Hexafluoroisopropylidene Diphthalic Anhydride Research Articles

Low-temperature crosslinked soluble polyimide as a dielectric for organic thin-film transistors: enhanced electrical stability and performance

We have prepared a low-temperature cross-linked soluble polyimide (SPI) as a dielectric material for organic thin-film transistors (OTFTs) to improve their electrical stability. Two types of SPIs (DOCDA/6FHAB and 6FDA/6FHAB) were synthesized by a one-step polymerization process using 5-(2,5-dioxytetrahydrofuryl)-3-methyl-3-cyclohexene-1,2-dicarboxylic anhydride (DOCDA) and hexafluoroisopropylidene diphthalic anhydride (6FDA) as the dianhydrides and 2,2-bis(3-amino-4-hydroxyphenyl)hexafluoropropane (6FHAB) as a diamine. To further enhance the electrical performance, the SPI thin films were crosslinked with methylated/ethylated (hydroxymethyl)benzoguanamine (HMBG) through a low temperature process at 160 °C. Crosslinking considerably improved the insulating properties, resulting in a substantial reduction in leakage current from 10−7 A cm−2 to 10−9 A cm−2 at 2.0 MV cm−1. When crosslinked SPIs were used as gate dielectrics in OTFTs, device stability and reliability, as measured by the off-current, threshold voltage, and hysteresis, improved significantly. Our results demonstrate the potential of crosslinked SPIs as effective gate dielectric materials for advanced organic thin-film transistors.

Optically active polyimides with different thermal histories of their preparation.

Optically active linear polyimides and hyperbranched poly (amic acid-imide) were prepared by using procedures varying in particular in the maximum temperature employed in their synthesis. The two types of linear polyimides were based on 4,4'-(hexafluoroisopropylidene)diphthalic anhydride and 1,2-diaminocylohexane enantiomers or 4,4'-(hexafluoroisopropylidene)diphthalic anhydride and 2,2'-diamino-1,1'-binaphthalene enantiomers. The amine-terminated hyperbranched poly (amic acid-imide) was prepared from 4,4'-(hexafluoroisopropylidene)diphthalic anhydride and 4,4',4″-triaminotriphenylmethane, and its end groups were modified with the chiral selectors N-acetyl-D-phenylalanine or N-acetyl-L-phenylalanine. The final structure of the products was analyzed by IR spectroscopy, and their optical activity was evaluated and confirmed by polarimetry or circular dichroism.

Novel high performance poly(sulfone-ether-amide-imide)s

A novel sulfone ether amide diamine was prepared through a two-step synthetic route. At first, 3,3′-((sulfonyl bis(1,4-phenylene))bis(oxy))dianiline was prepared from nucleophilic aromatic substitution reaction of 3-aminophenol with 4,4′-dichlorodiphenyl sulfone in the presence of K2CO3. In the second step, the reaction of this compound with isophthaloyl chloride resulted in the preparation of a unique aromatic diamine containing amide, ether, and sulfone groups. Then three different kinds of poly(sulfone-ether-amide-imide)s were prepared via polycondensation reaction of the synthesized diamine with different dianhydrides including pyromellitic dianhydride, benzophenonetetracarboxylic dianhydride, and hexafluoroisopropylidene diphthalic anhydride. The structures of synthesized precursors, monomer, and prepared polymers were characterized using elemental analysis, 1H-NMR and FT-IR spectroscopy methods. Inherent viscosity, molecular weight, thermal behavior and stability, flame retardancy, and solubility of polymers were studied. As the polymers showed high thermal stability and also improved solubility, they can be used as heat and fire resistant materials.

Development of CO2-Selective Polyimide-Based Gas Separation Membranes Using Crown Ether and Polydimethylsiloxane.

