thermal or chemical imidization method. The inherent viscosities of the resulting poly (amic acid) precursors were 1.37-1.56 dL/g, and these polymers could be cast and thermally converted into transparent, flexible, and tough polyimide films. The polyimides displayed higher solubility in polar solvents such as NMP, DMSO and m-cresol. The glass transition temperatures of these polymers were recorded at 180-264 °C. All of these novel polyimides held 10% weight loss at the temperature above 430 °C and left more than 50% residue even at 800 °C in air, as well as have outstanding mechanical properties with the tensile strengths of 91.6-114.1 MPa and elongations at breakage of 10.1-15.7%. Wide-angle X-ray diffraction measurements revealed that these polyimides were predominantly amorphous.     

Synthesis of novel fluorinated hyperbranched polyimides with excellent optical properties

Novel anhydride‐terminated fluorinated hyperbranched polyimides (FHBPIs) were successfully prepared by condensation of a triamine monomer, 1,3,5‐tris(2‐trifluoromethyl‐4‐aminopheoxy) benzene (TFAPOB), and various aromatic dianhydride monomers with different linear length. UV–vis spectra indicate high optical transparency of FHBPI films with a UV–vis absorption edge of 350–395 nm. FHBPIs show increased mechanical properties with the linear length of dianhydride monomer. Young's moduli of FHBPI range from 2.37 to 2.56 Gpa, similar to those of their linear analogs. These FHBPI films also present a minimum birefringence value as low as 0.0025 at 650 nm and have low optical absorption in the optical communication wavelengths of 1310 and 1550 nm. Rib‐type optical waveguide device fabricated by FHBPI‐4d demonstrated an obvious near‐field mode pattern of the waveguide. © 2009 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 47: 6269–6279, 2009     

Synthesis of novel poly(meth)acrylates containing tetracyanocyclopropyl groups as piezoelectric chromophores and their properties

p‐(2,2,3,3‐Tetracyanocyclopropyl)phenoxyethyl acrylate ( 5a ) and p‐(2,2,3‐tetracyanocyclopropyl)phenoxyethyl methacrylate ( 5b ) were prepared by the reactions of bromomalononitrile with p‐(2‐acryloyloxyethoxy)benzylidenemalononitrile and p‐(2‐methacryloyloxyethoxy)benzylidenemalononitrile, respectively. Monomers 5a and 5b were polymerized with free‐radical initiators to obtain polymers with multicyanocyclopropane functionalities in the pendant group. The resulting polymers were soluble in acetone, and the inherent viscosities were 0.25–0.30 dL/g. Solution‐cast films showed thermal stability up to 300 °C with glass‐transition temperatures of 140–156 °C. The dipole moments of 5a and 5b , calculated by the atom superposition and electron delocalization molecular orbital method, were 7.58–7.30 D. Piezoelectric coefficients (d₃₁) of the poled polymer films were 1.8–1.9 pC/N, acceptable values for piezoelectric device applications. © 2001 John Wiley & Sons, Inc. J Polym Sci Part A: Polym Chem 40: 379–384, 2002     

Synthesis of novel fused azecine ring systems through application of the tert-amino effect

Novel fused azecine ring systems were synthesized via the microwave-assisted thermal isomerization of terphenyl or biphenyl-pyridazine compounds possessing a vinyl and a tert-amino group, through application of a new extension of the tert-amino effect. Substrates for the ring closure were prepared from ortho-dihalobenzene or pyridazinone by consecutive Suzuki couplings with ortho-sec-amino- and formylphenylboronic acids, followed by Knoevenagel condensation of the aldehydes obtained.     

Synthesis and photochemical properties of novel pentamethylated norbornadiene containing polyimides

A novel pentamethylated norbornadiene (NBD) based dianhydride, α,α′‐bis‐(3,4,5,6,7‐pentamethylcyclopenta‐2,4‐dienyl)meta‐xylene‐1,2‐dianhydride (3), was prepared from α,α′‐bis‐(pentamethylcyclopentadienyl)meta‐xylene (1) and acetylene dicarboxylic acid. The bis‐adduct formed via Diels–Alder reaction afforded tetra‐acid (2), which was chemically cyclodehydrated to lead the targeted dianhydride (3). New polyimides containing NBD moieties in the main chain were prepared from the dianhydride monomer (3) and various aromatic diamines. The chemical structure of the polymers was confirmed by both ¹H and ¹³C NMR analysis. Their Molecular weights were also measured by SEC. All of these polyimides are soluble at room temperature in common organic solvents, such as chloroform, dichloromethane, THF, DMSO, DMF, and NMP, and show good thermal stabilities. The photochemical isomerization of the NBD into quadricyclane (QC) was investigated by UV/vis spectrophotometry from polymer films using visible sunlight as irradiation source. It was found that the kinetic rate of the conversion NBD‐QC which proceeded smoothly is a first kinetic order. The stored energies released by the transformation of QC groups into NBD ones of the irradiated polymer films were also evaluated by DSC measurement and were found to be around 90 kJ mol^?1. © 2011 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2011     

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