Gas permeability and permselectivity of photochemically crosslinked copolyimides

A series of copolyimides were prepared from 2,4,6-trimethyl-1,3-phenylenediamines (3MPDA), 3,3′,4,4′-benzophenone tetracarboxyl dianhydride (BTDA), and pyromellitic dianhydride (PMDA). Modification of the copolyimides by ultraviolet irradiation were carried out. Gas permeabilities of H₂, O₂, and N₂ through the copolyimides and photochemically crosslinked copolyimides were measured at temperatures from 30 to 90°C. The relationships between gas permeabilities and temperature are in agreement with the Arrhenius equation. The structure of photochemically crosslinked copolyimides were characterized by Fourier transform infrared and gel measurement methods. Linear relationships between both log P and E_p and the volume fraction of PMDA–3MPDA exist. Photochemically crosslinking modification result in a decrease in gas permeability and an increase in E_p and α(H₂/N₂) for all the copolyimides. For H₂/N₂ separation, photochemically crosslinked copolyimides are of higher gas permeabilities and permselectivities simultaneously than normal polyimides. © 1999 John Wiley & Sons, Inc. J Appl Polym Sci 73: 521–526, 1999     

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     

Synthesis and characterization of novel borosiloxane‐containing aromatic copolyimides with excellent thermal stability and low coefficient of thermal expansion

The properties of borosiloxane‐containing copolyimides with borosiloxane in the main chain and in the side chain were studied. Two series of borosiloxane‐containing copolyimides were synthesized by the reaction of 3,3′,4,4′‐biphenyltetracarboxylic dianhydride (s‐BPDA ) and 2,3′,3,4′‐biphenyltetracarboxylic dianhydride (a‐BPDA ) with p ‐phenylenediamine (PDA ), 4,4′‐oxydialinine (4,4′‐ODA ) and different borosiloxane diamine monomers (BSiAs ). The synthesized borosiloxane‐containing copolyimides exhibited better solubility than borosiloxane‐free copolyimides and showed high glass transition temperatures (320–360 °C), excellent thermal stability (570–620 °C for T ₁₀), great elongation at break (10% ? 14%) and a low coefficient of thermal expansion (14–24 ppm °C^?1). More specifically, the copolyimides containing BSiA‐2 formed nano‐scale protrusions and the copolyimides containing BSiA‐1 formed micro‐scale protrusions. The contact angles of the copolyimides increased from 72° for neat copolyimide to 96° for 5% of borosiloxane in the main chain of the copolymer up to 107° for 10% of borosiloxane in the side chain of the copolymer. © 2017 Society of Chemical Industry     

Preparation and properties of thermally stable copolyimides based on novel second‐order nonlinear–optical chromophore containing diamines

Thermally stable copolyimides were prepared from two novel second‐order nonlinear optical chromophores containing diamines, 4‐nitro‐4′‐[N‐(4,6‐di‐β‐aminoethylamino)‐1,3,5‐triazin‐2‐yl]aminoazobenzene (M1) and 4‐nitro‐4′‐[N‐(4,6‐di‐4‐aminophenylamino)‐1,3,5‐triazin‐2‐yl]aminoazobenzene (M2); two codiamines, 4,4′‐diamino‐3,3′‐dimethyl diphenylmethane (MMDA) and bis‐(3‐aminopropyl)‐1,1′,3,3′‐tetramethyldisiloxane (SiDA); and 3,3′,4,4′‐diphenyl ether tetracarboxylic acid dianhydride (OPDA). All copolyimides possess high glass transition temperatures (T_g's) between 237 and 271°C. Copolyimides based on M2 do not exhibit an obvious change in T_g as the M2 content is increased, while those based on M1 show a slight decrease in T_g as the M1 content is increased. All copolyimides exhibit high thermal decomposition temperatures. The copolyimides are soluble in aprotic solvents such as NMP, DMAc, DMF, DMSO, and 1,4‐butyrolactone. Some are even soluble in common low boiling point solvents such as THF and chloroform. The refractive index of a copolyimide is increased as the chromophore content is increased, while the birefringence of a copolyimide does not exhibit strong dependence on the chromophore content. © 2000 John Wiley & Sons, Inc. J Appl Polym Sci 76: 1619–1626, 2000     

