Synthesis and properties of organosoluble polyimides based on 2,2′-diphenoxy-4,4′,5,5′-biphenyltetracarboxylic dianhydride

A novel method for the preparation of 2,2′-diphenoxy-4,4′,5,5′-biphenyltetracarboxylic dianhydride have been investigated. This new dianhydride contains flexible phenoxy side chain and a twist biphenyl moiety and it was synthesized by the nitration of an N-methyl protected 3,3′,4,4′-biphenyltetracarboxylic dianhydride and subsequent aromatic nucleophilic substitution with phenoxide. The overall yield was up to 75%. The dianhydride was polymerized with five different aromatic diamines to afford a series of aromatic polyimides. The polyimide properties such as inherent viscosity, solubility, UV transparency and thermaloxidative properties were investigated to illustrate the contribution of the introduction of phenoxy group at 2- and 2′-position of BPDA dianhydride. The resulting polyimides possessed excellent solubility in the fact that the polyimide containing rigid diamines such as 1,4-phenylenediamine and 4,4′-oxydianiline were soluble in various solvents such as N-methyl-2-pyrrolidone, N,N-dimethylacetamide, dimethyl sulfoxide and chloroform. The glass-transition temperatures of the polymers were in the range of 255-283 °C. These polymers exhibited good thermal stability with the temperatures at 5% weight loss range from 470 to 528 °C in nitrogen and 451 to 521 °C in air, respectively. The polyimide films were found to be transparent, flexible, and tough. The films had a tensile strength, elongation at break, and Young's modulus in the ranges 105-168 MPa, 15-51%, 1.87-2.38 GPa, respectively.     

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.     

Synthesis and characterization of novel polyimides derived from 2-amino-5-[4-(4′-aminophenoxy)phenyl]-thiazole with some of dianhydride monomers

A new kind of aromatic unsymmetrical diamine monomer containing thiazole ring, 2-amino-5-[4-(4′-aminophenoxy)phenyl]-thiazole (APPT), was synthesized. A series of novel polyimides were prepared by polycondensation of APPT with various aromatic dianhydrides via one-step process. The resulting polyimides held inherent viscosities of 0.40-0.71 dL/g and were easily dissolved in strong dipolar solvents. Meanwhile, strong and flexible polyimide films were obtained, which had thermal stability with the glass transition temperatures (T_g) of 268.2-328.8 °C in nitrogen, the temperature at 5% weight loss of 452-507 °C in nitrogen and 422-458 °C in air, and the residue at 800 °C of 54.18-63.33% in nitrogen, as well as exhibited outstanding mechanical properties with the tensile strengths of 105.4-125.3 MPa, elongations at breakage of 6-13%. These films also held dielectric constants of 3.01-3.18 (10 MHz) and showed predominantly amorphous revealed by wide-angle X-ray diffraction measurements.     

Polyimides from 2,3,3′,4′-biphenyltetracarboxylic dianhydride and aromatic diamines

A series of new polyimides were prepared from the reaction of 2,3,3′,4′-biphenyltetracarboxylic dianhydride (a-BPDA) with various aromatic diamines. The properties of the a-BPDA polyimides were compared with those of polyimides prepared from the reaction of 3,3′,4,4′-biphenyltetracarboxylic dianhydride (s-BPDA) with the same aromatic diamines. Films of the a-BPDA polyimides had higher glass transition temperatures (T_gs) and less color than the corresponding s-BPDA polyimide films. Light transmission at 500 nm, solar absorptivity, and thermal emissivity were determined on certain films. Films of similar polyimides based upon a-BPDA and s-BPDA containing meta linkages and others containing para linkages were each cured at 250, 300, and 350 °C. The films were characterized primarily by T_g, color, optical transparency, tensile properties, dynamic mechanical thermal analysis, and coefficient of thermal expansion. The a-BPDA meta linked polyimide films had tensile strengths and moduli higher than films of the a-BPDA para linked polyimide. The same phenomenon was not observed for the s-BPDA meta and para linked polyimides. The chemistry, mechanical, and physical properties of the polymers and films are discussed.     

