Copolyimides from 2,3,3′,4′-biphenyltetracarboxylic dianhydride and pyromellitic dianhydride with 4,4′-oxydianiline

A series of copolyimides were prepared via the polyamide acids (polyamic acids) from the reaction of 2,3,3′,4′-biphenyltetracarboxylic dianhydride (a-BPDA) and pyromellitic dianhydride (PMDA) with 4,4′-oxydianiline (4,4′-ODA) at dianhydride molar ratios of 9:1, 7:3, 1:1, 3:7 and 1:9. Homopolymers and a 1:1 polymer blend were also prepared. Films from the 7:3, 1:1 and 3:7 molar ratio polyamide acids reacted for 5-6 h at ambient temperature were brittle, whereas films from the same polyamide acids reacted for 24-48 h at ambient temperature were fingernail creaseable. The difference was apparently due to the initial formation of incompatible block domains that underway randomization upon longer reaction time. The differential scanning calorimetric (DSC) curves of some of the brittle films quenched after heating to 400 °C had two apparent glass transition temperatures (T_gs), indicative of two block domains. The creaseable films quenched after heating to 400 °C had single T_gs. Wide-angle X-ray diffraction showed all films to be amorphous even though the initial DSC curves showed strong endothermic peaks, generally associated with crystalline melts. These strong endotherms near the T_g region were thought to be due to relaxation of regions in the highly stressed films. Films of copolyamide acids from the reaction of 1:1 molar ratios of 3,3′,4,4′-oxydiphthalic anhydride/a-BPDA and 3,3′,4,4′-biphenyltetracarboxylic dianhydride/a-BPDA with 4,4′-ODA reacted for 6 h were fingernail creaseable. The chemistry and the properties of the copolymers are compared with those of the homopolymers.     

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.     

Novel polyimides derived from 2,3,3′,4′-benzophenonetetracarboxylic dianhydride

A series of polyimides (PIs) based on 2,3,3′,4′-benzophenonetetracarboxylic dianhydride (2,3,3′,4′-BTDA) and 3,3′,4,4′-BTDA were prepared by the conventional two-step process. The properties of the 2,3,3′,4′-BTDA based polyimides were compared with those of polyimides prepared from 3,3′,4,4′-BTDA. It was found that PIs from 2,3,3′,4′-BTDA have higher glass transition temperature and better solubility without sacrificing their thermal properties. Furthermore the rheological properties of PMR-15 type polyimide resins based on 2,3,3′,4′-BTDA showed lower melt viscosity and wider melt flow region (flow window) compared with those from 3,3′,4,4′-BTDA. The structure-property relations resulted from isomerism were discussed.     

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.     

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.     

A unique crystallization and double melting behavior of a polyimide derived from 3,3′,4,4′-biphenyltetracarboxylic dianhydride and 1,4-bis(3-aminopropyl)piperazine

A unique crystallization and melting behavior of a novel semicrystalline polyimide derived from 3,3′,4,4′-biphenyltetracarboxylic dianhydride and 1,4-bis(3-aminopropyl)piperazine were studied by differential scanning calorimetry (DSC) with and without temperature modulation and wide-angle X-ray diffraction (WAXD). Polymer samples isolated from a chloroform solution showed melting transitions in the DSC. However, WAXD traces showed crystallinity only after annealing above the glass transition, for about 2 h. For samples crystallized from the melt, crystallization could be achieved only in a narrow crystallization range of 200-220 °C, after 10 h. A maximum crystallinity of this polyimide was found to be 30%. Two distinct melting transitions were observed by DSC, which could be explained using a partial disordering—reorganization—final melting model.     

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.     