Synthesis of novel maleimide-terminated thioetherimide oligomer and its bulk copolymerization with reactive solvents

This paper reports the synthesis of a novel maleimide-terminated thioetherimide oligomer and its copolymerization with reactive solvents bearing vinyl. Starting from 3-chlorophthalic anhydride and 4-chlorophthalic anhydride, 2,2′,3,3′-thiodiphenyl tertracaboxylic dianhydride (3,3′-TDPA) and 3,3′,4,4′-thiodiphenyl tertracaboxylic dianhydride (4,4′-TDPA) were synthesized. Thereby, a novel maleimide-terminated thioetherimide oligomer was prepared from. 3,3′-TDPA, 4,4′-TDPA, 3,3′-dimethyl-4,4′-diaminodiphenylmethane (DMMDA) and maleic anhydride. Binary and ternary copolymer resin were derived from corresponding binary and ternary homogeous solution consisting of thioetherimide oligomer, reactive solvent N-vinylpyrrolidone (NVP) or N,N′-dimethylacrylamide (DMAA) and divinylbenzene (DVB) as modifier, initiated either by gamma ray irradiation or by benzoyl peroxide (BPO). Thermal and mechanical properties of copolymer resin are determined and compared in terms of the kind of reactive solvent, addition of modifier DVB. The effect of initiation approach on property of final copolymer resin were studied. Phase separation and sub-transition of ternary copolymer resin induced by BPO are observed, which could be accounted for by thermal movement of DMAA molecules during thermal initiation. Structure-property relationship of copolymer resin was discussed. The effect of monomer molar ratio of 3,3′-TDPA and 4,4′-TDPA on thermal and mechanical properties were investigated.     

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 characterization of benzimidazole‐based low CTE block copolyimides

A series of block and random copolyimide films were synthesized from various molar ratios of two diamines, rigid 2‐(4‐aminophenyl)‐5‐aminobenzimidazole (APBI) and flexible 4,4′‐oxydianiline (ODA) by polycondensation with dianhydride 3,3′,4,4′‐biphenyltetracarboxylic dianhydride. The contents of APBI ranged from 10 to 60 mol % in copolyimides. The copolyimide films obtained by thermal imidization of poly(amic acid) solutions, were characterized by TMA, DMA, TGA, DSC, wide‐angle X‐ray diffraction, FTIR, tensile testing, water uptake (WU), and dielectric constant measurements. Rigid heterocyclic diamine APBI with interchain hydrogen bonding capability, led to low coefficient of thermal expansion (CTE), high T_g, high thermal stability and better mechanical properties. Increasing the APBI mol % caused a gradual decrease in the CTE and increase in T_g, thermal stability and tensile strength properties of the copolyimides films. Moreover, significantly enhanced thermal and mechanical properties of the block copolyimides were also found as compared to random copolyimides. The block copolyimide with APBI content of 60 mol %, achieved excellent properties, that is, a low CTE (4.7 ppm/K), a high T_g at 377°C, 5% weight loss at 562°C and a tensile strength at 198 MPa. This can be interpreted because of comparatively higher degree of molecular orientation in block copolyimides. These copolyimides also exhibited better dielectric constant and WU. This combination of properties makes them attractive candidates for base film materials in future microelectronics. © 2013 Wiley Periodicals, Inc. J. Appl. Polym. Sci., 2013     

Gas Permeation Properties of Copolyimides from 1,4-Bis(3,4-dicarboxyphenoxy)benzene Dianhydride and 2,2-Bis(3,4- dicarboxyphenyl)hexafluoroisopropane Dianhydride

