Preparation and properties of novel fluorinated polyimides based on 2,2′,6,6′-tetrafluorobenzidine

Fluorinated polyimides were prepared from 2,2′,6,6′-tetrafluorobenzidine and four conventional dianhydride monomers by a solution polycondensation reaction followed by a chemical imidization. Polyimide based on 2,2′,6,6′-tetrafluorobenzidine and hexafluoroisopropylidene bis(3,4-phthalic anhydride) (6FDA) is soluble in organic solvents such as NMP, DMA, DMF, THF, chloroform, and acetone while those based on 2,2′,6,6′-tetrafluorobenzidine and pyromellitic dianhydride (PMDA), benzophenone-3,3′,4,4′-tetracarboxylic acid dianhydride (BTDA), diphenylether-3,3′,4,4′-tetracarboxylic acid dianhydride (ETDA) are not. Polyimide from 2,2′,6,6′-tetrafluorobenzidine and 6FDA possesses high optical transparency at 350–700 nm and has a in-plane refractive index of 1.558 at 632.8 nm. All polyimides exhibit glass transition temperatures above 350°C. They also possess very high thermal stability. © 1998 John Wiley & Sons, Inc. J Appl Polym Sci 70: 1605–1609, 1998     

Preparation and properties of organo‐soluble polyimides based on 4,4′‐diamino‐3,3‐dimethyldiphenylmethane and conventional dianhydrides

4,4′‐Diamino‐3,3′‐dimethyldiphenylmethane was used to prepare polyimides in an attempt to achieve good organo‐solubility and light color. Polyimides based on this diamine and three conventional aromatic dianhydrides were prepared by solution polycondensation followed by chemical imidization. They possess good solubility in aprotonic polar organic solvents such as N‐methyl 2‐pyrrolidone, N,N‐dimethyl acetamide, and m‐cresol. Polyimide from 4,4′‐diamino‐3,3′‐dimethyldiphenylmethane and diphenylether‐3,3′,4,4′‐tetracarboxylic acid dianhydride is even soluble in common solvents such as tetrahydrofuran and chloroform. Polyimides exhibit high transmittance at wavelengths above 400 nm. The glass transition temperature of polyimide from 4,4′‐diamino‐3,3′‐dimethyldiphenylmethane and pyromellitic dianhydride is 370°C, while that from 4,4′‐diamino‐3,3′‐dimethyldiphenylmethane and diphenylether‐3,3′,4,4′‐tetracarboxylic acid dianhydride is about 260°C. The initial thermal decomposition temperatures of these polyimides are 520–540°C. © 1999 John Wiley & Sons, Inc. J Appl Polym Sci 72: 1299–1304, 1999     

2,2′,6,6′-Tetrabromo-3,3′,5,5′-tetramethyl-4,4′-biphenol (TTB)–flame retardant copolycarbonates and copolyesters

2,2′,6,6′-Tetrabromo-3,3′,5,5′-tetramethyl-4,4′-biphenol (TTB) is a new flame retardant monomer possessing a high degree of chemical and thermal stability. This brominated biphenol can be directly incorporated as a comonomer in condensation polymerizations. An example is the preparation of copolycarbonates of TTB and 2,2-(4-hydroxyphenyl)propane (BPA) via the aqueous caustic phosgenation method. The reaction of TTB with either ethylene oxide or ethylene chlorohydrin affords 4,4′-bis(2-hydroxyethoxy)-2,2′,6,6′-tetrabromo-3,3′,5,5′-tetramethylbiphenyl (TTB-Diol). This diol is melt polymerized into a series of terephthalate copolymers with 1,4 butanediol. The above copolymers possess flame retardancy, thermal stability, and good mechanical properties. These high-bromine-content copolymers are blended with nonhalogen-containing polymers to afford blends with specific degrees of flame resistance.     

