Tough Polyimide Films Research Articles

Synthesis and properties of novel polyimides based on 10,10-bis[4-(4-aminophenoxy)phenyl]-9(10H)-anthrone

A new aromatic diamine bearing ether and pendant 9(10H)-anthrone groups, 10,10-bis[4-(4-aminophenoxy)phenyl]-9(10H)-anthrone was reacted with various aromatic dianhydrides to yield the corresponding cardo polyimides via the poly(amic acid) (PAA) precursors and thermal or chemical imidization. The PAAs were produced with moderate to high inherent viscosities of 0.91–1.53 dL/g. All the PAAs could be cast from DMAc solution and thermally converted into transparent, flexible and tough polyimide films with tensile strength of 79.6–115.2 MPa, tensile modulus of 1.97–2.48 GPa, and elongation at break of 10.8–21.7%. These polyimides were predominantly amorphous, and displayed excellent thermal stability with glass-transition temperature of 290–359 °C, 10% weight loss temperature of 522–566 °C, and the residue of 59–65% at 800 °C in nitrogen. Most of the polyimides obtained by chemical cyclodehydration procedure were found to be soluble in NMP, DMF and mcresol at room temperature.

High optical transparency, low dielectric constant and light color of organosoluble fluorinated polyimides based on 10,10-bis[4-(4-amino-3-trifluoromethylphenoxy)phenyl]-9(10H)-anthrone

A new aromatic diamine bearing ether, trifluoromethyl and anthrone groups, 10,10-bis[4-(4-amino-3-trifluoromethylphenoxy)phenyl]-9(10H)-anthrone (BATFPA) was prepared in three steps from anthrone. BATFPA was reacted with six conventional aromatic dianhydrides in N,N-dimethylacetamide (DMAc) to form the corresponding cardo fluorinated polyimides (PIs) via the poly(amic acid) (PAA) precursors with inherent viscosities ranging from 0.82 to 1.18 dL/g and thermal imidization. All the PAAs could be cast from DMAc solution and thermally converted into transparent, flexible and tough PI films with tensile strength of 63.5–101.7 MPa, tensile modulus of 1.94–2.85 GPa and elongation at break of 3.7–13.6%. The resulting PIs were predominantly amorphous and exhibited good solubility in dipolar solvents such as DMAc, N,N-dimethylformamide and N-methyl-2-pyrrolidinone at room temperature. In particular, the PI derived from 4,4′-hexafluoroisopropylidenediphthalic anhydride was even soluble in tetrahydrofuran. These new PIs displayed excellent thermal stability with Tg of 259–329 °C, 5% weight loss temperature (Td5) of 516–530 °C and the residue of 57–64% at 800 °C in nitrogen. Meanwhile, these PIs also had low moisture absorptions (0.36–0.83%), low dielectric constants (2.35–2.96 at 1 MHz), good optical transparency with cutoff wavelengths of ultraviolet–visible absorption at 336–408 nm and more than 80% transmittance at 600 nm.

Synthesis and characterization of thianthrene-containing preimidized soluble polyimide resins and the derived films with high refractive indices and good optical transparency

A series of organo-soluble polyimide (PI) resins were prepared from a newly designed and synthesized aromatic thianthrene-containing diamine, 2,7-bis(3-aminophenoxy)thianthrene (APOT) and various aromatic dianhydrides via a one-step high temperature polycondensation procedure with N-methyl-2-pyrrolidone (NMP) as the solvent. The derived PI resins were soluble in polar aprotic solvents, including NMP and N,N- dimethylacetamide (DMAc). For comparison, several unsoluble sulfur-containing PIs were prepared from anotherpara-substituted thianthrene-containing diamine, 2,7-bis(4-aminophenylenesulfanyl)thianthrene (APTT) and aromatic dianhydrides by a two-step polycondensation procedure via poly(amic acid) (PAA) precursors at elevated temperatures as high as 300 °C. Flexible and tough PI films with the tensile strength higher than 88 MPa were successfully cast from the APOT-PI resin solution at a relatively low curing temperature of 250 °C. The meta-substituted molecular skeleton in the APOT- PIs endowed the films good optical transparency with the transmittance higher than 83% at a thickness around 10 um, which was apparently higher than those of the para-substituted APTT-PI analogues. The sulfur-rich thianthrene moiety with high molar refraction endowed the APOT-PI films high refractive indices up to 1.7147 at 632.8 nm and low birefringence in the range of 0.0064–0.0133. In addition, the PI films showed good thermal stability with the glass transition temperatures (Tg) higher than 198.3 °C and 5% weight loss temperatures higher than 510 °C in nitrogen.

