Surface properties and blood compatibility of some aliphatic/aromatic polyimide blends

Two binary polyimide (PI) blends having a common monomer, diamine and dianhydride, were prepared. The first system was composed of PIs obtained from an alicyclic and flexible dianhydride, namely 5‐(2,5‐dioxotetrahydrofurfuryl)‐3‐methyl‐3‐cyclohexene‐1,2‐dicarboxylic acid anhydride (DOCDA) and two aromatic diamines, 4,4′‐oxydianiline (ODA) and p‐phenylenediamine (PPD), respectively. In the second system, ODA was combined with DOCDA and (hexafluoroisopropyldiene)diphtalic dianhydride (6FDA). Incorporation of aliphatic and asymmetric DOCDA moieties, hexafluoropropyldiene groups and ether linkages in the molecular structure of PI blends, poly(DOCDA/PPD)/poly(DOCDA‐ODA) and poly(6FDA‐ODA)/poly(DOCDA‐ODA) influenced the surface tension parameters, surface and interfacial free energy, and the work of spreading of water, maintaining the surface hydrophobic characteristics of both systems. In addition, it has been found out that surface hydrophobicity and surface roughness are properties that can be correlated with the red blood cells and platelets compatibility. POLYM. ENG. SCI., 2013. © 2012 Society of Plastics Engineers     

Synthesis of a new siloxane‐containing alicyclic dianhydride and the derived polyimides with improved solubility and hydrophobicity

The structural transformation strategy of cis‐5‐norbornene‐endo‐2,3‐dicarboxylic anhydride (NA) was performed by esterification. The double bond on the diester of NA showed adequate hydrosilylation reactivity with Si? H bonds of phenyl‐containing disiloxane. Thereby, a new siloxane‐containing alicyclic dianhydride, 5,5′‐exo‐(1,3‐dimethyl‐1,3‐diphenyl‐disiloxane‐1,5‐diyl)bisbicyclo[2,2,1]heptane‐2,3‐endo‐dicarboxylic anhydride 6 was successfully synthesized starting from NA, 1,3‐dimethyl‐1,3‐diphenyldisiloxane and platinum complex catalyst. The whole synthetic route of dianhydride 6 consisted of esterification, hydrosilylation, saponification, acidification, and dehydration. A series of polyimides (PIs) were prepared from dianhydride comonomers of 6 and 4,4′‐biphenyltetracarboxylic dianhydride (BPDA) in different molar ratio together with the diamine 4,4′‐oxydianiline (ODA). The thermal and mechanical properties of PIs showed somewhat decrease with increasing content of dianhydride 6. The solubility of PIs increased with the increasing content of dianhydride 6, and further calculation from Bragg's equation indicated that average interchain distance (d‐spacing value) increased with increasing content of siloxane and alicyclic segments in the backbone of PIs. It was revealed that the hydrophobicity of PIs increased with the increasing content of dianhydride 6 . Polyimide 7g , which was prepared from 100% 6 and ODA, showed water adsorption of less than 0.7% and contact angle against water of 101.1°. © 2012 Wiley Periodicals, Inc. J Appl Polym Sci., 2013     

Mixed gas and pure gas transport properties of copolyimide membranes

Copolyimides were synthesized from dianhydride of 4,4′‐(hexafluoroisopropylidene)diphthalic anhydride (6FDA) with various diamine contents of 4,4′‐oxydianiline (ODA) and 2,3,5,6‐tetramethyl‐1,4‐phenylenediamine (TeMPD) by chemical imidization in a two‐step procedure. Polyimides (PIs) were characterized using thermogravimetric analysis, Fourier transform infrared spectroscopy, differential scanning calorimetry, as well as specific volume and free volume. The gas transport properties for pure gas and blends of CO₂ and CH₄ for the homopolymers and 6FDA‐ODA/TeMPD copolymers were investigated at 35°C and 150 psi pressure. In pure gas permeation, permeability of CO₂ and CH₄ increased with increasing TeMPD content in the diamine moiety, whereas the ideal selectivity decreased with increasing TeMPD content. In the mixed gas permeation, permeabilities and separation factor were measured as a function of CO₂ feed molar fraction for five PI membranes. The behavior of pure gas and mixed gas permeabilities and separation factor of CO₂/CH₄ mixtures as the chemical nature of the diamine and the CO₂ molar fraction in the feed gas were varied and are discussed in detail. © 2012 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2013     

