Polyimides from 1,5-bis(4-amino-2-trifluoromethylphenoxy)naphthalene and aromatic tetracarboxylic dianhydrides

A new trifluoromethylated bis(ether amine), 1,5-bis(4-amino-2-trifluoromethylphenoxy)naphthalene, was synthesized in two steps starting from 1,5-dihydroxynaphthalene and 2-chloro-5-nitrobenzotrifluoride via nucleophilic aromatic substitution and catalytic reduction. A series of novel fluorinated polyimides with moderate to high molecular weights were synthesized from the diamine with various aromatic tetracarboxylic dianhydrides using a conventional two-stage process. All polyimides could afford flexible and tough films and most of them were soluble in strong polar solvents such as N-methyl-2-pyrrolidone (NMP) and N,N-dimethylacetamide (DMAc). The polyimides showed glass-transition temperatures (T_g) in the range of 253-315 °C (by DSC) and softening temperatures (T_s) in the range of 250-300 °C (by TMA). Decomposition temperatures for 5% weight loss all occurred above 500 °C in both air and nitrogen atmospheres. The dielectric constants of these polymers ranged from 3.17 to 3.64 at 1 MHz. The properties of these fluorinated polyimides were also compared with those of polyimides prepared from 1,5-bis(4-aminophenoxy)naphthalene with the same dianhydrides.     

Synthesis and nonlinear optical properties of novel Y-type polyimides with enhanced thermal stability of dipole alignment

2,3-Bis-(3,4-dicarboxyphenylcarboxyethoxy)-4′-nitrostilbene dianhydride (4) was prepared and reacted with 1,4-phenylenediamine, 4,4′-oxydianiline, 4,4′-diaminobenzanilide and 4,4′-(hexafluoroisopropylidene)dianiline to yield novel polyimides 5-8 containing 2,3-dioxynitrostilbenyl groups as NLO-chromophores, which constituted parts of the polymer backbones. The resulting polyimides 5-8 were soluble in polar solvents such as acetone and DMF. Polymers 5-8 showed a thermal stability up to 300 °C in TGA thermograms with T_g values obtained from DSC thermograms in the range of 135-160 °C. The SHG coefficients (d₃₃) of poled polymer films at the 1064 cm⁻¹ fundamental wavelength were around 5.26 × 10⁻⁹ esu. The dipole alignment exhibited exceptionally high thermal stability even at 30 °C higher than T_g and there was no SHG decay below 170-190 °C due to the partial main chain character of polymer structure, which was acceptable for NLO device applications.     

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 characterization of fluorinated polyimides for pervaporation of n-heptane/thiophene mixtures

Soluble fluoro-polyimides have been synthesized by reacting of a fluorine-containing aromatic dianhydride, 2,2′-bis(3,4-dicarboxyphenyl)hexafluoropropane dianhydride, with aromatic diamine to yield poly(amic acid)s which were then cyclized to yield polyimide by chemical imidization method. The polyimides have excellent solubility both in strong bipolar solvents, such as NMP and DMAc, and in common organic solvents, such as THF and dioxane, etc. The glass transition temperature of these polyimides were determined by DSC and ranged from 281 to 289 °C. Thermogravimetric analysis indicated that these polyimides have good thermal stability with initial thermal decomposition temperature of 520-526 °C. The polyimide asymmetric membranes were prepared by phase inversion method and the inner structure was observed by method of SEM. The pervaporation properties of the prepared polyimides asymmetric membranes for n-heptane/thiophene mixtures were investigated at 40-77 °C and the permeation flux and the sulfur enrichment factor of the polyimide membranes are in the range of 0.56-1.68 kg/m² h and 3.12-2.24, respectively. The result demonstrated that the pervaporation method could be very effective method for desulfurization by polyimides asymmetric membranes with ultrathin skin.     

