Transparent Polyimides Research Articles

Transparent, High Glass-Transition Temperature, Shape Memory Hybrid Polyimides Based on Polyhedral Oligomeric Silsesquioxane

Optically transparent polyimides with excellent thermal stability and shape memory effect have potential applications in optoelectronic devices and aerospace industries. A series of optically transparent shape memory polyimide hybrid films are synthesized from 2,2-bis(3,4-dicarboxyphenyl)hexafluoropropane dianhydride (6FDA) and 2,2′-bis-(trifluoromethyl)biphenyl-4,4′-diamine (TFMB) with various polyhedral oligomeric silsesquioxane (POSS) contents and then subjected to thermal imidization. The hybrid films show good optical transparency (>80% at 400 nm and >95% at 500 nm) with cutoff wavelengths ranging from 318 to 336 nm. Following the incorporation of the inorganic POSS structure, the hybrid films exhibit excellent thermal stability with glass transition temperature (Tg) ranging from 351 to 372 °C. The hybrid films possess the highest Tg compared with the previously-reported shape memory polymers. These findings show that POSS is successfully utilized to develop transparent polyimides with excellent thermal stability and shape memory effect.

Colorless Partially Alicyclic Polyimides Based on Tröger’s Base Exhibiting Good Solubility and Dual Fluorescence/Phosphorescence Emission

This study proposes a molecular design and synthetic route to novel colorless, transparent polyimides that exhibit dual fluorescence/phosphorescence emission at long wavelengths applicable to solar...

Recent Trends on Transparent Colorless Polyimides with Balanced Thermal and Optical Properties: Design and Synthesis

AbstractRecently, colorless and transparent plastic substrates with high glass transition temperature and suitable thermo‐mechanical properties are in high demand in optoelectronic device industries, due to their various optical applications. Colorless polyimides (CPIs) exhibit both high thermo‐mechanical stability as well as high transparency that are suitable for optoelectronic applications. The most recent (2010–2018) developments on CPIs, in terms of design and synthesis of new monomers and their effects on the thermo‐optical properties of the obtained CPIs, are reviewed in this article.

Effects of γ-radiation on the performances of optically transparent shape memory polyimides with a low glass transition temperature

Recently, shape memory polyimides (SMPIs) with varying glass transition temperature (Tg) and optical transparency have been developed widely. While, rare reports were focused on the evaluation of the durability of SMPIs in the complex and volatile space environments. This paper presents the simulated γ-radiation accelerated experiment of two kinds of optically transparent SMPIs with a Tg of 178 °C and 196 °C, respectively. The effects of γ-radiation on chemical structure, optical transmittance, shape memory behavior, thermomechanical property, thermal stability, and mechanical properties were investigated. Although SMPIs have endured γ-radiation for 1 × 106 Gy, the chemical structure, Tg, optical transmittance, thermal stability, and the shape memory behavior remained unchanged. Also, SMPIs with a Tg of less than 200 °C could maintain their high tensile strengths and elongations at break (>109.5 MPa, >7.6%) after being exposed to 1 × 106 Gy γ-radiation, which shows great potential application in space active deformation structures and devices.

Biobased transparent polyimides with excellent solubility and mechanical properties using myo-inositol derived diamines

Here, we develope a kind of biobased transparent polyimides (PIs) with excellent solubility and mechanical properties by using myo-inositol derived diamines. Two biobased diamines M1 and M2 were synthesized through a protection reaction of –OH units of myo-inositol followed by the substitution and subsequent reduction reactions. Myo-inositol based PIs were prepared via the microwave-assisted polymerization of biobased diamines and commercial dianhydrides. These PIs were soluble in various common solvents even in CH2Cl2 and acetone at room temperature. The biobased PIs also showed good optical transparency with T450nm values of over 82%. Moreover, all the PI films possessed outstanding mechanical properties with tensile modulus of over 3.5 GPa, which was higher than that of most of petroleum-based PIs. In addition, the PI films containing –OH units were obtained via a simple deprotection reaction of myo-inositol based PIs.

Correlation of stress and optical properties in highly transparent polyimides for future flexible display

High transmittance and low birefringence are desirable optical properties in polyimide films which are promising flexible substrates in next generation display devices. However, thermal processes for the fabrication of polyimide films can cause anisotropic changes in the optical properties due to its rod-like molecular structure. Here we report the changes in optical retardation in transparent fluorinated polyimide films with sub-nanometer resolution and dimensional stability induced by deformation at high temperatures. As deformation is increased, the optical retardation is changed much prominently with enhancing thermo-dimensional stability. During thermal strain, in-plane molecular orientation is preferentially improved and stress-optical coefficient that quantifies the change in out of plane optical retardation is derived to be around 6×10–6 m2/N, which is higher compared to conventional plastic optical films. The experimental findings suggest that optimized process conditions for display substrates should be determined to address both changes in the optical and thermal stabilities. We suggest that this study can be useful information for large-scale film process to be further utilized in fabrication of the transparent polyimide films.

