PMDA ODA Research Articles

Effect of Water Absorption on Electric Properties of Temperature-Resistant Polymers.

The effects of water absorption on the electric resistivity and dielectric constant of polyimide (PI) and poly(ethylene terephthalate) (PET) were investigated, and the mechanism of deterioration in electrical insulation properties was discussed. The polyimides are poly(oxydianiline pyromellitimide) (PMDA-ODA) and poly(para-phenylene diamine biphenyltetracarboxydiimide) (BPDA-PDA). These polymer films were immersed in pure water for various immersion times at room temperature, and the water absorption ratio was evaluated. The electric resistance for these films was measured at room temperature using a high-resistance meter, and the dielectric constant at room temperature was measured using an LCR meter in a frequency range of 200 kHz to 2 MHz. The absorption ratios at equilibrium absorption for PMDA-ODA, BPDA-PDA, and PET were 2.7, 2.5, and 0.5%, respectively. The critical volume fraction of the percolation threshold of electric conductivity due to water absorption was 0.034 for both PMDA-ODA and BPDA-PDA. On the other hand, PET did not show a significant decrease in the resistivity. For both PIs and PET, the dielectric constant observed could be explained by a series model of the respective capacitances of pure water and polymer. Actually, the resistivity of samples cut from the edges of the film after water absorption was almost the same value as that in the dry state. These results suggest that the absorbed water molecules are not uniformly dispersed in the film but are localized at the edges of the film even after the absorption equilibrium has been reached.

Bio-molecule adenine building block effectively enhances electromagnetic interference shielding performance of polyimide-derived carbon foam

Heteroatom doping porous carbon material possess a variety of attractive functionality such as electrical properties, catalytic properties and adsorptive capability. As an important building block of DNA, adenine has following characteristics: 1. Heterocyclic structure 2. Potential interaction modes 3. Flexible structure tailor ability 4. Available from biomass. In this study, adenine-containing polyimide (API) foam has been prepared by freeze-drying, and is used as polymer precursor of nitrogen doping carbon foam (ACF). The carbon foam (PCF) prepared by adenine-free PI foam (PMDA ODA PI) is used as a comparison. The results show that the nitrogen content of ACF after carbonization at 1000 °C (ACF-1000) is as high as 4.35%, which is about twice higher than PCF-1000 (1.90%). The conductivity of ACF-1000 is 7.11 × 10−1 s cm−1, which is 38.06% larger than PCF-1000 (5.15 × 10−1 s cm−1). The electromagnetic interference shielding effectiveness (EMI SE) of ACF-1000 is 41.1 dB, which is 26.85% higher than PCF-1000 (32.4 dB). The SSE/d (defined as the SE divided by the thickness and density of the shielding material) of ACF-1000 is 13569 dB cm2/g, which is 66.41% higher than PCF-1000 (8154 dB cm2/g). This work shows that adenine is a promising nitrogen-doping building block for polymer-derived carbon materials. The introduction of adenine structure into the polymer is helpful for improving the EMI shielding performance of carbonized products.

An efficient pure polyimide ammonia sensor

PMDA–ODA polyimide, broadly known as Kapton, solution-cast coatings cured at low temperatures, act as ammonia sensors. Detection and quantification of ammonia (NH3) vapours from ammonia solutions of different molarities. A device is presented, demonstrating the real-time detection of ammonia vapors by the PMDA–ODA coatings.

Non-thermal polyimidization reaction using base–ionic liquid medium as a dual catalyst–solvent

A one-step synthesis of PMDA–ODA polyimide at ambient temperature was reported for the first time, in which a polyimidization reaction was rapidly accomplished in 99% yield in an imidazolium-based ionic liquid containing a non-nucleophilic base.

