Pyromellitic Dianhydride-oxydianiline Research Articles

Enhancement of polyimide and 3D graphene-polyimide through thermoforming and its effect on mechanical properties and associated creep phenomenon

Polyimides (PIs) are a class of polymers used in diverse applications due to their excellent thermal stability, outstanding chemical resistance, and superb mechanical properties. One of the most widely used PIs is Pyromellitic Dianhydride-Oxydianiline (PMDA-ODA) PI (Kapton®), which can be purchased as thin films or tubes, thus limiting its use to specific applications. In this work, a novel thermoforming process is proposed which facilitates forming of planar PI and novel three-dimensional graphene PI (3D-C/PI) shapes into 3D contours. Our thermoforming process allows the formation of various shapes, such as helical, angular, or cylindrical profiles, thus expanding PIs' usage to new applications. The effect of the thermoforming process on the PI's chemical composition, mechanical properties, and chemical resistance to oxidizing plasma environment are studied. Also investigated is the creep resistance of the thermoformed PI compared to pristine PI at various temperatures; an analytical creep model has been fitted to the experimental data. Our results show that accelerated creep tests of thermoformed and pristine PI result in the same deformation and that the thermoforming process has no influence on the PI's chemical composition or chemical resistance. We also found that 3D-C/PI presents excellent thermoformability and that thermoformed PI exhibits higher elasticity compared to pristine PI.

Organics on oxidic metal surfaces: a first-principles DFT study of PMDA and ODA fragments on the pristine and mildly oxidized surfaces of Cu(111).

Metal-organic hybrid materials are ubiquitous and a fundamental understanding of the hybrid-interface is key for the development of these hybrid material systems. In this work, using first-principles density-functional theory (including van der Waals (vdW) corrections), we study the fundamental physico-chemical properties of the molecular fragments of pyromellitic dianhydride oxydianiline (PMDA-ODA) on pristine Cu(111), as well as oxidic p4:O/Cu(111) in order to investigate the effect of mild oxidation of the metal substrate on PMDA-ODA adsorption. Firstly, we report the most favorable adsorption geometries amongst the various surface models and correlate the adsorption behavior with the electronic structure of the molecular fragments and the substrate layer. PMDA adsorbs weakly on both the clean and mildly oxidized copper surface via vdW forces while ODA adsorbs much stronger with a significant charge transfer between the substrates. Here, the oxidic layer is found to reduce the adsorption strength of both fragments and in particular, the ODA molecule interacts with the substrate via additional hydrogen bonding. Finally, our simulated scanning tunneling microscopy (STM) images suggest possible orientations of PMDA and ODA on clean and oxidic Cu surfaces to guide future experiments.

Surface Modification of Poly(biphenyl dianhydride-para-phenylene diamine) (BPDA-PDA) and Poly(pyromellitic dianhydride-oxydianiline) (PMDA-ODA) Polyimides with UV Photo-Oxidation

Poly(biphenyl dianhydride-para-phenylene diamine) (BPDA-PDA), Upilex-S, and poly(pyromellitic dianhydride-oxydianiline) (PMDA-ODA), Kapton HN, polyimides (PIs), were exposed to 253.7 nm and broad band radiation centered at 300 nm UV radiation which photo-activated the polymer surfaces in the presence of oxygen at atmospheric pressure. XPS analysis showed an increase in the O/C ratio on the modified surfaces which appeared mostly as the carbonyl moiety, although, treated Upilex-S samples also displayed an increase in C–O–C groups. The O/C ratio saturated more quickly for Upilex-S than Kapton. Good practical adhesion of sputtered Cu to the treated surfaces occurred at short treatment times while extensive exposure resulted in cohesive failure within the substrates at shorter treatment times for Upilex-S than Kapton.