Preparation of novel copoly(bis[4‐(3‐aminophenoxy)phenyl]sulfone/ 3,3′,4,4′‐benzophenonetetracarboxyl/ pyromellite)imide derivatives

Copolyimide derivatives were prepared from two carboxylic dianhydrides [3,3′,4,4′‐benzophenone tetracarboxylic dianhydride (BTDA) and pyromellitic anhydride (PMDA)] and a single diamine (bis[4‐(3‐aminophenoxy)phenyl]sulfone [BAPS]) following one‐step polymerization. Copolymers could be arranged in sequence through different molar ratios of dianhydride compounds. These polymers were characterized by viscosity, thermal and mechanical properties, solubility, etc. To understand the behavior of the properties, according to the ratio of the dianhydride compound, a copolymer having various properties could be obtained. Further, it was proved that their properties could be determined from the compositions. The solubility of copolyimides with a large molecular weight was moderately improved. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 88: 853–859, 2003     

Preparation and properties of novel processable polyimides derived from N,N‐bis(isocyanatoalkyl)‐1,2,4,5‐benzenetetracarboxylic‐1,2:4,5‐diimides

Two diisocyanate monomers containing methylene groups and built‐in imide structure have been prepared from the parent diacids via the Curtius–Weinstock rearrangement. Polyimides have been synthesized by solution polymerization of these isocyanates with pyromellitic dianhydride (PMDA), 3,3′,4,4′‐benzophenonetetracarboxylic dianhydride (BTDA), and hexafluoroisopropylidene‐2,2‐bis(phthalic‐anhydride) (6FDA). All monomers and polymers were characterized by conventional methods, and the physical properties of the polymers, including solution viscosity, solubility, thermal stability and thermal behaviour, were studied. © 2000 Society of Chemical Industry     

Resistive switching characteristics of polyimides derived from 2,2′‐aryl substituents tetracarboxylic dianhydrides

2,2′‐Position aryl‐substituted tetracarboxylic dianhydrides including 2,2′‐bis(biphenyl)‐4,4′,5,5′‐biphenyl tetracarboxylic dianhydride and 2,2′‐bis[4‐(naphthalen‐1‐yl)phenyl)]‐4,4′,5,5′‐biphenyl tetracarboxylic dianhydride were synthesized. A new series of aromatic polyimides (PIs) were synthesized via a two‐step procedure from 3,3′,4,4′‐biphenyl tetracarboxylic dianhydride and the newly synthesized tetracarboxylic dianhydrides monomers reacting with 2,2′‐bis[4′‐(3″,4″,5″‐trifluorophenyl)phenyl]‐4,4′‐biphenyl diamine. The resulting polymers exhibited excellent organosolubility and thermal properties associated with T_g at 264 °C and high initial thermal decomposition temperatures (T_5%) exceeding 500 °C in argon. Moreover, the fabricated sandwich structured memory devices of Al/PI‐a/ITO was determined to present a flash‐type memory behaviour, while Al/PI‐b/ITO and Al/PI‐c/ITO exhibited write‐once read‐many‐times memory capability with different threshold voltages. In addition, Al/polymer/ITO devices showed high stability under a constant stress or continuous read pulse voltage of ? 1.0 V. Copyright © 2011 Society of Chemical Industry     

Organosoluble polyimides derived from asymmetric 2‐substituted‐and 2,2′,6‐trisubstituted‐4,4′‐oxydianilines