Synthesis and properties of fluorinated polyimides. 3. Derived from novel 1,3-bis[3′-trifluoromethyl-4′(4″-amino benzoxy) benzyl] benzene and 4,4-bis[3′-trifluoromethyl-4′(4-amino benzoxy) benzyl] biphenyl

Novel diamine monomers, 1,3-bis[3′-trifluoromethyl-4′(4″-amino benzoxy) benzyl] benzene (IV) and 4,4-bis[3′-trifluoromethyl-4′(4-amino benzoxy) benzyl] biphenyl (V) have been synthesized. These monomers lead to several novel fluorinated polyimides on reaction with different commercially available dianhydrides like pyromellatic dianhydride (PMDA), benzophenone tetracarboxylic acid dianhydride (BTDA) or 2,2-bis(3,4-dicarboxyphenyl) hexafluoropropane (6FDA). The polyimides prepared from above two monomers on reaction with 6FDA are soluble in several organic solvents such as N,N-dimethyl formamide (DMF), N,N-dimethyl acetamide (DMAc) and tetrahydrofuran (THF). The polyimides prepared from PMDA/IV is soluble in DMF and N-methyl pyrollidone (NMP) on heating, whereas V/PMDA is insoluble in all solvents. BTDA/IV polyimide is also soluble in NMP, DMF and DMAc. These polyimide films have low water absorption rate 0.2-0.7% and low dielectric constant 2.74-3.2 at 1 MHz. These polyimides showed very high thermal stability even up to 531 °C for 5% weight loss in synthetic air and glass transition temperature up to 316 °C (by DSC) in nitrogen. All polyimides formed tough transparent films, with tensile strength up to 148 MPa, a modulus of elasticity up to 2.6 GPa and elongation at break up to 31% depending upon the exact repeating unit structure.     

Synthesis and characterization of novel fluorinated polyimides derived from 4,4′-[2,2,2-trifluoro-1-(3,5-ditrifluoromethylphenyl)ethylidene]diphthalic anhydride and aromatic diamines

A novel fluorinated aromatic dianhydride, 4,4′-[2,2,2-trifluoro-1-(3,5-ditrifluoromethylphenyl) ethylidene] diphthalic anhydride (9FDA), was synthesized, which was employed to polycondense with various aromatic diamines, including 4,4′-oxydianiline, 1,4-bis(4-aminophenoxy) benzene, 3,4′-oxydianiline and 1,4-bis(4-amino-2-trifluoromethylphenoxy)benzene to produce a series of fluorinated aromatic polyimides. The fluorinated polyimides obtained had inherent viscosities ranged of 0.61-1.14 dL/g and were easily dissolved both in polar aprotic solvents and in low boiling point common solvents. High quality polyimide films could be prepared by casting the polyimide solution on glass plate followed by thermal baking to remove the organic solvents and volatile completely. Experimental results indicated that the fluorinated polyimides exhibited good thermal stability with glass transition temperature ranged of 245-283 °C and temperature at 5% weight loss of 536-546 °C. Moreover, the polyimide films showed outstanding mechanical properties with the tensile strengths of 87.7-102.7 MPa and elongation at breaks of 5.0-7.8%, good dielectric properties with low dielectric constants of 2.71-2.97 and low dissipation factor in the range of 0.0013-0.0028.     

Synthesis and properties of novel soluble polyimides having a spirobisindane-linked dianhydride unit

A new synthetic procedure was elaborated allowing the preparation of semiaromatic dianhydride. N-Methyl protected 4-chlorophthalic anhydride was nitrated with HNO₃ to produce N-methyl-4-chloro-5-nitrophthalimide (1). The aromatic nucleophilic substitution reaction between 5,5′,6,6′-tetrahydroxy-3,3,3′,3′-tetramethyl-1,1-spirobisindane and 1 afforded spirobisindane-linked bis(N-methylphthalimide) (2), which was hydrolyzed and subsequently dehydrated to give the corresponding dianhydride (3). The latter was polymerized with five different aromatic diamines to afford a series of aromatic polyimides. The properties of polyimides such as inherent viscosity, solubility, UV transparency and thermal stability were investigated to illustrate the contribution of the introduction of spirobisindane groups into the polyimide backbone. The resulting polyimides were readily soluble in polar solvents such as chloroform, THF and N-methyl-2-pyrrolidone. The glass-transition temperatures of these polyimides were in the range of 254-292 °C. The tensile strength, elongation at break, and Young's modulus of the polyimide film were 68.8-106.6 MPa, 5.9-9.8%, 1.7-2.0 GPa, respectively. The polymer films were colorless and transparent with the absorption cutoff wavelength at 286-308 nm.     