Approaches to improve the film ductility of colorless cycloaliphatic polyimides

This study described approaches for improving the film ductility of colorless cycloaliphatic polyimides (PIs). An unexpected toughening effect was observed when a PI derived from pyromellitic dianhydride (PMDA) and 4,4′‐methylenebis(cyclohexylamine) was modified by copolymerization with a low isophoronediamine (IPDA) content of 5 to 30 mol%, despite there being no film‐forming ability in the homo PMDA/IPDA system. For example, at an IPDA content of 20 mol%, the copolymer showed significantly improved film toughness (maximum elongation at break, εb max = 57%), excellent optical transparency (light transmittance at 400 nm, T400 = 83.7%), and a high glass transition temperature (Tg = 317°C). This toughening effect can be interpreted on the basis of the concept of chain slippage. In this study, the PIs derived from bicyclo[2.2.2]octane‐2,3,5,6‐tetracarboxylic dianhydride (H‐BTA) with various diamines were also systematically investigated to evaluate the potential of H‐BTA‐derived systems. The combinations of H‐BTA with ether‐containing diamines led to highly tough PI films (εb max > 100%) with very high Tgs, strongly contrasting with the results of an earlier study. The observed excellent properties are related to the steric structure of H‐BTA. Our interest also extended to the solution processability. A copolyimide derived from H‐BTA with a sulfone‐containing diamine and an ether‐containing diamine achieved a very high optical transparency (T400 = 86.8%), a very high Tg (313°C), and good ductility (εb max = 51%) while maintaining solution processability. Thus, these approaches enabled us to dramatically improve the ductility of cycloaliphatic PI films that have, to date, been considered brittle.

Synthesis and properties of (A2+B4)-type hyperbranched polyimides with different terminal groups

To investigate the effect of terminal groups on the properties of hyperbranched polyimides (HBPIs) for potential optical applications, a series of HBPIs bearing different terminal groups have been synthesized through a novel aromatic CF3-containing tetra-amine, 4,4′-di[3,5-di(2-trifluoromethyl-4-aminophenoxy)phenoxy] sulfone, and a long chain dianhydride, 2,2-bis[4-(3,4-dicarboxyphenoxy)phenyl]hexafluoropropane, via a two-step polycondensation procedure. The synthesized HBPIs could form flexible and tough polyimide (PI) films, which exhibit good thermal stability with the glass transition temperatures of 191–234°C for differential scanning calorimetry measurement, the 5% weight loss temperatures of 533–610°C, and residual weights of 45.8–58.6% at 800°C under nitrogen atmosphere. The PI films have favorable mechanical properties with tensile strengths of 77–92 MPa, elongation at break of 3.55–7.99%, and initial modulus of 2.05–2.86 GPa. The films also exhibit the good transmittance of higher than 80% at 800 nm. The average refractive indices ( nav) and in-plane/out-of-plane birefringence (Δ n) measured at 632.8 nm are in the range of 1.5539–1.6022 and 0.0065–0.0077, respectively. The good transmittance in the visible region, tunable nav, and low Δ n are very suitable for optical applications.

Synthesis and properties of highly organosoluble and low dielectric constant polyimides containing non-polar bulky triphenyl methane moiety

Novel fluorinated aromatic polyimides were prepared by the conventional two-step imidization of 4.4′-(hexafluoroisopropylidene) diphthalic anhydride (6FDA) and diamines (TriPMPDA and TriPMMDA) bearing triphenyl methane moiety. Both of the flexible and tough polyimide films exhibited an intrinsic low dielectric constant (low-k) values of 2.56 and 2.33 at the frequency of 10kHz, respectively, due to the introduction of the bulky triphenyl methane side groups and the tortuous backbone structures. In addition, they showed light color, high thermal stability, moderate mechanical property, and more importantly, excellent solubility in common organic solvents (even completely dissolved in dichloromethane and chloroform). Thus, both of the functional polyimides possessed attractive potential applications in the field of high performance flexible polymer interlayer materials.