We report a new method for the preparation of asymmetric diamines using 4,4′‐oxydianiline (4,4′‐ODA) as the starting material. By controlling the equivalents of bromination agent, N‐bromosuccinimide, we were able to attach bromide and phenyl substituents at the 2‐ or 2,2′,6‐positions of 4,4′‐ODA. Thus, four new asymmetric aromatic diamines, 2‐bromo‐4,4′‐oxydianiline (6), 2,2′,6‐tribromo‐4,4′‐oxydianiline (7), 2‐phenyl‐4,4′‐oxydianiline (8) and 2,2′,6‐triphenyl‐4,4′‐oxydianiline (9), were synthesized by this method. Their structural asymmetry was confirmed using ¹H NMR spectroscopy. Asymmetric polyimides (PI10–PI13) were prepared from these diamines and three different dianhydrides (pyromellitic dianhydride (PMDA), 3,3′,4,4′‐biphenyltetracarboxylic dianhydride and 2,2‐bis(3,4‐dicarboxyphenyl)hexafluoropropane dianhydride) in refluxing m‐cresol. The formed polyimides, except PI10a derived from 6 and PMDA, were all soluble in m‐cresol without premature precipitation during polymerization. These polyimides with inherent viscosity of 0.41–0.96 dL g^?1, measured at a concentration of 0.5 g dL^?1 in N‐methyl‐2‐pyrrolidone at 30 °C, can form tough and flexible films. Because of the structural asymmetry, they also exhibited enhanced solubility in organic solvents. Especially, polyimides PI11a and PI13a derived from 7 and 9 with rigid PMDA were soluble in various organic solvents at room temperature. The structural asymmetry of the prepared polyimides was also evidenced from ¹H NMR spectroscopy. In the ¹H NMR spectrum of PI11a, the protons of pyromellitic moiety appeared in an area ratio of 1:2:1 at three different chemical shifts, which were assigned to head‐to‐head, head‐to‐tail and tail‐to‐tail configurations, respectively. These polyimides also exhibited good thermal stability. Their glass transition temperatures ranged from 297 to 344 °C measured using thermal mechanical analysis. © 2013 Society of Chemical Industry     

Morphology of polyimide fibers derived from 3,3′,4,4′‐biphenyltetracarboxylic dianhydride and 4,4′‐oxydianiline

As one member of high performance fibers, aromatic polyimide fibers possess many advantages, such as high strength, high modulus, high and low temperature resistance, and radiation resistance. However, the preparation of the high performance fibers is so difficult that the commercial fibers have not been produced except P84 with good flame retardancy. In this report, a polyimide was synthesized from 3,3′,4,4′‐biphenyltetracarboxylic dianhydride (BPDA) and 4,4′‐oxydianiline (ODA) and the fibers were prepared from its solution by a dry‐jet wet‐spinning process. The formation of the as‐spun fibers in different coagulation bath composition was discussed. Scanning electron microscope (SEM) was employed to study the morphology of the as‐spun fibers. As a result, the remnant solvent existed in the as‐spun fibers generated from coagulation bath of alcohol and water. There were many fibrils and microvoids with the dimension of tens of nanometers in the fibers. One could observe the obvious fibrillation and the drawn fibers. The measurement for the mechanical properties of the fibers with a drawing ratio of 5.5 indicated that tensile strength and initial modulus were 2.4 and 114 GPa, respectively. © 2004 Wiley Periodicals, Inc. J Appl Polym Sci 93: 669–675, 2004     

Synthesis and properties of new aromatic polyimides based on 2,2′‐dibromo‐4,4′,5,5′‐benzophenone tetracarboxylic dianhydride

New polyimides with enhanced thermal stability and high solubility were synthesized in common organic solvents from a new dianhydride, 2,2′‐dibromo‐4,4′,5,5′‐benzophenone tetracarboxylic dianhydride (DBBTDA). DBBTDA was used as monomer to synthesize polyimides by using various aromatic diamines. The polymers were characterized by IR and NMR spectroscopy and elemental analysis. These polyimides had good inherent viscosities in N‐methyl‐2‐pyrrolidinone (NMP) and also high solubility and excellent thermo‐oxidative stability, with 5 % weight loss in the range 433 to 597 °C. Copyright © 2004 Society of Chemical Industry     

Soluble and light‐colored polyimides from 2,3,2′,3′‐oxydiphthalic anhydride and aromatic diamines

A series of polyimides were prepared from 2,3,2′,3′‐oxydiphthalic anhydride (3,3′‐ODPA) with various aromatic diamines via three different synthetic procedures. The one‐step and two‐step methods with the thermal imidization of poly(amic acids) (PAAs) yielded polyimides with a relatively low inherent viscosity; these produced brittle films. The polyimides prepared by the two‐step method via the chemical imidization of PAA precursors exhibited a higher inherent viscosity and afforded tough and creaseable films. All the 3,3′‐ODPA based polyimides had a significantly higher solubility than the corresponding polyimides from 3,4,3′,4′‐oxydiphthalic anhydride. The films cast from 3,3′‐ODPA polyimides also showed high optical transparencies and less color, with an ultraviolet–visible absorption edge of 370–397 nm and low yellowness index values of 11.3–29.8. These polyimides exhibited glass‐transition temperatures in the range 211–289°C and showed no significant decomposition below 500°C under nitrogen or air atmospheres. © 2005 Wiley Periodicals, Inc. J Appl Polym Sci 97: 1352–1360, 2005     

