Block Copolyimides Research Articles

Aromatic block co-polyimide membranes for sour gas feed separations

Permeation properties of pure and gas mixture consisting of CO2, H2S, CH4, N2 and C2H6 through dense films of the block co-polyimides (6FDA-mPDA)-(6FDA-durene) are studied at 35–55°C and pressures of 100–500psi for combined separation of CO2, H2S and N2 from acid gas streams. The H2S composition in the gas mixture is up to 20vol%. This rigid block copolymer exhibits relatively constant or slightly decrease in pure gas permeability with increasing feed pressure for most of the penetrants. The pure gas CO2/CH4 and N2/CH4 selectivities are up to 61 and 2.6 respectively. The mixed gas studies also show relatively constant or slightly decrease in permeability coefficients with increase in pressure for most of the penetrants. One significant fact is that, at feed pressure of 500psi and 20vol% H2S in feed gas mixture (consisting of CO2, N2, CH4 and H2S), H2S/CH4 and CO2/CH4 separation factors are 23 and 27 respectively. These values are within the same order of magnitude or even better than those obtained in other state-of-the-art polymeric membranes that have been reported. Another unique feature of this co-polyimide is that, in addition to being selective to acid gas, it is also more selective to N2 as compare to CH4. Moreover, the CO2/CH4 separation factor does not suffer significant loss to the same degree as in the case of cellulose acetate (CA), even under these much more aggressive environments. This stability at moderate pressures and high H2S concentration is quite remarkable, as most reported studies are focused on low H2S concentrations and low pressures.

Gas transport properties in (6FDA‐RTIL)‐(6FDA‐MDA) block copolyimides

ABSTRACTThis article reports synthesis and structure property studies of block copolyimides synthesized using diamino room temperature ionic liquids (RTIL) as diamine monomers. Specifically, polyimide oligomers of different lengths were synthesized using 2,2‐bis (3,4‐carboxylphenyl) hexafluoropropane dianhydride (6FDA) and diamino RTIL (1,3‐di(3‐aminopropyl) imidazolium bis[(trifluoromethyl) sulfonyl] imide). These oligomers were copolymerized with 6FDA and m‐phenylenediamine (MDA) using in situ polymerization to form (6FDA‐RTIL)‐(6FDA‐MDA) block copolyimides. The impact of the length and relative concentration of 6FDA‐RTIL oligomer in the copolymer on the resulting thermal, physical, and gas transport properties was monitored. As the concentration of the 6FDA‐RTIL segments increased, the backbone of the block copolyimides became more flexible resulting in a decrease in the glass transition temperature (Tg) and an increase in the density. The permeabilities of the RTIL containing copolyimides were consistently lower than those of the base polyimide, 6FDA‐MDA, with some increase in selectivities. Interestingly, the permeabilities of films produced with the low molecular weight oligomers were very different than those produced with same composition of the high molecular weight oligomers. This may be indicative of very different morphologies within these copolyimides. © 2015 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2016, 133, 43077.

Synthesis and characterization of sulfonated block copolyimides derived from 4,4'‐sulfide‐bis(naphthalic anhydride) for proton exchange membranes

ABSTRACTA series of sulfonated copolyimides (SPIs) with hydrophilic segment length of 20–60 based on 4,4′‐sulfide‐bis(naphthalic anhydride) (SBNA) have been successfully synthesized to improve hydrolytic stability and proton conductivity. The SPI membranes were cast from their m‐cresol solutions, and they were characterized by determining the water uptake, water swelling ratio, mechanical properties, hydrolytic stability, oxidative stability, and proton conductivity. It was found that the water uptake of SPI membranes was low and decreased as the hydrophilic segment length increased, which led to good dimensional stability. In addition, the SPI membranes with low ion‐exchange capacity (IEC) value displayed excellent hydrolytic stability and retained good mechanical properties even after harsh hydrolysis testing, in which the block SPI with hydrophilic segment length of 40 had the best hydrolytic stability, while those with high IEC value showed an apparent decrease. All of the block SPI membranes show better conductivity than the random ones at the temperature range from 30 to 70°C. Interestingly, the proton conductivities of random SPI membranes were higher than that of corresponding block ones at 90°C. The block SPI with hydrophilic segment length of 40 gave the highest proton conductivity as the temperature increased among the block SPIs. © 2014 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2015, 132, 41501.