Synthesis and characterization of new spirobisindane-based poly(imide)s: Structure effects on solubility,thermal behavior,and gas transport properties

Two new poly(imide)s (PIs) are derived from a biphenylspirobisindane-diamine monomer and the commercial dianhydrides: 4,4′-hexafluoroisopropyliden diphthalic anhydride ( 6FDA ) and pyromellitic anhydride ( PMDA ). Using polycondensation reactions, these new PIs were synthesized, in high yields (>95%), successfully. The presence of the spirocenter in the main chain of newly synthesized PIs make them soluble in most common organic solvents, whereas the rigidity of the dianhydride monomer makes them be thermically stable at about 500 °C (T_d10%). PI derived from 6FDA had 1.2-time higher permeability to the gases, based on gas transport measurements, than those derived from PMDA , which showed slightly higher selectivity values. Nevertheless, both PIs of intrinsic microporosity (PIMs-PI) are more selective to gas pairs, considerably, compared to the previously reported PIs that have same dianhydride in the monomer spirocenter, but instead of biphenyl has an oxodibenzene moiety ( PI-1-6FDA ) one. In this work, correlation between the structural rigidity of PIMs-PI and their selectivity to the gases ( PIM-PI-B > PIM-PI-A > PI-1-6FDA ) is reported. © 2020 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2020 , 137, 48944.     

Chemical oxidation stability and anhydrous proton conductivity of polyimides/phosphoric acid/imidazole blends

Polyimides (PIs) based on 3,3′,4,4′‐tetracarboxylicdiphenyl ether dianhydride, 3,3′,4,4′‐benzophenonetetracarboxylic dianhydride, 4,4′‐diaminodiphenylsulfone and 4,4′‐methylenedianiline were synthesized. They are easily dissolved in many strong and polar solvents like dimethylformamide, N,N‐dimethylacetamide, 1‐methyl‐2‐pyrrolidinone, and dimethylsulfoxide. A new kind of anhydrous proton conducting system based on PI/H₃PO₄ and PI/H₃PO₄/imidazole (Imi) blends was prepared. The chemical oxidation stability of the composite membranes was studied. The flexible PIs have better chemical oxidation stability. The addition of phosphoric acid can accelerate the degradation process of PIs, while the addition of Imi in PI/H₃PO₄ blends can greatly improve their chemical oxidation stability, which becomes much better than that of pure PIs. The proton conductivity of PI/H₃PO₄ blends is still lower compared with that of polybenzimidazole/H₃PO₄ blends. After the addition of Imi, the anhydrous proton conductivity of PI/H₃PO₄ blends increases significantly with increasing Imi content. Copyright © 2006 Society of Chemical Industry     

Thermal and dielectric properties of electrospun fiber membranes from polyimides with different structural units

In this work, electrospinning technique was used to prepare low dielectric constant membranes. First, three kinds of polyimide (PI) fiber membranes were fabricated by electrospinning of poly(amic acid) (PAA) solutions which are from polycondensation of 4,4′‐oxidianiline (ODA) and three dianhydrides, pyromellitic dianhydride (PMDA), 2,2′‐bis(3,4‐dicarboxyphenyl) hexafluropropane dianhydride (6FDA) and 1,2,4,5‐cyclohexanetetracarboxylic dianhydride(HPMDA), followed by imidization at higher temperature. The relationship of the fiber morphology, thermostability and dielectric properties of the membranes with the polymer structure were discussed. Under the same conditions, PAAs with more flexible structure are easier to form low viscosity solution and fabricate high pore fraction membranes which are low dielectric constant materials. Under the coupling effect of fluorine‐containing groups and contribution of pores, the dielectric constant of 6FDA‐containing PI is lowered to 1.21 at 1 KHz with lower dielectric loss which accords with the calculated one. Also the 5% weight loss temperature of the three kinds of PIs is all higher than 400°C. The formed electrospun membranes are thermostable low dielectric constant materials. © 2015 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2016 , 133, 43081.     