Synthesis of pyrrones based on the reduction and cyclization of their o-nitrosubstituted polyimides precursors

Pyrrones derived from 1,2,4,5-tetraaminobenzene and pyromellitic dianhydride or 3,3′,4,4′-benzophenonetetracarboxylic dianhydride were prepared by catalytic reduction and cyclization of the poly(o-nitro)imides, obtained by polycondensation of 1,3-dichloro-4,6-dinitrobenzene with the dipotassium salt of pyromellitic diimide or 3,3′,4,4′-benzophenonetetracarboxylic diimide. These polymers were characterized by slightly better thermal stability as compared with the polymers of the same structure obtained by conventional methods. The model compound for these polymers has been also synthesized by catalytic reduction and cyclization of 1,3-bis(phthalimido)-4,6-dinitrobenzene.     

Synthesis and characterization of aromatic/cycloaliphatic poly(amide‐ imide‐imide)s from bis(4‐amino‐ 3,5‐dimethylphenyl) cycloalkane derivatives

A series of novel aromatic diamines containing cycloaliphatic moieties was synthesized by the reaction of cycloalkanones like cyclohexanone and cycloheptanone with 2,6‐dimethylaniline. The tetrimide diacid was synthesized using the prepared diamine with 3,3′,4,4′‐benzophenonetetracarboxylic acid dianhydride/pyromellitic dianhydride and p‐aminobenzoic acid. The polymers were prepared by treating the tetrimide diacid with different aromatic diamines. The structures of the monomers and polymers were identified using elemental analysis and Fourier transform infrared, ¹H NMR and ¹³C NMR spectroscopy. The polymers show excellent solubility. The polymers are amorphous and have high optical transparency. They also show good thermal stability and their T_g value is found to be in the range 268–305 °C. Copyright © 2007 Society of Chemical Industry     

Synthesis of 3,3′-Bis(2,2′,4,4′,6,6′-Hexanitortilbene)

This paper describes the synthesis of 3,3′bis(2,2′,4,4′,6,6′-hexanitrostilbene) (5). Based on the Ullmann reaction we prepared the title compound in nitrobenzene by using 3-chloro 2,2′,4,4′,6,6′-hexanitroztilbene (4) as the starting material and copper powder as the catalyst. (4) was reacted with hydrazine, not to yield a desired product, azo-3,3′bist(2,2′,4,4′,6,6′-hexanitrostilbene.) but to form a well-known explosive, 2,2′,4,4′,6,6′-hexanitrostibene (6). Differential scanning calorimetrical analysis has shown that (5) begins to decompose at the temperature of 298°C.     

Preparation of poly(amic acid) and polyimide derived from 3,3′,4,4′‐benzophenonetetracarboxylic dianhydride with different diamines by microwave irradiation

Polycondensation‐type poly(amic acid) (PAA) was synthesized with 3,3′,4,4′‐benzophenonetetracarboxylic dianhydride as a dianhydride monomer and 4,4′‐diaminodiphenylmethane and 4,4′‐oxydianiline as diamine monomers under microwave irradiation in dimethylformamide. Then, PAA was used to make polyimide (PI) by imidization at a low temperature. The structure and performance of the polymers were characterized with Fourier transform infrared (FTIR), proton nuclear magnetic resonance (¹H‐NMR), viscosity, X‐ray diffraction (XRD), and thermogravimetry (TG) curve analyses. The FTIR spectra of the polymers showed characteristic peaks of PI around 1779 and 1717 cm^?1. The ¹H‐NMR spectrum of PAA indicated a singlet at 6.55 ppm assigned to ? NHCO? and a singlet at 10.27 ppm assigned to carboxylic acid protons. The XRD spectrum demonstrated that the obtained PI had a low‐order aggregation structure with a d‐spacing of 0.5453 nm. The TG results revealed that the PI was thermally stable with 10% weight loss at 565°C in an N₂ atmosphere. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci 2008     