Aromatic polyimides with high melt index modified by 1,6-hexamethylenediamine

1,6-Hexamethylenediamine (HMDA) is utilized to synthesize copolyimides based on bisphenol-A dianhydride and 4,4-oxydianiline or 1,4-bis(4-aminophenoxy) benzene. The purpose of this study is to modify the processability of aromatic polyimides for textile processing and melt property requirements. Polyimides containing an aliphatic HMDA are synthesized via random and block copolymerizations. Variations in the aliphatic content produce a series of polyimides that have different thermal stability, mechanical properties, and processing characteristics. Based on the results, polyimides synthesized with 25 % HMDA have better mechanical properties compared to other contents of HMDA, and block copolyimides have better processability with higher melt index than random copolymers.

Preparation and proton conductivity of phosphoric acid-doped blend membranes composed of sulfonated block copolyimides and polybenzimidazole

A series of phosphoric acid (PA)-doped blend membranes composed of block or random sulfonated polyimides (SPIs) and polybenzimidazole (PBI) were prepared with similar PA contents to investigate the influence of chemical structures of SPIs on proton conductivity. The proton conductivity of a PA-doped blend membrane containing block-type SPI, PA-bSPI(80/20)/oPBI, was higher than that of the corresponding pristine block-type SPI, PA-SPI/PBI containing random-type SPI and Nafion membranes over a wide temperature range, and reached 0.37 S cm−1 at 90 °C and 98% relative humidity. The PA-bSPI(80/20)/oPBI membrane also showed distinct proton conductivity even at low humidity due to a new proton transport pathway among PA and sulfonic acid groups. Also, the novel PA-doped blend membrane showed higher proton conductivity than Nafion at both above 100 °C and below 0 °C under low relative humidity conditions. © 2013 Society of Chemical Industry

Synthesis and characterization of benzimidazole‐based low CTE block copolyimides

AbstractA 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 Tg, high thermal stability and better mechanical properties. Increasing the APBI mol % caused a gradual decrease in the CTE and increase in Tg, 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 Tg 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

Phase Separation and Water Channel Formation in Sulfonated Block Copolyimide

We compared experimental and simulated data to investigate the phase separation and water channel formation of proton exchange membranes (PEMs) for fuel cell. Sulfonated block copolyimides (SPIs) were adopted as model polymers for experiments and simulations, and Nafion was used as a reference. Nafion and SPIs were observed to have different microscopic structures such as constituent atoms, backbone rigidity, and the locations of sulfonic acid groups, all of which significantly affect phenomenological properties at the macroscopic level such as density, water uptake, and proton conductivity. In particular, SPIs show much weaker microphase separation than Nafion, mainly due to the lower mobility of sulfonic acid groups and the existence of acceptable sites for hydrogen bonding even in hydrophobic segments, which impedes water channel formation for proton transport. As a result, the phase separation behavior and the resulting water channel formation are the major factors affecting macroscopic properties of PEMs such as water uptake and proton transport.

Synthesis of copolyimides based on room temperature ionic liquid diamines

AbstractBlock copolyimides based on aromatic dianhydrides and diamines copolymerized with diamino room temperature ionic liquid (RTIL) monomers were synthesized over a range of compositions. Specifically, two diamino RTILs, 1,3‐di(3‐aminopropyl) imidazolium bis[(trifluoromethyl)sulfonyl] imide ([DAPIM] [NTf2]) and 1,12‐di[3‐(3‐aminopropyl) imidazolium] dodecane bis[(trifluoromethyl) sulfonyl] imide ([C12 (DAPIM)2] [NTf2]2) were synthesized using a Boc protection method. The two RTILs were reacted with 2,2‐bis(3,4‐carboxylphenyl) hexafluoropropane dianhydride (6FDA) to produce 6FDA‐RTILs oligomers that formed the RTIL component for the block copolyimides. The oligomers were reacted with 6FDA and m‐phenylenediamine (MDA) at oligomer concentration from 6.5 to 25.8 mol % to form block copolyimides. Increasing the concentration of the 6FDA‐RTIL oligomer in the block copolyimides resulted in a decrease in the thermal degradation temperature, glass transition temperature and an increase in the density. The gas permeability of the RTIL based block copolyimide decreased but the ideal permeability selectivity for CO2/CH4 gas pair increased relative to the pure 6FDA‐MDA. © 2010 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 48: 4036–4046, 2010

