Formation of ordered macroporous films from fluorinated polyimide by water droplets templating

Preparation of honeycomb-patterned films from one of soluble fluorinated polyimides in a humid atmosphere was reported in this paper. This polyimide was synthesized from 2,2′-bis(3,4-dicarboxyphenyl)hexafluoropropane dianhydride (6FDA) and 2,2-bis[4-(4-aminophenoxy)phenyl]hexafluoropropane (BDAF) by two-steps method, which has excellent solubility both in strong bipolar solvents or in common low boiling-point solvents. The glass transition temperature of 6FDA-BDAF polyimide was determined by DSC and as 238 °C. Thermogravimetric analysis indicated that soluble fluoro-polyimide has good thermal stability with maximum thermal decomposition temperature of 545 °C in nitrogen atmosphere. The honeycomb-patterned films were obtained by casting a drop of polymer solution on a solid substrate in a humid atmosphere. Some influence factors, such as the solution concentration, the type of the solvent and the humidity, were also tested.     

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.     

New fluorinated aromatic poly(ether-amide)s derived from 2,2′-bis(3,4,5-trifluorophenyl)-4,4′-diaminodiphenyl ether and various dicarboxylic acids

A new class of highly fluorinated aromatic poly(ether-amide)s was prepared through triphenyl phosphite-activated polycondensation of 2,2′-bis(3,4,5-trifluorophenyl)-4,4′-diaminodiphenyl ether (FPAPE) and four dicarboxylic acid comonomers. All the resulting polymers were thoroughly characterized by FT-IR, UV, and NMR spectroscopic methods. The effects of the fluorine atoms directly linked to the lateral phenyl rings as well as fluoro-containing phenyl groups attached to the macromolecular chains on some properties of the polymers were investigated by comparing with poly(ether-amide)s prepared from 4,4′-oxydianiline (4,4′-ODA) and 2,2′-diphenyl-4,4′-diaminodiphenyl ether (PAPE). The FPAPE-derived polymers exhibited excellent solubility in a variety of organic solvents. Results obtained from X-ray studies showed that the presence of the bulky fluoro-containing phenyl groups attached to the chains disrupts their structural order in a great amount, and leads to a decrease in crystallinity extent of the macromolecules. Furthermore, the highly fluorinated polymeric chains showed a significant enhancement in organo-solubility, heat-stability and T_g values when compared to their non-fluorinated counterparts.     

Synthesis and characterizations of 3,3′-bis(diphenylphosphinoamine)-2,2′-bipyridine and 3,3′-bis(diphenylphosphinite)-2,2′-bipyridine and their chalcogenides

New bis(phosphinoamine) and bis(phosphinite) derivatives of 2,2′-bipyridine were prepared through a single step reaction of 3,3′-diamino-2,2′-bipyridine or 3,3′-dihydroxy-2,2′-bipyridine with diphenylchlorophosphine, respectively. Their P = E chalcogenides (E = O, S, Se) were also prepared. All the new compounds were characterized by elemental analysis, IR and NMR spectroscopies. The molecular structure of 3,3′-bis(diphenylthiophosphinite)-2,2′-bipyridine was elucidated by single-crystal X-ray crystallography.     

Synthesis,structure and reactivity of novel palladiumdichloride-2,2′-bipyridine with 4,4′-bis(fluorous-ponytail)

With the readily available fluorous alkanols R_fCH₂OH, a series of novel fluorous-ponytailed bpy ligands, 4,4′-bis(R_fCH₂OCH₂)-2,2′-bpy (1a–e), were prepared and treated with [PdCl₂(CH₃CN)₂] to result in the corresponding novel Pd complexes [PdCl₂(4,4′-bis(R_fCH₂OCH₂)-2,2′-bpy)] (2a–e) where R_f = n-C₃F₇ (a), HCF₂(CF₂)₃ (b), HCF₂(CF₂)₇ (c), n-C₈F₁₇ (d), n-C₁₀F₂₁ (e). The new ligands and Pd complexes were spectroscopically characterized by multi-nuclei NMR (¹H, ¹⁹F and ¹³C), FTIR and high resolution mass (FAB). The structure for the Pd complex 2b, the first with fluorinated ponytails on bpy and not on phosphine, was also established by a single crystal X-ray diffraction study. The TGA data of both ligands and Pd complexes indicated that the Pd-complexes were resistant to higher temperatures than the corresponding ligands. The Pd catalysts derived from 2a–c showed an almost quantitative conversion and could be reused for eight runs with Heck reactions, in that the products and unspent reactants were directly removed by distillation. With the highest fluorine content in the series, Pd complex 2e was successfully applied in the Heck reaction using the fluorous biphasic catalysis strategy.     