A series of CO2-selective polyimides (CE-PDMS-PI-x) was synthesized by copolymerizing crown ether diamine (trans-diamino-DB18C6) and PDMS-diamine with 4,4′-(hexafluoroisopropylidene) di-phthalic anhydride (6FDA) through the polycondensation reaction. The structural characteristics of the copolymers and corresponding membranes were characterized by nuclear magnetic resonance (NMR), infrared spectroscopy (ATR-FTIR), thermogravimetric analysis (TGA), differential scanning calorimetry (DSC), X-ray diffraction (XRD), and gel permeation chromatography (GPC). The effect of PDMS loading on the CE-PDMS-PI-x copolymers was further analyzed and a very good structure–property relationship was found. A well-distributed soft PDMS unit played a key role in the membrane’s morphology, in which improved CO2-separation performance was observed at a low PDMS content (5 wt %). In contrast, the fine-grained phase separation adversely affected the separation behavior at a certain level of PDMS loading, and the PDMS was found to provide a flexible gas-diffusion path, affecting only the permeability without changing the selective gas-separation performance for the copolymers with a PDMS content of 20% or above.

The impact of the flexibility of photosensitive polyimide backbone on the properties of liquid-crystal alignment under non-polarised ultraviolet light

ABSTRACT In order to study the impact of the flexibility of photosensitive polyimide (PI) backbone on the properties of liquid crystal (LC) alignment under non-polarised ultraviolet light (NPUVL), two kinds of photosensitive PI with different backbone structures were synthesised through the polymerisation of 2,2-bis(3-amino-4-hydroxyphenyl)-hexafluoropropane (AHHFP) with 4,4ʹ-(Hexafluoroisopropylidene)diphthalic anhydride (6FDA) and 4,4ʹ-oxydiphthalic anhydride (ODPA) respectively. Polarising optical microscope showed that the irradiation time for ODPA-PI-CA is shorter that for 6FDA-PI-CA in order to induce uniform LC alignment. The reason was investigated in detail with the UV-Vis spectra and reaction kinetics of the photosensitive group.

Synthesis and Properties of Colorless Transparent Polyimides with Low CTE and High Tensile Strength

To develop the colorless transparent fluorinated polyimide (PI) with low coefficient of thermal expansion (CTE) and high tensile strength, a series of ternary copolymerized fluorinated PIs were synthesized by 4,4-(Hexafluoroisopropylidene) diphthalic anhydride (6FDA), 2,2'-bis(trifluoromethyl) benzidine (TFMB), and the third monomer 3,3',4,4'-biphenyltetracarboxylic dianhydride (BPDA). The physical properties of the PI films were effectively regulated and optimized by adjusting the ratio of the rigid BPDA and flexible 6FDA components. By increasing the BPDA content, the thermal stability, dimensional stability, and mechanical properties of the polymers were enhanced. Among them, the PI film which molar ratio of 6FDA and BPDA was 5 : 5 exhibited an excellent comprehensive performance with a λ0 of 372 nm, Tmax nearly 91%, the tensile strength beyond 108 MPa and possessed high glass-transition temperature Tg which was 315.8°С. Furthermore, the CTE of the PI film was calculated about 21 ppm/K in the range of 25–200°С, indicating great dimensional stability.

Fabrication of mixed matrix membranes with zinc ion loaded titanium dioxide for improved CO2 separation

To date, mixed matrix membranes with nano-filler was considered to be an effective method to enhance the gas permselectivity of membrane separation. In this work, mixed matrix membranes for the facilitated transport of CO2 were prepared. Hexafluoroisopropylidene diphthalic anhydride - based aromatic polyimide was applied as polymeric matrix, while the zinc ion functionalized titanium dioxide spherical nano-particle was selected as nano-filler. The physical property, chemical structure and membranes morphology were characterized by FT-IR, TG, XRD, SEM, CA and XPS. Gas permselectivity was investigated using binary mixture gas of CO2/N2 and CO2/CH4, respectively. The effects of nano-filler content, functional group, operation temperature on gas permselectivity were studied. Results show that the incorporation of spherical nano-filler can effectively restrict the polymer chain packing and lead to low crystallinity. By incorporation of zinc ion modified spherical nano-filler, the CO2 permeability increased about 68.7~78.7%. PI-TiO2-PDA-Zn2+ mixed matrix membranes with 7.5 wt% nano-filler addition displayed the highest CO2 permeability (145.37 Barrer for CO2/N2 feed gas and 108.36 Barrer for CO2/CH4 feed gas, 1 Barrer = 7.5 × 10-18 m2 s−1 Pa−1) and satisfied CO2/inert gas selectivity (CO2/N2 selectivity of 49.28 and CO2/ CH4 selectivity of 49.48). CO2 permeability increased and selectivity decreased with the elevated temperature. Besides, the membrane exhibited good stability in the 30 days testing.