Novel poly(thiourea‐ether‐imide)s derived from 4,4′‐oxydiphenyl‐bis(thiourea): probing the possibility for high‐temperature applications

Our interest in the fabrication of high‐performance polyimides has led to thiourea‐substituted poly(thiourea‐ether‐imide)s (PTEIs) with good retention of thermal properties along with flame retardancy. A new aromatic monomer, 4,4′‐oxydiphenyl‐bis(thiourea) (ODPBT), was efficiently synthesized and polymerized with various dianhydrides (pyromellitic dianhydride, 3,3′,4,4′‐benzophenonetetracarboxylic dianhydride and 4,4′‐(hexafluoroisopropylidene)diphthalic dianhydride) via two‐stage chemical imidization to fabricate a series of PTEIs. The structural characterization of ODPBT and the polymers was carried out using Fourier transform infrared, ¹H NMR and ¹³C NMR spectral techniques along with crystallinity, organosolubility, inherent viscosity and gel permeation chromatographic measurements. PTEIs bearing C?S and ? O? moieties in the backbone demonstrated an amorphous nature and were readily soluble in various amide solvents. The novel polymers had inherent viscosities of 1.16–1.23 dL g^?1 and molecular weights of ca 90 783–96 927 g mol^?1. Their thermal stability was substantiated via 10% weight loss in the temperature range 516–530 °C under inert atmosphere. The polyimides had glass transition temperatures of 260–265 °C. Incorporation of thiourea functionalities into polymer backbones is demonstrated to be an effective way to enhance their thermal properties and flame retardancy. Thus, ODPBT can be considered as an excellent candidate for use in the synthesis of high‐performance polymeric materials. Copyright © 2010 Society of Chemical Industry     

Microwave‐assisted and conventional polycondensation reaction of optically active N,N′‐(4,4′‐sulphonediphthaloyl)‐bis‐L‐leucine diacid chloride with aromatic diamines

3,3′,4,4′‐Diphenylsulfonetetracarboxylic dianhydride ( 1 ) was reacted with L‐leucine ( 2 ) in acetic acid and the resulting imide‐acid ( 3 ) was obtained in high yield. The diacid chloride ( 4 ) was prepared from diacid derivative ( 3 ) by reaction with thionyl chloride. The polycondensation reaction of diacid chloride ( 4 ) with several aromatic diamines such as 4,4′‐sulfonyldianiline ( 5a ), 4,4′‐diaminodiphenyl methane ( 5b ), 4,4′‐diaminodiphenylether ( 5c ), p‐phenylenediamine ( 5d ), m‐phenylenediamine ( 5e ), 2,4‐diaminotoluene ( 5f ), and 1,5‐diaminonaphthalene ( 5g ) was developed by using a domestic microwave oven in the presence of a small amount of a polar organic medium such as o‐cresol. The polymerization reactions were also performed under two conventional methods: low temperature solution polycondensation in the presence of trimethylsilyl chloride, and a short period reflux conditions. A series of optically active poly(amide‐imide)s with inherent viscosity of 0.25–0.42 dL/g were obtained with high yield. All of the above polymers were fully characterized by IR, elemental analyses, and specific rotation techniques. Some structural characterizations and physical properties of these optically active poly (amide‐imide) s are reported. © 2004 Wiley Periodicals, Inc. J Appl Polym Sci 91: 2992–3000, 2004     

Preparation and characterization of 3,3′,4,4′-benzophenone tetracarboxylic dianhydride-pyromellitic diahydride alternating polyimides

