Preparation and characterization of organosoluble polyimides based on 1,1-bis[4-(3,4-aminophenoxy)phenyl]cyclohexane and commercial aromatic dianhydrides

A bis(ether amine) III-A containing a cyclohexane cardo group, 1,1-bis[4-(4-aminophenoxy)phenyl]cyclohexane, was synthesized and used as a monomer to prepare polyimides VI-A with six commercial dianhydrides via three different procedures. The intermediate poly(amic acid)s had inherent viscosities of 0.83–1.69 dL g⁻¹ and were thermally or chemically converted into polyimides. Polyimides were also prepared by high-temperature direct polymerization in m-cresol and had inherent viscosities higher than the thermally or chemically cyclodehydrated ones. To improve the solubility of polyimides, six copolyimides were also synthesized from bis(ether amine) III-A with a pair of dianhydrides, which contained 3,3′,4,4′-diphenylsulfonetetracarboxylic dianhydride or 4,4′-hexafluoroisopropylidenediphthalic anhydride. Series VI-A polyimides were characterized by the good physical properties of their film-forming ability, thermal stability, and tensile properties. A comparative study of the properties, with the corresponding polyimides derived from 2,2-bis[4-(4-aminophenoxy)phenyl]propane, is also presented. © 2001 John Wiley & Sons, Inc. J Appl Polym Sci 82: 2750–2759, 2001     

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     

Synthesis and characterization of calix[4]arene‐containing polyimides

Three types of amino‐functionalized calixarenes, i.e. the diaminocalix[4]arenes 5,17‐diaminomethyl‐25,26,27,28‐tetrapropoxycalix[4]arene, 25,27‐diaminoethoxy‐26,28‐dihydroxycalix[4]arene and 5,11,17,23‐tetra‐tert‐butyl‐25,27‐diaminoethoxy‐26,28‐dihydroxycalix[4]arene, were synthesized and incorporated as comonomers into the backbones of aromatic polyimides. As a first step, polyimide precursors (poly(amic acid)s) were prepared by condensation reaction of diamine with dianhydride at the stoichiometric ratio. The diamine component was composed of synthesized diaminocalix[4]arene and commercial 4,4′‐oxydianiline combined in various molar ratios. The dianhydride used was 4,4′‐oxydiphthalic anhydride. The poly(amic acid)s were characterized using intrinsic viscosity measurements and their chemical composition was determined using ¹H NMR spectroscopy. The precursors were then transformed into the polyimides using a thermal treatment. Thermal and dynamic mechanical behaviour, wide‐angle X‐ray diffraction and solubility of the resulting polyimide films in selected solvents were evaluated. The structure–property relationship of the novel types of synthesized polyimides is discussed in terms of the calixarene monomer used and the fraction of it incorporated into the polymer backbone. Copyright © 2010 Society of Chemical Industry     

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

A 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 (T_gs) of the polymers were higher than 198°C, and the 5% weight loss temperatures (T_d5%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.     

Synthesis,characterization, and gas permeability of aromatic polyimides containing pendant phenoxy group

A diamine containing a pendant phenoxy group, 1-phenoxy-2,4-diaminobenzene, was synthesized and condensed with different aromatic dianhydrides [4,4′-oxydiphthalic dianhydride, 4,4′-(hexafluoroisopropylidene)diphthalic anhydride, 3,3′,4,4′-benzophenone tetracarboxylic dianhydride, 3,3′,4,4′-biphenyltetracorboxylic dianhydride, and pyromellitic dianhydride] by one-step synthesis at a high temperature in m-cresol to obtain polyimides in high yields. Most of the polyimides exhibited good solvent solubility and could be readily dissolved in chloroform, sym-tetrachloroethane, N,N-dimethylformamide, N,N-dimethylacetamide, and nitrobenzene. Their inherent viscosities were in the range of 0.33–1.16 dL/g. Wide-angle X-ray spectra revealed that these polymers were amorphous in nature. All these polyimides were thermally stable, having initial decomposition temperatures above 500°C and glass-transition temperatures in the range of 248–281°C. The gas permeability of 4,4′-oxydiphthalic dianhydride and 4,4′-(hexafluoroisopropylidene)diphthalic anhydride based polyimides was investigated with pure gases: He, H₂, O₂, Ar, N₂, CH₄, and CO₂. A polyimide containing a  C(CF₃)₂ linkage showed a good combination of permeability and selectivity. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci 2008     