Real-Time Characterization of Physical Changes in Polyimide Film Formation: From Casting to Imidization

Drying and imidization of PMDA–ODA solutions in NMP were investigated by a novel custom designed measurement system that tracks real time weight, thickness, surface temperature, and in-plane and out-of-plane birefringence. At low temperature drying stage, the weight and thickness reductions occurred rapidly as a result of solvent evaporation. All the parameters started leveling off while the out of plane birefringence steadily increased and reached a plateau at longer drying times. When the temperature was increased for imidization reaction, additional weight loss accompanied by temporary reduction of birefringence was observed due to evaporation of bound solvent as solvent molecules decomplexed from the polymer chains and plasticized the film. During the latter stage, out-of-plane birefringence rose rapidly due to increased intrinsic birefringence of the polymer chains due to imidization reaction and orientation of polymer chains with their chain axes preferentially oriented in the film plane. Throughout...

Local electrical modification of a conductivity-switching polyimide film formed bymolecular layer deposition

The electrical modification of a conductivity-switching polyimide film viamolecular layer deposition (MLD) is studied for ultrahigh density datastorage based on a scanning probe microscope (SPM). A PMDA–ODA (PMDA = 1, 2, 3, 5-benzenetetracarboxylicanhydride, ODA = 4, 4-oxydianiline) film as a recording medium is uniformly formed from a self-assembledmonolayer on a Au surface by MLD. It is demonstrated that the conductivity of the filmcan be changed by applying a voltage between a SPM probe and the film. Thisconductivity-switching phenomenon is discussed by the molecular orbital approach andconsidered to be caused by the charge transfer effect or carrier trapping effect ofPMDA–ODA.

FTIR study of the structures of vapor deposited PMDA–ODA film in presence of copper phthalocyanine

Orientation structure of vacuum deposited thin layer polyimide matrix in presence of copper phthalocyanine as a “guest”, by means of polarization and derivative FTIR spectroscopy has been studied. The polymer layers (500 nm thick) prepared by vacuum co-deposition of polyimide precursors – oxydianiline and pyromellitic dianhydride and copper phthalocyanine (9%), followed by mixed treatment (microwave and thermal) have been investigated. The SEM investigation of layers that are microwave and thermally treated at temperatures 200 and 300 °C have no considerable difference in the surface structure. FTIR analysis of spectra in the range of molecular vibration 1300–700 cm −1 demonstrates that polyimide films thermally treated at 200 °C showed lower order structure than polyimide films treated at 300 °C. After derivatization of the polyimide spectra two bands at 1125 cm −1 and 1116 cm −1 have appeared which are related to two types C–N deformation vibration. The structure of the layers treated at higher temperature (300 °C) is higher order and is fixed in one plane (after derivatization single narrow band at 1114 cm −1 has appeared; the band at 903 cm −1 is missing). It was found that after microwave treatment the time of thermal treatment has no considerable influence. Preliminary microwave treatment allows reducing of the duration of thermal treatment.

The study on imidization degree of polyamic acid in solution and ordering degree of its polyimide film

Polyamic acid (PAA) based on pyromellitic dianhydride and 4,4′-oxydianiline (PMDA–ODA) can be chemically converted to copolyamic acid-imide (PA-I) which is a partially converted PAA at ambient temperature by treatment with a mixture of acetic anhydride and pyridine. A systematic investigation by rotation viscometer and FT-IR revealed that phase separation in PA-I solution occurred when imidization degree was about 26%. Imidization degree of PA-I solution could be controlled by using adequate acetic anhydride amount, initial PAA concentration and imidization time. PA-I solutions with different imidization degree were converted to corresponding polyimide films by thermal imidization. WAXD showed that as imidization degree in PA-I solution increased, the degree of morphologic ordering of final PI film was improved, while tensile strength and modulus increased and ultimate elongation reduced slightly.