新型侧链型聚酰亚胺膜的制备及其渗透汽化分离性能

针对苯/环己烷混合物体系的特点,采用两种新型侧链二胺3,5-二氨基苯甲酸苯酯(PDA)和3,5-二氨基苯甲酸-4-三氟甲基苯酯(FPDA),制备了一系列由不同二酐与二胺单体如4,4'-二氨基二苯醚(ODA)和3,5-二氨基苯甲酸(DABA)聚合而成的用于渗透汽化分离苯/环己烷的聚酰亚胺膜,对其结构和各项性质进行了表征,并对膜材料的微观结构与宏观分离性能之间的关系进行了较为深入的研究。随着侧链二胺的引入,聚酰亚胺膜的分离效率随之持续增大,分离能力得以改善。渗透汽化实验结果表明,以6FDA为二酐单体的两类聚酰亚胺膜具有较优异的分离性能。乙二醇交联的6FDA-FPDA/ODA/DABA(1:7:2)膜综合渗透汽化分离性能最优。在50℃时,对于含苯50 %(质量)的苯/环己烷混合物,其渗透通量为9.84 kg·μm·m^-2·h^-1,分离因子达6.1。     

Effects of dianhydrides on the thermal behavior of linear and crosslinked polyimides

To determine the thermal characteristics of linear and crosslinked polyimides (PIs), BTDA, ODPA, and 6FDA were used to synthesize polyimides. Thermal degradation temperature and glass transition temperature of the resulting PIs were measured using thermogravimetric analysis (TGA) and differential scanning calorimetry (DSC). To measure the change in modulus and coefficient of thermal expansion (CTE) depending on dianhydride structure, a dynamic mechanical analyzer (DMA) and thermo‐mechanical analyzer (TMA) were used. The thermal degradation and glass transition temperature properties of linear PIs varied according to whether the linear chain adopted a bulky or flexible structure. Dynamic modulus and thermal expansion values of linear polyimides also showed good agreement with the TGA and DSC results. As we expected, linear polyimide with bulky 6FDA groups showed better thermal behavior than the flexible polyimides. Crosslinked polyimide nadic end‐capped (norbornene) with a bulky dianhydride group had a lower thermal degradation temperature and higher CTE than flexible BTDA and ODPA polyimides. Our results indicate that the mobility of the dianhydride group affects the thermal behaviors of linear and crosslinked polyimides in different ways. © 2014 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2015 , 132, 41412.     

Correlation of residual stress and adhesion on copper by the effect of chemical structure of polyimides for copper‐clad laminates

BACKROUND: Polyimide films coated on copper are a potential new substrate for fabricating printed circuit boards; however, adhesion between the copper and polyimide films is often poor. The relations between residual stress and adhesion strength according to the development of molecular orientation of polyimide films with different chemical backbone structure coated on copper were studied. RESULTS: The effect of chemical structures on properties including the residual stress and the adhesion strength were widely investigated for four different polyimides. Diamine 4,4′‐oxydianiline (ODA) and dianhydrides 1,2,4,5‐benzenetetracarboxylic dianhydride (PMDA), 4′‐(hexafluoroisopropylidene)diphthalic anhydride (6FDA), 4,4′‐oxydiphthalic anhydride (ODPA) and 3,3′,4,4′‐benzophenone tetracarboxylic dianhydride (BTDA) were used to synthesize polyimide. In an attempt to quantify the interaction of thermal mismatch with the polyimide films depending on various structures, residual stress experiments between polyimide film and Cu? Si wafer were carried out over a range of 25–400 °C using in situ thin film stress analysis. A universal test machine was used to conduct 180° peel test (ASTM D903‐98) of polyimide film from cooper foil. The residual stress on Cu? Si (100) wafer decreased in the order 6FDA‐ODA > BTDA‐ODA > ODPA‐ODA > PMDA‐ODA, and the interfacial adhesion strength decreased in the order BTDA‐ODA (5 N mm^?2) > ODPA‐ODA > PMDA‐ODA > 6FDA‐ODA. The results may suggest that the morphological structure, degree of crystallinity of chain orientation and packing significantly relate to the residual stress and adhesion strength in polyimide films. Wide‐angle X‐ray diffraction was used for characterizing the molecular order and orientation and X‐ray photoelectron spectroscopy was used for the analysis of components on copper after polyimide films were detached to confirm the existence of copper oxide chemical bonding and to measure the binding energy of elements on the copper surface. CONCLUSION: In this research, it is demonstrated that BTDA‐ODA polyimide has a low residual stress to copper, good adhesion property, good thermal property and low dielectric constant. Therefore, BTDA‐ODA would be expected to be a promising candidate for a two‐layer copper‐clad laminate. Copyright © 2007 Society of Chemical Industry     