An investigation into the improvement of adhesive strength of polyimides by incorporation of elastomeric nanoparticles

Copoly(styrene–butyl acrylate–ethyleneglycoldimethacrylate) (St–BA–EGDMA) nanoparticles were prepared using miniemulsion polymerization technique. Then the dispersed nanoparticles in DMAc were added to in situ condensation polymerization media of pyromellitic dianhydride (PMDA) and oxydianiline (ODA) and consequently, homogenous polyamic acid solution containing the nanoparticles was obtained. Novel polymer–polymer nanocomposites were prepared by casting of PMDA–ODA polyamic acid solution with various content of the above elastomeric nanoparticle (ENP) on a glass plate followed by thermal imidization. All samples were characterized after preparation by FT-IR spectroscopy, transition electron microscopy (TEM), thermal gravimetry analysis (TGA) and differential scanning calorimetery (DSC). To investigate the adhesion strength of polyimides filled with (St–BA–EGDMA) nanoparticles, lap shear strength (LSS) test was examined on different metallic surfaces. Effect of nanoparticles content on the adhesion properties of this polymer was considerable for aluminum surface. Lap-shear strength and adhesive energy of the bonded samples were found to initially increase with the increase in ENP wt%, but decrease after a critical value. It was shown that by increasing the nanoparticles amount up to 25 wt%, the adhesion strength of polyimides increased due to the good wetability of surfaces. After that and by increasing the nanoparticles amount, the adhesion strength decreased according to the diminished strength between polyimide chains. Scanning Electron Microscopy (SEM) micrographs of the fractured surfaces were taken to determine the failure mode. They showed that by increasing the nanoparticle content in the polyimide matrix, failure mode was converted from adhesion failure to cohesion one.

Adhesion Enhancement of Electroplated Cu/Electroless Ni Composite Layer to (PMDA-ODA)-Type Polyimide Films

In order to improve the adhesion strength of electroplated Cu/electrolessly plated Ni (EN)/PI laminates, four kinds of potassium hydroxide (KOH)-based solutions with different amounts of ethylenediamine were prepared and the surfaces of pyromellitic dianhydride-oxydianiline (PMDA-ODA)-type polyimide (PI) films were modified with these solutions. The surface of PI films was characterized by contact-angle measurements, X-ray photoelectron spectroscopy (XPS) and atomic force microscopy (AFM). The surface energy of PI films was calculated by the Owens–Wendt equation using the contact angle data of de-ionized water and diiodomethane (purity 99%). Adhesion strength of modified Cu/Ni/PI laminates was measured in terms of peel strength using the T-peel test. The results showed that the surface energy of PI films increased from 38.9 (unmodified) to 65.9 mJ/m2 (modified with solution No.4, i.e., solution containing 5 mol/l KOH and 90 mol/l ethylenediamine, for 180 s). XPS spectra showed that the surface of modified PI films incorporated a potassium-based product which is due to the formation of potassium polyamate in the modified layer through imide ring-cleavage reactions. AFM results revealed that the surface modification decreased the surface roughness of PI films, which is ascribed to the removal of the surface protrusions by etching during the modification process, and also revealed that it is desirable to modify PI films with a KOH-based solution containing a suitable amount of organic additive (ethylenediamine) to obtain a smooth EN layer. The T-peel test results showed that the peel strength of Cu/Ni/PI laminate reached a maximum when the PI film was modified with solution No. 4. The correlation between the peel strength and the surface energy of PI films revealed that the enhanced peel strength was mainly attributable to the increased surface energy of PI films by the modification process.

Characterization of Polymer Thin Films Sputtered onto a Copper Substrate with Two Kinds of Polyimide Targets

