Copolyimide Films Research Articles

Effect of oxygen plasma treatment and gold sputtering on morphological and local mechanical properties of copolyimide/gold micropatterned structures

Atomic force microscopy (AFM) was used to analyze rectangular 3‐dimensional patterned microstructures with different functionalities induced on copolyimide containing alicyclic sequences film surfaces by means of oxygen plasma treatment. The plasma power was ranged to be big enough to accelerate the plasma species towards the copolyimide surface, and the exposure time was not very small to generate a roughness that still can be monitored by AFM. To create the rectangular pattern, transmission electron microscopy grid masks were placed on the samples before treatment. Plasma‐induced micropatterning with alternating hydrophilic and hydrophobic surface chemistries was evaluated by measuring the adhesion forces between the gold‐covered AFM tip and the copolyimide surfaces. To fabricate 3‐dimensional metallic microstructures arranged in well‐defined areas, thin metal layers were sputtered on these pretreated copolyimide films. The AFM morphological aspects of the obtained metallic structures were correlated with the surface modifications induced by plasma treatment conditions. Functional indexes and functional volume parameters were also calculate to characterize the functional behavior of the surface, such as wear, lubrication, and contact. The AFM data were compared with those obtained using the small‐angle X‐ray scattering measurements.

Synthesis and characterization of porous polyimide films containing benzimidazole moieties

In this study, a series of porous polyimide films containing benzimidazole units were prepared through a phase separation process. The dibutyl phthalate was selected as porogen. The copolyimides were prepared by the reaction of 3,3′,4,4′-benzophenonetetracarboxylic dianhydride with two diamines of 2-(4-aminophenyl)-5-aminobenzimidazole (BIA) and 4,4′-diaminodiphenyl ether with various molar ratios. The resultant porous polyimide films exhibit optimum cell-size distributions. The effects of BIA on morphology, mechanical, and thermal properties of the porous films were explored. It was found that as the BIA content reached up to 30 mol%, the porous copolyimide film demonstrates remarkable thermal stability and admirable mechanical properties with the glass transition temperature of 294°C, 5% weight loss temperature in argon flow up to 545°C, and a tensile strength of 48 MPa. The incorporation of BIA into the polyimide chains brought the highly rigid structures and strong intermolecular interactions, resulting in the enhancement in the thermal stability and the mechanical properties.

Thermostable birefringent copolyimide films based on azobenzene-containing pyrimidine diamines

This work shows the key role played by the chemical structure of polyimides in the thermal stability of birefringence.

Fully transparent, non-volatile bipolar resistive memory based on flexible copolyimide films

Partially aliphatic homopolyimides and copolyimides were prepared from rel-(1′R,3S,5′S)-spiro[furan-3(2H),6′-[3]oxabicyclo[3.2.1]octane]-2,2′,4′,5(4H)-tetrone (DAn), 2,6-diaminoanthracene (AnDA), and 4,4′-oxydianiline (ODA) by varying the molar ratio of AnDA and ODA. We utilized these polyimide films as the resistive switching layer in transparent memory devices. While WORM memory behavior was obtained with the PI-A100-O0-based device (molar feed ratio of DAn : AnDA : ODA = 1 : 1 : 0), the PI-A70-O30-based device (molar feed ratio of DAn : AnDA : ODA = 1 : 0.7 : 0.3) exhibited bipolar resistive switching behavior with stable retention for 104 s. This result implies that the memory properties can be controlled by changing the polyimide composition. The two devices prepared from PI-A100-O0 and PI-A70-O30 showed over 90% transmittance in the visible wavelength range from 400 to 800 nm. The behavior of the memory devices is considered to be governed by trap-controlled, space-charge limited conduction (SCLC) and local filament formation.