Synthesis and characterization of soluble polyimides based on a new fluorinated diamine: 4-Phenyl-2,6-bis[3-(4′-amino-2′-trifluoromethyl-phenoxy) phenyl] pyridine

A new kind of pyridine-containing aromatic diamine monomer, 4-phenyl-2,6-bis[3-(4′-amino-2′-trifluoromethyl-phenoxy) phenyl] pyridine (m-PAFP), was successfully synthesized by a modified Chichibabin reaction of 3-(4′-nitro-2′-trifluoro-methyl-phenoxy)-acetophenone with benzaldehyde, followed by a catalytic reduction. A series of fluorinated pyridine-bridged aromatic poly(ether-imide)s were prepared from the resulting diamine monomer with various aromatic dianhydrides via a conventional two-step thermal or chemical imidization method. The inherent viscosities values of these polyimides were in the range of 0.56-1.02 dL/g, and they 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 polyimides had good thermal stability, with the glass transition temperatures (T_g) of 187-211 °C, the temperatures at 5% weight loss of 511-532 °C, and the residue at 800 °C in air was higher than 50%. These films also had dielectric constants of 2.64-2.74 at 10 MHz and low water uptake 0.53-0.66%. Wide-angle X-ray diffraction measurements revealed that these polyimides were predominantly amorphous. Moreover, the polymer films of these novel polyimides showed outstanding mechanical properties with the tensile strengths of 90.1-96.6 MPa, elongations at breakage of 8.9-10.7% and tensile modulus of 1.65-1.98 GPa.     

Synthesis and characterization of new polyimides containing pendent pentadecyl chains

A new unsymmetrical aromatic diamine, viz., 4-pentadecylbenzene-1,3-diamine was synthesized through a series of reaction steps starting from 3-pentadecylphenol. 4-Pentadecylbenzene-1,3-diamine was employed to synthesize a series of new polyimides by one-step polycondensation in m-cresol with four commercially available aromatic dianhydrides, viz., 3,3′,4,4′-biphenyltetracarboxylic dianhydride (BPDA), 3,3′,4,4′-benzophenonetetracarboxylic dianhydride (BTDA), 4,4′-oxydiphthalic anhydride (ODPA) and 4,4′-(hexafluoroisopropylidene)diphthalic anhydride (6-FDA). Inherent viscosities of resulting polyimides were in the range 0.33-0.67 dL/g and number average molecular weights were in the range 14,700-52,200 (GPC, polystyrene standard). Polyimides containing pendent pentadecyl chains were soluble in organic solvents such as chloroform, m-cresol, N,N-dimethylacetamide (DMAc), 1-methyl-2-pyrrolidinone (NMP), pyridine and nitrobenzene. Strong and flexible films of polyimides could be cast from their chloroform solutions. Polyimides exhibited glass transition temperature in the range 158-206 °C. The temperature at 10% wt. loss (T₁₀), determined by TGA in nitrogen atmosphere, of polyimides was in the range 470-480 °C indicating good thermal stability.     

Synthesis, characterization, and thermal properties of new silarylene-siloxane-acetylene polymers

New silarylene-siloxane-acetylene polymers have been synthesized by coupling reactions employing 1,3-bis(p-ethynylphenyl)-1,1,3,3-tetraphenyldisiloxane (3) as the key monomer. Their thermal properties have been evaluated by thermogravimetric analysis (TGA) and differential scanning calorimetry (DSC). All of the new polymers showed good thermal stability, with their temperatures at 5% weight loss (T_d5) being higher than 540 °C under nitrogen and higher than 460 °C in air. Their char yields at 1000 °C under N₂ were above 80%. Broad exothermic peaks, attributable to reaction of the acetylenic units, were observed by DSC analysis in the temperature range 270-450 °C.     