Polymer thin films were sputtered with two kinds of polyimide (PI) targets, pyromellitic dianhydride-oxydianiline (PMDA-ODA) and biphenyl dianhydride-p-phenylene diamine (BPDA-PDA), onto a copper substrate by a conventional RF sputtering with argon (Ar) and nitrogen (N2). These polymer thin films were characterized, and their adhesion and tribological properties were evaluated. Sputtering rate of the polymer thin film with PMDA-ODA target (sputtered PMDA-ODA thin film) with Ar was higher than that with BPDA-PDA target. Although the sputtering rate of the polymer thin film with the BPDA-PDA target (sputtered BPDA-PDA thin film) with Ar showed highest value at a pressure of 5 mTorr, that with N2 showed highest value at a pressure of 60 mTorr. Nitrogen content in the sputtered BPDA-PDA thin film with N2 increased compared to that of the sputtered BPDA-PDA thin film with Ar and target material (pristine). Although friction coefficients of these sputtered BPDA-PDA thin films with Ar were almost the same as those of the pristine PIs, that of the sputtered BPDA-PDA thin film with N2 was much higher than that of the pristine BPDA-PDA. The wear durability of the sputtered PMDA-ODA thin film with Ar was slightly higher than that of sputtered BPDA-PDA thin film. The wear durability of the sputtered BPDA-PDA thin film with N2 was much higher than that of the polymer thin film sputtered with Ar. The adhesion strength between the sputtered BPDA-PDA thin film with N2 and copper substrate was higher than that between the thin film sputtered with Ar and copper substrate. In addition, the sputtered BPDA-PDA thin film with N2 was introduced between the copper substrate and the sputtered BPDA-PDA thin film with Ar (Ar/N2 laminate). The adhesion strength of this laminate was higher value than that between the sputtered BPDA-PDA thin film with Ar and copper substrate.

(Co)polyimides from commonly used monomers, and their nanocomposites

Abstract Synthesis of (co)polyimides from aromatic dianhydrides (pyromellitic dianhydride (PMDA), symmetric 3,3′,4,4′-biphenyltetracarboxylic dianhydride (sBPDA)) and diamines (4,4′-oxydianiline (ODA), p-phenylenediamine (PDA)) commonly used for the production of commercial polyimides, as well as the preparation of their nanocomposites with SiO2 nanoparticles were performed with the aim to find ways to control technical performance of polyimides. The (co)polyimide films prepared under mild thermal imidization conditions were analyzed by FTIR, WAXD, DSC and TG, and characterized by transition temperatures and the temperatures of 5% and 10% mass loss, as well as tensile parameters. Films of PMDA/sBPDA–ODA copolyimides at the ambient temperature had a 20% higher ultimate strength and exhibited a higher tensile modulus than the reference polyimide (PMDA–ODA). However, lowering the transition temperature of the polyimide by partial substitution of an sBPDA monomeric unit for PMDA resulted in lowering the modulus at higher temperatures. The best performance was exhibited by semi-crystalline films of sBPDA–ODA/PDA copolyimide, which had a 35% higher ultimate strength and a 64% higher elongation at break at the ambient temperature than the reference polyimide (sBPDA–PDA), and also retained the strength and exhibited a 200% higher elongation at a temperature of 200 °C. Unexpectedly, the elongation at break of PMDA–ODA based (co)polyimide nanocomposites with hydrophobic SiO2 nanoparticles was greater than that of the baseline (co)polyimides. It was neither the case with PMDA–ODA nanocomposites with hydrophilic SiO2 nanoparticles, nor with sBPDA–PDA (co)polyimide based nanocomposites with hydrophobic SiO2 nanoparticles.

Characterization and tribological properties of two polyimide thin films sputtered onto a copper substrate

Two kinds of polyimide (PI), pyromellitic dianhydride-oxydianiline (PMDA-ODA) and biphenyl dianhydride-p-phenylene diamine (BPDA-PDA), thin films were sputtered onto a copper substrate by conventional RF sputtering with argon. These PI thin films were characterized, and their adhesion and tribological properties were evaluated. Elemental compositions and chemical bonding states of these thin films were analyzed with X-ray photoelectron spectroscopy (XPS). Oxygen and nitrogen concentrations in these thin films were less than those in bulk PIs. In addition, the amounts of C—O and C—N moieties in these PI thin films decreased as compared to the bulk PIs. Contact angles of water and methylene iodide on these PI thin films were higher than those on the bulk PIs. Surface energies of these PI thin films were calculated by measuring contact angles of water and methylene iodide. Surface energies of these PI thin films were lower than those of the bulk PIs and the polar components of these PI thin films were one-third of those of the bulk PIs. Friction coefficients of these thin films were almost the same as those of the bulk PIs. The abrasion durability of PMDA-ODA thin film was higher than that of BPDA-PDA thin film. The adhesion strength between the PMDA-ODA thin film and copper substrate was also higher than that between BPDA-PDA thin film and copper substrate.