Synthesis and property measurements of polyimides with substituted pyromellitic dianhydride for flexible printed circuits applications

Pyromellitic dianhydride‐based dianhydrides with bulky substituents, such as 1‐phenyl pyromellitic dianhydride and 1‐(4′‐trifluoromethylphenyl)pyromellitic dianhydride, were combined with bis(3‐aminophenyl)phenylphosphine oxide and 4,4′‐phenylene diamine to prepare polyimides with low coefficient of thermal expansion (～ 17 ppm/°C) and good adhesion (>100 g/mm). The polyimides were synthesized via a conventional two‐step process: preparation of poly(amic‐acid) followed by solution imidization with o‐dichlorobenzene. The molecular weights of the polyimides were controlled to 25,000 g/mol via off‐stoichiometry and the synthesized polyimides were characterized by Fourier transform infrared, nuclear magnetic resonance, differential scanning calorimetry, and thermogravimetric analysis. Their intrinsic viscosity and solubility were also measured, while adhesive property was measured via T‐peel test samples of Cu/polyimide. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2010     

Synthesis and memory characteristics of polyimides containing noncoplanar aryl pendant groups

A series of soluble aromatic polyimides were prepared from 2,2′-diphenyl-4,4′-biphenyl diamine (DPBD), 2,2′-bis(biphenyl)-4,4′-biphenyl diamine (BBPBD), 2,2′-bis[4-(naphthalen-1-yl)phenyl]-4,4′-biphenyl diamine (BNPBD) and 2,2′-bis(3,5-dimethoxyphenyl)-4,4′-biphenyl diamine (BMPBD) by polycondensation with 2,2′-bis[4′-(3′′,4′′,5′′-trifluorophenyl)phenyl]-4,4′,5,5′-biphenyl tetracarboxylic dianhydride via a two-step procedure. The resulting polymers were fully characterized and they exhibited excellent organosolubility, high thermal and dimensional stability. Resistive switching devices with the configuration of Al/polymer/ITO were constructed from these polyimides by using conventional solution coating process. Devices with the active layer based on DPBD, BBPBD and BNPBD exhibited nonvolatile and rewritable flash type memory characteristics with the turn-on voltage at ?2.0 to ?3.0 V and the turn-off voltage at 2.0–3.0 V. Whereas, device based on BMPBD demonstrated a bipolar write-once read-many times (WORM) memory capability with the writing voltage around ±3.0 V. The ON/OFF current ratio of these devices was of about 10⁶ and the retention times can be as long as 10⁴ s.     

Structural effects of pendant groups on thermal and electrical properties of polyimides

Two series of aromatic polyimides containing various‐sized alkyl side groups were synthesized by thermal imidization of the poly(amic acid)s prepared from the polyaddition of benzophenonetetracarboxylic dianhydride and hexafluoro‐isopropylidene bis(phthalic anhydride) with 4,4′‐methylenedianiline, 4,4′‐methylene‐bis(2,6‐dimethylaniline), 4,4′‐methylene‐bis(2,6‐diethylaniline), and 4,4′‐methylene‐bis(2,6‐diisopropylaniline). The extent to which alkyl substitutes affect the thermal properties of polyimides was examined by differential scanning calorimetry, thermomechanical analyzer, and thermogravimetric analysis techniques. The analytical results demonstrated that the incorporation of alkyl moieties causes a moderate increase in the coefficient of thermal expansion and a slight decrease in thermal stability. Notably, all polymers had a decomposition temperature exceeding 500°C. The glass transition temperature increases markedly when hydrogen atoms at ortho positions on aniline rings are replaced with methyl groups, but decreases with growing alkyl side group size. The dielectric measurements show that the polymer possessing a large alkyl side group would have the lower dielectric value. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 100: 4672–4678, 2006     