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 properties of new pyridine-bridged poly(ether-imide)s based on 4-(4-trifluoromethylphenyl)-2,6-bis[4-(4-aminophenoxy)phenyl]pyridine

A novel pyridine-containing aromatic diamine monomer, 4-(4-trifluoromethylphenyl)-2,6-bis[4-(4-aminophenoxy)phenyl]pyridine (FAPP), was synthesized via the modified Chichibabin pyridine synthesis of 4-(4-nitrophenoxy)-acetophenone with 4-trifluoromethyl-benzaldehyde, followed by a catalytic reduction. A series of fluorinated pyridine-bridged aromatic poly(ether-imide)s were prepared from the resulting diamine monomer with various aromatic dianhydrides via a conventional two-step process. The resulting polyimides exhibited good solubility in aprotic amide solvents and m-cresol, such as N,N-dimethylacetamide, N-methyl-2-pyrrolidone, and m-cresol, etc., which possessed the inherent viscosities of 0.76-0.91 dL/g. Strong and flexible poly(ether-imide) films were obtained, which showed excellent thermal properties with the glass transition temperatures of 268-353 °C, the temperature at 5% weight loss of 547-595 °C, and the residue at 700 °C of 65-74% in nitrogen, good mechanical properties with the tensile strengths of 87.6-104.2 MPa and elongations at breakage of 8.9-12.6%, and good optical transparency with the cut-off wavelengths of 357-380 nm, as well as low dielectric constants in the range of 2.49-3.04 at 1 MHz and low water uptake 0.43-0.69%. Furthermore, the resulted polyimides derived from FAPP were compared with non-fluorinated analogous polyimides and fluorinated analogous polyimides with trifluoromethyl groups in different positions, and the effects of substituents were also investigated and discussed.     

Preparation and properties of high performance bismaleimide resins based on 1,3,4-oxadiazole-containing monomers

In research towards high performance polymeric materials, two novel series of bismaleimide (BMI) resins based on 1,3,4-oxadiazole-containing monomers have been designed and prepared by the copolymeriziation reaction of 5-tert-butyl-1,3-bis[5-(4-maleimidophenyl)-1,3,4-oxadiazole-2-yl]benzene (Buoxd) or 4,4′-bis[5-(4-maleimidophenyl)-1,3,4-oxadiazole-2-yl]diphenyldimethylsilane (Sioxd) and 4,4′-bismaleimidodiphenylmethane (BMDM) in different feed ratios. The structures, thermal and dynamic mechanical properties of all the resulting BMI resins were carefully characterized by a combination of methods such as IR, DSC, TGA and DMA. Investigation of the copolymerization process has shown that with an increase of the weight ratio of Buoxd or Sioxd, melting transition temperature (T_m) of BMI monomer mixtures decreased and the exothermic polymerization temperature (T_p) increased. For all BMI monomer mixtures, a rapid polymerization process was observed in the early stage, as shown by the IR investigations. No glass transition was observed for the resulting BMI resins in the temperature range from 50 °C to 350 °C, indicating the formation of highly cross-linking networks. The initial thermal decomposition temperatures (T_d) of the BMI resins were in the range of 477-493 °C in nitrogen and 442-463 °C in the air. Dynamic mechanical analysis (DMA) of the composites made of the BMI resins and glass cloth showed high bending modulus not only at room temperature (E′, 1.9-5.3 GPa) but also at high temperature, e.g., 400 °C (E′, 1.7-4.4 GPa).     

Synthesis and properties of phthalonitrile-terminated oligomeric poly(ether imide)s containing phthalazinone moiety