Polyimides 7: Synthesis,characterization, and properties of novel soluble semifluorinated poly(ether imide)s

Three novel diamine monomers ( VI , VII , and VIII ) were synthesized. These diamine monomers lead to a number of semifluorinated poly(ether imide)s when reacted with different commercially available dianhydrides like pyromellitic dianhydride (PMDA), benzophenone tetracarboxylic acid dianhydride (BTDA), 2,2‐bis (3,4‐dicarboxyphenyl) hexafluoropropene (6FDA), and oxydiphthalic dianhydride (ODA) by thermal imidization route. Elemental analyses, IR and NMR techniques were used to characterize the monomers and polymers. The resulting polymers exhibited weight average molar masses up to 1.78 × 10⁵ g mol^?1 in GPC with respect to polystyrene standard and have very good solubility in several organic solvents such as NMP, DMF, DMAC, DMSO, chloroform, and THF. Very good solubility of these polymers in CDCl₃ enables their complete characterization by proton as well as ¹³C‐NMR techniques. The polymers showed very high thermal stability with decomposition temperature (5% weight loss) up to 511°C in air and high glass transition temperature up to 311°C depending upon the exact repeating unit structure. The polymer films showed high modulus (up to 2.9 GPa) as was evaluated by DMA. The polymers also showed very low water absorption (0.16%), low dielectric constant (2.35 at 1MHz) and very good optical transmission. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 103: 3025–3044, 2007     

Modification of cyanate ester resin by soluble polyimides

Soluble polyimides (PIs) were prepared as random or multiblock types with 4,4′‐(hexafluoroisopropylidene) diphthalic anhydride (6FDA) and 3,3′,4,4′‐biphenyltetracarboxylic dianhydride (s‐BPDA) as acid dianhydride components and 4,4′‐bis(m‐aminophenoxy) diphenyl sulfone (m‐BAPS) as a diamine component by a one‐pot process and used to improve the brittleness of the cyanate ester resin. Random‐type PIs were more effective as modifiers than multiblock‐type PIs. The morphologies of the modified resins depended on PI structure, molecular weight, and concentration. The most effective modification of the cyanate ester resin was attained because of a heterogeneous phase structure composed of a flat matrix phase and phase‐inverted structures of the modified resin; a 15 wt % inclusion of a random PI (weight‐average molecular weight = 63,400) composed of 6FDA, s‐BPDA, and m‐BAPS (0.5/0.5/1.0 molar ratio) led to a 65% increase in the fracture toughness for the modified resin with a slight loss of flexural strength and a retention of flexural modulus and glass‐transition temperature, compared with the values for the unmodified resin. Water absorptivity of the modified resin was comparable to that of the unmodified resin up to 400 h, and then, water absorption of the modified resins increased considerably. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 88: 1–11, 2003     

Synthesis of poly(propylene glycol)‐grafted polyimide precursors and preparation of nanoporous polyimides

A novel approach to prepare a polyimide nanofoam was explored by using a polyimide precursor grafted with a labile poly(propylene glycol) (PPG) oligomer. The PPG‐grafted polyimide precursor, poly((amic acid)‐co‐(amic ester)), was synthesized via partial esterification of poly(amic acid) derived from pyromellitic dianhydride (PMDA) and 4,4′‐oxydianiline (ODA) with bromo‐terminated poly(propylene glycol) in the presence of K₂CO₃ in hexamethylphosphoramide and N‐methylpyrrolidone. The precursor polymer film was spin‐coated onto a glass substrate, then imidized at 200 °C under nitrogen, and subsequently the PPG graft was decomposed by heating the film at 300 °C for 9 h in air, resulting in the PMDA/ODA polyimide nanofoam. The precursor polymers, polyimides and foamed polyimides were characterized by a variety of techniques including ¹H‐NMR spectroscopy, Fourier‐transform infrared (FT‐IR) spectroscopy, differential scanning calorimetry (DSC) and thermogravimetric analysis (TGA). The homogeneously distributed nano‐sized pores of 20–40 nm were observed by transmission electron microscopy (TEM) of the foamed polyimide. Copyright © 2004 Society of Chemical Industry     

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.     

