Synthesis and study of new polyamides with side oxadiazole rings

A series of six new aromatic polyamides with side oxadiazole rings has been synthesized by polycondensation reaction of aromatic diamines containing pendent substituted oxadiazole groups with a silicon‐containing diacid chloride [namely, bis(p‐chlorocarbonyl‐phenylene)diphenylsilane] or with a fluorine‐containing diacid chloride [namely, hexafluoroisopropylidene‐bis(p‐benzoyl chloride)]. All polymers were easily soluble in amidic solvents, such as N‐methylpyrrolidinone and dimethylformamide, and gave thin transparent films by casting such solutions. Very thin coatings were deposited onto silicon wafers and exhibited smooth, pinhole‐free surfaces in atomic force microscopy investigations. The polymers showed high thermal stability, with decomposition temperature >400°C. Some of them did exhibit a glass transition, in the range 152–276°C, with a reasonable interval between glass transition and decomposition. Four of these polymers showed blue photoluminescence, in the range 460–480 nm, which makes them promising candidates for future use as high‐performance materials in the construction of light‐emitting devices. © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 87: 714–721, 2003     

Thermal and electrical properties of copoly(1,3,4‐oxadiazole‐ethers) containing fluorene groups

A series of aromatic copolyethers containing 1,3,4‐oxadiazole rings and fluorene groups was prepared by nucleophilic substitution polymerization technique of 9,9‐bis(4‐hydroxyphenyl)fluorene, 1 , or of different amounts of 1 and an aromatic bisphenol, such as 4,4′‐isopropylidenediphenol or phenolphthalein, with 2,5‐bis(p‐fluorophenyl)‐1,3,4‐oxadiazole. The polymers were easily soluble in polar solvents like N‐methylpyrrolidone, N,N‐dimethylacetamide, N,N‐dimethylformamide, and chloroform and can be cast from solutions into thin flexible films. They showed high thermal stability, with decomposition temperature being above 425°C. The polymers exhibited a glass‐transition temperature in the range of 195–295°C, with a reasonable interval between glass‐transition and decomposition temperature. Electrical insulating properties of some polymer films were evaluated on the basis of dielectric constant and dielectric loss and their variation with frequency and temperature. The values of the dielectric constant at 10 kHz and 20°C were in the range of 3.16–3.25. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2009     

Synthesis and properties of polyimides containing bisphenol unit and flexible ether linkages

A series of novel polyimides was prepared from various diamines (with bisphenol units) and various aromatic tetracarboxylic dianhydrides via a two‐step (thermal imidization) method. The monomers and polymers were produced in high yields. The benzophenone series exhibited better solubility than the pyromellitic series and, especially, those with the alkyl (methyl)‐substituted ring exhibited good solubility and could be readily dissolved in polar aprotic solvents such as dimethylformamide and N,N′dimethylacetamide. The glass transition temperatures of all polyimides were found to be 235–322 and 223–332°C, respectively, by DSC and dynamic mechanical analysis. Thermogravimetric analyses indicated that the polymers were fairly stable up to 482–617°C (10 wt % loss in N₂) and 480–610°C (10 wt % loss in air). Wide‐angle X‐ray diffractograms revealed that most polyimides were predominantly amorphous. © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 87: 945–952, 2003     

Synthesis and characterization of organo‐soluble polyimides derived from a new spirobifluorene diamine

Polyimides exhibit outstanding thermal and thermo‐oxidative stability, excellent solvent resistance, good mechanical and electrical properties and superior chemical resistance. However, their practical applications are frequently limited by their infusible and insoluble nature. Structural modifications of the polymer backbone have been utilized to modify polyimide properties, either by reducing the interaction or by reducing the stiffness of the polymer backbone. Novel organo‐soluble polyimides containing spirobifluorene units were synthesized by the polycondensation of 2,7‐bis‐amino‐2′,7′‐di‐t‐butyl‐9,9′‐spirobifluorene with three aromatic dianhydrides. The one‐step polymerization procedure was conducted at 200 °C in m‐cresol, and the structures of the resulting polyimides were confirmed using infrared and NMR spectroscopy. The weight‐average molecular weights and polydispersities of the resulting polymers were in the ranges 20 600–341 000 and 1.02–1.30, respectively. The glass transition temperatures of the polyimides were in the range 289–322 °C, and the 10% weight loss in nitrogen appeared at a temperature higher than 435 °C and the residual weight at 800 °C was above 58%. The spiro segment has been introduced into polyimides, resulting in amorphous polyimides, conferring on them an enhanced solubility and leading to a significant increase in both glass transition temperature and thermal stability. These types of materials have potential for many applications. Copyright © 2010 Society of Chemical Industry     