Syntheses of Colorless and Transparent Polyimide Membranes for Microfiltration.

Herein, poly(amic acid) (PAA) was synthesized using 4,4’-(hexafluoroisopropylidene) diphthalic anhydride (6FDA) as a dianhydride and 2,2-bis(3-aminophenyl)hexafluoropropane (6FAm) and 2,2-bis(3-amino-4-hydroxyphenyl)hexafluoropropane (6FAm-OH) as diamines. Poly(vinyl alcohol) (PVA) at various contents (0–5.0 wt%) was blended with PAA to prepare a composite material. Then, colorless and transparent polyimide (CPI) composite films were prepared by applying various stages of heat treatment using the PAA/PVA blend film as a precursor. These film-type composites were immersed in water to completely dissolve PVA, a water-soluble polymer, and their pore sizes were investigated to determine their potential as a porous membrane. According to the results of scanning electronic microscopy (SEM), as the concentration of PVA increased from 0 to 5.0 wt% in the CPI/PVA composite films, the size of the pores resulting from the dissolution of water-soluble PVA increased. Further, the micrometer-sized pores were uniformly dispersed in the CPI films. The thermal properties, morphology, and optical transparency of the two types of CPI membranes synthesized using 6FAm and 6FAm-OH monomers were examined and compared.

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

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

Soluble copolyimides containing 4,4′-isopropylidenedicyclohexanol (HBPA) isomer units: Synthesis, characterization, thermal, mechanical, and optical properties

In this work, 4,4′-isopropylidenedicyclohexanol (HBPA)-based dinitro isomers mixture (H″BPBN and H′BPBN) was synthesized and separated, and the structures of dinitro isomers were confirmed by differential scanning calorimetry and proton nuclear magnetic resonance spectroscopy. A series of copolyimides were prepared from diamino monomers with different percentages of novel diamine H″BPDA and 4,4′-(hexafluoroisopropylidene) diphthalic anhydride via a conventional two-step procedure. All the copolyimides could afford flexible, tough, and transparent films with transmittance no less than 73% at 450 nm, which was attributed to the fact that nonplanar alicyclic diamine and the bulky and weakly polarizable trifluoromethyl hampered the formation of charge-transfer complex. Moreover, all the copolyimides were soluble not only in polar solvents such as N,N-dimethylformamide but also in low-boiling-point solvents such as dichloromethane, which was related to the fact that the existence of alicyclic diamine and bulky trifluoromethyl decreased the intermolecular force. In addition, the conformation effects of H″BPDA and H′BPDA on the aspects of thermal, mechanical, optical, and soluble performance of copolyimides were investigated and their structure–property relationships were discussed in detail.

Effects of Diamines on the Optical Properties of Poly(ether imide)s Derived from 2,2-Bis[4-(3,4-dicarboxyphenoxy)phenyl]propane Dianhydride (BPADA)