A series of aromatic copolyimides was prepared from 1,4-bis(3,4-dicarboxyphenoxy)benzene dianhydride (HQDPA) and 2,2-bis(3,4-dicarboxy-phenyl)hexafluoroisopropane dianhydride (6FDA) with 3,3′-dimethyl-4,4′-methyl-ene dianiline (DMMDA) by a chemical imidization. The gas permeability coefficients of the copolyimides to H₂, CO₂, O₂, N₂ and CH₄ were measured under 7atm. pressure. The fractional free volume of 6FDA–DMMDA is larger than that of HQDPA–DMMDA, while the chain segmental mobility of 6FDA–DMMDA is lower than that of HQDPA–DMMDA. The gas permeability of 6FDA–DMMDA is much higher than that of HQDPA–DMMDA but the perm-selectivity of 6FDA–DMMDA for H₂, CO₂, O₂, N₂ over CH₄ is lower than that of HQDPA–DMMDA. The experimental values of the gas permeability coefficients of the copolyimides are in satisfactory agreement with the values estimated from the gas permeability coefficients of the constituent homopolyimides and their weight fractions. © of SCI.     

Effects of molecular structure on the permeability and permselectivity of aromatic polyimides

Permeability coefficients of H₂, O₂, and N₂ were measured under 10 atm at the temperature from ambient temperature up to 150°C in a series of structurally different aromatic homo-and copolyimides, which were prepared from 4,4′-oxydianiline (ODA) or 4,4′-methylene dianiline (MDA) with various aromatic dianhydrides. The study shows that the molecular structure of the polyimides strongly influences gas permeability and permselectivity. As a result, the permeability coefficients of the polyimide membranes for each gas vary by over two orders of magnitude. In general, among the polyimide membranes studied, the increase in permeability of polymers is accompanied by the decrease in permselectivity, and the MDA-based polyimide membranes have higher permeability than ODA-based ones. Among the polyimides prepared from bridged dianhydrides, the permeability coefficients to H₂, O₂, and N₂ are progressively increased in the order BPDA <BTDA <ODPA ∼ TDPA <DSDA <SiDA <6FDA, while H₂/N₂ and O₂/N₂ permselectivity coefficients are progressively decreased in the same order. The copolyimide membranes, which were prepared from 3,3′,4,4′-biphenyltetracarboxylic dianhydride (BPDA), bis(3,4-dicarboxyphenyl)dimethylsilane dianhydride (SiDA), and ODA, have favorable gas separation properties and are useful for H₂/N₂ separation applications. © 1996 John Wiley & Sons, Inc.     

Thermal,mechanical and structural investigation of copolyimide–silica hybrids containing phosphine oxide

In this study, a novel hybrid copolyimide was synthesized from copolyamic acid solutions (PAAs) obtained by the reaction between bis(3-aminophenoxy-4-phenyl)phenylphosphine oxide (m-BAPPO), 3,3′-diaminodiphenyl sulfone (DDS) and 3,3′,4,4′-benzophenone tetracarboxylic dianhydride (BTDA), followed by thermal imidization. Hybrid materials containing 5% SiO₂ were synthesized by sol–gel technique. The polyimide–silica hybrids were characterized by Fourier Transform Infrared spectroscopy (FTIR) and scanning electron microscopy (SEM). Thermogravimetric analysis showed that the weight loss of hybrids is shifted to the higher temperature compared to the neat copolyimide. The contact angle measurements confirmed the hydrophobic surface of hybrids. Moreover, the gas permeability measurements were also done to take a step for forthcoming gas separation studies. The tensile modulus and strength of the copolyimides are good.     

Properties of copolyimides prepared from different tetracarboxylic dianhydrides and diamines

Various copolymides were prepared from two acid dianhydrides (BPDA, 3,3′,4,4′-biphenyl tetracarboxylic dianhydride; PMDA, pyromelitic dianhydride) and two diamines (PPD, p-phenylene diamine; ODA, 4,4′-oxydianiline). The thermal and mechanical properties of these polyimides were examined in detail. By appropriately selecting the ratios of the acid dianhydride component and the diamine component, polyimide films having desirable mechanical and thermal characteristics can be obtained. Further, it was proved that there is a correlation between the properties and the compositions of the copolyimides and that the properties could be estimated from the compositions by the use of multiple regression analysis. © 1996 John Wiley & Sons, Inc.     

