Organosoluble and light-colored fluorinated polyimides from 4-tert-butyl-[1,2-bis(4-amino-2-trifluoromethylphenoxy)phenyl]benzene and aromatic dianhydrides

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 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°.

Morphology and properties of porous polyimide films prepared through thermally induced phase separation

Porous polyimide (PI) synthesized from 4,4′-oxydiphthalic anhydride (ODPA) and 4,4′-diaminodiphenyl ether (ODA) monomers is a promising material with an ultralow-dielectric constant.

Effects of tert-butyl substitutes of fluorinated diamine on the properties of polyimides

To investigate the effect of tert-butyl substitutes on the properties of fluorinated polyimides (PIs), 1,4-bis(4-amino-2-trifluoromethylphenoxy)benzene (1), 1,4-bis(4-amino-2-trifluoromethylphenoxy)-2- tert-butylbenzene (2), and 1,4-bis(4-amino-2-trifluoromethylphenoxy)-2,5-di- tert-butylbenzene (3), which were synthesized in this study. Three series of organosoluble and light-colored PIs were synthesized from 1, 2, and 3 with four dianhydrides 1,2,3,4-cyclobutanetetracarboxylic dianhydride (CBDA), pyromellitic dianhydride, 3,3′,4,4′-biphenyl tetracarboxylic dianhydride, and 4,4′-oxydiphthalic anhydride and prepared through a typical two-step polymerization method. These obtained PIs with tert-butyl substituents were soluble in amide polar solvents and even in less polar solvents. The glass transition temperatures ( Tg) of PIs with two tert-butyl substitutes can be reached at 327.7°C, and the 5% weight loss temperatures of PI derived from CBDA were lowest at 439.7°C. These PI films had cutoff wavelengths between 301.2 and 400.0 nm and the transparency at 450 nm between 43.0 and 86.2%. Compared with diamine 1, we found that the introduction of tert-butyl side group of the diamine improved the solubility and Tg of PIs, but decreased the optical transmittance and thermal stability of PIs.

Synthesis and characterization of highly soluble and optically transparent polyimides derived from novel fluorinated pyridine-containing aromatic diamine

A novel fluorinated pyridine-containing aromatic diamine monomer, 4-phenyl-2,6-bis[2-(4-amino-2-trifluoromethyphenoxy)phenyl]pyridine ( o, p-6FPAPP), was prepared in a three-step synthetic route. This aromatic diamine was then employed to synthesize a series of fluorinated pyridine-containing polyimides (PIs) by polycondensation with various aromatic dianhydrides via the conventional two-step method. The inherent viscosities of the resulting poly(amic acid)s (PAAs) and PIs were in the range of 0.71–0.89 and 0.62–0.84 dL/g; all the PIs obtained by chemical imidization were readily soluble in common organic solvents such as N, N-dimethylformamide (DMF), N, N-dimethylacetamide (DMAc), N-methyl-2-pyrrolidone (NMP), dimethyl sulfoxide (DMSO), tetrahydrofuran (THF) and so on. Meanwhile, transparent, strong and flexible PI films were obtained, which had good thermal stability, with the glass transition temperature ( Tg) of 195.2°C–232.7°C, the temperature at 10% weight loss of 530.2°C–546.0°C in nitrogen atmosphere, and good optical transparency with the cutoff wavelengths of 354–382 nm, as well as outstanding mechanical properties with tensile strengths of 96.4–105.8 MPa, tensile modulus of 1.57–1.88 GPa and elongations at break of 9.5%–13.4%. The PI films were also found to possess low water uptake of 0.52%–0.67%.