Highly transparent and soluble polyimides with synergistic effects of pyridine and cyclohexane

In order to prepare novel polyimides (PI) with high transparency and solubility in common solvents, three diamine monomers containing pyridine or methyl-substituted pyridine and cyclohexane, 1,1′-bis[4-(5-amino-2-pyridinoxy)phenyl]cyclohexane (IIIa), 1,1′-bis[4-(5-amino-3-methyl-2-pyridinoxy)phenyl]cyclohexane (IIIb), and 1,1′-bis[4-(5-amino-2-methyl-6-pyridinoxy)phenyl]cyclohexane (IIIc), were synthesized and characterized. The diamine monomer (IIIa) was subsequently polymerized with 3,3′,4,4′-oxydiphthalic anhydride, 4,4′-(hexafluoroisopropylidene)-diphthalic anhydride (6FDA) to obtain PIs, PI-1 and PI-2. Furthermore, PI-3 (IIIb/6FDA) and PI-4 (IIIc/6FDA) were prepared for structure–property comparison studies. The structures of the resulting PIs were characterized by fourier transform infrared spectroscopy (FT-IR), X-ray diffraction, and elemental analysis. The physical properties of the PI films were investigated by thermogravimetric analysis, differential scanning calorimetric analysis, dynamic mechanical analysis, and ultraviolet–visible spectroscopy. In general, the PIs showed excellent thermal properties and good mechanical properties. Most had good solubility in polar organic solvents such as N, N-dimethylacetamide, N, N-dimethylformamide, N-methylpyrrolidone (NMP), m-cresol, and even soluble in low boiling solvents such as tetrahydrofuran (THF) and CHCl3. The PI films also exhibited high optical transmittance of 94–97% at 500 nm and cut-off wavelength at 345–359 nm. In summary, the introduction of methyl, cyclohexane, and pyridine groups into the backbone was shown to improve the solubility and transparency of PI films.

Synthesis and properties of transparent polyimides derived from 1,4-cyclohexylene bis(trimellitate anhydride)

A series of polyimides (PIs) derived from 1,4-cyclohexylene bis(trimellitate anhydride) (TACH) was synthesized by conventional two-step method with chemical imidization. The resulting PIs had glass transition temperatures ( Tgs) in the range of 188–240°C and exhibited good mechanical properties with tensile strengths of 50.0–90.2 MPa, tensile moduli of 2.2–3.9 GPa, and elongations at break of 2.9–5.8%. These PI films showed high optical transparency with cut-off wavelengths of 345–369 nm and high transmittance at 500 nm with more than 84%. Compared with PIs derived from 1,4-bis(3,4-dicarboxyphenoxy)cyclohexane dianhydride, the TACH-based PIs showed higher Tg, better solubility, and competitive transparency.

High performance polyimides with good solubility and optical transparency formed by the introduction of alkyl and naphthalene groups into diamine monomers

Highly soluble and optically transparent polyimides with excellent thermal stability were prepared by the introduction of alkyl and naphthalene groups into a single diamine monomer under microwave-assisted polymerization.

Synthesis and characterization of organosoluble, transparent, and hydrophobic fluorinated polyimides derived from 3,3′-diisopropyl-4,4′-diaminodiphenyl-4′′-trifluoromethyltoluene

A novel aromatic fluorinated diamine monomer, 3,3′-diisopropyl-4,4′-diaminodiphenyl-4′′-trifluoromethyltoluene, was synthesized by coupling of 2-isopropylaniline and 4-(trifluoromethyl)benzaldehyde and its structure was confirmed by Fourier transform infrared spectroscopy, nuclear magnetic resonance, elemental analysis, and mass spectrometry, and then used to prepare a series of fluorinated polyimides (FPIs) by polycondensation reaction with various commercial dianhydrides via conventional one-step method. The obtained FPIs present excellent solubility in most organic solvents and enough to cast into tough and flexible films. All the FPI films show good optical transparency and light color with the cutoff wavelengths in range of 307–362 nm and the average transmittance above 86%. These polymer films also exhibit high glass transition temperature in range of 261–331°C and thermal stability with 10% weigh loss above 463°C under nitrogen atmosphere. Furthermore, they exhibit outstanding mechanical properties with tensile strengths of 65.9–94.3 MPa, elongation at break of 11.4–13.8%, Young’s modulus of 1.6–1.9 GPa, and low dielectric constants in range of 2.75–3.10 at 1 MHz as well as prominent hydrophobicity with the contact angle in the range of 87.3–93.9°.