Addition polyimides. IV. Effect of structure on thermal characteristics

Chain extension reaction of bis(m-maleimido phenyl) methyl phosphine oxide (BP) with 4,4′-diaminodiphenylmethane (BP–M), 4,4′-diaminodiphenyl ether (BP–E), 3,3′- and 4,4′-diaminodiphenyl sulfone (BP–DDS_m and (BP-DDS_m respectively), tris (m-aminophenyl) phosphine oxide (BP–TAP), and 9,9-bis(p-aminophenyl) fluorene (BP–BAF) was carried out by refluxing 1:0.3 molar solution of BP:diamine. The melting temperature and exothermic peak associated with curing of BP decreased by such chain extension. The thermogravimetric analysis indicated more than 60% residual weight at 800°C in nitrogen atmosphere in BP–DDS_m, BP–DDS_p, and BP–TAP resins. These resins can be processed at low temperature and can be used for fabrication of composites with improved properties.     

Preparation and characterization of soluble copoly(aryl ether ketone)s containing hindering structures

New copoly(aryl ether ketone)s have been synthesized by polycondensation of 2,2′,3,3′,6,6′‐hexaphenyl‐4,4′‐diphenol, 2,2′‐p‐hydroxyphenyl‐iso‐propane, and 4,4′‐difluorobenzophenone. The technology of ¹³C‐NMR was used to determine contents of the two bisphenols in the copolymers. Chain structure was characterized by illustrating average block length (L_A, L_C) in terms of portion of the triads (AKA, CKC, AKC). The obtained copoly(aryl ether ketone)s have the properties of excellent solubility, high heat‐resistance, good tensile strength, and good selectivity for gas permeability. © 2000 John Wiley & Sons, Inc. J Appl Polym Sci 78: 20–24, 2000     

Equilibrium of one-pot polymerization of polyimide

One-pot polymerization of polyimide from 3,3′,4,4′-biphenyl tetracarboxylic dianhydride (BPDA) and 4,4′-oxydianiline (ODA) was examined. The equilibrium in the polyimide with water was examined in detail in p-chlorophenol solution during the polymerization. The equilibrium constant was expressed by log K = 1.50 + 1433 (1/T). The polymerization reaction is exothermic. The molecular weight increased with decrease of temperature. © 1996 John Wiley & Sons, Inc.     

Synthesis of aromatic poly(urea‐imide) with heterocyclic side‐chain structure

The poly(urea‐imide) copolymers with inherent viscosity of 0.81–1.08 dL/g were synthesized by reacting aryl ether diamine or its polyurea prepolymer with various diisocyanate‐terminated polyimide prepolymers. The aryl ether diamine was obtained by first nucleophilic substitution of phenolphthalein with p‐chloronitrobenzene in the presence of anhydrous potassium carbonate to form a dinitro aryl ether, and then further hydrogenated to diamine. The polyimide prepolymers were prepared by using 4,4′‐diphenylmethane diisocyanate to react with pyromellitic dianhydride, 3,3′,4,4′‐benzophenonetetracarboxylic dianhydride, or 3,3′,4,4′‐sulfonyldiphthalic anhydride by using the direct one‐pot method to improve their solubility, but without sacrificing thermal property. These copolymers are amorphous and readily soluble in a wide range of organic solvents such as N‐methyl‐2‐pyrrolidone, dimethylimidazole, N,N‐dimethylacetamide, dimethyl sulfoxide, N,N‐dimethylformamide, m‐cresol, and sulfolane. All the poly(urea‐imides) have glass transition temperatures in the range of 205–240°C and show a 10 wt % loss at 326–352°C in nitrogen and 324–350°C in air. The tensile strength, elongation at break, and initial modulus of these copolymer films range from 42 to 79 MPa, 5 to 16%, and 1.23 to 2.02 GPa, respectively. © 1999 John Wiley & Sons, Inc. J Appl Polym Sci 74: 1719–1730, 1999     