Synthesis and characterization of new redox-active and electrochromic polyimides with (4-morpholinyl)triphenylamine units

A series of electroactive aromatic polyimides with (4-morpholinyl)triphenylamine units in the backbone were prepared from a newly synthesized diamine monomer, 4,4′-diamino-4″-(4-morpholinyl)triphenylamine, and aromatic tetracarboxylic dianhydrides via the conventional two-step polycondensation technique. Flexible and tough polyimide films could be obtained via the thermal curing of their precursor poly(amic acid) films. The polyimides showed high glass-transition temperatures (Tg) between 290–313°C, and they did not show significant decomposition before 500°C in air or nitrogen atmosphere. Cyclic voltammograms of the polyimide films on the indium-tin oxide (ITO)-coated glass substrate exhibited a pair of reversible oxidation waves with low onset oxidation potentials of 0.43–0.53V (vs. Ag/AgCl) in acetonitrile solution. They also exhibited multicolor electrochromic behavior between their neutral and oxidized states changing from pale yellow to cyan and bluish purple.

Aromatic polyimides with tertbutyl-substituted and pendent naphthalene units: synthesis and soluble, transparent properties

A novel non-coplanar aromatic diamine monomer, 3,3′-ditertbutyl-4,4′-diaminodiphenyl-4″-naphthylmethane (TAPN) was synthesized by a condensation reaction of 2-tertbutylaniline and 1-naphthaldehyde under catalyst hydrochloric acid. The structure of the monomer was confirmed by FTIR, NMR, elementary analysis and mass spectrometry. A series of aromatic polyimides (PIs) were synthesized via conventional one-step polycondensation from TAPN and various commercial aromatic dianhydrides. All of the PIs exhibit excellent solubility in common organic solvents, even in low boiling point solvents such as chloroform (CHCl3), tetrahydrofuran (THF) and acetone. The PIs present outstanding thermal stability with the glass transition temperature (T g) ranged from 299 °C to 350 °C, and the temperature at 10% weight loss ranged from 490 °C to 504 °C, and high optical transparency with the cutoff wavelengths of 306–356 nm. Moreover, the flexible and tough PI films have prominent mechanical properties with tensile strengths in the range of 77.6–90.5 MPa, tensile modulus in the range of 1.8–2.4 GPa and elongation at break in the range of 6.3%–9.5%, as well as lower dielectric constant (2.89–3.12 at 1 MHz) and lower moisture absorption (0.35%–0.66%).

Synthesis and properties of new aromatic polyimides containing redox‐active anthraquinone moieties

AbstractA novel anthraquinone‐containing bis(ether amine) monomer, 2,6‐bis(4‐aminophenoxy)anthraquinone, was synthesized from readily available reagents. A series of novel aromatic polyimides were prepared from the newly synthesized diamine monomer with various aromatic tetracarboxylic dianhydrides. The intermediate poly(amic acid)s had inherent viscosities of 0.67–1.12 dL g−1, and those derived from less stiff dianhydrides could be solution‐cast and thermally cyclodehydrated into flexible and tough polyimide films. The polyimides exhibited glass transition temperatures between 270 and 297 °C, and they were fairly stable up to a temperature of 500 °C in air or nitrogen. The electrochemical and electrochromic properties of one of the polyimides were investigated. The polymer could undergo two reversible steps of electrochemical reduction, with a color change from a colorless neutral state to pink and rose‐red reduced states. © 2012 Society of Chemical Industry

Synthesis and characterization of novel semi-alicyclic polyimides from methyl-substituted tetralin dianhydride and aromatic diamines