Shear‐enhanced crystallization of a thermoplastic polyimide derived from 3,3′,4,4′‐oxydiphthalic dianhydride and 4,4′‐oxydianiline

The aim of this work is to investigate the effect of consecutive shear on the crystallization of an amorphous aromatic polyimide (PI) derived from 3,3 ′ ,4,4 ′ ‐oxydiphthalic dianhydride (3,3 ′ ,4,4 ′ ‐ODPA) and 4,4 ′ ‐oxydianiline (ODA). At 260 °C, the increase of shear rate or shear time leads to the increase of crystallinity. Indeed, increasing shear rate can also accelerate the crystallization behavior. Moreover, it was found that a new melting peak appeared at higher temperature for long time or high rate sheared sample. The enhancement of crystallization behavior appears directly linked to the increase of crystal thickness. Particularly, the effect of shear temperature was investigated, and the results revealed that the crystallization of the PI was more sensitive to shear at 260 °C, which was 10° above the glass transition temperature (250 °C) of the PI. Possible mechanism was proposed to illustrate the effect of consecutive shear on the crystallization of the PI polymer. © 2007 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 45: 2344–2349, 2007     

Synthesis and characterization of novel fluorinated polyimides derived from 4-phenyl-2,6-bis[4-(4′-amino-2′-trifluoromethyl-phenoxy)phenyl]pyridine and dianhydrides

A series of organo-soluble polyimides were prepared from a novel fluorinated diamine monomer, 4-phenyl-2,6-bis[4-(4′-amino-2′-trifluoromethylphenoxy)phenyl]pyridine and various commercial aromatic dianhydrides. These polyimides had good solubility in common organic solvents. The obtained strong and flexible PI films exhibited excellent thermal stability with the decomposition temperature (at 5% weight loss) of above 561 °C and the glass transition temperature in the range of 258-312 °C. Moreover, the polymer films showed good electrical insulating property, low dielectric constant and low water uptake due to the introduction of fluorinated substitutes in the polymer backbone. The remarkable combined features ensure these polymers to be ideal candidate materials for advanced microelectronic industry and other related applications.     

High Tg polyimide nanofoams derived from pyromellitic dianhydride and 1,1-bis(4-aminophenyl)-1-phenyl-2,2,2-trifluoroethane

New routes for the synthesis of high T_g thermally stable polymer foams with pore sizes in the nanometer regime have been developed. Foams were prepared by casting well-defined microphase-separated block copolymers comprised of a thermally stable block and a thermally labile material. At properly designed volume fractions the morphology provides a matrix of the thermally stable material with the thermally labile material as the dispersed phase. Upon thermal treatment, the thermally unstable block undergoes thermolysis generating pores, the size and shape of which are dictated by the initial copolymer morphology. Triblock copolymers comprised of a high T_g, amorphous polyimide matrix with poly(propylene oxide) as the thermally decomposable coblock, were prepared. The copolymer synthesis was conducted through the poly(amic acid) precursor and subsequent cyclodehydration to the polyimide by either thermal or chemical means. Dynamic mechanical analysis confirmed microphase separated morphologies for all copolymers, irrespective of the propylene oxide block lengths investigated. Upon decomposition of the thermally labile coblock, a 9–18% reduction in density was observed, consistent with the generation of a foam which was stable to 400°C. © 1996 John Wiley & Sons, Inc.     