Atomic layer deposition of polyimide thin films

The atomic layer deposition (ALD) of different polyimide thin films has been studied. We have demonstrated self-limiting ALD deposition of PMDA–DAH, PMDA–EDA, PMDA–ODA and PMDA–PDA thin films at 160 °C. The maximum deposition rate of 5.8 Å cycle−1 was obtained for the PMDA–DAH process. Although the deposition rate was high at 160 °C, a sudden decrease was observed when the temperature was increased. Regardless of the process studied, no film growth was obtained at 200 °C or above. Deposited polyimide films were analysed by FTIR, AFM and TOF-ERDA. According to the FTIR measurements, imide bonds were formed already in as-deposited films indicating polyimide formation without any additional thermal treatment.

The effect of silica size on the friction and wear behaviors of polyimide/silica hybrids by sol–gel processing

In order to investigate the effect of silica size on the friction and wear behaviors of PI hybrids, polyimide/silica (PI/SiO 2) hybrids with different size of silica were successfully synthesized through an in situ sol–gel reaction from pyromellitic dianhydride-4,4′-oxydianiline (PMDA—ODA) and tetraethoxysilane (TEOS). The size of silica in the hybrids was 100–800 nm. The friction and wear test for pure PI and its hybrids was carried out on a ball-on-disc wear tester under dry sliding conditions. Tensile tests on the PI/SiO 2 hybrids showed that the strength and toughness of PI/SiO 2 hybrids were improved simultaneously when the size of silica was less than 300 nm. The friction coefficient and wear rate of the PI hybrids firstly decreased and then increased with increasing the size of silica. The friction coefficient of the hybrid with 100 nm SiO 2 was the lowest and ca.20% lower in contrast with that of pure PI. However, the lowest wear rate was recorded for the hybrid with 300 nm SiO 2, ca.20% lower than that of neat PI. These behaviors were attributed to the size effect of silica in PI matrix. Scanning electron microscopy (SEM) revealed that an appropriate size of silica in PI matrix could effectively reduce adhesive wear of PI and restrain the formation of bigger debris.

High-permeability fluorinated polyimide microcapsules by vapor deposition polymerization

Spherical microcapsules (∼1 mm in diameter and ∼1 μm in wall thickness) to be used as inertial confinement fusion targets were prepared from 6FDA–ODA polyimide by vapor deposition polymerization. Compared with the previously developed PMDA–ODA polyimide microcapsules, the 6FDA–ODA microcapsules were ∼50-fold more permeable to gases including He, D 2, O 2, N 2, Ar, and Ne, considerably more transparent in the UV–visible spectrum, and of marginally lower Young's modulus, tensile strength, and elongation at break. The microcapsules possessed amorphous morphology with an amorphous d-spacing of 5.8 Å as determined by wide-angle X-ray diffraction. The cryogenic permeability of helium was measured between 133 and 295 K, and the activation energy for permeation was determined to be 12.3 kJ/mol.

Residual stress and microstructures of aromatic polyimide with different imidization processes

Processing of polyimide (PI) from precursor polyamic acid (PAA) solution involves simultaneous imidization, evaporation of solvent and crystallization, so imidization process influences the final properties of PI. The residual stress at the interface between the most popular PI (PMDA–ODA) and the aluminum substrate was measured by X-ray diffraction method and the relationship between the microstructure and the mechanical properties was investigated for PI with different imidization processes. The residual stress and the mechanical properties of PI depend on the imidization process. The skeletal structure is suggested to be changed by the amount of residual solvent during imidization process, which brings the difference in the residual stress.

Chemical durability of polyimide blend films

The chemical durability of blends based on pyromellitic dianhydride–oxydianiline (PMDA–ODA) and benzophenone tetracarboxylic dianhydride–oxydianiline (BTDA–ODA) polyimides with nylon 6 is described. The stabilities of the blend films in conc. H 2SO 4 and in 40% aqueous NaOH are equivalent to that of the control film and slightly better than commercially available Kapton™ film, but the stability of the PMDA based blend films in dilute NaOH (1.5%) is better compared to the control film. The weight gains of the films in solvents like dichloromethane, methyl ethyl ketone and water are dependent on the nature of the solvent and its interaction with the blend, but the BTDA based blend films show overall better chemical resistance.