Preparation and properties of melt‐processable polyimides based on fluorinated aromatic diamines and aromatic dianhydrides

Two series of melt‐processable polyimides were prepared from 4,4′‐bis(3‐amino‐5‐trifluoromethylphenoxy)biphenyl (m‐6FBAB) and 4,4′‐bis(4‐amino‐5‐trifluoromethylphenoxy) biphenyl (p‐6FBAB) with various aromatic dianhydrides. The effects of the chemical structures of the polyimides on their properties, especially the melt processability and organic solubility, were investigated. The experimental results demonstrate that some of the fluorinated aromatic polyimides showed good melt processability at elevated temperatures (250–360°C) with relatively low melt viscosities and could be melt‐molded to produce strong and tough polyimide sheets. Meanwhile, the polyimides showed excellent organic solubility in both polar aprotic solvents and common solvents to give stable polyimide solutions with high polymer concentrations and relatively low viscosities. Thus, we prepared high‐quality polyimide films by casting the polyimide solutions on glass plates followed by baking at relatively low temperatures. The polyimides derived from m‐6FBAB showed better melt processability and solubility than the p‐6FBAB based polymers. The melt‐processable polyimides showed a good combination of thermal stability and mechanical properties, with decomposition temperatures of 547–597°C, glass‐transition temperatures in the range 205–264°C, tensile strengths of 81.3–104.9 MPa, and elongations at break as high as 19.6%. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci, 2008     

Synthesis and properties of silicon-containing polyamides

A series of aromatic polyamides incorporating silicon together with phenylquinoxaline or with hexafluoroisopropylidene groups has been synthesized by solution polycondensation of a silicon-containing diacid chloride with aromatic diamines having phenylquinoxaline rings or hexafluoroisopropylidene groups. These polymers are easily soluble in polar aprotic solvents, such as N-methylpyrrolidinone and dimethylformamide, and in tetrahydrofurane, and can be solution-cast into thin, transparent films having low dielectric constant, in the range of 3.26 to 3.68. These polymers show high thermal stability with decomposition temperature being above 400°C and glass transition temperature in the range of 236°C to 275°C. © 1997 John Wiley & Sons, Inc. J Appl Polym Sci 65:1533–1538, 1997     

Synthesis,characterization, and structure-property relationships of aromatic polyimides containing 4,4′-diaminotriphenylmethane

This work reports two series of structurally different aromatic polyimides based on 4,4´-diaminodiphenylmethane (DPM) and 4,4´-diaminotriphenylmethane (TPM) and three commercial dianhydrides. All TPM-based polyimides formed membranes due to their high molecular weight (inherent viscosities ~0.93–1.14 dl/g), they exhibited high thermal stability (5 %: 490–544 °C), glass transition temperatures between 269 and 293 °C, and reasonable mechanical properties. The incorporation of pendant phenyl moieties in the TPM-based polyimides has a strong effect producing an improvement in solubility, thermal stability, density and gas permeability coefficient in comparison with DPM-based polyimides. The most interesting polyimide TPM-6FDA, containing phenyl and trifluoromethyl as bulky pendant groups, showed higher gas permeability coefficient for CO₂ (23.73 Barrer) and the best ideal selectivity to the gas pair CO₂/CH₄ (α = 28.93).     