Adhesion property of novel polyimides containing fluorine and phosphine oxide moieties

Novel diamine monomers containing fluorine and phosphine oxide - bis(3-aminophenyl)-3,5-bis(trifluoromethyl)phenyl phosphine oxide (mDA6FPPO) and bis(3-aminophenyl)-4-(trifluoromethyl)phenyl phosphine oxide (mDAFPPO) - were utilized to prepare polyimides with dianhydrides such as 6FDA, BTDA or ODPA by the conventional two-step route, i.e. preparation of poly(amic acid) followed by solution imidization. The polyimides were characterized by FT-IR, NMR, DSC, and intrinsic viscosity measurements. The adhesion property of the polyimides was evaluated via a peel test with bare Cu foil, as well as silane/Cr-coated Cu foil, and failure surfaces were analyzed by SEM/EDX to elucidate the failure mechanism. The results were compared with those from the polyimides prepared from bis(3-aminophenyl)phenyl phosphine oxide (mDAPPO) containing only the phosphine oxide moiety, 1,1-bis(4-aminophenyl)-1-phenyl-2,2-trifluoroethane (3FDAm) containing only the fluorine moiety, and a commercial 3,3′-diaminodiphenylsulfone (mDDS). The polyimides with 3FDAm exhibited the highest T _g, followed by the mDAPPO-, mDA3FPPO-, and mDA6FPPO-based polyimides, but the mDAPPO-based polyimides exhibited the highest adhesion properties, followed by mDA3FPPO, mDA6FPPO, mDDS, and 3FDAm, which is attributed to the phosphine oxide and fluorine moieties.     

Synthesis and properties of flourine-containing polyimides

A series of new flourine-containing polyimides have been synthesized from the condensation of 2,2,-bis[4-(4-aminophenoxy)phenyl]propane, 2,2-bis[4-(4-amino-phenoxy)phenyl]-1,1,1,3,3,3-hexafluoropropane, or 2,2bis[4-(4-amino-2-trifluoro-methylphenoxy)phenyl]-1,1,1,3,3,3-hexafluoropropane with various aromatic dianhydrides. The electric constant at 1 KHz in the flourine-containing polyimides decreases from 3.51 to 2.72 as flourine content increases. The poly(amic acid)s had inherit viscosities of 0.52–1.23 dL/g, depending on the diamines and dianhydrides. Most of the resulting polymers showed an amorphous nature and afforded flexible and tough films. The amount of moisture absorption decreases as flourine content in polyimides increases. The glass transition temperatures of these polyimides were in the range of 287–328°C, and the 10% weight loss temperatures were above 542°C in the nitrogen. © 1997 John Wiley & Sons, Inc. J Appl Polym Sci 66: 609–617, 1997     

Adhesion property of novel polyimides with 1‐[3′,5′‐bis(trifluoromethyl)phenyl] pyromellitic dianhydride

Novel polyimides were synthesized from 1‐[3′,5′‐bis(trifluoromethyl)phenyl] pyromellitic dianhydride (6FPPMDA) by a conventional two‐step process: the preparation of poly(amic acid) followed by solution imidization via refluxing in p‐chlorophenol. The diamines used for polyimide synthesis included bis(3‐aminophenyl)‐3,5‐bis(trifluoromethyl)phenyl phosphine oxide, bis(3‐aminophenyl)‐4‐trifluoromethylphenyl phosphine oxide, and bis(3‐aminophenyl)phenyl phosphine oxide. The synthesized polyimides were designed to have a molecular weight of 20,000 g/mol by off‐stoichiometry and were characterized by Fourier transform infrared, NMR, differential scanning calorimetry, and thermogravimetric analysis. In addition, their intrinsic viscosity, solubility, water absorption, and coefficient of thermal expansion (CTE) were also measured. The adhesion properties of the polyimides were evaluated via a T‐peel test with bare and silane/Cr‐coated Cu foils, and the failure surfaces were investigated with scanning electron microscopy. The 6FPPMDA‐based polyimides exhibited high glass‐transition temperatures (280–299°C), good thermal stability (>530°C in air), low water absorption (1.46–2.16 wt %), and fairly low CTEs (32–40 ppm/°C), in addition to good adhesion properties (83–88 g/mm) with silane/Cr‐coated Cu foils. © 2005 Wiley Periodicals, Inc. J Appl Polym Sci 96: 1801–1809, 2005     