Highly transparent and organosoluble polyimides derived from 2,2′-bis[4-(5-amino-2-pyridinoxy) phenyl] propane

Two new isomers containing pyridine ring diamine monomers, 2,2′-bis[4-(5-amino-2-pyridinoxy)phenyl] propane (1b) and 2,2′-bis[4-(6-amino-3-pyridinoxy)phenyl] propane (2b), were prepared via a simple nucleophilic reaction of 2-chloro-5-nitropyridine and 5-bromo-2-nitropyridine with bisphenol A in the presence of potassium carbonate, respectively. A series of polyimides (PIs) were obtained from the heterocyclic diamine with various commercially available aromatic dianhydrides via the conventional two-step method. These obtained PIs were investigated in aspects of their solubility, thermal, mechanical, and optical properties for studying the effects of the heteroaromatic rings into the main chain. At the same time, the impact of the two isomers introduced into the PI was discussed in detail.

Comparative study of transparent polyimides derived from bis(ether anhydride)s and bis(ester anhydride)s using 2,2′-bis(trifluoromethyl)biphenyl-4,4′-diamine

Two series of polyimides (PIs) derived from bis(ether anhydride)s and bis(ester anhydride)s using 2,2′-bis(trifluoromethyl)biphenyl-4,4′-diamine were synthesized via solution polycondensation. The poly(ether imide)s could be formed by the conventional one-step method, while the poly(ester imide)s were only afforded by the two-step procedure. The resulting PIs had glass transition temperatures ( Tgs) in the range of 224–320°C and exhibited good mechanical properties with tensile strength in the range of 80.5–96.5 MPa, tensile moduli 2.7–6.9 GPa, and elongations at break 1.5–17.3%. It was found that the PIs derived from bis(ether anhydride)s showed higher thermal stability, better solubility, and transparency but lower Tg and higher water absorption compared with bis(ester anhydride)-based PIs due to the different ether and ester linkages.

Design and synthesis of organosoluble and transparent polyimides containing bulky substituents and noncoplanar structures

ABSTRACTA new diamine monomer, 3,3′‐diisopropyl‐4,4′‐diaminophenyl‐4″‐phenyltouene, was designed, synthesized, and then polymerized with five commercial dianhydrides to obtain a series of novel polyimides via a one‐step method. The obtained polymers showed excellent solubility in most common solvents, even in low‐boiling solvents, such as chloroform, dichloromethane, and tetrahydrofuran. They exhibited a high thermal stability with the glass‐transition temperature in the range 262–318°C and 10% weight loss temperatures in the range 464–488°C under a nitrogen atmospheres. Meanwhile, these polymer films also displayed a high optical transparency with a cutoff wavelength in the range 305–365 nm; prominent mechanical properties with a tensile strength of 65.6–94.9 MPa, a Young's modulus of 1.6–2.8 GPa, and an elongation at break of 9.3–13.7%; a low dielectric constant in the range of 2.91–3.18 at 1 MHz; and an outstanding hydrophobicity with a contact angle above 90.6°. © 2015 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2016, 133, 43266.

Synthesis and characterization of novel highly soluble and optical transparent polyimides containing tert-butyl and morpholinyl moieties

A series of novel organo-soluble and optical transparent polyimides were synthesized via conventional one-step polycondensation from a novel diamine, 3,3′-diterbutyl-4,4′-diaminodiphenyl-4″-morpholinophenylmethane (TAMPM) and various commercial aromatic dianhydrides. The structures of monomer and polymers were confirmed by FT-IR and NMR. The solubility, thermal stability, optical transparency, dielectric and hydrophobic properties of polyimides were investigated. The results showed polymers presented excellent solubility in common organic solvents, such as N,N-dimethylformamide (DMF), N,N-dimethyl acetamide (DMAc), dimethyl sulfoxide (DMSO), N-methyl-2-pyrrolidone (NMP), chloroform (CHCl3), tetrahydrofuran (THF) and dichloromethane (CH2Cl2). The polymers exhibited prominent thermal stability and high optical transparency with the glass transition temperature (T g) in the range of 311–355 °C, and the cutoff wavelengths in the range of 287–344 nm. Furthermore, all of the polymers also presented low dielectric constants in the range of 2.85–3.16 at 1 MHz, and outstanding hydrophobic properties with the contact angle in the rang of 85.1–94.2 o.