Synthesis and characterization of polyimides from novel 1-(3′,5′-bis(trifluoromethyl)benzene) pyromelliticdianhydride (6FPPMDA)

Mono-substituted dianhydride monomer, 1-(3′,5′-bis(trifluoromethyl)phenyl) pyromellitic dianhydride (6FPPMDA), was prepared via the Suzuki cross coupling reaction followed by oxidation and cyclodehydration. The monomer was characterized by FT-IR, NMR, elemental analyzer (EA) and melting point apparatus. For comparison, 1-(4′-trifluoromethylphenyl)pyromellitic dianhydride (3FPPMDA) and 1-phenyl pyromellitic dianhydride (PPMDA) were also utilized. The dianhydrides were used to prepare polyimides with aromatic diamines such as bis(3-aminophenyl) 3,4-bis(trifluoromethyl)phenyl phosphine oxide (mDA6FPPO), bis(3-aminophenyl) 4-(trifluoromethyl)phenyl phosphine oxide (mDA3FPPO), bis(3-aminophenyl) phenyl phosphine oxide (mDAPPO) and 1,1-bis(4-aminophenyl)-1-phenyl-2,2,2-trifluoroethane (p3FDAm). The polyimides were synthesized via a two-step process; preparation of poly(amic-acid) in p-chlorophenol with isoquinoline, followed by solution imidization at the reflux temperature for 12 h. Polymer characterization was carried out by FT-IR, NMR, GPC, DSC and TGA, and their solubility, solution viscosity, water absorption, CTE, dielectric constant and refractive index were also evaluated.     

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 and characterization of soluble poly(ether imide)s based on 2,2′-bis(4-aminophenoxy)-9,9′-spirobifluorene

A series of aromatic poly(ether imide)s containing 9,9′-spirobifluorene moieties in the main chain have been synthesized via the polycondensation of 2,2′-bis(4-aminophenoxy)-9,9′-spirobifluorene with a variety of aromatic dianhydrides. In the diamine monomer, the two aminophenoxyfluorene entities are orthogonally arranged and are connected through an sp³ carbon atom (the spiro center). The resulting poly(ether imide)s have a polymer backbone which is periodically twisted with an angle of 90° at each spiro center. This structural feature, which restricts the close packing of the polymer chains and reduces inter-chain interactions, leads to amorphous poly(ether imide)s with good solubility in common organic solvents. In addition, the rigidity of the main chain of these polymers appears to be preserved due to the spiro-structure. As a result, these poly(ether imide)s exhibit a high T_g and excellent thermal stability.     

Preparation and properties of polyimides based on bis[3,5‐dimethyl‐4‐(4‐aminophenoxy)phenyl]methane

A series of polyimide (PI) thin films were synthesized based on bis[3,5‐dimethyl‐4‐(4‐aminophenoxy)phenyl]methane and conventional aromatic dianhydrides. The structures and properties of the thin films were measured with Fourier transform infrared, NMR, thermogravimetric analysis, dynamic mechanical analysis, and impedance analysis. The PI films exhibited glass‐transition temperatures in the range of 211–300°C and possessed initial thermal decomposition temperature reaching up to 457–482°C in air and 461–473°C in nitrogen. Some PI films had high solubility in organic solvents such as 1‐methyl‐2‐pyrrolidinone, N,N‐dimethylformamide, N,N‐dimethylacetamide, dimethyl sulfoxide, m‐cresol, tetrahydrofuran, and CHCl₃. The mechanical properties of these films were also examined. The dielectric constants of the films were in the range of 2.8–3.3 at 25°C. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci 104: 1265–1270, 2007     

Synthesis and properties of poly(ether imide)s derived from 2,5‐bis(3,4‐dicarboxyphenoxy)biphenyl dianhydride and aromatic ether–diamines

A series of poly(ether imide)s (PEIs) with light colors and good mechanical properties were synthesized from 2,5‐bis(3,4‐dicarboxyphenoxy)biphenyl dianhydride and various aromatic ether–diamines via a conventional two‐step polymerization technique that included ring‐opening polyaddition at room temperature to poly(amic acid)s (PAAs) followed by thermal imidization. The precursor PAAs had inherent viscosities ranging from 0.71 to 1.19 dL/g and were solution‐cast and thermally cyclodehydrated to flexible and tough PEI films. All of the PEI films were essentially colorless, with ultraviolet–visible absorption cutoff wavelengths between 377 and 385 nm and yellowness index values ranging from 10.5 to 19.9. These PEIs showed high thermal stabilities with glass‐transition temperatures of 206–262°C and decomposition temperatures (at 10% weight loss) higher than 478°C. They also showed low dielectric constants of 3.39–3.72 (at 1 MHz) and low water absorptions below 0.85 wt %. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2009     