Highly refractive polyimides containing pyridine and sulfur units: synthesis and thermal,mechanical, solubility and optical properties

Two series of isomers containing pyridine and sulfur unit aromatic diamine monomers, 4,4′‐bis(5‐amino‐2‐pyridinylsulfanyl)diphenyl sulfide ( 2a ), 4,4′‐bis(6‐amino‐3‐pyridinylsulfanyl)diphenyl sulfide ( 2b ) and 4,4′‐bis(5‐amino‐6‐methyl‐2‐pyridinylsulfanyl)diphenyl sulfide ( 2c ), 4,4′‐bis(5‐amino‐4‐methyl‐2‐pyridinylsulfanyl)diphenyl sulfide ( 2d ), were designed and synthesized. Aimed at clarifying the structure–property relationships of pyridine‐ and sulfur‐containing high refractive polymers, 2a was polymerized with various dianhydrides to prepare polyimides PI ‐1?PI ‐7 and 2b , 2c , 2d were reacted with 4,4′‐[p ‐thiobis(phenylenesulfanyl)]diphthalic anhydride to prepare polyimides PI ‐8?PI ‐10. The polyimides showed excellent optical properties with average refractive indices ranging from 1.7006 to 1.7620 and birefringence as low as 0.0056. Meanwhile, comparative studies on their properties including solubility, thermal and mechanical, and optical transparency properties were performed. Some property differences of the isomers caused by the sequence changes were found. © 2017 Society of Chemical Industry     

Synthesis and characterization of soluble random copolyimides

Random copolyimides with different proportions of a diamine component were prepared by polymerizing different compositions of diamines with various dianhydrides and imidized thermally to 260°C. The imidization percent of poly(amic acid) was characterized at various temperatures by infrared spectroscopy. The homopolyimide based on bis[4‐(3‐aminophenoxy)phenyl]sulfone and pyromellitic dianhydride was the only one soluble. By changing the compositions of bis[4‐(3‐aminophenoxy)phenyl]sulfone and other diamines with pyromellitic dianhydride in N‐methyl‐2‐pyrrolidone, soluble random copolyimides could be prepared. By random copolymerization, the thermal properties and viscosities of homopolyimide could be controlled. All the soluble polyimides prepared in this work were amorphous because of the lack of stereoregularity. © 1999 John Wiley & Sons, Inc. J Appl Polym Sci 74: 272–277, 1999     

Synthesis and characterization of novel soluble pyridine‐containing polyimides based on 4‐phenyl‐2,6‐bis[4‐(4‐aminophenoxy)phenyl]‐pyridine and various aromatic dianhydrides