Three novel series of soluble and curable phthalonitrile-terminated oligomeric poly(ether imide)s containing phthalazinone moiety were synthesized from an excess amount of three dianhydrides and phthalazinone-based diamine, followed by reacting with 4-(3-aminophenoxy)phthalonitrile (APPh) in a two-step, one-pot reaction, respectively. The phthalonitrile oligomers containing phthalazinone moiety were cured in the presence of 4,4′-diaminodiphenylsulfone (DDS). The oligomers and the crosslinked polymers were characterized by DSC, FT-IR and elemental analysis. These phthalonitrile oligomers containing phthalazinone groups were found to be soluble in some aprotic solvents, such as chloroform, pyridine, m-cresol and N-methyl-2-pyrrolidone (NMP). The crosslinked polymers were insoluble in all solvents. The thermal properties of the oligomers and the crosslinked polymers were evaluated using DSC and TGA analysis. The phthalonitrile oligomers showed high glass transition temperatures (T_gs) in the range of 214-256 °C and high decomposition temperatures with 10% weight loss (T_d10%) ranging from 523 to 553 °C. The crosslinked polymers showed excellent thermal stability with the 10% weight loss temperatures ranging from 543 to 595 °C, but did not exhibit a glass transition temperature upon heating to 350 °C.     

Synthesis of soluble and thermally stable polyimide from new diamine bearing N-[4-(9H-carbazol-9-yl)phenyl] formamide pendent group

A new aromatic diamine monomer, N-(4-(9H-carbazol-9-yl)phenyl)-3,5-diaminobenzamide, was successfully prepared in four steps using carbazole as starting material and polymerized with three aromatic tetracaboxylic acid dianhydrides via the conventional two-stage synthesis including the polyaddition and chemical cyclodehydration to produce a series of the aromatic polyimides. The polyimides were characterized by FT-IR, ¹H NMR, and ¹³C NMR spectroscopy, differential scanning calorimetric (DSC) and thermo gravimetric analysis (TGA) analysis. The polyimides with inherent viscosities in the range of 0.38–0.46 dL/g showed excellent solubility in various solvents such as N-methyl-2-pyrrolidinone (NMP), N,N-dimethylacetamide (DMAc), N,N-dimethylformamide (DMF), pyridine and dioxane. DSC showed the glass transition temperatures (T_g) in the range of 277–288 °C. TGA showed that all polymers were stable, with 10% weights loss recorded above 524 °C in air atmosphere. Preliminary tests on films of the polyimides indicate that the materials are brittle.     

Synthesis and properties of novel aromatic poly(ester-imide)s bearing 1,5-bis(benzoyloxy)naphthalene units

Two series of new aromatic poly(ester-imide)s were prepared from 1,5-bis(4-aminobenzoyloxy)naphthalene (p-1) and 1,5-bis(3-aminobenzoyloxy)naphthalene (m-1), respectively, with six commercially available aromatic tetracarboxylic dianhydrides via a conventional two-stage synthesis that included ring-opening polyaddition to give poly(amic acid)s followed by chemical imidization to polyimides. The intermediate poly(amic acid)s obtained in the first stage had inherent viscosities of 0.41-0.84 and 0.66-1.37 dl/g, respectively. All the para-series and most of the meta-series poly(ester-imide)s were semicrystalline and showed less solubility. Two of the meta-series poly(ester-imide)s derived from less rigid dianhydrides were amorphous and readily soluble in polar aprotic solvents, and they could be solution-cast into transparent and tough films with good mechanical properties. The meta-series polymers derived from rigid dianhydrides were generally semicrystalline and showed less solubility. Except for one example, the meta-series poly(ester-imide)s displayed discernible T_gs in the range 239-273 °C by DSC. All of these two series poly(ester-imide)s did not show significant decomposition below 450 °C in nitrogen or in air.     

Synthesis of new polyazines by 1,4 photochemical or anionic polymerization of 1,2-diaza-1,3-butadienes

Photochemical and anionic polymerizations of 1,2-diaza-1,3-butadienes are described. Photochemical polymerization was smoothly performed by irradiation of some 1-aminocarbonyl-1,2-diaza-1,3-butadienes with high pressure mercury arc (λ = 300 nm) in the presence of allyltributylstannane. Molecular weights (M_w) in the range 14.6-559 × 10² g/mol were obtained. The TGA curve revealed a first weight loss starting at about 200 °C of some 85%, and a second starting at about 300 °C. The DSC showed the glass transition (T_g) at about −34 °C. Anionic polymerization was performed by treatment of some 1-alkoxycarbonyl-1,2-diaza-1,3-butadienes with n-butyllithium. Molecular weights (M_w) in the range 8.44-242 × 10² g/mol were obtained.     