The asymmetrical alicyclic dianhydride 3,4-dicarboxy-1,2,3,4-tetrahydro-6-methyl-1-naphthalene succinic dianhydride (MTDA, II) was synthesized from 4-methylstyrene and maleic anhydride under nitric oxide catalysis with a yield >70%. A series of semi-alicyclic polyimides (PIs) (PI–IIa∼PI–IId) were prepared by a one-step high temperature polycondensation procedure from MTDA and various aromatic diamines. For comparison, another series of PIs (PI–Ia∼PI–Id) were prepared from the analogous dianhydride 3,4-dicarboxy-1,2,3,4-tetrahydro-1-naphthalene succinic dianhydride (TDA, I) and the same diamines. The asymmetrical molecular structure of MTDA endowed the derived PIs with good solubilities in common solvents and high optical transparencies in the ultraviolet and visible light regions by decreasing the intramolecular or intermolecular interactions of the polymer chains. The flexible and tough PI films exhibited good thermal stability up to 400 °C and showed glass transition temperatures in the range of 204–271 °C. The PI films exhibited good optical transparency with transmittances >80% at 400 nm, a cut-off wavelength <300 nm and a refractive index <1.54. A series of semi-alicyclic PIs have been synthesized from an alicyclic dianhydride MTDA and various aromatic diamines by a one-step high temperature polycondensation procedure. Flexible and tough PI films have been cast from their solution in common solvents. The PI films exhibited good thermal stability and good transparency in the ultraviolet-visible (UV-vis) light region.

Novel organosoluable aromatic polyimides derived from unsymmetrical 1,3-bis(4-aminophenoxy)naphthalene and aromatic dianhydrides

A novel unsymmetrical diamine, 1,3-bis(4-aminophenoxy)naphthalene, was prepared through the nucleophilic displacement of 1,3-dihydroxynaphthalene with p-fluoronitrobenzene in the presence of potassium carbonate, followed by catalytic reduction with hydrazine. A series of novel aromatic polyimides containing bis(phenoxy)naphthalene units were synthesized from the unsymmetrical diamine and a range of aromatic tetracarboxylic dianhydrides via the usual two-step procedures that included ring-opening polyaddition and thermal/chemical cyclodehydration. The poly(amic acid)s had inherent viscosities ranging from 0.65 to 2.01 dL/g. All the poly(amic acid)s could be converted thermally into transparent, flexible, and tough polyimide films. Most of the polyimides were soluble in organic solvents, such as dimethylacetamide, N-methyl-2-pyrrolidone, m-cresol, or o-chlorophenol due to the unsymmetrical and bulky pendant naphthalene groups. The tensile strength and elongation at break of the polyimide films ranged from 74 to 97 MPa and 4 to 7%, respectively. These polyimides had glass transition temperatures ranging from 221 to 312 °C. Thermogravimetric analysis revealed these polymers to be fairly stable up to 500 °C, and the 10% weight loss temperature were recorded in the range of 531–580 °C in nitrogen and 522–570 °C in air. The substituted position effect of bis(phenoxy)naphthalene on the properties of the polyimides were investigated. The polyimides derived from unsymmetrical 1,3-substituted bis(4-aminophenoxy) naphthalene showed better solubility without sacrificing their thermal and mechanical properties due to the unsymmetrical and bulky pendant effects.

Synthesis and characterization of novel polyimides derived from 4-phenyl-2, 6-bis [3-(4-aminophenoxy)-phenyl]-pyridine diamine and aromatic dianhydrides