Imidization processes of aromatic polyimide by temperature modulated DSC

Processing of polyimide (PI) from precursor polyamic acid (PAA) involves simultaneous imidization, evaporation of residual solvent and crystallization. These overlapped processes were analyzed by temperature modulated differential scanning calorimetry (T-MDSC). Glass transition temperature ( T g) of precursor PAA was manifested by T-MDSC, and it was 107°C for pyromellitic dianhydride–oxidianiline (PMDA–ODA) PAA cast from N-methyl-2-pyrrolidone (NMP) solution. The thermal cyclization reaction from PAA to PI is considered to progress randomly. The solvent system for casting PAA, influenced the conversion to PI, which is found to affect the T g of PAA.

A study of film thickness dependence of the graphitizability of PMDA–ODA polyimide-derived carbon film

PMDA–ODA (pyromellitic dianhydride–4,4′-oxydianiline) polyimide (PI) films with thickness of 2–26 μm were synthesized and heat-treated at 2200–2500°C. The effect of film thickness on both the graphitizability of the PI-derived carbon film and the crystalline organization of the initial PI film was investigated by X-ray diffraction. The degree of graphitization of the resultant carbon film was observed to increase with decreasing initial PI film thickness, corresponding to the film thickness dependence of the crystalline ordering in the initial PI films. Structural factors related to PI film thickness are discussed for understanding the graphitizability of the resultant carbon.

The effect of curing history on the residual stress behavior of polyimide thin films

The effect of curing history on the residual stress behaviors in semiflexible structure poly(4,4′-oxydiphenylene pyromellitimide) (PMDA–ODA) and rigid structure poly(p-phenylene biphenyltetracarboximide) (BPDA–PDA) polyimide was investigated. Depending upon the curing history and different structures of polyimide, the residual stress behaviors and the morphology of polyimide thin films were detected in situ by using a wafer bending technique and wide angle X-ray diffraction (WAXD), respectively. For the rigid structure BPDA–PDA polyimide, the residual stress and the slope decreased from 11.7 MPa and 0.058 MPa/°C to 4.2 MPa and 0.007 MPa/°C as the curing temperature increased, and the annealing process is done. However, for the semiflexible structure PMDA–ODA, the change of the residual stress and the slope was relatively not significant. In addition, it was found that the cured polyimide prepared at a higher temperature with a multistep curing process showed a higher order of chain in-plain orientation and packing order than does the polyimide film prepared at a lower temperature with a one-step curing process. These residual stress behaviors of polyimide thin films show good agreement with WAXD results, such as polyimide chain order, orientation, and intermolecular packing order, due to curing history. Specifically, it shows that the effect of curing history on residual stress as well as morphological change was significant in rigid BPDA–PDA polyimide but, not in semiflexible PMDA–ODA polyimide. Therefore, it suggests that the morphological structure depends upon curing history, and the polyimide backbone structure might be one of important factors to lead the low residual stress in polyimide thin films. © 1999 John Wiley & Sons, Inc. J Appl Polym Sci 74: 3287–3298, 1999

The effect of curing history on the residual stress behavior of polyimide thin films