Gas Transport Properties of Asymmetric Block Copolyimide Membranes

We have synthesized fluorinated block copolyimides with different block chain lengths by chemical imidization in a two-pot procedure and prepared the asymmetric coployimide membranes using the dry-wet phase inversion process. The gas transport properties of the asymmetric membranes were measured using a high vacuum apparatus equipped with a Baratron absolute pressure gauge at 76 cmHg and 35 °C. We demonstrated that the skin layer thicknesses and the gas transport properties of the asymmetric membranes depended on the copolyimide structures. The phase separation in the block copolyimide solution instantaneously occurred so that the skin layer of the asymmetric block copolyimide membrane became thinner than that of the asymmetric random copolyimide membrane and the gas permeance of the asymmetric block copolyimide membrane had a high value. The apparent skin layer thickness of the asymmetric block coployimide membrane was 230 nm. The asymmetric copolyimide membrane indicated an O2 permeance of 2:7 × 10−4 [cm3(STP)/(cm2 sec cmHg)] (270 [GPU]) and an O2/N2 selectivity of 4.3.

Fluorenyl cardo copolyimides containing poly(ethylene oxide) segments: Synthesis, characterization, and evaluation of properties

AbstractA set of new block copolyimides containing fluorenyl cardo moieties (FR) in the polyimide blocks and poly(ethylene oxide) (PEO) sequences has been prepared using the two‐step method of polyimide synthesis. The combination of both moieties led to novel copolyimides with good solubility in a variety of solvents, which could easily be processed into films. Copolyimides with PEO content from 30 to 56 wt % were amorphous, showed good mechanical properties, and absorbed less water than other PEO‐containing polyimides previously reported. Copolyimides with higher PEO content (60 and 65%) showed crystallinity and yielded soft films. All of the copolymers showed two glass transition temperatures, the first one around −25 °C attributed to the PEO segments, and the second one at much higher temperature, which corresponded to the polyimide domains. The thermal degradation occurred in two steps, the first one being associated with the degradation of the PEO segments and the second one with the generalized aromatic polyimide decomposition. © 2008 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 46: 8170–8178, 2008

Thermally stable and organosoluble cardo binaphthylene based poly(amide imide)s and poly(ester imide)s

AbstractA new imide‐containing dicarboxylic acid based on a twisted binaphthylene unit, 2,2′‐bis(N‐trimellitoyl)‐1,1′‐binaphthyl (1), was synthesized from 1,1′‐binaphthyl‐2,2′‐diamine and trimellitic anhydride in glacial acetic acid. The structure of compound 1 was fully characterized with spectroscopic methods and elemental analysis. Series of thermally stable and organosoluble poly(amide imide)s (4a–4d) and poly(ester imide)s (5a–5d) with similar backbones were prepared by the triphenyl phosphite and diphenylchlorophosphate activated direct polycondensation of diimide dicarboxylic acid 1 with various aromatic diamines and diols, respectively. With due attention to the structural similarity of the resulting poly(amide imide)s and poly(ester imide)s, most of the differences between these two block copolyimides could be easily attributed to the presence of alternate amide or ester linkages accompanied by imide groups in the polymer backbone. The ultraviolet maximum wavelength values of the yellowish polymers were determined from their ultraviolet spectra. The crystallinity of these copolyimides was estimated by means of wide‐angle X‐ray diffraction, and the resultant polymers exhibited a nearly amorphous nature, except for the polymers derived from benzidine and 4,4′‐binaphthol. The poly(amide imide)s exhibited excellent solubility in a variety of highly polar aprotic solvents, whereas the poly(ester imide)s showed good solubility in less polar solvents. According to differential scanning calorimetry analyses, polymers 4a–4d and 5a–5d had glass‐transition temperatures between 331 and 357°C and between 318 and 342°C, respectively. The thermal behaviors of the obtained polymers were characterized by thermogravimetric analysis, and the 10% weight loss temperatures of the poly(amide imide)s and poly(ester imide)s were between 579 and 604°C and between 566 and 577°C in nitrogen, respectively. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 100: 3203–3211, 2006