A new kind of pyridine‐containing aromatic diamine monomer, 4‐phenyl‐2,6‐bis[4‐(4‐aminophenoxy)phenyl]‐pyridine (PAPP), was successfully synthesized by a modified chichibabin reaction of benzaldehyde and a substituted acetophenone, 4‐(4‐nitrophenoxy)‐acetophenone (NPAP), followed by a reduction of the resulting dinitro compound 4‐phenyl‐2,6‐bis[4‐(4‐nitrophenoxy)phenyl]‐pyridine (PNPP) with Pd/C and hydrazine monohydrate. The aromatic diamine was employed to synthesize a series of new pyridine‐containing polyimides by polycondensation with various aromatic dianhydrides in N‐methy‐2‐pyrrolidone (NMP) via the conventional two‐step method, i.e., ring‐opening polycondensation forming the poly (amic acid)s and further thermal or chemical imidization forming polyimides. The inherent viscosities of the resulting polyimides were in the range of 0.79–1.13 dL/g, and most of them were soluble in common organic solvents such as N,N‐dimethylacetamide (DMAc), NMP, and tetrahydrofuran (THF), etc. Meanwhile, strong and flexible polyimide films were obtained, which had good thermal stability, with the glass transition temperatures (T_g) of 268–338°C and the temperature at 5% weight loss of 521–548°C in air atmosphere, as well as outstanding mechanical properties with tensile strengths of 89.2–112.1 MPa and elongations at break of 9.5–15.4%. The polyimides also were found to possess low dielectric constants ranging from 2.53 to 3.11. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci 104: 212–219, 2007     

Preparation and properties of soluble copolysulfoneimide and performance of solvent‐resistant ultrafiltration membrane

Soluble copolysulfoneimides were synthesized by thermal two‐step method in solution of N‐methyl‐2‐pyrrolidone. The used aromatic diamines were bis[4‐(3‐aminophenoxy)phenyl]sulfone (BAPS‐m) and 3,3′‐diaminosulfone, and dianhydrides were pyromellitic dianhydride, 4,4′‐oxyphthalic anhydride, and 3,3′,4,4′‐diphenylsulfone tetracarboxylic dianhydride. The molar ratio of diamines was changed to reduce the content of BAPS‐m. The thermal and mechanical properties of polyimides were investigated. The polyimide ultrafiltration membrane with molecular weight cut‐off of 10 kDa could be successfully prepared by phase‐inversion method. Various solvent (water, alcohols, acetone, and hexane) fluxes were measured to investigate solvent‐resistance and membrane behavior during solvent permeation. The activation energy relationship between hexane flux and viscosity with temperature was also studied. © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 85: 1024–1030, 2002     

Synthesis and thermal,mechanical and gas permeation properties of aromatic polyimides containing different linkage groups

Two series of aromatic polyimides containing various linkage groups based on 2,7‐bis(4‐aminophenoxy)naphthalene or 3,3′‐dimethyl‐4,4′‐diaminodiphenylmethane and different aromatic dianhydrides, namely 4,4′‐(4,4′‐isopropylidenediphenoxy)bis(phthalic anhydride), 4,4′‐(hexafluoroisopropylidene)bis(phthalic anhydride), 3,3′,4,4′ benzophenonetetracarboxylic dianhydride, 9,9‐bis[4‐(3,4‐dicarboxyphenoxy)phenyl]fluorene dianhydride and 4,4′‐(4,4′‐hexafluoroisopropylidenediphenoxy)bis(phthalic anhydride), were synthesized and compared with regard to their thermal, mechanical and gas permeation properties. All these polymers showed high thermal stability with initial decomposition temperature in the range 475–525 °C and glass transition temperature between 208 and 286 °C. Also, the polymer films presented good mechanical characteristics with tensile strength in the range 60–91 MPa and storage modulus in the range 1700–2375 MPa. The macromolecular chain packing induced by dianhydride and diamine segments was investigated by examining gas permeation through the polymer films. The relationships between chain mobility and interchain distance and the obtained values for gas permeability are discussed. © 2014 Society of Chemical Industry     

Preparation and Properties of Cyano-Containing Polyimide Films Based on 2,6-Bis(4-aminophenoxy)- benzonitrile