Synthesis,characterization, thermal and optical properties of soluble polyimides derived from an unsymmetrical diamine

A new unsymmetrical diamine monomer, 2,4‐diaminophenyl [4′‐(2′′,6′′‐diphenyl‐4′′‐pyridyl)phenyl]ether, was successfully synthesized by nucleophilic substitution of 1‐chloro‐2,4‐dinitrobenzene with 4‐(2′,6′‐diphenyl‐4′‐pyridyl) phenol. The diamine monomer was characterized by FTIR, ¹H and ¹³C NMR, and elemental analysis techniques and used for the preparation of novel polyimides (PIs) by reaction with commercially available tetracarboxylic dianhydrides such as pyromellitic dianhydride, 3,3′,4,4′‐benzophenone tetracarboxylic dianhydride, and bicyclo[2.2.2]‐oct‐7‐ene‐2,3,5,6‐tetracarboxylic dianhydride. These PIs with inherent viscosities ranged from 0.43 to 0.48 dL/g were readily soluble in many organic solvents and afforded tough and flexible films by solution casting. These polymers exhibited T_gs between 237 and 294°C, and 10% weight loss temperatures in excess of 500°C with up to 56% char yield at 600°C in air. Their maximum fluorescence emission in dilute (0.2 g/dL) NMP solution appeared at 450 nm. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2010     

An insight on the effect of rubbing textile fiber on morphology of some semi-alicyclic polyimides for liquid crystal orientation

Two semi-alicyclic PIs were prepared from bicyclo[2.2.2]oct-7-ene-2,3,5,6-tetracarboxylic dianhydride (BOCA) and the aromatic diamines: 4,4′-oxydianiline (ODA) or 4-(4-{[4-(4-aminophenoxy)phenyl]sulfonyl}phenoxy)aniline (pBAPS). The obtained films are transparent in visible domain, having a cut-off wavelength of 294 nm for poly(BOCA–ODA) and 264 nm for poly(BOCA– p BAPS), respectively. Atomic force microscopy images indicate a better surface organization after rubbing with cotton velvet (V_C) comparatively with cellulose diacetate (V_CD). Contact angle measurements reveal a slight increase of hydrophobicity after patterning as a result of dipolar forces intensification and geometrical constraints of the macromolecular chains. The alignment properties of both PIs, tested with N-(4-methoxybenzylidene)-4-butylaniline, are more obviously for processing with V_C. Also, the contrast between the dark and bright states is higher for poly(BOCA– p BAPS)/V_C comparatively with poly(BOCA–ODA)/V_CD, since its larger surface malleability generates deeper microgrooves.     

Highly Thermal Stable Polyimides Applied in Flexible Resistive Memory

Flexible memory devices are one of the most crucial elements in the wearable electronics. In this work, polyimides (PIs)-based flexible resistive memory devices with an excellent thermal and mechanical durability are demonstrated. Four kinds of functional PIs are derived from the heterocyclic diamines including 2,6-diaminodibenzo-p-dioxin (OODA) and 2,6-diaminothianthrene, and dianhydrides including 4,4′-(hexafluoroisopropylidene)diphthalic anhydride (6FDA) and 3,3′,4,4′-biphenyltetracarboxylic dianhydride. PI with diamine of OODA and dianhydride of 6FDA (PI(OODA_6FDA)) possesses outstanding thermal and mechanical properties with a high glass transition temperature of 352 °C, a low coefficient of thermal expansion of 28.1 ppm K⁻¹, and a high elongation at break of 10%. In addition, PI(OODA_6FDA)-based memory shows write-once-read-many behavior with a high on/off current ratio of 10⁶ and a stable data retention, attributed to the donor–acceptor charge transfer between the polymer chains. The retained current levels at a low resistive state can be observed even with thermal treatment at 200 °C for 24 h or 1000 times cyclic bending at a bending radius of 5 mm. These results demonstrate the potential of heterocyclic PIs for flexible resistive memory.     

Thermoplastic character of polyimide blends

Polyimide blends consisting of pyromellitic dianhydride/4,4′-oxydianiline (PMDA/ODA) and biphenyl-tetracarboxylic dianhydride/p-phenylene diamine (BPDA/PDA) show a distinct glass transition behavior at temperatures lower than each component does. Disruption of molecular packing by blending of polymers having dissimilar interaction sites leads to a significant increase in molecular mobility at much lower temperatures. This is examined by laminating two pieces of film cast from the blend and measuring the adhesive strength at the interface. A strong adhesion, 11.5 N/cm (6.6 lbf/in) by 180° peel test, was achieved indicating interpenetration of polyimide molecules. It was also found that the polyimide blends can be converted into highly ordered states by mechanical deformation of the blends above their glass transition temperatures (T_gs).     

