One‐pot synthesis of polyetherimides from bis(chlorophthalimide) and dichlorodiphenylsulfone in diphenylsulfone

Polyetherimides and copolymers have been synthesized in one pot from bis(chlorophthalimide), dichlorodiphenylsulfone, and bisphenolate using diphenylsulfone as the solvent. The inherent viscosities of the obtained polyimides are in the range of 0.32–0.72 dL/g, and the structures of polyimides were confirmed by IR and elemental analyses. All of the polyimides have good solubility in common organic solvents. The 5% weight‐loss temperatures of the polyimides were 429–507°C in air. The glass transition temperatures (T_g) of 4,4′‐(9‐fluorenylidene) diphenol‐based polyimides are in the range of 253–268°C. The T_g of bisphenol A‐based polyimides is in the range of 198–204°C, while the T_g change inconspicuously when the ratios of diphenylsulfone increase. The wide‐angle X‐ray diffraction showed that all polyimides prepared are amorphous. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 102: 4584–4588, 2006     

Synthesis and properties of novel polyimides from 3‐(4‐aminophenylthio)‐N‐aminophthalimide

A novel, asymmetric diamine, 3‐(4‐aminophenylthio)‐N‐aminophthalimide, was prepared from 3‐chloro‐N‐aminophthalimide and 4‐aminobenzenethiol. The structure of the diamine was determined via IR and ¹H‐NMR spectroscopy and elemental analysis. A series of polyimides were synthesized from 3‐(4‐aminophenylthio)‐N‐aminophthalimide and aromatic dianhydrides by a conventional two‐step method in N,N‐dimethylacetamide and by a one‐step method in phenols. These polyimides showed good solubility in 1‐methyl‐2‐pyrrolidinone, m‐cresol, and p‐chlorophenol, except polyimide from pyromellitic dianhydride, which was only soluble in p‐chlorophenol. The 5% weight loss temperatures of these polyimides ranged from 460 to 498°C in air. Dynamic mechanical thermal analysis indicated that the glass‐transition temperatures of the polyimides were in the range 278–395°C. The tensile strengths at break, moduli, and elongations of these polyimides were 146–178 MPa, 1.95–2.58 GPa, and 9.1–13.3%, respectively. Compared with corresponding polyimides from 4,4′‐diamiodiphenyl ether, these polymers showed enhanced solubility and higher glass‐transition temperatures. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2008     

Light‐colored fluorinated polyimides based on 2,5‐bis(4‐amino‐2‐trifluoromethylphenoxy)biphenyl and various aromatic dianhydrides

A novel trifluoromethyl‐containing aromatic diamine monomer, 2,5‐bis (4‐amino‐2‐trifluoromethylphenoxy)biphenyl (2), was prepared through the nucleophilic substitution reaction of 2‐chloro‐5‐nitrobenzotrifluoride and phenylhydroquinone in the presence of potassium carbonate to yield the intermediate dinitro compound (1), followed by catalytic reduction with hydrazine and Pd/C. A series of fluorinated polyimides (code 5a–f) were synthesized from diamine (2) with six commercially available aromatic dianhydrides using a standard two‐stage process with thermal or chemical imidization of poly(amic acid). Most of fluorinated polyimides showed good solubility at a concentration of 5–10 wt % and even in pyridine and dioxane. For improving solubility of 5c, copolyimides (5c/a–f) were also prepared from 2 and a pair of dianhydrides (3c/a–f), which were mixed in the molar ratio 1:1. All the polyimide films had a tensile strength in the range from 73 to 112 MPa, an elongation at break within a range of 9–23%, and an initial modulus in the range of 1.6–2.2 GPa. These polyimides exhibited glass transition temperatures of 220–267°C and showed no significant decomposition below 500°C under either nitrogen or air atmosphere. In comparison with the analogous nonfluorinated polyimides based on 2,5‐bis (4‐aminophenoxy) biphenyl (2′), the fluorinated polyimides showed better solubility as well as reduced color intensity, lower dielectric constant, and moisture absorption. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 102: 4101–4110, 2006     

Molecular simulation of the glass transition and proton conductivity of 2,2′‐benzidinedisulfonic acid and 4,4′‐diaminodiphenylether‐2,2′‐disulfonic acid‐based copolyimides as polyelectrolytes for fuel cell applications

The glass transition temperatures (T_gs) and proton conductivities of polyimides synthesized from naphthalene‐1,4,5,8‐tetracarboxylic dianhydride (NTDA), 2,2′‐benzidinedisulfonic acid (BDSA), 4,4′‐diaminodiphenylether‐2,2′‐disulfonic acid (ODADS), and non‐sulfonated diamine monomers have been predicted using molecular dynamics simulations. The specific volumes for two dry and four hydrated NTDA‐based polyimides were plotted versus temperatures above and below T_gs to obtain the glass transition temperatures. The simulation results suggest that the ODADS‐based polyimide membranes exhibit lower T_gs and thus better mechanical properties than the BDSA‐based polyimides, which may be attributed to the high mobility of backbones of ODADS as supported by the vectorial autocorrelation function (VACF) results of this study. In addition, comparison of the simulated T_gs for the dry and hydrated ODADS‐based polyimides has shown that water content in polyimides can affect their T_gs. The proton conductivities of a representative polyimide in both dry and hydrated conditions have been obtained from molecular dynamics simulations of the proton and hydronium ion diffusion. The simulated conductivity for the hydrated NTDA‐ODADS/BAPB cell is in reasonable agreement with the experimental value obtained from the AC impedance method. The relationship between the chemical composition, chain flexibility, and the glass transition and proton conduction of these NTDA‐based polyimides was explored on the basis of VACF and pair correlation function analysis. Copyright © 2006 Society of Chemical Industry     