Synthesis and properties of ultralow dielectric constant porous polyimide films containing trifluoromethyl groups

ABSTRACTIn this research, a series of porous copolyimide (co‐PI) films containing trifluoromethyl group (CF3) were facilely prepared via a phase separation process. The co‐PI were synthesized by the reaction of benzophenone‐3,3′,4,4′‐tetracarboxylic dianhydride (BTDA) with two diamines of 4,4′‐diaminodiphenyl ether (ODA) and 3‐trifluoromethyl‐4,4'‐diaminodiphenyl ether (FODA) with various molar ratios. The flexible and tough porous co‐PI films with about 300 μm thickness and 8∼10 μm average diameter could be obtained by solution casting conveniently. The thermal properties of the obtained porous co‐PI films were excellent with a glass transition temperature at 270 °C ∼ 280 °C and only 5% weight loss in temperature from 530 °C to 560 °C under nitrogen atmosphere. In addition, the dielectric and hydrophobic properties of porous co‐PI films were remarkably improved owing to the presence of trifluoromethyl groups (CF3) in the polymer chains. Moreover, our synthesized porous co‐PI films also showed good mechanical properties. © 2016 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2017, 134, 44494.

Synthesis and properties of low coefficient of thermal expansion copolyimides derived from biphenyltetracarboxylic dianhydride with p-phenylenediamine and 4,4′-oxydialinine

Abstract A series of copolyimides were prepared by thermal imidization of poly(amic acid)s (PAAs) derived from 3,3′,4,4′-biphenyltetracarboxylic dianhydride (s-BPDA), 2,3′,3,4′-biphenyltetracarboxylic dianhydride (a-BPDA), p-phenylenediamine (PDA) and 4,4′-oxydialinine (4,4′-ODA) commonly used for the production of commercial polyimides. The flexible copolyimide films were obtained from that the molar ratio of s-BPDA, a-BPDA, PDA and 4,4′-ODA was 9:1:8:2 (Co-PIs-3), 8:2:9:1 (Co-PIs-5) and 8:2:8:2 (Co-PIs-6). These obtained copolyimide films were characterized by Fourier transform-infrared spectroscopy(FT-IR), wide angle X-ray (WAXD), Thermogravimetric (TG), dynamic mechanical thermal analysis (DMA), thermomechanical analysis (TMA), field-emission scanning electron microscopy (FE-SEM) and mechanical properties measurement. The results showed that three copolyimides remained semi-crystalline and exhibited high glass transition temperature (Tg), high thermal stability, great ultimate tensile strength and low coefficient of thermal expansion (CTE). The Co-PIs-5 had lower crystallinity, lower CTE, greater elongation at break, higher Tg and thermal stability and the greater dense extent, compared with Co-PIs-3 and Co-PIs-6. Structure and property relations of the prepared polyimides were also briefly discussed. The results revealed that the copolymerization of s-BPDA/PDA with a small number of 4,4′-ODA/a-BPDA was a useful means for enhancing flexibility without sacrificing low CTE.

Fluorine and phosphine oxide containing homo and copolyimides

Abstract In recent years the synthesis of fluorinated polyimides has become an active area of research. In this study perfluoroalkyl and phosphine oxide containing diamine monomer, bis(3,3′-aminophenyl)-(3,3,4,4,5,5,6,6,7,7,8,8,8-tridecafluorooctyl) phosphine oxide (mDA13FAPO), was successfully prepared. mDA13FAPO was reacted with four different commercial dianhydrides (BTDA, PMDA, ODPA and 6FDA) and corresponding homopolyimides were prepared by thermal and solution imidization techniques. However, homopolyimides of mDA13FAPO exhibited poor film forming properties. In order to overcome this problem different amounts of mDA13FAPO containing copolyimides with BTDA and ODA were prepared. The flame retardancy of the copolyimides was examined by limiting oxygen index measurements. The surface energies of the copolyimides were determined by contact angle measurements. mDA13FPO containing homopolyimides exhibited moderate Tg values (194–233 °C), good thermal stability and excellent solubility. The presence of ODA greatly improved the film forming properties and crack-free, creasable copolyimide films were obtained. As the amount of mDA13FAPO was increased, the flame retardancy and the water contact angles of the copolyimides increased while the surface energies and the glass transition temperatures decreased.