Colorless and high organosoluble polyimides from 2,5-bis(3,4-dicarboxyphenoxy)-t-butylbenzene dianhydride and aromatic bis(ether amine)s bearing pendent trifluoromethyl groups

A series of polyimides III_a-h characterized by colorlessness, high transparency, high solubility, and good mechanical property, was synthesized from the aromatic dianhydride, 2,5-bis(3,4-dicarboxyphenoxy)-t-butylbenzene dianhydride (I), and various aromatic diamines (II_a-h) with pendent trifluoromethyl group via polyaddition, chemical imidization, and direct cast films. The III series showed more colorless than the polyimides (V and VI series) of 2,2-bis(3,4-dicarboxyphenyl)hexafluoropropane dianhydride (6FDA) contained, the VI series was synthesized from the II with 6FDA. These films III had cut-off wavelengths between 371 and 376 nm, as well as b* value (a yellowness index) ranging from 3.0 to 4.7. In fact, it is so far the most colorless aromatic polyimide in our systematical researches. The III series had inherent viscosity ranging from 0.72 to 1.33 dL/g and showed excellent solubility in a variety of organic solvents. They were soluble in a concentration of 5-10% in the amide polar solvent, ether solvent, and chlorinated solvent. These films showed strength tensile of 97-123 MPa, dielectric constants of 2.78-3.28 (1 MHz), and moisture absorptions of 0.11-0.36 wt%. The glass transition temperature of the III series was recorded at 214-259 °C, the 10% weight loss temperature was over 468 °C, and the residue was more than 47% at 800 °C in nitrogen.     

Morphology control of various aromatic polyimides by using phase separation during polymerization

Morphology control of various aromatic polyimides representative as poly(4,4′-oxydiphenylene pyromelliteimide) was examined by using the phase separation during solution polymerization. Polymerizations of aromatic dianhydrides and aromatic diamines to the polyimides were carried out in poor solvents at 240-330 °C for 6 h with no stirring. Polymerization concentrations were from 0.25% to 3.0%. The polyimides were obtained as yellow precipitates. Two categorized morphologies were created, which were particles and crystals exhibiting lath-like and plate-like habits. These morphologies of polyimides could be selectively controlled by the polymerization conditions. The higher concentrations, less miscible solvents and lower temperatures were preferable to yield the particles via liquid-liquid phase separation. On the contrary, the lower concentration, miscible solvents and higher temperature were desirable to yield the crystals. The polyimide precipitates showed high crystallinity and possessed excellent thermal stability at which the 10 wt% loss temperatures in N₂ were in the range of 590-694 °C.     

Synthesis and characterization of novel polyimides derived from 2,6-bis[4-(3,4-dicarboxyphenoxy)benzoyl]pyridine dianhydride and aromatic diamines

A novel pyridine-containing aromatic dianhydride monomer, 2,6-bis[4-(3,4-dicarboxyphenoxy)benzoyl]pyridine dianhydride, was synthesized from the nitro displacement of 4-nitrophthalonitrile by the phenoxide ion of 2,6-bis(4-hydroxybenzoyl)pyridine, followed by acidic hydrolysis of the intermediate tetranitrile and cyclodehydration of the resulting tetraacid. A series of new polyimides holding pyridine moieties in main chain were prepared from the resulting dianhydride monomer with various aromatic diamines via a conventional two-stage process, 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 0.51-0.68 dL/g, and most of them were soluble in aprotic amide solvents and cresols, such as N,N-dimethylacetamide, N-methyl-2-pyrrolidone, and m-cresol, etc. Meanwhile, some strong and flexible polyimide films were obtained, which have good thermal stability with the glass transition temperatures of 221-278 °C, the temperature at 5% weight loss of 512-540 °C, and the residue at 800 °C of 60.4-65.3% in nitrogen, as well as have outstanding mechanical properties with the tensile strengths of 72.8-104.4 MPa and elongations at breakage of 9.1-11.7%. The polyimides also were found to possess low dielectric constants.     