Synthesis and characterization of novel soluble fluorinated aromatic polyamides derived from fluorinated isophthaloyl dichlorides and aromatic diamines

Two series of fluorinated aromatic polyamides derived from two novel monomers, 5-(4-trifluoromethylphenoxy)isophthaloyl dichloride (3FPC) and 5-(3,5-bistrifluoromethyl-phenoxy)isophthaloyl dichloride (6FPC) with various aromatic diamines were synthesized and characterized. Experimental results indicated that the fluorinated aromatic polyamides showed good solubility in many organic solvents. The solubility of the polyamides was affected by the trifluoromethyl substituents and the pendent phenoxy groups in the polymer backbone. The fluorinated polyamides have good thermal stability with the glass transition temperature of 206-285 °C, the temperature at 5% weight loss of 442-460 °C in nitrogen. The polyamide films also exhibited good mechanical properties and excellent electrical and dielectric properties. The fluorinated groups in the polymer backbone have played an important role in the improvement of electrical and dielectric performance of polymer.     

Preparation and properties of novel soluble aromatic polyetherimides from 1,1′-bis[4-(3,4-dicarboxyphenoxy)phenyl]-1-phenyl-2,2,2-trifluoroethane dianhydride and aromatic diamines

New aromatic polyetherimides containing the 1,1′-bis[4-(3,4-dicarboxyphenoxy)phenyl]-1-phenyl-2,2,2-trifluoroethane dianhydride unit were prepared by a conventional two-step method from 1,1′-bis[4-(3,4-dicarboxyphenoxy)phenyl]-1-phenyl-2,2,2-trifluoroethane dianhydride and several diamines. This procedure yielded high molecular weight polyetherimides with inherent viscosities of 0.22–1.29 dL/g. Most of the corresponding polyetherimides were soluble in organic solvents such as N-methyl-2-pyrrolidone, N, N-dimethylformamide, N,N-dimethylacetamide, and methylene chloride under ambient temperature. The glass transition temperatures (T_g) of these polymers were in the range of 207–264°C and the temperatures of 10% weight loss were over 520°C at a heating rate 20°C/min in nitrogen. © 1996 John Wiley & Sons, Inc.     

Structure–property relationship of polyimides based on pyromellitic dianhydride and short‐chain aliphatic diamines for dielectric material applications

Most polyolefins that are used for dielectric materials exhibit a low dielectric constant and operating temperatures up to 70°C. Polyimides offer a means to a higher dielectric constant material by the introduction of a polar group in the polymer backbone and are thermally stable at temperatures exceeding 250°C. A common dianhydride, pyromellitic dianhydride (PMDA), is reacted with various short‐chain diamines to produce polymers with high imide density. Homopolymers and copolymers synthesized had dielectric constants ranging from 3.96 to 6.57. These materials exhibit a dielectric constant twice that of biaxially oriented polypropylene and therefore a twofold increase in capacitance as well as maintaining low dissipation factors that are acceptable for this application. The experimental dielectric constants of these materials are also compared to density functional theory calculations and exhibit a close relationship. © 2013 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 130: 1276‐1280, 2013     

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.     