Summary A series of cyano-containing polyimides were synthesized from 2,6-bis(4-amino- phenoxy)benzonitrile and some aromatic dianhydride monomers by solution polycondensation. The poly(amic acid) films could be obtained by solution-cast from N-methyl-2-pyrrolidinone solutions and thermally converted into tough polyimide films. Structure and physical properties of thin films of those polyimides were measured by FTIR, TGA, dynamic mechanical analysis and LCR hitester et al. Results showed that the polyimides prepared from 2,6-bis(4-aminophenoxy)- benzonitrile and 2,2-bis[4-(3,4-dicarboxyphenoxy)phenyl]propane dianhydride or 4,4’-(hexafluoropropylidene)diphthalic anhydride exhibited more excellent energy-damping characteristic and excellent solubility in NMP, DMF, DMAc, DMSO, THF and CHCl₃, whereas the polyimides from 2,6-bis(4-aminophenoxy)benzonitrile and 3,3’,4,4’-biphenyltetracarboxylic dianhydride or Pyromellitic dianhydride were insoluble in polar and nonpolar organic solvents. All polyimides indicated higher glass transition temperatures, excellent thermal stability and tensile properties. Incorporating a nitrile group into the polyimide backbone would enhance the dielectric constant of the polyimide films.     

Structure and properties for conterminously linked polymer of copoly(amic acid) with triallyl isocyanurate and bismaleimide

The copoly(amic acid)s were prepared from two various diamines 2,2′‐bis (4‐aminophenoxy phenyl) hexafluoropropane or 2,2′‐bis (4‐aminophenoxy phenyl) propane and amine‐terminated oligosiloxane, respectively, with aromatic tetracarboxylic dianhydride (3,3′,4,4′‐benzophenone tetracarboxylic dianhydride). The resulted copoly(amic acid) with various mole ratio of triallyl isocyanurate (TAIC)/4,4′‐bismaleimidophenylmethane (BMI) were subsequently thermally imidized to the corresponding copolyimides. These polymers were characterized using viscometer, differential scanning calorimetry, thermogravimetric analyses, dynamic mechanical analysis (DMA), dielectric analyzer, and scanning electron microscope. The dielectric constant (D_K) and dissipation factor (D_f) of copolyimides with TAIC/BMI were much lower than that of copolyimides without TAIC/BMI. Furthermore, the formation of copolyimides also would enhance their thermal stability and solubility. DMA of copolymers showed only a glass transition temperature (T_g), indicating a random structure and an amorphous state. The morphology of copolyimides revealed no phase separation. This indicates that the homogeneous state has been achieved in this coreaction system. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci, 2008     

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     

Synthesis of biphenylated cyanate esters: Thermomechanical resin comparisons within two isomeric series

Three isomeric tetraaryl cyanate esters containing biphenyl moieties {bis‐[4‐(4′‐cyanatophenyl)phenyl]propane, 2,2‐bis‐[4‐(3′‐cyanatophenyl)phenyl]propane, and 2,2‐bis‐[4‐(2′‐cyanatophenyl)phenyl]propane} and three isomeric triaryl cyanate esters {2‐(4′‐hydroxyphenyl)‐2‐[4′‐(4‐hydroxyphenyl)phenyl]propane, 2‐(4′‐hydroxyphenyl)‐2‐[4′‐(3‐hydroxyphenyl)phenyl]propane, and 2‐(4′‐hydroxyphenyl)‐2‐[4′‐(2‐hydroxyphenyl)phenyl]propane} were synthesized from their corresponding bisphenols. The structures of the monomers were confirmed with IR and ¹H‐NMR spectroscopy. The curing behavior was investigated with differential scanning calorimetry. Cyanate esters were cured thermally in the absence of a catalyst and were characterized by dynamic mechanical analysis. The results were compared to the properties of commercial bisphenol A polycyanurate. Of the three tetraaryl isomers, 2,2‐bis‐[4‐(2′‐cyanatophenyl)phenyl]propane had the highest melting point, and its corresponding resin had the lowest glass‐transition temperature (T_g). The para isomer displayed the highest T_g value of the three novel tetraaryl resins. The triaryl dicyanate isomers were low‐melting solids, with the ortho and meta isomers existing as liquids at room temperature. The T_g value of the para‐triaryl isomer was the highest of the three triaryl isomers and was about the same as that of bisphenol A polycyanurate. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2011