Four kinds of 3,3′,4,4′-benzophenone tetracarboxylic dianhydride (BTDA)-pyromelliitic dianhydride (PMDA) alternating polyimide (BTDA-PMDA API) were obtained by reacting 1 mol BTDA with 2 mol diamines to form BTDA chain-extended diamines (BTDA CED), followed by the addition of 1 mol PMDA to yield the BTDA-PMDA alternating polyamic acids (BTDA-PMDA APA), and finally by imidizing them thermally. BTDA CED were characterized by elemental analysis, infrared (IR), and ¹H-NMR spectroscopy. The structures of BTDA-PMDA APA and BTDA-PMDA API were investigated by IR and ¹H-NMR spectroscopy, and their thermal properties and interfacial tension were also studied. Furthermore, the characteristic properties of BTDA-PMDA API were compared with their corresponding homopolyimides from BTDA (BTDA HPI) and from PMDA (PMDA HPI). It was found that the alternating condensation polymerization is an effective method to modify polyimides interfacial tension with a small influence on the thermal stability. © 1997 John Wiley & Sons, Inc. J Appl Polym Sci 64: 1585–1593, 1997     

Synthesis of 3′,4′‐disubstituted terthiophenes. Characterization and electropolymerization. I. 3′,4′‐dibromo‐2,2′:5′,2″‐terthiophene in photovoltaic display

Recent studies on conducting polymers have demonstrated that polymers of 3‐substituted thiophene produce very stable compounds. Although this kind of substitution improves the regularity, structural defects still exist. To overcome this drawback, the polymerization of 3,4‐disubstituted thiophene is proposed as a convenient way of synthesizing regular, highly conjugated conductive polymers. Our interest is thus focused on the synthesis of tetra‐substituted thiophene derivatives, their polymerization, electrochemical properties, spectral characteristics, oxidizing potential, and the feasibility of photocells development. In this article, we report the synthesis and characterization of 3′,4′‐dibromo‐2,2′:5′,2″‐terthiophene which, as such or modified, may be a good starting product for obtaining new monomers of 3′,4′‐disubstituted terthiophenes, that would allow the effect of the substituents on the properties of the respective polymers to be studied. In addition, the monomer was electropolymerized and the resulting deposit was electrochemically and morphologically characterized. Two conclusions were drawn: first, more uniform and homogeneous layers than those of polythiophene are obtained; second, the thin layers of the polymer, electron acceptors, absorb in the visible. Finally, photocells were assembled to investigate their photovoltaic effect. Although the so prepared solar cells showed some photovoltaic effect, the yield was low.© 2006 Wiley Periodicals, Inc. J Appl Polym Sci 102: 5314–5321, 2006     

Viscosity temperature relationship for dilute solutions of poly[2,2′-(alkylene-arylene)-5,5′-bibenzimidazolyl]

Various copolymers having benzimidazole rings along with alkylene and arylene groups in the backbone were prepared from 3,3′-diaminobenzidine tetrahydrochloride dihydrate and dicarboxylic acids in polyphosphoric acid. The viscosities of these polymers in concentrated sulphuric acid (98%) have been determined at 30, 40 and 50°C. There is no systematic variation in the value of K′ (Huggins constant) with temperature. Values of Q and A in the expression η = A exp(Q/RT) were obtained for these polymer samples in H₂SO₄. On the basis of the ‘A’ values, it has been concluded that most of these polymers were stiff chains with the exception of those containing cis-vinylene groups in the backbone.     

Proton Conducting Membranes Based on Poly(2,2′‐imidazole‐5,5′‐bibenzimidazole)

Poly(2,2′‐imidazole‐5,5′‐bibenzimidazole) (PBI‐imi) was synthesized via the polycondensation between 3,3′,4,4′‐tetraaminobiphenyl and 4,5‐imidazole‐dicarboxylic acid. Effects of the reaction conditions on the intrinsic viscosity of the synthesized polymers were studied. The results show that the molecular weight of the polymers increases with increasing monomer concentration and reaction time, and then levels off. With higher reaction temperature, the molecular weight of the polymer is higher. With the additional imidazole group in the backbone, PBI‐imi shows improved phosphoric acid doping ability, as well as a little higher proton conductivity when compared with widely used poly[2,2′‐(m‐phenylene)‐5,5′‐bibenzimidazole] (PBI‐ph).Whereas, PBI‐imi and PBI‐ph have the similar chemical oxidation stability. PBI‐imi/3.0 H₃PO₄ composite membranes exhibit a proton conductivity as high as 10^–4 S cm^–1 at 150 °C under anhydrous condition. The temperature dependence of proton conductivity of acid doped PBI‐imi can be modeled by an Arrhenius equation.