The effect of curing history on the residual stress behaviors in semiflexible structure poly(4,4′-oxydiphenylene pyromellitimide) (PMDA–ODA) and rigid structure poly(p-phenylene biphenyltetracarboximide) (BPDA–PDA) polyimide was investigated. Depending upon the curing history and different structures of polyimide, the residual stress behaviors and the morphology of polyimide thin films were detected in situ by using a wafer bending technique and wide angle X-ray diffraction (WAXD), respectively. For the rigid structure BPDA–PDA polyimide, the residual stress and the slope decreased from 11.7 MPa and 0.058 MPa/°C to 4.2 MPa and 0.007 MPa/°C as the curing temperature increased, and the annealing process is done. However, for the semiflexible structure PMDA–ODA, the change of the residual stress and the slope was relatively not significant. In addition, it was found that the cured polyimide prepared at a higher temperature with a multistep curing process showed a higher order of chain in-plain orientation and packing order than does the polyimide film prepared at a lower temperature with a one-step curing process. These residual stress behaviors of polyimide thin films show good agreement with WAXD results, such as polyimide chain order, orientation, and intermolecular packing order, due to curing history. Specifically, it shows that the effect of curing history on residual stress as well as morphological change was significant in rigid BPDA–PDA polyimide but, not in semiflexible PMDA–ODA polyimide. Therefore, it suggests that the morphological structure depends upon curing history, and the polyimide backbone structure might be one of important factors to lead the low residual stress in polyimide thin films. © 1999 John Wiley & Sons, Inc. J Appl Polym Sci 74: 3287–3298, 1999

High resolution x-ray photoelectron spectroscopy and INDO/S–CI study of the core electron shakeup states of pyromellitic dianhydride-4,4′-oxydianiline polyimide

Pyromellitic dianhydride-4,4′-oxydianiline (PMDA–ODA) polyimide films have been studied using high resolution x-ray photoelectron spectroscopy and model semi-empirical INDO/S–CI calculations. Experimental and theoretical C 1s, N 1s, and O 1s spectra are presented, and found to be in good agreement with each other. Shakeup features of the spectra are identified, and their electronic nature analyzed theoretically. The highly nonstoichiometric ratio between the carbonyl and the ether O 1s main peaks is quantitatively explained by the calculations, where the nonstoichiometry is shown to be the result of stronger carbonyl than ether shakeup. Conformational effects on the shakeup spectra, due to torsion between the PMDA and ODA units, were investigated theoretically and found to be small for PMDA–ODA.

Structure-property correlation for thin films of semi-interpenetrating polyimide networks. I. Miscibility, curing, and morphology studies

Three different semi-interpenetrating polymer network (semi-IPN) polyimide systems were prepared through blending in solution by using 2 different polyimides, BPDA–PDA and PMDA–ODA (E), and 2 different oligomers, bismaleimide (MDAB) and phenylthynyl-terminated BPDA–PDA (BPDA–PDA–PEPA) oligomers. The oligomers are used as crosslinkers to modify the morphology of polyimides. The results show that both MDAB and PEPA are miscible with BPDA–PDA, but MDAB is immiscible with PMDA–ODA (E). Fourier transform infrared spectrum, dynamic mechanical thermal analysis data, and calculated crosslinking density indicate that there are crosslinking networks in these semi-IPN polyimide systems. In addition, the density and wide-angle X-ray diffraction results confirm that the molecular ordering and packing order are reduced by the addition of oligomers for these semi-IPN polyimide systems. © 1998 John Wiley & Sons, Inc. J. Appl. Polym. Sci. 70: 261–272, 1998

Structure–property correlation for thin films of semi‐interpenetrating polyimide networks. I. Miscibility, curing, and morphology studies

Three different semi-interpenetrating polymer network (semi-IPN) polyimide systems were prepared through blending in solution by using 2 different polyimides, BPDA–PDA and PMDA–ODA (E), and 2 different oligomers, bismaleimide (MDAB) and phenylthynyl-terminated BPDA–PDA (BPDA–PDA–PEPA) oligomers. The oligomers are used as crosslinkers to modify the morphology of polyimides. The results show that both MDAB and PEPA are miscible with BPDA–PDA, but MDAB is immiscible with PMDA–ODA (E). Fourier transform infrared spectrum, dynamic mechanical thermal analysis data, and calculated crosslinking density indicate that there are crosslinking networks in these semi-IPN polyimide systems. In addition, the density and wide-angle X-ray diffraction results confirm that the molecular ordering and packing order are reduced by the addition of oligomers for these semi-IPN polyimide systems. © 1998 John Wiley & Sons, Inc. J. Appl. Polym. Sci. 70: 261–272, 1998