A new kind of pyridine-containing aromatic diamine monomer, 4-phenyl-2, 6-bis [3-(4-aminophenoxy)phenyl]-pyridine( m-PAPP),was synthesized by a modified Chichibabin reaction of benzaldehyde and a substituted acetophenone, 3-(4-nitrophenoxy)-acetophenone( m-NPAP), and a reduction of the resulting dinitro compound 4-phenyl-2, 6-bis[3-(4-nitrophenoxy)phenyl]-pyridine ( m-PNPP) with Pd/C and hydrazine monohydrate, successively. A series of novel aromatic polyimides were prepared from the diamine with various aromatic dianhydrides via a conventional two-step thermal or chemical imidization method. The inherent viscosities of the resulting poly (amic acid) precursors were 1.37–1.56 dL/g, and these polymers could be cast and thermally converted into transparent, flexible, and tough polyimide films. The polyimides displayed higher solubility in polar solvents such as NMP, DMSO and m-cresol. The glass transition temperatures of these polymers were recorded at 180–264 °C. All of these novel polyimides held 10% weight loss at the temperature above 430 °C and left more than 50% residue even at 800 °C in air, as well as have outstanding mechanical properties with the tensile strengths of 91.6–114.1 MPa and elongations at breakage of 10.1–15.7%. Wide-angle X-ray diffraction measurements revealed that these polyimides were predominantly amorphous.

Synthesis and characterization of soluble polyimides based on a new fluorinated diamine: 4-Phenyl-2,6-bis[3-(4′-amino-2′-trifluoromethyl-phenoxy) phenyl] pyridine

A new kind of pyridine-containing aromatic diamine monomer, 4-phenyl-2,6-bis[3-(4′-amino-2′-trifluoromethyl-phenoxy) phenyl] pyridine ( m-PAFP), was successfully synthesized by a modified Chichibabin reaction of 3-(4′-nitro-2′-trifluoro-methyl-phenoxy)-acetophenone with benzaldehyde, followed by a catalytic reduction. A series of fluorinated pyridine-bridged aromatic poly(ether-imide)s were prepared from the resulting diamine monomer with various aromatic dianhydrides via a conventional two-step thermal or chemical imidization method. The inherent viscosities values of these polyimides were in the range of 0.56–1.02 dL/g, and they could be cast and thermally converted into transparent, flexible, and tough polyimide films. The polyimides displayed higher solubility in polar solvents such as NMP, DMSO and m-cresol. The polyimides had good thermal stability, with the glass transition temperatures ( T g) of 187–211 °C, the temperatures at 5% weight loss of 511–532 °C, and the residue at 800 °C in air was higher than 50%. These films also had dielectric constants of 2.64–2.74 at 10 MHz and low water uptake 0.53–0.66%. Wide-angle X-ray diffraction measurements revealed that these polyimides were predominantly amorphous. Moreover, the polymer films of these novel polyimides showed outstanding mechanical properties with the tensile strengths of 90.1–96.6 MPa, elongations at breakage of 8.9–10.7% and tensile modulus of 1.65–1.98 GPa.

Synthesis and Characterization of Highly Refractive Polyimides Derived from Thiophene-Containing Aromatic Diamines and Aromatic Dianhydrides

Aromatic thiophene-containing diamines, 2,5-bis(4-aminophenylsulfanyl)thiophene (APST) and 2,5-bis{2′-[5′-(4′′-aminophenyl)sulfanyl]thienyl}thiophene (APSTT), were synthesized and polymerized with a sulfur-containing dianhydride, 4,4′-[p-thiobis(phenylenesulfanyl)]diphthalic anhydride (3SDEA) and 4,4′-oxydiphthalic anhydride (ODPA), respectively, to afford four poly(amic acid)s (PAAs) with inherent viscosities of 0.41 to 1.68 dL/g. Flexible and tough polyimide (PI) films obtained from the PAA precursors showed good thermal, mechanical, and optical properties. The glass-transition temperatures (Tg) of the PIs were in the range of 157−220 °C, determined by differential scanning calorimetry (DSC), and 160−216 °C by dynamic mechanical analysis (DMA), depending on the dianhydride used. The 10% weight loss temperatures were in the range of 354−456 °C, showing relatively high thermally resistant characteristics of the PI films. The PI films also showed good optical transparency above 500 nm, which agreed well wi...