A novel class of organosoluble and light-colored fluorinated polyamides derived from 2,2-bis(4-amino-2-trifluoromethylphenoxy)biphenyl or 2,2-bis(4-amino-2-trifluoromethylphenoxy)-1,1-binaphthyl

Two series of novel fluorinated aromatic polyamides were prepared from 2,2^′-bis(4-amino-2-trifluoromethylphenoxy)biphenyl (2) and 2,2^′-bis(4-amino-2-trifluoromethylphenoxy)-1,1^′-binaphthyl (4) with various aromatic dicarboxylic acids using the phosphorylation polycondensation technique. The polyamides had inherent viscosities ranging from 0.43 to 0.62 dl/g and 0.36 to 0.74 dl/g, respectively. All the fluorinated polyamides were soluble in many polar organic solvents such as N,N-dimethylacetamide (DMAc), N-methyl-2-pyrrolidinone, and afforded transparent, light-colored, and flexible films upon casting from DMAc solvent. These polyamides showed glass-transition temperatures in the ranges of 190-240 °C (for the 6 series from diamine 2) and 247-255 °C (for the 7 series from diamine 4) by differential scanning calorimetry, softening temperatures in the ranges of 196-230 °C (6 series) and 241-291 °C (7 series) by thermomechanical analysis, and decomposition temperatures for 10% weight loss above 420 °C in both nitrogen and air atmospheres.     

Microstructure and properties of 3,3′,4,4′‐biphenyltetracarboxylic dianhydride (BPDA)‐p‐phenylene diamine (PDA) polyimide/poly(vinylsilsesquioxane) hybrid nanocomposite films

Hybrid nanocomposite films of poly(vinylsilsesquioxane) (PVSSQ) and polyimide (PI) (PI/PVSSQ) were prepared via sol‐gel process from triethoxyvinylsilane (VSSQ) and thermal imidization from 3,3′,4,4′‐biphenyltetracarboxylic dianhydride (BPDA)‐p‐phenylene diamine (PDA) polyamic acid (BPDA‐PDA PAA). We investigated the microstructure; interfacial interaction; and optical, thermal, dielectric, and mechanical properties of the hybrid films. The phase morphologies and degree of surface roughness were evaluated by scanning electron microscope (SEM) and atomic force microscope (AFM), respectively. It was found that the surface topography was influenced by the composition of PVSSQ. Hydrogen bonding interactions between polyimide (PI) matrix and PVSSQ domains were proved with FT‐IR spectroscopy. The transparency of the hybrid films was found to be dependent on the PVSSQ content. Incorporating of the PVSSQ in the hybrid composites increased the glass transition temperature of PI. Dielectric constants of the hybrid films were in the range of 2.37–3.59. Properties of the PI films were also significantly enhanced by adding 5–30 wt % of PVSSQ. For comparison, we also prepared the hybrid composites of PI and mixtures of VSSQ and tetraethoxysilane (TEOS) and the PI/silica hybrid composite containing 30 wt % of silica obtained from TEOS. © 2004 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 42: 5189–5199, 2004     

Synthesis and characterization of novel fluorinated polyimides derived from 1,1′-bis(4-aminophenyl)-1-(3-trifluoromethylphenyl)-2,2,2-trifluoroethane and aromatic dianhydrides

A novel fluorinated aromatic diamine 1,1′-bis(4-aminophenyl)-1-(3-trifluoromethylphenyl)-2,2,2-trifluoroethane (6FDAM) was synthesized in a simple procedure, which was then employed to prepare a series of fluorinated polyimides with commercial aromatic dianhydrides, such as pyromellitic dianhydride (PMDA), 2,2-bis(3,4-dicarboxyphenyl)hexafluoropropane (6FDA), 3,3′,4,4′-benzophenonetetracarboxylic dianhydride (BTDA) and 4,4′-oxydiphthalic anhydride (ODPA). The polyimides exhibited good solubility in strong dipolar solvents such as NMP, DMAc, DMF and m-cresol as well as some of low boiling point organic solvents of THF and CHCl₃, etc. Experimental results indicated the polyimides possessed low moisture adsorptions of 0.42-0.95%, low dielectric constant of 2.71-2.95 at 1 MHz, high dielectric strength of 92.0-122.6 kV/mm and good optical transparency with cutoff wavelengths of UV-vis at 330-375 nm. The polyimides also exhibited good mechanical properties as well as excellent thermal and thermo-oxidative stability. The fluorinated polyimides possessed better solubility, lower dielectric constant and water adsorption as well as higher optical transparency than the representative non-fluorinated polyimide derived from PMDA and 4,4′-oxydianiline (ODA).     