Synthesis and properties of copolyimides based on ternary dianhydrides and dibasic diamines

A series of copolyimides were prepared by thermal imidization of polyamide acids derived from 3,3′,4,4′-biphenyltetracarboxylic dianhydride, 2,3′,3,4′-biphenyltetracarboxylic dianhydride, pyromellitic dianhydride, p-phenylenediamine and 4,4′-oxydialinine commonly used for the production of commercial polyimides. The flexible copolyimide films characterized by ultra-low coefficient of thermal expansion were obtained and characterized by FTIR, WAXD, TG, DMA, TMA, FE-SEM and tensile properties measurement. The results showed that three copolyimides remained semi-crystalline and exhibited high glass transition temperature, high thermal stability, and great ultimate strength.

Preparation and characterization of inherently heat‐sealable polyimides with high glass transition temperatures

ABSTRACTA series of inherently heat‐sealable copolyimides (CPIs) with high glass transition temperatures were synthesized from 2,3,3′,4′‐oxydiphthalic anhydride (aODPA) and bicomponent diamines, 4,4′‐oxydianiline (ODA) and para‐phenylenediamine (PDA). The PI chain rigidity was manipulated by the regulation of the diamine ratio, and its effects on the heat sealability and thermal resistance of the derived CPI films were investigated in detail. The results show that these films are in possession of both good heat sealability and thermal resistance due to the synergetic effect of the asymmetry of aODPA and the rigidity of PDA. It is also found that there exists one critical PDA content that distinguishes the heat‐sealing behaviors of the CPI films, and the relevant mechanism was established. Especially for CPI‐5, the heat‐sealing strength is up to 350 N m−1 simultaneously with a relatively high Tg of 310°C. © 2015 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2016, 133, 43058.

Synthesis, characterization and properties of aromatic copolyimides containing Bi-benzimidazole moiety

A new aromatic heterocyclic diamine monomer, 2,2-bis (4’-aminophenyl)- 5,5-bi-1H-benzimidazole (BAPBBI), was synthesized via a one-step reaction of 3,3’,4,4’-biphenyltetramine and p-aminobenzoic acid in polyphosphoric acids with the high yield and purity. FTIR, 1H NMR, 13C NMR, mass spectra and elemental analysis were employed to confirm the chemical structures. A series of copolyimide films containing the bi-benzimidazole moieties were prepared by the reaction of pyromellitic dianhydride (PMDA), 4,4’-oxydianiline (ODA) and BAPBBI with various molar ratios. The combination of polybenzimidazole and polyimide by introducing BAPBBI into the main chains brings the highly rigid structure and the enhanced macromolecular interactions, resulting in the enhancement in the thermal stability and the mechanical properties. For instance, these polyimides are endowed with a higher glass transition temperature of 408–438 °C and an initial thermal decomposition of 550–580 °C. They exhibit a strong tensile strength of 123–233 MPa, and a tensile moduli of 2.66–12.84 GPa without post stretching. Meanwhile the stretched films at 450 °C exhibited the enhanced mechanical properties with the tensile strength of 195–554 MPa and the tensile modulus of 4.69–38.57 GPa.

Three-Dimensional Nanostructures with Biocidal Activity Created on a Siloxane-Containing Copolyimide Film

Surface morphological characteristics of a copolyimide film prepared from a fluorine-based dianhydride combined with an aliphatic siloxane-based diamine and an aromatic containing ether linkages one, were studied before and after oxigen plasma treatment using atomic force microscopy (AFM). The three-dimensional texture parameters calculated from the AFM data have highlighted a more pronounced surface morphology (higher average roughness and developed interfacial area ratio), improved bearing properties and no predominant orientation, as the plasma exposure time was increased from 6 to 10 minutes, using the same power (40 W). The reactive groups generated on the binding surface have facilitated the interaction with a biocidal agent, such as silver nitrate. This creates silver-containing nanoparticles, of about 120-150 nm, uniformly distributed on the copolymer surface, with a density of 10±2 particles/μm2. The functionalization with the biocidal agent of the flourinated copolyimide surface was conducted for testing its antimicrobial properties, namely the inhibition/destruction of Escherichia coli bacterium.