Synthesis and characterization of highly optical transparent and low dielectric constant fluorinated polyimides

Multitrifluoromethyl-substituted aromatic diamines, 1,1-bis[4-(4′- amino-2′-trifluoromethylphenoxy)phenyl]-1-(3″-trifluoromethylphenyl)-2,2,2-trifluoroethane (12FDA) and 1,1-bis[4-(4′-amino-2′-trifluoromethylphenoxy)phenyl]-1-[3″,5″-bis (trifluoromethyl)phenyl]-2,2,2-trifluoroethane (15FDA) were synthesized, which were employed to react with various aromatic dianhydrides to yield a series of highly fluorinated polyimides. The fluorinated polyimides synthesized showed great solubility with inherent viscosities of 0.47–0.69 dL/g. The strong and tough polyimide films exhibited good thermal stability with the glass transition temperature ( T g) of 209–239 °C and outstanding mechanical properties with the tensile strengths of 88–111 MPa and tensile modulus of 2.65–3.17 GPa. Dielectric constants of as low as 2.49 and low moisture absorptions (0.17–0.66%) were measured. The fluorinated polyimide films (7–10 μm in thickness) also showed highly optical transparency with light transmittance at 450 nm of as high as 97.0% and cutoff wavelength of as low as 298 nm. The average refractive indices and birefringence of the fluorinated polyimide films were measured in the range of 1.5060–1.5622 and 0.0036–0.0095, respectively. PI-7 and PI-8 exhibited low light-absorption in the near-infrared region, especially at the optocommunication wavelength of 1310 nm and 1550 nm.

Organo-soluble and transparent polyimides containing phenylphosphine oxide and trifluoromethyl moiety: Synthesis and characterization

A series of aromatic polyimides (PI-II a–d) containing lateral phenylphosphine oxide (PPO) and trifluoromethyl (–CF 3) moiety were prepared from an aromatic diamine, 2,5-bis[(4-amino-2-trifluoromethylphenoxy)phenyl]diphenyl-phosphine oxide (BATFDPO) and various aromatic dianhydrides via a two-step chemical imidization procedure. In parallel, for comparison, another series of polyimides (PI-I a–d) without trifluoromethyl were synthesized from a diamine, 2,5-bis[(4-aminophenoxy)-phenyl]diphenylphosphine oxide (BADPO) and the same dianhydrides. It was found that both of the two series of polyimides (PIs) were soluble in polar aprotic solvents, such as N-methyl-2-pyrrolidinone (NMP) and the solubility of PI-II a–d was highly enhanced by the introduction of the bulky –CF 3 group. Flexible and tough PI films with tensile strengths higher than 70 MPa were cast from the PI solution. The introduction of –CF 3 moiety slightly sacrificed the thermal stability and mechanical properties of the PI films. For example, PI-II a–d showed 5% weight loss at 472–476 °C, which was about 50 °C lower than those of their PI-I a–d analogues. However, –CF 3 group apparently improved the optical transparency and decreased the refractive indices of the PI films. PI-II d derived from BATFDPO and 4,4’-hexafluoroisopropylidenediphthalic anhydride (6FDA) exhibited the highest optical transparency with the transmittance of 90% at 400 nm and the refractive index as low as 1.5511 at 1310 nm.

Optically Transparent Sulfur-Containing Polyimide−TiO2 Nanocomposite Films with High Refractive Index and Negative Pattern Formation from Poly(amic acid)−TiO2 Nanocomposite Film

A series of semialicyclic polyimides (PIs) have been successfully prepared by the polycondensation of two alicyclic dianhydrides, 1,2,3,4-cyclobutanetetracarboxylic dianhydride (CBDA) and 1,2,4,5-cyclohexanetetracarboxylic dianhydride (CHDA) with two sulfur-containing aromatic diamines, 4,4′-thiobis[(p-phenylenesulfanyl)aniline] (3SDA) and 2,7-bis(4-aminophenylenesulfanyl)thianthrene (APTT), respectively, by a two-step polymerization procedure via the soluble poly(amic acid) (PAA) precursors. Flexible and tough PI films were obtained with a tensile strength greater than 82 MPa and elongation at breaks higher than 12%. The films showed good thermal and thermal-oxidative stability without significant weight loss up to 400 °C, both in air and nitrogen. The glass-transition temperatures of the PIs ranged from 236.5 to 274.1 °C. Good optical transparency, including the cutoff wavelengths lower than 350 nm and transmittances higher than 80% at 400 nm, was achieved for all the PI films. The refractive indices of the PI films were in the range of 1.6799–1.7130 measured at 632.8 nm, which agreed well with the values calculated by the time-dependent density functional theory (TD-DFT). In addition, PAA-IIa (CHDA-3SDA) showed a good affinity with silica-modified TiO2 nanoparticles. The hybrid system with 45 wt % load of TiO2 nanoparticles, combined with the photobase generator N-{[(4,5-dimethoxy-2-nitrobenzyl)oxy]carbonyl}2,6-dimethylpiperidine (DNCDP) exhibited good photolithographic characteristics. A fine negative pattern with a resolution of approximately 4 µm was successfully printed on the hybrid film. The cured PI-IIa−TiO2 hybrid film exhibited a refractive index of 1.8100 at 632.8 nm.