The objective of this study was to investigate the effects of diamines with ether group or/and trifluoromethyl (-CF3) group on the optical properties of polyimides. A series of poly(ether imide)s (PEIs) (III) were prepared from 2,2-bis[4-(3,4-dicarboxyphenoxy) phenyl]propane dianhydride (BPADA) with various aromatic diamines (Ia-h) including non-fluorinated diamines (Ia-d) and the corresponding trifluoromethyl-substituted diamines (Ie-h). The fluorinated PEIs IIIe-h based on fluorinated diamines were nearly colorless with cutoff absorption wavelength (λ0) below 370 nm and with solubility higher than that of the corresponding CF3-free analogues (IIIa-d). Meanwhile, they had lower dielectric constants in the range of 2.91–3.21 at 1 MHz coupled with water absorptions below 0.70% and contact angles against water beyond 108°. The III series had tensile strength of 84.3–94.4 MPa, modulus of elasticity of 3.6–8.9 GPa and elongation at break of 9.4–25.3%, together with temperatures of 5% weight loss (T5%) beyond 510 °C. Compared to the IV series based on 4,4-(hexafluoroisopropylidene) diphthalic anhydride (6FDA), the corresponding III series exhibited better thermal and mechanical properties coupled with good optical properties, especially the fluorinated PEIs IIIe-h.

Synthesis and Properties of High Thermally Stable and Organosoluble Poly(pyridine imide)s with Pendent Diethylaminophenyl Groups

A novel diamine monomer 4-(4-diethylaminophenyl)-2,6-bis(4-aminophenyl)pyridine (APAP) was successfully synthesized, and then a series of poly(pyridine imide)s was prepared from APAP with five commercial dianhydrides: pyromellitic dianhydride (PMDA), 3,3′,4,4′-biphenyltetracarboxylic dianhydride (BPDA), 4,4′-oxydiphthalic anhydride (ODPA), 3,3′,4,4′-benzophenone tetracarboxylic dianhydride (BTDA), and 4,4′-(hexafluoroisopropylidene)diphthalic anhydride (6FDA) via a two-step solution polycondensation method. The structure of APAP was characterized by FT-IR, NMR, and MS. The resulting polymers have good solubility in polar solvents, such as NMP, DMF, and DMSO. Furthermore, they exhibited outstanding thermal stability. The glass transition temperature (Tg) of polymers range from 326 to 346 °C, and the temperature at 5 % and 10 % weight loss in the range of 527 °C to 570 °C and 550 °C to 601 °C, respectively. Moreover, they also presented excellent hydrophobicity with contact angels in the range of 88.4 ° to 94.0 °.

Synthesis and Characterization of Novel Poly(urethane-imide) Nanocomposites Containing Nanoencapsulated Phase Change Materials

A novel poly(urethane-imide) has been shown to be effective phase change material for thermal energy storage. Poly(urethane-imide) based material was synthesized by the reaction of 4,4′-diphenylmethane diisocyanate, polypropylene glycol, 4,4′-(hexafluoroisopropylidene)diphthalic anhydride and paraffin/SiO2 in dimethylformamide. The product was characterized by FTIR spectroscopy, thermogravimetric analysis, X-ray diffraction, scanning electronic microscopy and differential scanning calorimetry. The resulting product is composed of quasispherical particles with diameter of 162–405 nm. The melting and freezing temperatures are about 64 and 66°C for the paraffin and 69 and 71°C for the synthesized product, respectively. The synthesized pure poly(urethane-imide) have been also characterized by FTIR and NMR spectroscopy and other techniques.

Inhibition of Polyimide Photodegradation by Incorporation of Titanate Nanotubes into a Composite

The effect of UV light exposure on the properties of hexafluoroisopropylidene-diphthalic anhydride–oxydianiline (6FDA–ODA) polyimide (PI) and polyimide–titanate nanotube (TiNT/PI) composites has been studied using Raman spectroscopy, optical microscopy, nanoidentation and TEM. The degree of polymer photodegradation was estimated by measuring the change in affinity to a positively charged dye (methylene blue, MB). The mechanism of photoassisted transformations in polyimides usually involves scission of polymer chains accompanied by appearance of active radicals, which undergo further rapid transformations to more stable phenol, amine, and carboxylic functional groups. The accumulation of these groups can increase the degree of adsorption of charged dyes in the photodegraded polymer. It was found that neat PI showed a significantly increased capacity to adsorb MB after irradiation with UV, reaching a plateau after 1 h. In contrast, TiNT/PI composite demonstrated a much slower rise in concentration of adsorbed MB even after 4 h of UV exposure. Raman spectra indicated cleavage of C=O and C–F bonds in PI while only the C–F bond was damaged in TiNT/PI. Shorter cracks (≈ 40 µm long) appeared in TiNT/PI composites whereas macro cracks (> 100 µm) were visible in neat PI after 3 h of UV exposure. Brittleness was studied by comparing plasticity index which varied from 0 to 1 (0 corresponding to the most brittle material and 1 the most ductile one). Plasticity index reduced by 51% and 2% for PI and TiNT/PI, respectively after 3 h UV irradiation, indicating that TiNT can protect underlying PI from further damage. The hardness of neat PI decreased whereas, for TiNT/PI, it increased under UV, suggesting crosslinking of broken polymer chains with nanotubes.Graphical Photodegradation of a titanate nanotubes/polyimide composite can lead to cross-linking of broken polymer chains by nanostructured material, resulting in increased hardness.