Studies on the photodegradation of polarized UV‐exposed PMDA–ODA polyimide films

AbstractPolarized Fourier transform infrared (FTIR) and ultraviolet‐visible (UV‐VIS) spectroscopy were used to investigate the photodegradation direction of polarized UV (PUV)‐irradiated polyimide (PI) films based on pyromellitic dianhydride (PMDA) and 4,4′‐oxydianiline (ODA). PI films strongly absorb below 350 nm, resulting in a photochemical reaction of the PI. PUV irradiation of the PI film caused a decrease of all existing peaks and formation of new peaks at 3258, 1748, and 1710 cm−1 in the IR, due to degradation of the PI molecules. The preferential degradation of PI molecules parallel to the PUV irradiation direction results in the predominant orientation of the remaining PI molecules perpendicular to the PUV irradiation direction. But rubbing of the PI films induced orientation of the PI molecules parallel to the rubbing direction. © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 86: 3072–3077, 2002

Effect of film thickness on the electrical properties of polyimide thin films

Dielectric constant and conduction current of thin/ultrathin films of polyimides on substrates with thicknesses of 80–2000nm were measured by using a small electrode system. Polyimides used in this study were poly(diphenylmethane-2,3,5-tricarboxycyclopentyl aceticimide, TCA-DDM) and poly(pyromellitic dianhydride oxydianiline, PMDA-ODA). With decreasing film thickness, the dielectric constant decreased but the conduction current increased. Using IR reflection absorption spectroscopy, we found that the polyimide chains are oriented parallel to the electrodes. The dependence of the dielectric constants on film thickness was explained by the orientation of polymer chains.

Damage-depth profiling of ion-irradiated polyimide films with a variable-energy positron beam

Various polyimide layers [2.2–2.6 μm of hexafluoroisopropylidene bis(phthalic anhydride-oxydianiline), pyromellitic dianhydride-oxydianiline, and 3,3′-4,4′-biphenyltetracarboxylic dianhydride-p-phenylenediamine] spin-coated on silicon substrates were studied with a variable-energy positron beam in combination with a Doppler-broadened annihilation radiation technique. From the experiments, the thickness of the layers was estimated with the VEPFIT routine. These values corresponded well to the values determined from interferometry and ellipsometry. Irradiation of the polyimides with 1 × 1015 boron ions/cm2 at an energy of 180 keV led to a strong chemical modification of the irradiated top layer. This caused the inhibition of positronium formation in the irradiated layer, which was observed as a lowering of the annihilation line S parameter. The thickness of the modified layer was estimated to be 700–800 nm. This value did not agree with the ellipsometric measurements but corresponded to the maximum implantation depth of boron ions calculated with TRIM (Transport of Ions in Matter) code. The positron results appeared somewhat larger than the TRIM estimates. Reasons for these relations are discussed. © 2000 John Wiley & Sons, Inc. J Polym Sci B: Polym Phys 38: 3062–3069, 2000

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.

Metal/polymer interfaces with designed morphologies

The morphology of a metal/polymer interface is important for many properties, e.g. its adhesional strength. Starting from the basic processes occurring in the initial stages of metal/polymer interface formation, it is possible to obtain different morphologies by variation of the preparation conditions. In this report we present selected examples from our own work of how metal/polymer interfaces with different morphologies can be prepared by evaporating noble metals (Au, Ag, Cu) onto chemically different polymers, i.e. bisphenol-trimethyl cyclohexane polycarbonate (TMC-PC), pyromellitic dianhydride-oxydianiline (PMDA-ODA) polyimide (PI), and on Teflon AF 1601. The interfaces were characterized using transmission electron microscopy (TEM), X-ray photoelectron spectroscopy (XPS), and atomic force microscopy (AFM). The combination of these techniques allows one to determine morphological parameters such as the concentration and distribution of metal clusters at the surface and in the near-surface region. Using low deposition rates and elevated temperatures, spread-out metal/polymer interfaces can be formed, whereas the use of high deposition rates and moderate temperatures results in relatively sharp interfaces. Another approach to obtain a defined morphology is to form large metal clusters of 10-30 nm diameter on the polymer surface and embed them into the polymer in a controlled manner by a subsequent annealing process. First experiments on the macroscopic adhesion of Au and Cu on TMC-PC showed that the initially low peel strength could be increased substantially by subsequent annealing above the glass transition temperature.