Synthesis and properties of novel fluorinated epoxy resins based on 1,1-bis(4-glycidylesterphenyl)-1-(3′-trifluoromethylphenyl)-2,2,2-trifluoroethane

A novel fluorinated epoxy resin, 1,1-bis(4-glycidylesterphenyl)-1-(3′-trifluoromethylphenyl)-2,2,2-trifluoroethane (BGTF), was synthesized through a four-step procedure, which was then cured with hexahydro-4-methylphthalic anhydride (HMPA) and 4,4′-diaminodiphenyl-methane (DDM). As comparison, a commercial available epoxy resin, bisphenol A diglycidyl ether (BADGE), cured with the same curing agents was also investigated. We found that the BGTF gave the exothermic starting temperature lower than BADGE no mater what kind of curing agents applied, implying the reactivity of the former is higher than the latter. The fully cured fluorinated BGTF epoxy resins have good thermal stability with glass transition temperature of 170-175 °C and thermal decomposition temperature at 5% weight loss of 370-382 °C in nitrogen. The fluorinated BGTF epoxy resins also showed the mechanical properties as good as the commercial BADGE epoxy resins. The cured BGTF epoxy resins exhibited improved dielectric properties as compared with the BADGE epoxy resins with the dielectric constants and the dissipation factors lower than 3.3 and dissipation 2.8 × 10⁻³, respectively, which is related to the low polarizability of the C-F bond and the large free volume of CF₃ groups in the polymer. The BGTF epoxy resins also gave low water absorption because of the existence of hydrophobic fluorine atom.     

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.     

Novel fluorinated polyimides derived from 9,9-bis(4-amino-3,5-difluorophenyl)fluorene and aromatic dianhydrides

Novel fluorinated polyimides (PIs) were prepared from 9,9-bis(4-amino-3,5-difluorophenyl)fluorene with three aromatic dianhydrides via a one-step high-temperature polycondensation procedure. These obtained PIs showed excellent solubility and could be readily soluble in a variety of organic solvents such as NMP, DMAc, DMF, CHCl₃, CH₂Cl₂ and THF. All the PIs could afford flexible and strong films with low dielectric constants (2.62-2.79 at 1 MHz) and low moisture absorptions (0.18-0.41%). Thin films of these PIs exhibited high optical transparency and light color, with the cutoff wavelength at 341-355 nm and transmittance higher than 80% at 450 nm. Meanwhile, these PIs possessed eminent thermal stability, with decomposition temperatures (T_d) above 570 °C in both air and nitrogen atmospheres and glass transition temperatures (T_g) beyond 376 °C. Moreover, these fluorinated PI films showed low surface free energy and hydro-oleophobic character. The contact angles on the films for water and glycerol were in the range of 102.3-107.9° and 94.0-100.3°, respectively. In comparison with the analogous PI non-containing fluorine group, these fluorinated PIs showed better solubility, higher optical transparency, lower dielectric constants and lower surface free energy.     

Spectroscopic, thermal and structural studies of cocrystal of 2,2′-diamino-4,4′-bis(1,3-thiazole) with 4,4′-bipyridine, 1,2-bis(4-pyridyl)ethylene and 1,3-bis(4-pyridyl)propane

Three new cocrystals based upon 2,2′-diamino-4,4′-bis(1,3-thiazole) (DABTZ) with 4,4′-bipyridine (4,4′-bipy), 1,2-bis(4-pyridyl)ethylene (bpe) and 1,3-bis(4-pyridyl)propane (bpp): [(DABTZ) (4,4′-bipy)], [(DABTZ) (bpe)] and [(DABTZ) (bpp)] have been synthesized and characterized by elemental analysis, IR-, ¹H NMR-, ¹³C NMR spectroscopy and studied by thermal and X-ray crystallography. Self-assembly of these compounds in the solid state is likely caused by both hydrogen bonding, and π-π stacking.     