Transparent Aromatic Polyimides Derived from Thiophenyl-Substituted Benzidines with High Refractive Index and Small Birefringence

2,2′-Bis(thiophenyl)benzidine (BTPB) and 2,2′-bis(4-chlorothiophenyl)benzidine (BCTPB) were synthesized via a benzidine rearrangement reaction of the corresponding hydrazobenzene derivatives obtained after the reduction of (3-nitrophenyl)(phenyl)sulfane and (4-chlorophenyl)(3-nitrophenyl)sulfane, respectively. Transparent polyimides (PIs) with high refractive indices and small birefringences as well as good thermomechanical stabilities were synthesized by the conventional two-step thermal polycondensation of BTPB and BCTPB with five different dianhydrides in N-methyl-2-pyrrolidone. 3,3′,4,4′-Biphenyltetracarboxylic dianhydride (BPDA)/BCTPB PI, a fully aromatic and non-fluorinated PI, with a highly distorted noncoplanar conformation of the main chain was transparent and colorless with a transmittance of ∼83% and >88% at 450 nm and in the visible region, respectively. In addition, all six non-fluorinated sulfur-containing aromatic PIs exhibited high average refractive indices (1.7112–1.7339), and small bire...

Synthesis and characterization of organosoluble and transparent polyimides derived from trans‐1,2‐bis(3,4‐dicarboxyphenoxy)cyclohexane dianhydride

ABSTRACTA novel dianhydride, trans‐1,2‐bis(3,4‐dicarboxyphenoxy)cyclohexane dianhydride (1,2‐CHDPA), was prepared through aromatic nucleophilic substitution reaction of 4‐nitrophthalonitrile with trans‐cyclohexane‐1,2‐diol followed by hydrolysis and dehydration. A series of polyimides (PIs) were synthesized from one‐step polycondensation of 1,2‐CHDPA with several aromatic diamines, such as 2,2′‐bis(trifluoromethyl)biphenyl‐4,4′‐diamine (TFDB), bis(4‐amino‐2‐trifluoromethylphenyl)ether (TFODA), 4,4′‐diaminodiphenyl ether (ODA), 1,4‐bis(4‐aminophenoxy)benzene (TPEQ), 4,4′‐(1,3‐phenylenedioxy)dianiline (TPER), 2,2′‐bis[4‐(3‐aminodiphenoxy)phenyl]sulfone (m‐BAPS), and 2,2′‐bis[4‐(4‐amino‐2‐trifluoromethylphenoxy)phenyl]sulfone (6F‐BAPS). The glass transition temperatures (Tgs) of the polymers were higher than 198°C, and the 5% weight loss temperatures (Td5%s) were in the range of 424–445°C in nitrogen and 415–430°C in air, respectively. All the PIs were endowed with high solubility in common organic solvents and could be cast into tough and flexible films, which exhibited good mechanical properties with tensile strengths of 76–105 MPa, elongations at break of 4.7–7.6%, and tensile moduli of 1.9–2.6 GPa. In particular, the PI films showed excellent optical transparency in the visible region with the cut‐off wavelengths of 369–375 nm owing to the introduction of trans‐1,2‐cyclohexane moiety into the main chain. © 2015 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2015, 132, 42317.

High transparent polyimides containing pyridine and biphenyl units: Synthesis, thermal, mechanical, crystal and optical properties

Two series of isomeric pyridine-containing aromatic diamine monomers, 2,2′-bis(5-amino-2-pyridinoxy)biphenyl (2a), 4,4′-bis(5-amino-2-pyridinoxy)biphenyl (2b), and 4,4′-bis(5-amino-6-methyl-2-pyridinoxy)biphenyl (2c), 4,4′-bis(5-amino-3-methyl-2-pyridinoxy)biphenyl (2d), 4,4′-bis(5-amino-4-methyl-2-pyridinoxy)biphenyl (2e) were successfully synthesized. Aimed at clarifying the structure-property relationships of containing pyridine and biphenyl high-performance polymers, polyimides PI-(1–5) were synthesized via a two-step thermal imidization derived from 2b and various commercially aromatic anhydrides and polyimide PI-(6–9) was synthesized derived from 2,2′-bis(3,4-dicarboxyphenyl) hexafluoropropane dianhydride (6FDA) and 2a, 2c, 2d and 2e. Furthermore, comparative studies on their properties including solubility, thermal and mechanical, optical properties, and crystalline were thoroughly performed. Some property differences of the isomers caused by the sequence changes were found.

Synthesis and characterization of transparent polyimides derived from ester-containing dianhydrides with different electron affinities

Transparent polyimides derived from ester-containing dianhydrides with different electron affinities were synthesis and the different properties caused by different ester linkages were well investigated.

Synthesis and properties of transparent polyimides derived from trans-1,4-bis(2,3-dicarboxyphenoxy)cyclohexane dianhydride

A series of transparent polyimides was prepared from trans-1,4-bis(2,3-dicarboxyphenoxy)cyclohexane dianhydride (trans-3,3′-CHDPA) with various aromatic diamines via one-step solution polycondensation.

Highly transparent polyimides derived from 2-phenyl-4,6-bis(4-aminophenoxy)pyrimidine and 1,3-bis(5-amino-2-pyridinoxy)benzene: preparation, characterization, and optical properties

Heterocyclic polyimides were prepared from two novel diamines with anhydrides, which exhibit outstanding solubility and optical transparency properties.