Electrochemically and electrochromically stable polyimides bearing tert-butyl-blocked N,N,N′,N′-tetraphenyl-1,4-phenylenediamine units

A new class of electrochemically active polyimides with di-tert-butyl-substituted N,N,N′,N′-tetraphenyl-1,4-phenylenediamine units was prepared from N,N-bis(4-aminophenyl)-N′,N′-bis(4-tert-butylphenyl)-1,4-phenylenediamine and various aromatic tetracarboxylic dianhydrides via a conventional two-step procedure that included a ring-opening polyaddition to give poly(amic acid)s, followed by chemical or thermal cyclodehydration. Most of the polyimides are readily soluble in many organic solvents and can be solution-cast into tough and amorphous films. They had useful levels of thermal stability, with relatively high glass-transition temperatures (276-334 °C), 10% weight-loss temperatures in excess of 500 °C, and char yields at 800 °C in nitrogen higher than 60%. Cyclic voltammograms of the polyimide films cast on the indium-tin oxide (ITO)-coated glass substrate exhibited two reversible oxidation redox couples at 0.70-0.74 V and 1.05-1.08 V vs. Ag/AgCl in acetonitrile solution. The polyimide films revealed excellent stability of electrochromic characteristics, with a color change from colorless or pale yellowish neutral form to green and blue oxidized forms at applied potentials ranging from 0.0 to 1.3 V. These anodically coloring polymeric materials exhibited high optical contrast of percentage transmittance change (Δ%T) up to 44% at 413 nm and 43% at 890 nm for the green coloration, and 98% at 681 nm for the blue coloration. After over 50 cyclic switches, the polymer films still exhibited good redox and electrochromic stability.     

Synthesis and properties of novel organosoluble polyimides derived from 1,4-bis[4-(3,4-dicarboxylphenoxy)]triptycene dianhydride and various aromatic diamines

A novel triptycene-based dianhydride, 1,4-bis[4-(3,4-dicarboxylphenoxy)]triptycene dianhydride, was prepared from 4-nitro-N-methylphthalimide and potassium phenolate of 1,4-dihydroxytriptycene (1). The aromatic nucleophilic substitution reaction between 4-nitro-N-methylphthalimide and 1 afforded triptycene-based bis(N-methylphthalimide) (2), which hydrolyzed and subsequently dehydrated to give the corresponding dianhydride (3). A series of new polyimides containing triptycene moieties were prepared from the dianhydride monomer (3) and various diamines in m-cresol via conventional one-step polycondensation method. Most of the resulting polyimides were soluble in common organic solvents, such as chloroform, THF, DMAc and DMSO. The polyimides exhibited excellent thermal and thermo-oxidative stabilities with the onset decomposition temperature and 10% weight loss temperature ranging from 448 to 486 °C and 526 to 565 °C in nitrogen atmosphere, respectively. The glass transition temperatures of the polyimides were in the range of 221-296 °C. The polyimide films were found to be transparent, flexible, and tough. The films had tensile strengths, elongations at break, and tensile moduli in the ranges 95-118 MPa, 5.3-16.2%, and 1.03-1.38 GPa, respectively. Wide-angle X-ray diffraction measurements revealed that these polyimides were amorphous.     

Highly optically transparent/low color polyimide films prepared from hydroquinone- or resorcinol-based bis(ether anhydride) and trifluoromethyl-containing bis(ether amine)s

Two series of novel polyimides (5a-g and 6a-g) containing flexible ether linkages and pendent trifluoromethyl (CF₃) groups were synthesized from 1,4-bis(3,4-dicarboxyphenoxy)benzene dianhydride (3a) and 1,3-bis(3,4-dicarboxyphenoxy)benzene dianhydride (3b) with various CF₃-substituted aromatic bis(ether amine)s (4a-g) via ring-opening polyaddition to poly(amic acid)s, followed by thermal or chemical imidization. These polyimides were readily soluble in a variety of organic solvents and could be solution-cast into flexible and tough films. The cast films exhibited high optical transparency and almost no color, with a UV-vis absorption edge of 368-382 nm and a very low b^∗ value (a yellowness index) of 6.2-15.5. They had good thermal stability with glass-transition temperatures of 186-288 °C, and most of them did not show significant decomposition before 500 °C. Moreover, these polyimide films also possessed low dielectric constants of 2.79-3.49 (at 1 MHz) and low water uptakes (<0.65 wt%).     