Polyimides from isomeric biphenyltetracarboxylic dianhydrides and the effects of chemical structure on solubility

A series of homopolyimides and copolyimides was synthesized by the solution condensation of biphenyltetracarboxylic dianhydride (BPDA) isomers and various diamines followed by chemical imidization. These polyimides had intermediate to high molecular weights with inherent viscosities of 0.34–1.01 dL/g for homopolyimides and 0.48–1.02 dL/g for copolyimides. Thermogravimetric analysis indicated that the aromatic polyimides were stable up to 500°C, and the 5% weight loss temperatures were recorded in the range of 506–597°C in an air atmosphere and in the range of 517–601°C in a nitrogen atmosphere, depending on the diamines used. The glass transition temperatures of aromatic homopolyimides were above 271°C, while the glass transition temperatures of the copolyimides increased with an increase in the 2, 2′, 3, 3′‐BPDA‐component. The effects of the chemical structure of the polymer chain on the solubility were investigated. It was found that the solubility of BPDA‐based polyimides could be improved by the introduction of flexible units, nonlinear and non‐coplanar units, and copolymerization. The polyimides with nonlinear and non‐coplanar units derived from 2, 2′, 3, 3′‐BPDA appeared to have prominently enhanced solubility in polar aprotic solvents and polychlorocarbons when compared with the homopolyimide derived from 3, 3′, 4, 4′‐BPDA.     

One-step synthesis of aromatic polyimides based on 4,4′-diaminotriphenylmethane

The feasibility of using a one-step high-temperature polycondensation for the synthesis of aromatic polyimides, based on 4,4′-diaminotriphenylmethane (DA-TPM), was studied. It was found that the reaction of DA-TPM with various aromatic dianhydrides in nitrobenzene at 180–200°C resulted in the formation of the high molecular weight soluble polyimides, PI-TPM. The reaction solutions cooled to ambient temperature were used for casting films. These PI-TPM films significantly exceeded their prototypes obtained by the thermal imidization of poly(amic acids) in terms of solubility and tensile properties. All studied polyimides demonstrated well-distinguished glass transition at 260–320°C. © 1996 John Wiley & Sons, Inc.     

Polyimides based on furanic diamines and aromatic dianhydrides: synthesis,characterization and properties

Novel polyimides containing furan moieties were prepared from the resulting furanic diamine monomers with various aromatic dianhydrides including 1,2,4,5-benzene-tetracarboxylic dianhydride, 3,3′,4,4′-biphenyltetracarboxylic dianhydride, 4,4′-oxydiphthalic anhydride, and hexafluoroisopropylidene 2,2-bis(phthalic anhydride), via a two-step process. The resulting polyimides were characterized by solubility tests, viscosity measurements, FTIR, ¹H NMR spectroscopy, differential scanning calorimetric (DSC), and thermogravimetric analysis (TGA) analysis. The polyimides with inherent viscosities in the range of 0.048–0.095 L/g showed excellent solubility in aprotic amide and organic solvents, such as N,N-dimethylacetamide, N-methyl-2-pyrrolidinone, dimethylformamide and acetone, chloroform, etc. DSC showed glass transition temperatures (T _g) in the range of 116–143 °C. These polymers showed excellent thermal stability up to 390 °C.     

Synthesis and properties of novel soluble and high Tg poly(ether imide)s from diamine containing 4,5‐diazafluorene and trifluoromethyl units

The synthesis and properties of soluble, high T_g and transparent aromatic polyimides containing 4,5‐diazafluorene and trifluoromethyl units in the polymer backbone on the basis of a novel diamine monomer, 9,9‐di[4‐(4‐amino‐2‐trifluoromethyl phenoxy)phenylene]‐4,5‐diazafluorene, are described. Incorporation of 4,5‐diazafluorene and trifluoromethyl groups into rigid polyimides improves their solubility and transparency without decreasing their physical properties. All of the thermal imidization polyimides are soluble at room temperature in aprotic and protic polar solvents such as N,N‐dimethylacetamide, N,N′‐dimethylformamide, dimethylsulfoxide, pyridine and m‐cresol and can be solution cast into transparent, flexible and tough films. These films have a UV–visible absorption cutoff wavelength at 386–407 nm and light transparencies of 73%–84% at a wavelength of 550 nm. In addition, the polymers exhibit high thermal stability with a glass transition temperature (T_g) of 305 to 362 °C and 5% weight loss at temperatures ranging from 525 to 543 °C in nitrogen and from 521 to 538 °C in air. The polyimide films possess tensile strengths in the range 79 ? 113 MPa, a tensile modulus of 1.75 – 2.10 GPa and elongations at break of 7% ? 16%. © 2014 Society of Chemical Industry     