Synthesis and gas transport properties of novel hyperbranched polyimide–silica hybrid membranes

Physical and gas transport properties of hyperbranched polyimide (HBPI)—silica hybrid membranes prepared with a dianhydride monomer, 4,4′‐(hexafluoroisopropylidene)diphthalic anhydride (6FDA), and triamine monomers, 1,3,5‐tris(4‐aminophenoxy)triazine (TAPOTZ), and 1,3,5‐tris(4‐aminophenyl)benzene (TAPB), were investigated and compared with those of 6FDA‐TAPOB HBPI system synthesized from 6FDA and 1,3,5‐tris(4‐aminophenoxy)benzene (TAPOB). Glass transition and 5% weight‐loss temperatures of the 6FDA‐based HBPI–silica hybrid membranes were increased with increasing silica content. 6FDA‐TAPOTZ HBPI system, however, showed relatively low 5% weight‐loss temperatures, suggesting thermal instability of triazine‐ring in the TAPOTZ moiety. CO₂/CH₄ permselectivity of the HBPI–silica hybrid membranes were increased with increasing silica content, tending to exceed the upper bound for CO₂/CH₄ separation. This result indicated that free volume elements effective for CO₂/CH₄ separation were created by the incorporation of silica for the HBPI–silica hybrid systems. Especially, 6FDA‐TAPB HBPI system had high gas permeabilities and CO₂/CH₄ separation ability, arising from high fractional free volume and characteristic size and distribution of free volume elements. © 2012 Wiley Periodicals, Inc. J. Appl. Polym. Sci., 2013     

Microwave assisted polycondensation of polyimides by [4,4′‐(hexafluoroisopropylidene)diphthalic anhydride,pyromellitic dianhydride] and [2,4,6‐trimethyl‐m‐phenylenediamine]. Power,time, and solvent effect

The microwave assisted polycondensation of two polyimides were studied using pyromellitic dianhydride (PMDA), and 4,4′‐(hexafluoroisopropyliden)diphthalic anhydride (6FDA) as dianhydride monomers and 2,4,6‐trimethyl‐m‐phenylenediamine (TrmPD), as diamine monomer, under microwave irradiation in DMF and DMSO solvents. The structure and performance of polymers were characterized by Fourier Transform Infrared Spectroscopy (FTIR), viscosity, density, and Thermogravimetric Analysis (TGA). The results show that the polyimides can be obtained in a short reaction time with high intrinsic viscosity and high yield. The effect of the presence of a bridging group, ? C(CF₃)₂? , in the monomer structure is apparent in the permeability parameters of the macromolecules as polymer (6FDA‐TrmPD) always presents better results than polymer (PMDA‐TrmPD). Properties as density and T_g increases with the time exposition to the microwave irradiation. Polyimides obtained present good thermal properties because they began to lose weight in a range of 8–16% at high temperature as 450°C. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2010     

Synthesis of soluble and thermally stable polyimides from 3,5‐diamino‐N‐(4‐(8‐quinolinoxy) phenyl) aniline and various dianhydrides

Three novel polyimides (PIs) having pendent 4‐(quinolin‐8‐yloxy) aniline group were prepared by polycondensation of a new diamine with commercially available tetracarboxylic dianhydrides, such as pyromellitic dianhydride, 3,3′,4,4′‐benzophenone tetracarboxylic dianhydride, and bicyclo[2.2.2]‐oct‐7‐ene‐2,3,5,6‐tetracarboxylic dianhydride. These PIs were characterized by FTIR, ¹H NMR, and elemental analysis; they had high yields with inherent viscosities in the range of 0.4–0.5 dl g⁻¹, and exhibited excellent solubility in many organic solvents such as N,N‐dimethyl acetamide, N,N′‐dimethyl formamide, N‐methyl pyrrolidone (NMP), dimethyl sulfoxide, and pyridine. These PIs exhibited glass transition temperatures (T_g) between 250 and 325° C. Their initial decomposition temperatures (T_i) ranged between 270 and 450°C, and 10% weight loss temperature (T₁₀) up to 500°C with 68% char yield at 600°C under nitrogen atmosphere. Transparent and hard polymer films were obtained via casting from their NMP solutions. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2011