New heat stable and processable poly(amide-ether-imide)s derived from 5-(4-trimellitimidophenoxy)-1-trimellitimido naphthalene and various diamines

New aromatic diimide-dicarboxylic acid having flexible ether linkage, 5-(4-trimellitimidophenoxy)-1-trimellitimido naphthalene, was synthesized by the reaction of trimellitic anhydride with 5-(4-aminophenoxy)-1-naphthylamine. Then, a series of novel aromatic poly(amide-ether-imide)s were prepared by the phosphorylation polycondensation of the synthesized monomer with various aromatic diamines. A model compound was synthesized by the reaction of the monomer with aniline. The resulting polymers with inherent viscosities of 0.43-0.70 dl/g were obtained in high yield. All new compounds including the naphthalene-based monomer, model compound, and the resulted polymers were characterized by FT-IR and NMR spectroscopic methods. The ultraviolet λ_max values of the poly(amide-ether-imide)s were also determined. The resulted polymers exhibited a good solubility in a variety of high polar solvents such as N,N-dimethylacetamide (DMAc), N,N-dimethylformamide (DMF), dimethyl sulfoxide (DMSO), N-methyl-2-pyrrolidone (NMP), and pyridine. For some of the polymers obtained the crystallinity behavior was estimated by means of wide-angle X-ray diffraction (WXRD) method, and the resulted polymers exhibited nearly an amorphous nature. Thermal stability of the obtained polymers was determined by thermogravimetric analysis (TGA/DTG), and the 10% weight loss temperatures of the one-step degraded poly(amide-ether-imide)s were found to be in the range between 528 and 551 °C in nitrogen. From differential scanning calorimetric (DSC) analyses, the polymers showed T_gs between 276 and 307 °C. Cyclic voltammetry (CV) measurements of a typical polymer showed that they are also electrochemically stable.     

Novel aromatic poly(amide-hydrazide)s based on the bipyridine. Part I: Synthesis, characterization and thermal stability

A series of new poly(amide-hydrazide)s were obtained by the direct polycondensation of 5-amino 5′-carbohydrazido-2,2′-bipyridine with commercially available diacids by means of triphenyl phosphite and pyridine in the N-methyl-2-pyrrolidone (NMP) solutions containing dissolved LiCl. The resulting hydrazide containing polymers exhibited inherent viscosities in the 0.42-0.64 dL/g range. All copolymers were soluble in polar solvents such as NMP and dimethyl sulfoxide (DMSO). Most of the amorphous hydrazide copolymers formed flexible and tough films by solvent casting. The poly(amide-hydrazide)s had glass-transition temperatures (T_g) between 178 and 206 °C. All hydrazide copolymers could be thermally converted into the corresponding poly(amide-oxadiazole) approximately in the region of 300-400 °C, as evidenced by the DSC thermograms. The oxadiazole polymers and copolymers showed a dramatically decreased solubility and higher T_g when compared to their respective hydrazide prepolymers. They exhibited T_gs of 197-248 °C and were stable up to 450 °C in air or nitrogen.     