Synthesis and properties of novel polyimides from 3‐(4‐aminophenylthio)‐N‐aminophthalimide

A novel, asymmetric diamine, 3‐(4‐aminophenylthio)‐N‐aminophthalimide, was prepared from 3‐chloro‐N‐aminophthalimide and 4‐aminobenzenethiol. The structure of the diamine was determined via IR and ¹H‐NMR spectroscopy and elemental analysis. A series of polyimides were synthesized from 3‐(4‐aminophenylthio)‐N‐aminophthalimide and aromatic dianhydrides by a conventional two‐step method in N,N‐dimethylacetamide and by a one‐step method in phenols. These polyimides showed good solubility in 1‐methyl‐2‐pyrrolidinone, m‐cresol, and p‐chlorophenol, except polyimide from pyromellitic dianhydride, which was only soluble in p‐chlorophenol. The 5% weight loss temperatures of these polyimides ranged from 460 to 498°C in air. Dynamic mechanical thermal analysis indicated that the glass‐transition temperatures of the polyimides were in the range 278–395°C. The tensile strengths at break, moduli, and elongations of these polyimides were 146–178 MPa, 1.95–2.58 GPa, and 9.1–13.3%, respectively. Compared with corresponding polyimides from 4,4′‐diamiodiphenyl ether, these polymers showed enhanced solubility and higher glass‐transition temperatures. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2008     

A study on the preparation and properties of alicyclic polyimides based on 3-carboxylmethylcyclopentane–1,2,4-tricarboxylic acid dianhydride

Alicyclic polyimides were prepared from 3-carboxylmethyl-cyclopentane–1,2,4-tricarboxylic acid dianhydride and conventional aromatic diamines. These polyimides possess good solubility in strong polar solvents, such as N-methyl pyrrolidone, N,N-dimethyl acetamide, N,N-dimethyl formamide, and m-cresol. They are transparent and colorless. The glass transition temperatures are about 181°C, and the initial thermal decomposition temperatures in N₂ were observed to be 441–477°C. © 1998 John Wiley & Sons, Inc. J Appl Polym Sci 67:2105–2109, 1998     

Fast and eco‐friendly synthesis of novel soluble thermally stable poly(amide‐imide)s modified with siloxane linkage with reduced dielectric constant under microwave irradiation in TBAB,TBPB and MeBuImCl via isocyanate method

A new series of poly(amide‐imide)s (PAI) modified with a siloxane linkage was synthesized under microwave radiation in ionic liquids and organic salts via the isocyanate method. The polymerization reactions of a novel siloxanic diacid monomer with 4,4′‐methylene‐bis(4‐phenylisocyanate) MDI were studied in ammonium, phosphonium, and imidazolium‐type organic salts. These poly(amide‐imide‐siloxane)s (PAI‐Si)s were obtained with high yields and good inherent viscosities ranging from 0.30 to 0.55 dL/g. The normally high softening temperatures and poor solubility of PAIs in organic solvents were improved via the incorporation of the flexible siloxane segments into the polymer backbone. The PAI‐Sis showed glass transition temperatures around 100°C and their 10% mass loss was about 300°C. They have a char yield in the range of 30–40% at 800°C. Calculated limiting oxygen index values of the polymers were about 30; therefore, they can be considered as self‐extinguishing. The dielectric constants of these silane‐containing PAIs (2.5) are lower than common siloxane‐free polyimides (～ 3). Their good thermal stability, enhanced solubility, and low dielectric constants suggest they may function as electrical insulators. © 2012 Wiley Periodicals, Inc. J. Appl. Polym. Sci., 2013     

Synthesis and properties of photoluminescent copolymer containing 1,3,4‐oxadiazole and carbazole rings