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

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

Permeation of xylene isomers through nitrile gloves

The physical parameters of the xylene isomers (the positional isomers o-, m-, and p-xylenes and the skeletal isomer ethyl benzene) responsible for the differing permeation behavior of the isomers through lined unsupported 0.41 mm thick nitrile glove material were investigated. An ASTM type permeation cell at 30°C, constant mixing conditions, hexane liquid collection, and capillary column gas chromatography/mass spectrometry of samples taken from the collection side every ten minutes allowed break through times t_b and steady-state sections to be defined. While pure isomers had distinct break through times t_b(m-xylene = p-xylene < ethyl benzene = o-xylene), steady-state permeation rates P_s(p-xylene > m-xylene > ethyl benzene = o-xylene), lag times t_l(m-xylene < p-xylene = ethyl benzene < o-xylene), and diffusion coefficients D_p(m-xylene < p-xylene = ethyl benzene < o-xylene), such behavior was lost in a equal volume mixture (t_b, t_l, P_s, and D_p were equivalent). The average P_s of the mixture isomers of equal volumes did not differ from that expected from the individual pure isomer P_s values. The results for the pure isomers were attributed to o-xylene and ethyl benzene being similarly sterically hindered, the p-xylene being the flattest and most symmetrical molecule and having no dipole moment, and m-xylene being intermediate in steric structure. The pure isomer t_l were directly related to viscosity divided by the log octanol-water coefficient, while their log P_s was inversely related to dipole moment times the logarithm of the capacity factor for water for a reversed-phase high-performance liquid chromatography column. In an equivolume mixture of the isomers, isomer interactions caused equivalence for all permeation kinetic parameters, indicating that the kinetics of mixture constituents is not predictable from the behavior of the pure constituents, although mass transfer appears additive. © 1997 John Wiley & Sons, Inc. J Appl Polym Sci 63: 1713–1721, 1997     

Synthesis and optical properties of two series of soluble acridine-containing copolyimides

Two series of copolyimides were designed and synthesized by one-step polycondensation of two diamines, 3,6-diaminoacridine (Acridine) and 4,4′-(9H-fluoren-9-ylidene)bisphenylamine (FBPA), with a dianhydride 4,4′-(hexafluoroisopropylidene)diphthalic anhydride (6FDA) or 3,3′,4,4′-benzophenonetetracarboxylic dianhydride (BTDA), respectively. The copolyimides were named as AFFx (Acridine-FBPA-6FDA polyimide) and AFBx (Acridine-FBPA-BTDA polyimide), respectively, where x (x = 0, 1, 3, 5 10, 15 and 20) represents the mole percentage of acridine among the sum of two diamines. Characterization of the polymers was conducted by using FT-IR, EA, GPC, TGA, DSC, UV-vis and FL techniques. The Mw and MWD of AFFx are in the range of 2.29-5.09 × 10⁴ and 1.93-2.72, respectively, as determined using GPC. AFFx could be dissolved in some low boiling point solvents such as THF, CH₂Cl₂, CHCl₃, etc. Thin AFFx films could be prepared by spin coating its CHCl₃ or THF solution onto glass. The temperature of 10% weight loss (T₁₀) for the copolyimides was above 540 °C. The emission maximum of AFFx in solution at the excitation wavelength of 480 nm was near 545 nm. And that of AFBx solution at the excitation wavelength of 390 nm was near 525 nm. UV-vis and FL spectra of the copolyimides indicated that the main chromophores in the copolyimides were acridine moieties and the excitation energy transfer from fluorene moieties to acridine moieties could take place. The copolyimides maybe a potential thermostable light-emitting material for organic light-emitting diodes.     