Synthesis and properties of novel fluorinated polynaphthalimides derived from 1,4,5,8-naphthalenetetracarboxylic dianhydride and trifluoromethyl-substituted aromatic bis(ether amine)s

A series of novel fluorinated polynaphthalimides (PNIs) (2a-g) were synthesized from 1,4,5,8-naphthalenetetracarboxylic dianhydride (NTDA) and trifluoromethyl (CF₃)-substituted aromatic bis(ether amine)s (1a-g) by high-temperature solution polycondensation in m-cresol using isoquinoline as catalyst. Almost all the PNIs were readily soluble in polar solvents such as N-methyl-2-pyrrolidone (NMP) and N,N-dimethylacetamide (DMAc) and could be solution-cast to transparent and tough films with high tensile strengths. The PNIs exhibited high thermal stability, with glass-transition temperatures of 262-383 °C, 10% weight loss temperatures above 528 °C in nitrogen or air, and char yields at 800 °C in nitrogen higher than 50%. In comparison with analogous PNIs without the -CF₃ substituents, these fluorinated PNIs revealed an enhanced solubility and better film-forming capability.     

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.     

Study of electrochemical stability of conducting polymers by bidimensional spectroelectrochemistry: p- and n-doping of poly(4,4′-bis(butylthio)-2,2′-bithiophene) films

UV-vis bidimensional spectroelectrochemistry has been applied to the study of the electrochemical stability of conducting polymer films during p- and n-doping processes. Specifically, poly(4,4′-bis(butylthio)-2,2′-bithiophene) has been chosen as example to prove the usefulness and suitability of this multi-response technique to characterize polymer stability during p- and n-doping. It was found that oxidative doping and corresponding de-doping alone did not result in noticeable polymer film degradation. However, in experiments involving both p- and n-doping of this conducting polymer, soluble species arising from the polymer film were detected in solution for the first time, indicating a lower electrochemical stability of the film under these experimental conditions. Moreover, bidimensional spectroelectrochemistry has enabled us not only to detect the soluble degradation products, but also the potential range in which the degradation takes place.     

Elastic modulus of the crystalline regions of polyimide derived from poly(amic acid)–biphtalic dianhydride and p-phenylene diamine

The elastic modulus E_l of the crystalline regions in the direction parallel to the chain axis was measured by X-ray diffraction for polyimide derived from polyamic acid (biphthalic dianhydride and p-phenylene diamine). These specimens were cured by two different routes: curing at 200 °C, and at 400 °C for 1 h, respectively (2STEPS), and curing from 80 °C to 400 °C stepwise (nine steps) for 1 h at each step (STEPWISE). The E_l values of 54–169 GPa were obtained for the STEPWISE specimen and 80–178 GPa for the 2STEPS specimen, depending on the meridional reflection employed for measurement of the E_l value. A linear relationship between the E_l value and the fiber identity period was obtained from each meridional diffraction, such that the E_l value increased with an increase in the fiber identity period. The E_l value of the fully extended structure was estimated to be 210 GPa. These are considered to be due to the coexistence of polymorphs with different skeletal structures. The crystalline regions of the 2STEPS specimen seems to consist of a more extended skeleton than those of the STEPWISE specimen. © 1999 John Wiley & Sons, Inc. J Polym Sci B: Polym Phys 37: 3294–3301, 1999     

Preparation and properties of new soluble aromatic polyimides from 2,2′-bis(3,4-dicarboxyphenoxy)biphenyl dianhydride and aromatic diamines

A new aromatic tetracarboxylic dianhydride having a crank and twisted noncoplannar structure, 2,2′-bis(3,4-dicarboxyphenoxy)biphenyl dianhydride, was synthesized by the reaction of 4-nitrophthalonitrile with biphenyl-2,2′-diol, followed by hydrolysis and cyclodehydration. The biphenyl-2,2′-diyl-containing aromatic polyimides having inherent viscosities up to 0.66 dL/g were obtained by the conventional two-step procedure starting from the dianhydride monomer and various aromatic diamines. Most of the polyimides were readily soluble in amide-type solvents such as N,N-dimethylacetamide and N-methyl-2-pyrrolidone. The aromatic polyimides had glass transition temperatures in the range of 205–242°C, and began to lose weight around 415°C, with 10% weight loss being recorded at about 500°C in air. © 1998 John Wiley & Sons, Inc. J. Polym. Sci. A Polym. Chem. 36: 2021–2027, 1998