The luminescent copolymer 2‐phenyl‐5‐[3′‐(methacrylamido)phenyl]‐1,3,4‐oxadiazole and vinylcarbazole (PMAPO–VCZ), combining hole‐facilitating moiety, carbazole ring, and electron‐facilitating moiety, 1,3,4‐oxadiazole, as side groups, was synthesized by a radical polymerization of the olefinic monomer PMAPO and VCZ. For comparison, the homopolymer P‐PMAPO was also synthesized by similar procedures. The solubility, thermal, and optical properties of the copolymers were investigated. The synthesized copolymer was soluble in common organic solvents but the homopolymer of PMAPO was dissolved only by hot THF. Thermogravimetric analysis and differential scanning calorimetry measurements showed that the copolymer and homopolymer exhibit good thermal stability up to 360 and 340°C with glass‐transition temperatures higher than 105 and 65°C, respectively. The photoluminescence properties were investigated. The results showed that the copolymer emits blue and blue‐green light and the emission spectra of monomer and polymers exhibit obvious solvent effect. With the increase of polarity of solvents, the fluorescence spectra distinctly change, appearing with a red shift at room temperature. The concentration‐dependent emission spectra change significantly with the increase of concentration. In addition, when N,N‐dimethylaniline (DMA) was gradually added to the solution of copolymers, the emission intensity of fluorescence was dramatically increased. However, when the concentration of DMA was increased beyond a certain level, the emission intensity of fluorescence gradually decreased. © 2004 Wiley Periodicals, Inc. J Appl Polym Sci 92: 2777–2783, 2004     

Thermomechanical characterization of thermoplastic polyimides containing 4,4'‐methylenebis(2,6‐dimethylaniline) and polyetherdiamines

In this work, we synthesized polyimides by incorporating an aromatic diamine monomer with a methylene linker, 4,4'‐methylenebis(2,6‐dimethylaniline) (MBDMA), to make a robust main chain along with aliphatic polyetherdiamine backbone linkers to reduce rigidity. We designed the polymers to exhibit thermal properties in between those of conventional aromatic polyimides and polymers with wholly aliphatic ether diamine links. Through dynamic mechanical analysis and differential scanning calorimetry, it is shown that control of the molar ratios of the aromatic MBDMA (4,4'‐methylenebis(2,6‐dimethylaniline)) and the composition and size of the aliphatic polyetherdiamine can be used to tune the glass transition. The polymers were characterized by GPC, FTIR, NMR, thermomechanical and calorimetric analysis, and microhardness testing. POLYM. ENG. SCI., 59:221–232, 2019. © 2018 Society of Plastics Engineers     

Synthesis and characterization of nonlinear optical side-chain polyimides containing the thiadiazole chromophores

Thermally stable second-order nonlinear optical (NLO) polyimides were synthesized using a standard condensation polymerization technique. The polyimides were prepared from 4,4′-(hexafluoroisopropylidene)diphthalic anhydride (6FDA) and pyromellitic dianhydride (PMDA) with two aromatic azo- and diazo-diamine derivatives as the NLO chromophores. The resulting polyimides were characterized by FTIR, ¹H-NMR, UV-vis spectroscopies, differential scanning calorimetry, thermogravimetric analysis, and gel permeation chromatography. The weight-average molecular weights of polyimides determined by gel permeation chromatography (GPC) were in the range of 32,100 to 39,300 (M_w/M_n = 1.58–1.74). All the polyimides exhibited an excellent solubility in many of the aprotic polar organic solvents, manifesting that these polyimides offer good processability. The glass transition temperature for the resulting polyimides was in the range of 152 to 194°C and most of them showed high thermal stability. Particularly, the polyimides containing diazo group and PMDA backbone showed an enhanced thermal stability and glass transition temperature. The second harmonic generation (SHG) coefficients (d₃₃) of the poled polyimide films range from 43.71 to 80.49 pm/V at 532 nm. Further, it is noticed that there was no SHG decay below 180°C because of the partial main-chain character of the polyimide structure, which is acceptable for nonlinear optical device applications. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2012     

Fabrication and characterization of soluble,high thermal,and hydrophobic polyimides based on 4‐(3,5‐dimethoxyphenyl)‐2,6‐bis(4‐aminophenyl)pyridine