Preparation of novel fluorinated block copolyimide membranes for gas separation

AbstractWe synthesized novel fluorinated block copolyimides with various diamine compositions and block chain lengths by chemical imidization in a two‐pod procedure. We describe the gas‐transport properties of the novel block copolyimide membranes. We demonstrate that the gas‐transport properties of the copolyimide membranes strongly depended on the block chain lengths. The gas permeabilities of the copolyimide membranes increased with increasing block chain length, and the gas selectivities increased with decreasing lengths. We clarify that the gas diffusivity of the block copolyimide membrane dominated the gas‐transport properties. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 100: 2436–2442, 2006

Preparation of novel sulfonated block copolyimides for proton conductivity membranes

In this article novel sulfonated block copolyimides with various diamine compositions and block chain lengths were synthesized by chemical imidization using a two-pot procedure. The proton conductivities of the block copolyimide membranes were measured as functions of the relative humidity and temperature using four-point-probe electrochemical impedance spectroscopy. The proton conductivity of the membranes strongly depended on the block chain lengths and increased with an increase in the block chain lengths. The proton conductivity of NTDA-BDSA-b-6FAP (112/48) as the block copolyimide membrane was approximately 0.35 S cm−1 which indicated a higher value when compared to that determined for Nafion®. Copyright © 2005 John Wiley & Sons, Ltd.

Synthesis and Gas Permeation Properties of Star-like Poly(ethylene oxide)s Using Hyperbranched Polyimide as Central Core

A series of star-like poly(ethylene oxide)s were synthesized using anhydride-terminated hyperbranched polyimides as the central cores and poly(ethylene oxide)s (PEOs) as the linear arms. Their physical and gas permeation properties were investigated in comparison with those of PEO segmented block copolyimides (PEO-PIs). The solubility of star-like PEOs was affected by the terminal groups. The amine-terminated star-like PEOs displayed better solubility property than the methoxy- and acetamido-terminated ones. The DSC and dynamic mechanical spectroscopy suggested the morphology of star-like PEOs was different from that of PEO-PIs. The thermo-mechanical property of amine-terminated star-like PEOs was significantly improved by cross-linking with ethylene glycol diglycidyl ether. The star-like PEO membranes were much more permeable to CO2 than to N2 and even to H2. However, their CO2 separation performance was slightly lower than that of PEO-PIs, probably due to the difference in the morphology. The AgBF4-doped star-like PEO membrane with a loading of 40 wt% (corresponding to 67 wt% in PEO matrix) showed a very high ideal selectivity of C2H4/C2H6 of more than 100 with a low ethylene permeability of 1.5×10−10 cm3 (STP) cm−1 s−1 cm Hg−1 in single-component permeation at 2 atm and 308 K. However, the permselectivity decreased down to 14 in mixed gas permeation. The permeation behavior was discussed based on the solubility and diffusivity.

Synthesis of polyimides and segmented block copolyimides by transimidization

The transimidization reaction has been successfully utilized to prepare a series of segmented block copolyimides. The synthesis and polymerization of an AX-type amino imide monomer containing the tetrahydro[5]helicene unit were accomplished. The AX-type amino imide monomer is stable during isolation and purification, owing to its inert X (e.g., N-pyridyl) group, but yet readily underwent a self-transimidization reaction and produced polyimide. Because of the presence of two reactive ends, such an AX-type polyimide could be incorporated into a series of block copolyimides by reaction with commercially available dianhydrides and diamines. All the copolymers showed two distinct glass-transition temperatures, typically around 250 and 430 °C. © 2000 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 38: 3991–3996, 2000

Copolyimides containing internal acetylene units as a high-performance polyimide molecular composite

Random and block copolyimides made of biphenyltetracarboxylic dianhydride (BPDA) and 3,3'-diaminodiphenylacetylene (intA), p-phenylenediamine (PDA), and 4,4'-oxydianiline (ODA) were prepared. Random copolyimides were prepared by adding BPDA into an N-methylpyrrolidone (NMP) solution of diamine mixtures, followed by thermal imidization. The ratio of PDA and intA or ODA was 7:3. Block copolyimides were prepared by the reaction of amine-terminated BPDA/PDA units and anhydride-terminated BPDA/intA (or ODA) units. The ratio of PDA and intA or ODA was also set at 7:3. For the polyimides containing internal acetylene units, exotherms appeared on DSC measurements starting from 320C, which shows that crosslinking is occurring. Cold-drawing of polyamide acid films gave polyimide films with a higher modulus. High-temperature treatment to induce crossblinking did not lower the high modulus afforded by the cold-drawing. Crosslinking afforded a higher Tr, and a higher modulus at higher temperatures. Laminate processing was performed at 400C with a pressure of 100kgcm"2. The copolyimides containing internal acetylene units gave laminate films whose interfaces are strongly bonded through the crosslinking reaction. It was confirmed that the laminate films maintained the high modulus afforded by crosslinking.