Structural effect of monomer type on properties of copolyimides and copolyimide-silica hybrid materials

In this work, the effect of two different diamine monomers, containing phosphine oxide, on thermal, mechanical and morphological properties of copolyimides and their hybrid materials was investigated. Gas separation properties of the synthesized copolyimides were also analysed. Two different diamine monomers with phosphine oxide were bis(3-aminophenyl) phenylphosphine oxide (BAPPO) and bis(3-aminophenoxy-4-phenyl) phenylphosphine oxide (m-BAPPO). In the synthesis of copolyimides 3,3?-diamino-diphenyl sulfone (DDS) was also used as the diamine, as well as 2,2?-bis(3,4-dicarboxyphenyl)hexafluoropropane dianhydride (6FDA). Copolyimide films were prepared by thermal imidization. Hybrid materials containing 5 % SiO2 were synthesised further by sol-gel technique. The Fourier-transform infrared spectroscopy (FTIR), Nuclear magnetic resonance spectroscopy (NMR) confirmed the expected structure. Dynamic mechanical analysis (DMA) demonstrated that m-BAPPO based copolyimides had lower glass transition temperatures (Tg) than BAPPO based copolyimides. m-BAPPO containing copolyimide without silica shifted the thermal decomposition temperature to a higher value. The moduli and strength values of BAPPO diamine containing copolyimide and its hybrid were higher than those of m-BAPPO containing materials. The contact angle measurements showed the hydrophobicity. Scanning electron microscope (SEM) analysis exhibited the silica particles dispersion in the copolyimides. These copolyimides may be used in the coating industry. The CO2 permeability and the permselectivity were the highest among the other values in this study, when m-BAPPO containing copolyimide in the absence of silica was used. The gas permeabilities obtained from this work were in this decreasing order: PCO2 > PO2 > PN2.

Colorless and transparent copolyimide nanocomposites.

Copolyimides (Co-PIs) were synthesized from 2,2'-bis(trifluoromethyl) benzidine (TFB) and different ratios of 4,4'-(hexafluoroisopropylidene) diphthalic anhydride (6FDA) and pyromellitic dianhydride (PMDA). The Co-PI films were obtained from poly(amic acid) (PAA) by solution-casting through typical chemical and thermal imidizations. The thermal properties and optical transparency of the Co-PI films with various PMDA monomer contents were investigated. It was found that with increasing PMDA content, the thermal transition temperatures of the Co-PI films increased. Co-PI nanocomposites were prepared with various amounts of organically modified hectorite (STN) on a TFB:6FDA:PMDA = 1.0:0.9:0.1 mole ratio Co-PI hybrid film to examine the thermal properties, morphology, and optical transparency. The thermo-optical properties of the Co-PI hybrid films deteriorated with increasing clay content. However, the coefficient of thermal expansion (CTE) and oxygen barrier properties of the PI hybrid films improved with increasing clay content.

Atomic oxygen resistant phosphorus-containing copolyimides derived from bis[4-(3-aminophenoxy)phenyl] phenylphosphine oxide

Commercially available Kapton polyimide commonly used in various kinds of spacecrafts travelling in Low Earth Orbits (LEO) is severely degraded upon atomic oxygen (AO) exposure. An effective approach is to introduce the AO resistant component i.e., phenylphosphine oxide (PPO) in polymer. A series of copolyimide films has been successfully synthesized from random copolymerization of a PPO based monomer bis[4-(3-aminophenoxy)phenyl] phenylphosphine oxide (mBAPPO), 4,4′-diaminodiphenyl ether (4,4′-ODA) and 3,3′,4,4′-biphenyl tetracarboxylic dianhydride (sBPDA). The glass transition temperature (T g ) and mechanical properties were examined by differential scanning calorimetry and universal mechanical testing machine, respectively. The tensile strength, elongation, and T g of the copolyimide films decreased with the increase of PPO content. The effects of PPO content on the morphology and structure evolvement of copolyimide films were also studied. AO exposure tests were performed using a ground-based AO effects simulation facility. Phosphorus-containing polyimide composite films formed a layer of dense polyphosphate network on the PI film after AO exposure protecting the underlying polymers from further degradation. This layer decreased the mass loss rate and outstandingly improved the AO resistance of PI films. The results of all the studies indicate that these phosphorus-containing copolyimide films can achieve great potential as polymeric materials for potential space applications in LEO and a space durable replacement for Kapton.