Synthesis and characterization of polyetherimides containing multiple ether linkages and pendent pentadecyl chains

4‐(4‐(4‐(4‐Aminophenoxy)‐2‐pentadecylphenoxy)phenoxy)aniline (APPPA) was synthesized starting from cashew nut shell liquid‐derived bisphenol, i.e. 4‐(4‐hydroxyphenoxy)‐3‐pentadecylphenol, by nucleophilic substitution reaction with 4‐chloronitrobenzene followed by reduction of the formed 4‐(4‐nitrophenoxy)‐1‐(4‐(4‐nitrophenoxy)phenoxy)‐2‐pentadecylbenzene. Three new polyetherimides containing multiple ether linkages and pendent pentadecyl chains were synthesized by one‐step high‐temperature solution polycondensation of APPPA in m‐cresol with three aromatic dianhydrides, i.e. 3,3′,4,4′‐oxydiphthalic anhydride, 4,4′‐(hexafluoroisopropylidene)diphthalic anhydride and 3,3′,4,4′‐biphenyltetracarboxylic dianhydride. Inherent viscosities and number‐average molecular weights of the polyetherimides were in the ranges 0.66–0.70 dL g^?1 and 17 100–29 700 g mol^?1 (gel permeation chromatography, polystyrene standards), respectively, indicating the formation of reasonably high molecular weight polymers. The polyetherimides were soluble in organic solvents such as chloroform, dichloromethane, tetrahydrofuran, pyridine, m‐cresol, N,N‐dimethylformamide, N,N‐dimethylacetamide, N‐methylpyrrolidone and dimethylsulfoxide, and could be cast into transparent, flexible and tough films from their solutions in chloroform. The polyetherimides exhibited glass transition temperatures (T_g) in the range 113–131 °C. The lowering of T_g could be attributed to the combined influence of flexibilizing ether linkages and pentadecyl chains which act as ‘packing‐disruptive’ groups. The temperature at 10% weight loss (T₁₀), determined from thermogravimetric analysis in nitrogen atmosphere, was in the range 460–470 °C demonstrating good thermal stability. The virtues of solubility and large gap between T_g and T₁₀ mean that the polyetherimides containing pendent pentadecyl chains have possibilities for both solution as well as melt processability. © 2015 Society of Chemical Industry     

Synthesis and properties of poly(ester imide) copolymers from 3,3′,4,4′-biphenyltetracarboxylic dianhydride, 2,2′-bis(trifluoromethyl)benzidine,and 4-aminophenyl-4′-aminobenzoate

A series of poly(ester imide) (PEsI) copolymers were synthesized using 3,3′,4,4′-biphenyltetracarboxylic dianhydride (4,4′-BPDA), 2,2′-bis(trifluoromethyl)benzidine (TFMB), and 4-aminophenyl-4′-aminobenzoate (APAB) as the monomers. Wide-angle x-ray diffraction results revealed that the average interchain distances of these polymers ranged from 4.6 to 5.7 Å, increasing with the increase of TFMB contents. PEsI-0.3 and PEsI-0.4 exhibited a glass transition temperature (T_g) of 445 and 455°C, respectively, while no distinctive T_g was observed for the PEsI copolymers when the APAB content was >50 mol%. The coefficients of thermal expansion (CTE) of these PEsI copolymers ranged from 3.8 to 24.2 ppm K⁻¹, increasing with the increase of TFMB contents. The PEsI copolymers exhibited a modulus of 5.7–7.8 GPa, a tensile strength of 282–332 MPa, and an elongation-at-break of 10.2%–23.3%. Furthermore, these copolymers exhibited a dielectric constant of 2.53–2.76, and a low dissipation factor (D_f) of 0.0026–0.0032 at 10 GHz in dry state. Because of their excellent combined properties, these PEsI copolymers are promising candidates as dielectric substrate materials for the applications in next generation flexible printed circuit boards operating at high frequencies.