Polyimide-polyethylene glycol block copolymers: synthesis, characterization, and initial evaluation as a biomaterial.

Block copolyimides with varying amounts of polyethylene glycol (PEG) were synthesized and characterized by copolymerization of diaminodiphenyl ether (DDE), amino terminated PEG, and benzophenone tetracarboxylic acid dianhydride (BTDA). Strong materials were obtained, with enhanced flexibility as compared to the parent DDE-BTDA polyimide homopolymer. Incorporation of PEG led to an increase in water absorption by these copolymers, and hydrophilicity was increased as reflected by a decrease in air-water-polymer contact angle. These materials supported less cell adhesion in vitro than the parent polyimide homopolymer. Short term in vivo evaluation of these copolymers showed reduced fibrous encapsulation than was observed in the absence of PEG.

Synthesis and properties of new block copolymers based on polydimethylsiloxane and tetraphenylethylene‐containing polyimide

AbstractNew polydimethylsiloxane (PDMS)‐polyimide block copolymers were synthesized by the solution polycondensation of aminopropyl‐terminated polydimethylsiloxane, 1,1‐bis(4‐aminophenyl)‐2,2‐diphenylethylene, and 3,3′,4,4′‐benzophenonetetracarboxylic dithioanhydride in pyridine. New 1,3‐bis(3‐aminopropyl)tetramethyldisiloxane (BADS)‐based random copolyimides were also prepared. The inherent viscosities of all the random and block copolyimides were in the range of 0.13–0.90 dL/g in N‐methyl‐2‐pyrrolidone. These copolymers were soluble in N,N‐dimethylacetamide, N‐methyl‐2‐pyrrolidone, and m‐cresol. All the BADS‐based random copolymers and PDMS‐containing copolymers with PDMS content above 42 wt % were soluble in tetrahydrofuran and chloroform. Transparent or somewhat cpaque films were prepared by casting from the reaction solutions. The BADS‐based random copolyimides had one glass transition temperature (Tg) in the whole composition ranges, which showed single phase nature of the copolymers. On the other hand, the PDMS‐polyimide block copolymers had double TgS, indicating phase‐separated morphology. The block copolymers containing PDMS content above 73 wt % behaved like a high temperature elastomer. © 1993 John Wiley & Sons, Inc.

Preparation and Properties of Molecular Composite Films of Block Copolyimides Based on Rigid Rod and Semi-Flexible Segments

Molecular composite films of block copolyimides consisting of semi-flexible poly-N,N′-(oxydi-p-phenylene)pyromellitimide (PIOD) and rigid-rod poly-N,N′-(p-phenylene)-pyromellitimide were prepared by the usual two step ring-opening polyaddition and subsequent thermal imidization method, starting from pyromellitic dianhydride and either the aromatic diamines or their N-trimethylsilyl-substituted derivatives. The block copolyimide films were transparent and yellow in color over the whole composition ranges, and changed from brittle to ductile films with increasing PIOD content. As the PIOD content increased, the tensile modulus decreased monotonically, while the elongation at break and fracture energy increased in a similar fashion. The behavior of the tensile strength, however, was rather complicated.

Structure of polyimide compositions prepared from mixtures of polyamic acids

Polyimide compositions have been investigated, prepared by cyclization from mixtures of polyamic acids of various structure. A phase inversion occurs when the relative content of constituents in the mixture is varied; outside the region of inversion the stiff component is dispersed as rods, the flexible one as spheres. The crystallographic parameters and the texture of the crystallizable component are the same as in the homopolyimide. From the point of view of molecular structure the compositions represent mixtures of block copolyimides with homopolyimides. The size of blocks is considerably larger in chemical cyclization than in thermal cyclization.