Preparation of microporous carbon films from fluorinated aromatic polyimides

Pyrolysis and carbonization behaviors of fluorinated aromatic polyimide films synthesized from fluorinated dianhydrides and diamines were investigated by thermogravimetric and mass spectrometric measurements. Evolution of fluorine compound gases and related species was observed during the pyrolysis in the temperature range from 450 to 700 °C, in addition to the evolution of CO and CO₂ due to the imide ring degradation. By the carbonization of these fluorinated polyimides at 600-1000 °C, highly microporous carbons were obtained without any activation process, of which adsorption/desorption isotherm of N₂ gas was typical type I and pore size distribution was sharp at around 0.55 nm in width. Surface area increased with increasing fluorine content in the repeating unit of fluorinated polyimide: the polyimide with the highest fluorine content of 31.3 mass% gave a high microporous surface area of 1342 m² g⁻¹ and micropore volume of 0.44 mL g⁻¹.     

Synthesis and characterization of highly refractive polyimides derived from 2,7-bis(4′-aminophenylenesulfanyl)thianthrene-5,5,10,10-tetraoxide and aromatic dianhydrides

New polyimides (PIs) containing thioether and sulfonyl groups in their main chains have been developed. These PIs were synthesized by a two-step polycondensation procedure from several dianhydrides such as 4,4′-[p-thiobis(phenylenesulfanyl)] diphthalic anhydride (3SDEA), 4,4′-oxydiphthalic anhydride (ODPA), 4,4′-[sulfonylbis(phenylenesulfanyl)] diphthalic anhydride (pDPSDA) and a new sulfonyl and sulfur-containing aromatic diamine, 2,7-bis(4′-aminophenylenesulfanyl)thianthrene-5,5,10,10-tetraoxide (APTTT). All of the PIs show good thermal and optical properties such as optical transparency higher than 80% at 450 nm for a thickness of ca. 10 μm, glass transition temperatures higher than 250 °C, thermal decomposition temperatures (T_10%) in the range of 504-514 °C. Because of the two sulfonyl groups at each monomer unit in the polymer main chain, all of the PIs show good transparency maintaining relatively high refractive index.     

Synthesis and photochromic behavior of new polyimides containing azobenzene side groups

Aromatic polyimides containing side azobenzene groups have been synthesized by low-temperature solution polycondensation of certain aromatic dianhydrides with aromatic diamines containing preformed side azobenzene groups followed by chemical imidization at 100 °C in the presence of pyridine and acetic anhydride. The weight average molecular weight of these polymers is in the range of 16,000-129,000. The glass transition temperature of these polyimides is in the range of 185-230 °C. The polymer architecture presents a special characteristic, one of the azobenzene aromatic units being in the main chain of the polymer. This situation is intermediary between main-chain and side-chain azobenzene-containing polymers. The photochromic behavior, determined by the trans-cis isomerization process of azo-groups, in solution and in solid state, was evaluated. The synthesized polyimides were studied by spectral methods (UV, IR), thermal analysis and molecular modeling. A preliminary study concerning the surface structuration capacity of the polyimides was accomplished. Good results were obtained using Nd:YAG laser at 355 nm, at an incident fluence of 35 mJ/cm² (situated below the laser ablation limit).     

Colorless polyimides from 2,3,3′,4′-biphenyltetracarboxylic dianhydride (α-BPDA) and various aromatic bis(ether amine)s bearing pendent trifluoromethyl groups

A series of organosoluble and light-colored polyimides (III) was prepared from 2,3,3′,4′-biphenyltetracarboxylic dianhydride (α-BPDA) with various fluorinated aromatic bis(ether amine)s via two-step method with thermal or chemical imidization of poly(amic acid)s yielded polyimides. The III series had inherent viscosity of 0.74-1.01 dl/g and showed excellent solubility in a variety of organic solvents. They were soluble in the amide polar solvent, ether-type solvent, and chlorinated solvent. These polyimide films also showed a high optical transparency and less color intensity, with an ultraviolet-visible absorption edge of 369-382 nm and low b^* values (a yellowness index) of 5.0-11.7. Glass-transition temperature of the III series was recorded at 244-319 °C and higher than the isomeric polyimides V series. Compared with the nonfluorinated polyimides IV, the III series showed lighter-colored and lower dielectric constants and moisture absorptions. The good tensile properties and excellent thermal properties of the III series were also observed.     