A novel aromatic diamine monomer, 4‐(3,5‐dimethoxyphenyl)‐2,6‐bis(4‐aminophenyl)pyridine (DPAP) was successfully synthesized by 4′‐nitroacetophenone and 3,5‐dimethoxybenzaldehyde as raw material. The structure of DPAP was confirmed by Fourier transform infrared, nuclear magnetic resonance, and mass analysis. A series of polyimides (PIs) were obtained by polycondensation with various dianhydrides via the conventional two‐step method. These PIs showed good solubility in organic solvents. They also presented high thermal stability, the glass transition temperatures (T_g) of polymers were in the range of 325–388 °C, and the temperature at 10% weight loss was in the range of 531–572 °C. Furthermore, these polymers also exhibited outstanding hydrophobicity with the contact angles in the range of 89.1°–93.5°. Moreover, the results of wide‐angle X‐ray diffraction (WAXD) confirmed these polymers showed amorphous structure. © 2017 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2018 , 135, 45827.     

Transparent and organosoluble cardo polyimides with different trans/cis ratios of 1,4‐diaminocyclohexane via aromatic nucleophilic substitution polymerization

Two series of cardo polyimides were prepared from 1,4‐bis(4‐fluorophthalimide)cyclohexane with different trans/cis ratios and phenolphthalein/o‐cresolphthalein via aromatic nucleophilic substitution reaction. The inherent viscosities of the synthesized polymers were found to be 0.55–0.66 dL g^?1 in N,N′‐dimethylacetamide. The cardo polyimides showed excellent solubility in organic solvents, high glass transition temperatures (T_g) of 275–312 °C and moderate thermal stability with 5% weight loss temperatures (T_d5%) of 415–441 °C in nitrogen and 370–436 °C in air. The polyimide films exhibited high optical transparency with cut‐off wavelengths of 350–355 nm and moderate mechanical properties. The different properties of the polymers caused by trans and cis configurations of 1,4‐diaminocyclohexane were also investigated. It was found that with an increasing content of trans configuration of 1,4‐diaminocyclohexane in the polyimide backbone, T_g of the polyimides increased as well as T_d5%, while the solubility gradually decreased. The polyimide films had good optical transparency regardless of trans/cis configuration. © 2018 Society of Chemical Industry     

Investigations on the polyimides derived from unfunctionalized symmetric cyclopentyl‐containing alicyclic cardo‐type dianhydride

This study presents an investigation on polyimides derived from a unfunctionalized symmetric cyclopentyl‐containing alicyclic cardo‐type dianhydride with ester linkage 1,1‐bis(4‐(3,4‐dicarboxylbenzoyloxy)phenyl)cyclopentylene dianhydride (BDPCP) that was readily accessed starting from cyclopentanone through two steps in high yield. Two series of polyimides, Cardo‐type series (CPI‐x) and analogous aromatic series (ArPI‐x) were prepared from condensation of BDPCP and aromatic 3,3′,4,4′‐Oxydiphthalic dianhydride with four aromatic diamines, respectively. Comparative studies revealed that CPI polymers show more favorable properties including better solubility in organic solvents, higher transparency with lower cut‐off wavelength (λ₀) ranging in 395–375 nm than 425–405 nm, lower water absorption ranging in 0.66–1.14% and surface energy 23.71–32.77 mN/m than 1.01–1.28% and 29.52–41.99 mN/m of ArPI analogs. Meanwhile, CPI series exhibit considerable mechanical properties with tensile strengths ranging in 87.6–102.9 MPa, elongations at break 6.6–8.9%. Owing to the moderate strain in cyclopentyl ring, CPI series retain good thermal properties with the glass transition temperature (T_g) in the range of 217–271°C. Dynamic dielectric measurement revealed that Cardo‐type dianhydride BDPCP endows CPI‐4 film with lower dielectric constant (ε′) 3.34 at 1 MHz and 25°C and dielectric loss (ε′′) 0.0064 at 1 kHz and 25°C than 3.49 and 0.013 for ArPI‐4 film. © 2015 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2015 , 132, 42670.