Formation of metal–polymer interfaces by metal evaporation: influence of deposition parameters and defects

Metal–polymer interfaces with different but well defined morphologies were prepared by evaporating noble metals (Au, Ag, Cu) onto chemically different polymers, i.e. bisphenol-trimethyl cyclohexane polycarbonate (TMC-PC), pyromellitic dianhydride-oxydianiline (PMDA-ODA) polyimide (PI), polystyrene (PS) and the low-k dielectric Teflon AF 1601. The interfaces were characterised using transmission electron microscopy (TEM), X-ray photoelectron spectroscopy (XPS) and atomic force microscopy (AFM). The combination of these techniques allowed one to determine morphological parameters such as concentration and distribution of metal clusters at the surface and in the near-surface region. In addition, radiotracer measurements yielded exact metal condensation coefficients C and was used to determine the extent of diffusion of metal atoms into the polymers. First experiments on the macroscopic adhesion of Cu on TMC-PC showed that the initially low peel strength can be increased substantially by subsequent annealing above the polymer glass transition temperature, T g.

Anisotropy in the thermal shrinkage of polyimide film

Anisotropy in a polyimide film was investigated in a quantitative manner by a nonlinear regression of the thermal shrinkage data obtained from thermomechanical analysis. The thermally induced shrinkage of this pyromellitic dianhydride–oxydianiline polyimide film at 573 K was directionally anisotropic in the film plane by as much as about 0.4%. The direction of maximum thermal shrinkage was inclined by about π/6 rad from the machine direction of the film. The thermal shrinkage behavior of the polyimide films in the vicinity of the glass-transition temperature (Tg) showed an unusual anisotropic response. On the basis of a correlation between the anisotropy in the thermal shrinkage of the films and the molecular orientation of the polyimide, this characteristic thermal shrinkage behavior around Tg is suggested to be due to a recovery of the free volume lost by a physical aging process. © 2000 John Wiley & Sons, Inc. J Polym Sci B: Polym Phys 38: 3222–3229, 2000

Thickness dependence of the anisotropy in thermal expansion of PMDA-ODA and BPDA-PDA thin films

The thickness dependence of the anisotropy in thermal expansion of poly(pyromellitic dianhydride oxydianiline) (PMDA-ODA) with flexible chains and poly(biphenylene tetracarboxylic dianhydride p-phenylene diamine) (BPDA-PDA) ranging from 2.5 to 20 μm has been investigated. The lateral (in-plane) coefficient of thermal expansion (CTE) of PMDA-ODA and BPDA-PDA increases with increasing film thickness; in contrast, the vertical (out-of-plane) CTE of PMDA-ODA and BPDA-PDA decreases with increasing film thickness. The vertical CTE of PMDA-PDA is 4–7 times larger than the lateral CTE. The vertical CTE of BPDA-PDA is 14–20 times larger than the lateral CTE. It is believed that the thickness dependence of the anisotropy in CTE is caused by the in-plane orientation of the polyimide main chain. Since BPDA-PDA has a rigid-rod-like structure, this leads to a better in-plane orientation and a larger anisotropy in CTE than PMDA-ODA.