Synthesis and properties of organosoluble polyimides based on 1,1-bis[4-(4-amino-2-trifluoromethylphenoxy)phenyl]cyclohexane

New aromatic diamine with cyclohexane cardo group substituted with trifluoromethyl group in the side chain, 1,1-bis[4-(4-amino-2-trifluoromethylphenoxy)phenyl]cyclohexane (II), was prepared through the nucleophilic substitution reaction of 1,1-bis(4-hydroxyphenyl)cyclohexane and 2-chloro-5-nitrobenzotrifluoride in the presence of potassium carbonate, to yield the intermediate dinitro compound I, followed by catalytic reduction with hydrazine and Pd/C to afford the diamine II. Fluorinated polyimides (IVa-g) were prepared from the II with various aromatic dianhydrides via thermal or chemical imidization of poly(amic acid). These polyimides had inherent viscosity ranging from 0.72 to 1.16 dl/g and showed excellent solubility in a variety of organic solvents. They were soluble in a concentration of 10% in the amide polar solvent, and 1-5% in the other testing solvents. IV films showed good mechanical properties, excellent thermal stability. The 10% weight loss temperature was above 476 °C in nitrogen or air, and the glass transition temperature was recorded at 214-278 °C. In comparison of the IV series with the analogous nonfluorinated polyimides (V series) based on 1,1-bis[4-(4-aminophenoxy)phenyl]cyclohexane (II′), IV series revealed better solubility, lighter-colored and lower dielectric constants and moisture absorptions. Their films had cut-off wavelengths in the range of 364-414 nm, b^* value (a yellowness index) ranging from 3.3 to 66.3, dielectric constants of 3.02-3.55 (1 MHz), with moisture absorption of 0.16-0.36 wt%.     

Synthesis and nonlinear optical properties of soluble fluorinated polyimides containing hetarylazo chromophores with large hyperpolarizability

The novel fluorinated polyimides with side-chain nonlinear optical (NLO) chromophores were synthesized from hydroxyl polyimides, followed by the Mitsunobu reaction with NLO chromophores. Molecular structural characterization for the resulting polymers was achieved by ¹H NMR, FT-IR, UV-Vis spectra, elemental analysis and gel permeation chromatography (GPC). The polymers exhibit excellent solubility in common organic solvents, good film-forming properties, high glass transition temperature (T_g) in the range from 193 to 200 °C and thermal stability up to 290 °C. The polyimides P1 and P2 containing hetarylazo chromophores with large hyperpolarizability possess a high electro-optic (EO) coefficient (r₃₃), which is larger than that of the polyimide P3 attached DR1. Excellent temporal stability and low optical losses in the range of 1.9-2.1 dB/cm at 1.55 μm were observed for these polymers. Such new NLO fluorinated polyimides are distinguished by an excellent combination of NLO activity, temporal stability, and optical loss.     

Synthesis and characterization of novel polyimides derived from 1,1-bis[4-(4′-aminophenoxy)phenyl]-1- [3″,5″-bis(trifluoromethyl)phenyl]-2,2,2-trifluoroethane

A novel fluorinated aromatic diamine monomer, 1,1-bis[4-(4′-aminophenoxy)phenyl]-1-[3″,5″-bis(trifluoromethyl)phenyl]-2,2,2-trifluoroethane(9FTPBA), was synthesized by coupling 3′,5′-bis(trifluoromethyl)-2,2,2-trifluoroacetophenone with 4-nitrophenyl phenyl ether under the catalysis of trifluoromethanesulfonic acid, followed reduced by reductive iron and hydrochloric acid. A series of new fluorine-containing polyimides having inherent viscosities of 0.96-1.23 dl/g was synthesized from the novel diamine with various commercially available aromatic dianhydrides using a standard two-stage process with thermal imidization and chemical imidization of poly(amic acid) films. All the fluorinated polyimides were soluble in many polar organic solvents such as NMP, DMAc, DMF, and m-cresol, as well as some of low boiling point organic solvents such as chloroform and acetone. The polymer films have good thermal stability with the glass transition temperature of 223-225 °C, the temperature at 5% weight loss of 535-568 °C in nitrogen, and have outstanding mechanical properties with the tensile strengths of 68-89 MPa, initial moduli of 2.14-2.19 GPa, and elongations at breakage of 3.2-10.5%.