Preparation of colorless polyimide hybrid films with enhanced optical, chemical and thermal resistance

In the present study, we prepared a polyimide hybrid film with improved transparency and chemical resistance by introducing cycloaliphatic epoxy-functionalized oligosiloxanes (CEOS) into polyimides. First, colorless polyamic acid (CPAA) was prepared from 4,4'-(hexafluoroisopropylidene) diphthalic anhydride and 3,3'-diaminodiphenyl sulfone, and then cross-linking and imidization reactions were carried out through the reaction between epoxy rings in CEOS and carboxylic acid groups in CPAA. The characteristics of polyimide hybrids were investigated by Fourier transform infrared, thermogravimetric analysis, scanning probe microscopy and scanning electron microscopy. The chemical resistance of the hybrid was examined by dropping an organic solvent on the surface of the hybrid film. The CEOS and CPAA hybrid of 1:2 molar ratio exhibited optimal chemical resistance and thermal stability. The surface roughness of the hybrid film showed very smooth morphology without any phase separation between CEOS and CPAA. The transparency of the film in visible light region was higher than original CPI films.

Synthesis and optical properties of semi-fluorinated poly(ether imide)s derived from non-fluorinated 1,4-bis(3,4-dicarboxyphenoxy)benzene dianhydride (HQDPA) and trifluoromethyl-substituted diamines

Abstract

Thermally cross-linked diaminophenylindane (DAPI) containing polyimides for membrane based gas separations

This study aims to expand structure-property relationships of diaminophenylindane (DAPI)-containing polyimides and the influence of thermal cross-linking on gas transport properties of such materials. A polyimide synthesized from hexafluoroisopropylidene diphthalic anhydride (6FDA), DAPI, and diaminobenzoic acid (DABA) in a molar ratio of 0.5/0.33/0.17, 6FDA0.5-DAPI0.33/DABA0.17, was crosslinked by thermal decarboxylation. After cross-linking, pure gas permeability of 6FDA0.5-DAPI0.33/DABA0.17 increased with increased cross-linking time; gas permeability increased by about 30% after cross-linking at 353 °C for 40 min. This increase in permeability correlated with an increase in d-spacing measured by wide angle x-ray scattering, suggesting an increase in inter-chain spacing upon cross-linking. Minimal changes in O2/N2 and N2/CH4 selectivities occurred with increased thermal cross-linking time for 6FDA0.5-DAPI0.33/DABA0.17. However, CO2/CH4 and C2H4/C2H6 pure gas selectivities increased with thermal treatment, suggesting a potential narrowing of free volume distribution.

Coating properties of 1H,1H-perfluorooctylamine-terminated polyimides based on hexafluoroisopropylidene diphthalic anhydride and 1,4,5,8 naphthalenetetracarboxylic dianhydride