Development of In-Plane Orientation in Pyromellitic Dianhydride-Oxydianiline Polyimide Film on Substrate during Thermal Imidization

The development of in-plane orientation in pyromellitic dianhydride-oxydianiline (PMDA-ODA) polyimide film coated on silicon substrate during thermal imidization was investigated by means of FT-IR spectroscopy. The increase in thermal imidization temperature caused the decrease in the degree of in-plane orientation in spite of the increased chain rigidity. It suggests that the chain immobilization limit the development of the in-plane orientation during thermal imidization. The residual solvent was found to decrease the degree of in-plane orientation probably due to the increase of the chain immobilization rate as indicated by the quantitative measurements of the degree of imidization and the residual solvent content as a function of imidization time at various temperatures.

Effect of an interfacial layer on adhesion strength deterioration between a copper thin film and polyimide substrates

Copper (Cu) was sputtered onto a polyetheretherketon (PEEK) film and onto three types of polyimide (PI) films; pyromellitic dianhydride-oxydianiline (PMDA-ODA), biphenyl dianhydride- para-phenylene diamine (BPDA-PDA) and biphenyl dianhydride-oxydianiline (BPDA-ODA). All films were pre-treated with oxygen plasma. We measured the adhesion strength between the Cu thin film and these polymer substrates and found that Cu/PMDA-ODA, Cu/BPDA-ODA and Cu/PEEK laminates showed strong adhesion, but Cu/BPDA-PDA laminate showed weak adhesion. These results show that the ether moiety between the two benzene rings in ODA (oxydianiline) would play an important role in the adhesion between a Cu thin film and a PI substrate. Furthermore, we found that the adhesion strength of the Cu/BPDA-PDA laminate could be significantly improved by a nickel (Ni) interfacial layer. Adhesion strength between a Cu thin film and a PMDA-ODA polyimide substrate is reduced from 10.0 to 2.0 N/m by heat treatment at 150°C in air. We introduced an interfacial layer of indium-tin-oxide (ITO) between the PI and Cu (Cu/ITO/PI) in order to prevent the oxidation of Cu and PI. The adhesion strength of the Cu/ITO/PMDA-ODA film was about 8.0 N/m even after heat treatment at 150°C in air for 3 days. Moreover, the adhesion strength of the Cu/ITO/BPDA-PDA film was maintained over 4.0 N/m even after heat treatment at 150°C in air for 3 days.

Polyimide/Polyimide Molecular Composite Films: Difference between Reactive Oligoimide and Reactive Polyimide as the Matrix Component

Polyimide/polyimide molecular composite (MC) films were prepared by blending precursor solutions of a rigid polyimide and a reactive oligoimide or a reactive polyimide that contains acetylene units in the backbone in a 7:3 ratio, followed by casting, drying and thermal imidization at 300 °C. 3, 3′, 4, 4′-Biphenyltetracarboxylic dianhydride (BPDA), pyromellitic dianhydride (PMDA), p-phenylenediamine (PDA), oxydianiline (ODA) and 3, 3′-diaminodiphenylacetylene ( m-intA) were used as acid dianhydride and diamine monomers for the preparation of polyimide. The rigid components were prepared from PMDA or BPDA and PDA. The matrix components were prepared from PMDA or BPDA and ODA or m-intA. The polyimide/polyimide MCs have exotherm on DSC due to the reaction of internal acetylene units, which indicates that the MC films are laminate processable. Tensile measurements revealed that the tensile modulus of the MCs utilizing reactive oligoimides is 20–30% higher than that of the MCs utilizing reactive polyimides. Viscoelastic analyses of the MC films showed that the crosslinking of the acetylene units gave polyimides that have a very high glass transition temperature.

Effect of Surface-Influenced Order on Thermal Expansivity of Polymer Thin Films

Variations of the thermal expansion coefficient of thin polyimide films as a function of film thickness (40−260 nm) have been measured by monitoring film thickness as a function of temperature using X-ray reflectivity from samples of poly(pyromellitic dianhydride oxydianiline) (PMDA−ODA) films spin-cast onto silicon wafers. The effective expansion coefficient of the film decreases with decreasing thickness and is consistent with a bilayer model in which an interfacial region of constant thickness is formed for each film. The expansion coefficient of this surface or interfacial region is less than one-third the coefficient of the interior of the films. A simple method is described whereby the thermal expansion coefficient may be determined by reflectivity.