Phenylethynyl terminated oligoimides derived from 3,3′,4,4′-diphenylsulfonetetracarboxylic dianhydride and their adhesive properties

A series of phenylethynyl terminated oligoimides based on 3,3′,4,4′-diphenylsulfonetetracarboxylic dianhydride (DSDA), m-phenylene diamine (m-PDA) or/and 1,4-bis(4-amino-2-trifluoromethylphenoxy)benzene (6FAPB) with calculated molecular weight of 5000 g mol⁻¹ were synthesized. The effect of molecular structure on solubility and melt viscosity of oligoimides as well as the thermal properties of cured polyimide resins was investigated. Experimental results indicated that the oligoimides have good solubility in strong polar solvents to afford homogeneous solutions with the solid content as high as 50 wt%. The oligoimides exhibited better solubility and lower minimum melt viscosity at relatively lower temperature with the incorporation of flexible 6FAPB. These oligoimides could be thermally cured at 320-380 °C to give thermosetted resins. The cured resins have good thermal stability with the glass transition temperatures of 278-329 °C and the onset decomposition temperatures higher than 500 °C. Adhesive properties of polyimides adhered to stainless steel at various conditions were evaluated by lap shear strength test. It was found that the LSS at room temperature increased with the molar ratio of 6FAPB increasing. The polyimides with combination of rigid and flexible structures exhibited good adhesive properties. With the increasing of curing temperature, the lap shear strength of polyimides at elevated temperature maintained at a high level due to the formation of strong bond.     

Novel organosoluble and colorless poly(ether imide)s based on 1,1-bis[4-(3,4-dicarboxyphenoxy)phenyl]cyclohexane dianhydride and trifluoromethyl-substituted aromatic bis(ether amine)s

A series of novel fluorinated poly(ether imide)s (IV) having inherent viscosities of 0.70-1.08 dL/g were prepared from 1,1-bis[4-(3,4-dicarboxyphenoxy)phenyl]cyclohexane dianhydride (I) and various trifluoromethyl (CF₃)-substituted aromatic bis(ether amine)s II_a-g by a standard two-step process with thermal and chemical imidization of poly(amic acid) precursors. These poly(ether imide)s showed excellent solubility in many organic solvents and could be solution-cast into transparent, flexible, and tough films. These films were essentially colorless, with an ultraviolet-visible absorption edge of 375-380 nm and a very low b^∗ value (a yellowness index) of 5.5-7.3. They also showed good thermal stability with glass-transition temperatures of 207-269 °C, 10% weight loss temperatures in excess of 474 °C, and char yields at 800 °C in nitrogen more than 62%. In comparison with analogous V series poly(ether imide)s without the -CF₃ substituents, the IV series polymers showed better solubility, lower color intensity, and lower dielectric constants.     

Synthesis and characterization of a novel arylacetylene oligomer containing POSS units in main chains

A novel arylacetylene oligomer containing octamethyl POSS units in main chains was prepared from difluoride octamethyl POSS (diexo-(CH₃)₈Si₈O₁₁F₂) and diethynylbenzene (DEB) by Grignard reaction and characterized by FT-IR, NMR, WAXD, GPC, DSC, and TGA. The curing reaction kinetic of the oligomer was studied by Kissinger and Ozawa methods and the kinetic parameters were obtained. The cured polymer had good thermal and thermal-oxidative properties. TGA analyses demonstrated that the thermal decomposition temperature (T_d5) of the cured polymer in nitrogen and air were 503 and 479 °C, respectively.     

Synthesis of soluble polyimides for vertical alignment of liquid crystal via one-step method

A series of polyimides (PIs) were copolymerized from 4-dodecyloxy-biphenyl-3′,5′-diaminobenzoate (DBPDA), 3,3′-dimethyl-4,4′-methylene-dianiline (DMMDA) and 4,4′-oxydi(phthalic anhydride) (ODPA) via one-step method. The PIs possessed excellent solubility in polar aprotic solvents and easily formed thin flexible films by solution casting. The glass-transition temperatures (T_gs) of the PIs were in the range of 219-242 °C and thermal decomposition temperatures in nitrogen occurred above 350 °C. The resultant PI films exhibited high transparency at wavelengths greater than 400 nm and induced excellent uniform vertical alignment of liquid crystal (LC). Even after the rubbing process, the pretilt angles of LC were still above 89°. The PI seems to be a prospective material for alignment layers in flexible displays.