Quaternary copolyimides with various monomer contents: Thermal property and optical transparency

Several quaternary copolyimides (Co-PIs) were prepared using various molar ratios of two dianhydrides and two diamines: 4,4’-(hexafluoroisopropylidene) diphthalic anhydride (6FDA), 1,2,4,5-benzenetetracarboxylic dianhydride (pyromellitic dianhydride) (PMDA), 2,2’-bis(trifluoromethyl)benzidine (TFB), and trans-1,4-cyclohexanediamine (CHDA). Copolymerization of the monomers afforded poly(amic acid)s (PAA), which were solution-cast onto glass plates and subjected to thermal imidization to yield the Co-PI films. These Co-PI films showed no significant decomposition below 500 °C in a N2 atmosphere. Finally, the films were colorless and exhibited high optical transparencies, with UV-vis. absorption edges of 342-367 nm and low yellow index (YI) values of 1.72–5.09.

Synthesis and characterization of novel piezoelectric nitrile copolyimide films for high temperature sensor applications

A series of amorphous polyimides and copolyimides that contained nitrile were obtained by a two-step procedure. The first step consisted of a polycondensation reaction of 4,4’-oxydiphtalic anhydride (ODPA) with one or two aromatic diamines, namely 1,3-Bis-2-cyano-3-(3-aminophenoxy)phenoxybenzene (diamine 2CN) and 1,3-Bis(3-aminophenoxy)benzene (diamine 0CN). In the second step, a thermal cyclodehydration converted each poly(amic acid) or copoly(amic acid) into their corresponding polyimide films. The piezoelectric response was improved after corona poling of the films. A maximum d33 modulus value of 16 pC N−1 was obtained for the polymide with two cyano groups (poly 2CN). The polarization also showed time and thermal stability up to 160 °C. Additionally, the thermal stability of the amorphous polyimides, (β-CN)APB/ODPA, was studied by determining the glass transition temperature (Tg) and thermal decomposition through differential scanning calorimetry (DSC) and thermogravimetric analysis (TG), respectively. The high piezoelectric response (1–16 pC N−1), Tg (160–180 °C) and degradation temperature (315–450 °C) make such polyamides excellent candidates for use as high temperature sensors.

Poly(benzoxazole-amide-imide) copolymers for interlevel dielectrics: interchain hydrogen bonding, molecular arrangement and properties

A series of novel random poly(benzoxazole-amide-imide) copolymers were synthesized via the poly(amic acid)s from the reaction of 5-amino-2-(4-aminophenyl)benzoxazole (BOA) and 4-amino-N-(4-aminophenyl)benzamide (DABA) with 3,3′,4,4′-biphenyltetracarboxylic dianhydride (BPDA). The corresponding homopolyimides were also prepared for comparison. The chemical composition, interchain hydrogen bonding and molecular arrangement of the copolyimides in solid films were investigated by attenuated total reflectance Fourier transform infrared (ATR-FTIR) spectroscopy, computation techniques and wide angle X-ray diffraction (WAXD). The results indicated that the interchain hydrogen bonds were most likely formed between the amide oxygen atoms and -N-H bands. And the ordered chain packing structures of copolyimide films were completely different from those of the homopolyimide films probably due to the directional interchain hydrogen bonding interactions. The properties of the copolyimides were also well-characterized by tensile tests, dynamic mechanical analysis (DMA), thermal gravimetric analysis (TGA) along with water absorption, solubility and peel tests. All of the obtained copolyimide films exhibited high tensile strength (321 ~ 332 MPa) and modulus (6.76 ~ 8.03 GPa) without any stretching. Moreover, the glass transition temperatures (Tgs) and 5 % weight-loss temperatures of the copolyimides in nitrogen were above 322 and 560 °C, respectively. Additionally, the copolyimide films also exhibited low water absorption, excellent chemical resistance and good adhesion properties suitable for interlevel dielectrics in microelectronics.