Synthesis and characterization of highly refractive polyimides from 4,4′‐thiobis[(p‐phenylenesulfanyl)aniline] and various aromatic tetracarboxylic dianhydrides

AbstractAn aromatic sulfur‐containing diamine 4,4′‐thiobis[(p‐phenylenesulfanyl) aniline] (3SDA) was synthesized and polymerized with a sulfur‐containing dianhydride 4,4′‐[p‐thiobis(phenylenesulfanyl)]diphthalic anhydride (3SDEA) and three nonsulfur aromatic tetracarboxylic dianhydrides, respectively to afford four poly(amic acid)s (PAAs) with the inherent viscosities of 0.54–1.04 dL/g. Flexible and tough polyimide (PI) films obtained from the PAA precursors showed good thermal, mechanical, and optical properties. The glass transition temperatures (Tgs) of the PIs ranged from 179.1–227.2 °C determined by differential scanning calorimetry (DSC), and 173.8–227.3 °C by dynamic mechanical analysis (DMA), depending on the dianhydride used. The 10% weight loss temperatures were in the range of 500–536 °C, showing high intrinsic thermal‐resistant characteristics of the PI films. The PI films also showed good optical transparency above 500 nm, which agreed well with the calculated absorption spectra using the time‐dependent density functional theory. The average refractive indices (nav) measured at 632.8 nm were 1.7191–1.7482, and the in‐plane/out‐of‐plane birefringences (Δn) were 0.0068–0.0123. The high refractive indices originate from the high sulfur contents, good molecular packing, and the absence of bulky structures. The relatively small birefringence mainly results from the flexible thioether linkages structures of the diamine. © 2007 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 45: 5606–5617, 2007

Novel poly(pyridine imide) with pendent naphthalene groups: Synthesis and thermal, optical, electrochemical, electrochromic, and protonation characterization

AbstractA new diamine containing a pyridine heterocyclic group and a naphthalene substituent, 4‐(2‐naphthyl)‐2,6‐bis(4‐aminophenyl) pyridine (NBAPP), was synthesized with the Chichibabin reaction and used in the preparation of poly(pyridine imide) by direct polycondensation with 4,4′‐hexafluoroisopropylidenediphathalic anhydride in N‐methyl‐2‐pyrrolidinone (NMP). The poly(pyridine imide) derived from diamine NBAPP with naphthalene substituents was highly organosoluble: it was soluble in tetrahydrofuran, NMP, N,N‐dimethylacetamide (DMAc), N,N‐dimethylformamide, and γ‐butyrolactone at room temperature and in pyridine, dimethyl sulfoxide, and cyclohexanone upon heating at 70 °C. The poly(pyridine imide) was converted into lightly colored, optically transparent, flexible, and tough polyimide films via casting onto glass from a DMAc solution. This polymer exhibited good thermal stability (temperature of 10% weight loss = 527 °C) in air and high dielectric constants (as high as 4.20 at 1 kHz). The polyimide films had a tensile strength of 102 MPa and a tensile modulus of 1.8 GPa. As for the optical properties, the polymer exhibited UV–vis absorption bands in the region of 223–450 nm and possessed strong green‐yellow fluorescence (500 nm) after being protonated with acid. © 2007 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 45: 2367–2374, 2007

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

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.