This study attempted to prepare polyimide coatings (PIs) containing 6FDA (hexafluoroisopropylidene diphthalic anhydride) and/or NTDA (1,4,5,8 naphthalenetetracarboxylic dianhydride) in various ratios. 1% of these polyimide chains were terminated with 1H,1H-perfluorooctylamine (PFOA) and PFOA, and terminated polyimide coatings (PIFs) were prepared in the same ratios as PIs. Coatings were produced on aluminum substrates by a 75-μm wire-wound applicator and thermally imidized. Finally, thermal, wear, and physical properties of PIFs and PIs were compared to each other. PIFs exhibited higher abrasion resistance than PIs due to the presence of PFOA. The increase in 6FDA content also resulted in elevated abrasion resistance. Both NTDA and 6FDA compounds improved thermal stability. The increase in NTDA content raised the Tg values of the polyimides. PIFs exhibited higher static water contact angle values than PIs, but the existence of microcracks decreased their hydrophobicity. The gloss values of PIFs were excellent. Improved values were obtained for pencil hardness, crosscut adhesion, and MEK (methyl ethyl ketone) rubbing properties for all coatings. In addition to the pencil hardness test, a pendulum hardness test was also carried out. The presence of PFOA affected pendulum hardness values positively, and the increase in the amount of 6FDA on polymer backbone improved the pendulum hardness values despite the rigidity of NTDA.

Design and synthesis of novel porphyrinated polyimide nanofibers as dissolved oxygen sensor: The role of electro-activity and orientation

Two novel porphyrinated polyimides, 3,3′,4,4′-biphenyltetracarboxylic dianhydride (BPDA)/4,4′-Oxydianiline (ODA)/iron 5,10-bis(4-aminophenyl)-15,20-diphenylporphyrin (FeDATPP) and 4,4′-hexafluoroisopropylidene diphthalic anhydride (6FDA)/ODA/FeDATPP, abbreviated as BOFe and 6OFe, were synthesized and electrospun into nanofibers for dissolved oxygen (DO) sensing. The effects of electro-activity (i.e., electron-withdrawing ability of BPDA, 6FDA and FeDATPP when these units were binding with DO) and the roles of the nanofiber orientation in DO sensing were investigated. Electrochemical characterization indicates that the current values in Cyclic Voltammograms (CV) exhibits linear correlation with the DO concentration, with the correlation coefficient R2 varying from 0.9461 to 0.9958, suggesting the excellent DO sensing performance of the synthesized porphyrinated polyimides. Meanwhile, it is found that the oxygen reduction behaviors in DO sensing were vastly altered due to the different electro-activity and orientation structures of the porphyrinated polyimides nanofibers. An unusual side-on porphyrin-O2 configuration and charge transfer mechanism during DO sensing were clarified upon molecular simulation. The present work provides two novel porphyrinated polyimides for DO sensor applications.

Thermal rearranged poly(imide-co-ethylene glycol) membranes for gas separation

Thermal rearrangement of α-functional polyimide membranes into poly(benzoxazole) improves the permselectivity performance compared to the precursor polymer. This is due to the bimodal cavity size distribution generated through the TR process. The cavity volume can be further increased by including segments within the polyimide that undergo degradation at a lower temperature than the TR process. The loss of these segments leaves behind cavity space that can be used to increase gas permeability. This is achieved here for copolymers based on 4,4′-hexafluoroisopropylidene diphthalic anhydride (6FDA) and 3,3′-dihydroxy-4,4’-diamino-biphenyl (HAB) with poly (ethylene glycol) segments, where the PEG segments undergo thermal degradation below the PI to PBO transition temperature. HAB-6FDA-PEG copolymer membranes, with different weight % PEG, had poor permselectivity for CO2-N2 and CO2-CH4 separation. Undertaking thermal treatment to degrade the PEG segments but retaining the PI polymer resulted in an increased fractional free volume of the resulting membrane and higher gas permeability, but a corresponding loss of CO2 selectivity. Producing TR-PBO from the copolymers through thermal rearrangement at 450 °C, improved the gas permeability of the resulting membranes by over an order of magnitude, as well as improving the CO2 selectivity. This was attributed to the degradation of the PEG segments increasing the FFV of the membranes, resulting in over a third of the polymers' morphology being free volume. The resulting TR-PBO membranes formed from copolymers with PEG segment had enhanced permselectivity performance compared to TR-PBO formed from the polyimide homopolymer.