Effect of the chemical structure of aromatic-cycloaliphatic copolyimide films on their surface morphology, relaxation behavior and dielectric properties

Aromatic—cycloaliphatic copolyimides are synthesized by polycondensation reaction of dimethylsubstituted diamine-diphenyl methane with a mixture of an aromatic dianhydride namely benzophenonetetracarboxylic dianhydride (BTDA) with a cycloaliphatic dianhydride namely 1, 2, 3, 4-cyclopentanetetracarboxylic dianhydride (CPDA) taken in various molar ratios. The resulted copolyimides are characterized with regard to their solubility, inherent viscosity, molecular weight distribution and thermal stability. The quality of free-standing films prepared from the polymers is thoroughly studied by atomic force microscopy (AFM) technique. Dielectric properties of four representative films are investigated in detail in a large frequency range, from 1 to 106 Hz, and in a wide temperature domain, from −150 to 300 °C, and their variations are correlated with polymer structure and composition.

Synthesis and characterization of benzimidazole‐based low CTE block copolyimides

AbstractA series of block and random copolyimide films were synthesized from various molar ratios of two diamines, rigid 2‐(4‐aminophenyl)‐5‐aminobenzimidazole (APBI) and flexible 4,4′‐oxydianiline (ODA) by polycondensation with dianhydride 3,3′,4,4′‐biphenyltetracarboxylic dianhydride. The contents of APBI ranged from 10 to 60 mol % in copolyimides. The copolyimide films obtained by thermal imidization of poly(amic acid) solutions, were characterized by TMA, DMA, TGA, DSC, wide‐angle X‐ray diffraction, FTIR, tensile testing, water uptake (WU), and dielectric constant measurements. Rigid heterocyclic diamine APBI with interchain hydrogen bonding capability, led to low coefficient of thermal expansion (CTE), high Tg, high thermal stability and better mechanical properties. Increasing the APBI mol % caused a gradual decrease in the CTE and increase in Tg, thermal stability and tensile strength properties of the copolyimides films. Moreover, significantly enhanced thermal and mechanical properties of the block copolyimides were also found as compared to random copolyimides. The block copolyimide with APBI content of 60 mol %, achieved excellent properties, that is, a low CTE (4.7 ppm/K), a high Tg at 377°C, 5% weight loss at 562°C and a tensile strength at 198 MPa. This can be interpreted because of comparatively higher degree of molecular orientation in block copolyimides. These copolyimides also exhibited better dielectric constant and WU. This combination of properties makes them attractive candidates for base film materials in future microelectronics. © 2013 Wiley Periodicals, Inc. J. Appl. Polym. Sci., 2013

Plasma Modification of Surface Wettability and Morphology for Optimization of the Interactions Involved in Blood Constituents Spreading on Some Novel Copolyimide Films

Novel copolyimides (cPIs) based on 3,3′,4,4′-benzophenonetetracarboxylic dianhydride, 4,4′-diaminodiphenylmethane (DDM) and 1,6-diaminohexane (DAH) were synthesized. Their surface wettability was improved by plasma enhancement of polar component contribution to surface tension from 10 to 50 %. Interfacial energy reduction up to 2.07–2.95 mN/m was depicted in spreading work values that reveal the manner in which cPIs interact with blood constituents. The results showed that by increasing of the aliphatic DAH content in the polymer chain, the rejection of platelets is higher, prohibiting thrombosis and favoring cohesion with plasma proteins. The different water sorptions of the samples were evaluated by considering their morphologies and chemical affinities to water. When DAH prevails to DDM, water sorption capacity is lowered from 6.36 to 4.96 % db, presumably due to a higher chain packing efficiency. Atomic force microscopy data revealed that surface roughness is <8 nm for all polymers, even after plasma treatment, preventing clot formation.