Anisotropic network formation by the photopolymerization of new monomers derived from 4‐hydroxybenzenethiol

New polymerizable difunctional liquid crystals of monomers derived from 4‐hydroxybenzenethiol were synthesized, characterized, and photopolymerized by the formation of anisotropic films. These films were obtained by the irradiation of the monomers in the mesophase with UV light before they were macroscopically oriented in glasses treated on the surface with polyimide and uniaxially rubbed. The monomers showed smectic and nematic mesophases. The thin films, uniaxially oriented, were optically transparent. The orientation was verified by IR dichroism, which showed a preferential order of mesogens. © 2005 Wiley Periodicals, Inc. J Appl Polym Sci 97: 1812–1817, 2005     

Synthesis and properties of novel polyimides derived from 2,6-bis(4-aminophenoxy-4′-benzoyl)pyridine with some of dianhydride monomers

A new kind of aromatic diamine monomer containing pyridine unit, 2,6-bis(4-aminophenoxy-4′-benzoyl)pyridine (BABP), was synthesized successfully. The Friedel-Crafts acylation of phenyl ethyl ether with 2,6-pyridinedicarbonyl chloride formed 2,6-bis(4,4′-dihydroxybenzoyl)-pyridine (BHBP), BHBP was changed into 2,6-bis(4-nitrophenoxy-4′-benzoyl)-pyridine (BNBP) by the nucleophilic substitution reaction of it and p-chloronitrobenzene, and BNBP was reduced with SnCl₂ and HCl in ethanol to form the diamine monomer BABP finally, the diamine monomer BABP could be obtained in quantitative yield. A series of novel polyimides were prepared by polycondensation of BABP with various aromatic dianhydrides in N-methy-2-pyrrolidone (NMP) via the conventional two-step method. Experimental results indicated that some of the polyimides were soluble both in strong dipolar solvents (N-methy-2-pyrrolidone or N,N-dimethylacetamide) and in common organic solvents tetrahydrofuran. The resulting polyimides showed exceptional thermal and thermooxidative stability, no weight loss was detected before a temperature of 450 °C in nitrogen, and the values of glass-transition temperature of them were in the range of 208-324 °C. Wide-angle X-ray diffraction measurements revealed that these polyimides were predominantly amorphous.     

Synthesis and characterization of polyimides from 4‐(diphenyl phosphine oxide)phenyl pyrromellitic dianhydride

A novel rigid‐rod type dianhydride monomer with phosphine oxide moiety, 4‐(diphenyl phosphine oxide)phenyl pyrromellitic dianhydride (POPPMDA), was synthesized via the Suzuki coupling reaction of 4‐(diphenyl phosphine oxide)phenyl boronic acid (POBB) and 1‐bromo‐2,3,5,6‐tetramethyl benzene (B4MB), followed by oxidation and cyclodehydration. The monomer was characterized by FTIR, NMR, EA, and melting point analyzer and utilized to synthesize polyimides with diamines such as bis(3‐aminophenyl)phenyl phosphine oxide (mDAPPO) and p‐phenylene diamine (pPDA) by varying their ratio. The polyimides were prepared via a conventional two‐step synthesis: preparation of poly(amic‐acid), followed by solution imidization. The polyimides were characterized by FTIR, NMR, DSC, TGA, and TMA, and their solubility, intrinsic viscosity, and adhesive properties were also evaluated. The polyimides exhibited high T_g (342–362°C), good thermal stability (>500°C), excellent adhesive property (134–107 g/mm), and low CTE (28–17 ppm/°C). © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2012     

Organosoluble and optically transparent fluorine-containing polyimides based on 4,4′-bis(4-amino-2-trifluoromethylphenoxy)-3,3′,5,5′-tetramethylbiphenyl

A novel fluorinated diamine monomer, 4,4′-bis(4-amino-2-trifluoromethylphenoxy)-3,3′,5,5′-tetramethylbiphenyl, was prepared by a nucleophilic chloro-displacement reaction of 3,3′,5,5′-tetramethyl-4,4′-biphenol with 2-chloro-5-nitrobenzotrifluoride and subsequent reduction of the intermediate dinitro compound. The diamine was reacted with aromatic dianhydrides to form polyimides via a two-step polycondensation method; formation of poly(amic acid)s, followed by thermal imidization. All the resulting polyimides were readily soluble in many organic solvents and exhibited excellent film forming ability. The polyimides exhibited high T_g (312-351 °C), good thermal stability, and good mechanical properties. Low moisture absorptions (0.2-1.1 wt%), low dielectric constants (2.54-3.64 at 10 kHz), and low color intensity were also observed.