Synthesis of cardo containing asymmetric poly(ether‐naphthalimide‐phthalimide)s

A series of cardo based asymmetric polyimides containing bulky rigid naphthalimide and phthalimide groups were prepared from asymmetric monomer bishaloimide and bisphenols by solution polycondensation. Bishalo(naphthalimide‐phthalimide) monomers containing different terminal leaving groups (Cl, F, NO₂) were synthesized, and the reactivity difference of these monomers was compared for the successful synthesis of polyimides. The inherent viscosities of the polyimides were in the range 0.51 ? 0.60 dL g^?1 in N ‐methyl‐2‐pyrrolidone at 30 °C. These polyimides demonstrated good organosolubility and mechanical properties with tensile strengths of 93 ? 120 MPa, tensile moduli of 3.5 ? 5.3 GPa and elongations at break of 2.8% ? 4.3%. The polyimides showed high glass transition temperatures (T _g) ranging from 330 to 363 °C. The 10% weight loss (T _10%) of asymmetric polyimides reached 436 ? 500 °C in nitrogen and 417 ? 476 °C in air. The water uptake of the polyimides was in the range 0.35% ? 0.72%. © 2017 Society of Chemical Industry     

Electron‐beam irradiation of low‐density polyethylene in the presence of phenolic stabilizer,carboxylic acid stabilizer,or both

The effects of Irganox 1010 and citric acid as antioxidants and modifiers of the network structure and mechanical and thermal properties of low‐density polyethylene (LDPE) during electron‐beam crosslinking with different irradiation doses (up to 120 kGy) were investigated. The results showed that the addition of these stabilizers had a retarding effect on the gel fraction of LDPE within the investigated range of electron‐beam‐irradiation doses. However, a noticeable effect on the gel fraction was found for the LDPE formulations compounded with citric acid alone or with its mixture with Irganox 1010 (in an equal ratio), as illustrated by a study of the gel‐fraction/dose relationships. Tensile testing measurements showed that the addition of both stabilizers caused a slight reduction in the stress at break and an increase in the strain at break. On the other hand, the thermal properties of the LDPE batches crosslinked with electron‐beam irradiation were greatly improved as a result of the compounding with these stabilizers, as shown by thermogravimetric analysis studies. In this respect, the temperatures at different weight losses, the temperatures of the maximum rate of thermal decomposition, and the activation energies indicated that compounding with citric acid was more effective for stabilization against thermal decomposition than compounding with Irganox alone or a mixture. © 2005 Wiley Periodicals, Inc. J Appl Polym Sci 96: 1275–1286, 2005     

Structure and optical investigation of the effect of electron beam‐irradiation in poly‐allyl‐diglycol‐carbonate

The effect of electron beam irradiation on the structural and optical properties of Poly‐Allyl‐Diglycol‐Carbonate CR‐39 solid state nuclear track detector was investigated. Samples from CR‐39 detector were irradiated with electron beam with doses at levels between 10 and 140 kGy. The structural and optical modifications in the electron beam irradiated CR‐39 samples have been studied as a function of dose using different characterization techniques such as FTIR spectroscopy, Vickers hardness, refractive index and color difference measurements. The electron beam irradiation in the dose range 25–140 kGy led to a more compact structure of CR‐39 polymer, which resulted in an improvement in its hardness with an increase in the refractive index. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2010     

Study of conformational changes in poly(3‐dodecylthiophene) dependent on backbone stereoregularity using a spin‐probe technique

Poly(3‐dodecylthiophene) (P3DDT), with different amounts of head‐to‐head configuration defects, was characterized by ultraviolet–visible, ¹H‐NMR, photoluminescence, and Raman spectra. The heat‐induced conformational sample changes were studied by electron paramagnetic resonance (EPR). For the study of these changes, a spin‐probe technique was used, in which 5‐doxyl‐stearic acid methyl ester was applied as a spin probe. From the EPR spin‐probe spectra, rotational correlation times and order parameters were calculated. The heat‐induced conformational changes of P3DDT were accompanied by a monotonic decrease in the rotational correlation time up to approximately ?33°C (240 K) and then by an increase in the range of the glass‐transition temperatures, with the maximum being near room temperature and depending on the effective conjugation length. Afterward, the rotational correlation times had a decreasing tendency up to 90°C (363 K). © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 88: 2215–2223, 2003     

Photo‐patterning of smart light‐modulation gel

A novel method for fabricating desired patterns of smart light‐modulation gels, which consist of thermoresponsive N‐isopropylacrylamide (NIPAM) gel particles containing pigment, was developed. The patterns were fabricated by photo‐patterning of dispersion of colored NIPAM gel particles in photosensitive poly(vinylalcohol)‐styrylpyridinium solution. The pattern showed drastic color changes in response to the surrounding temperature changes. By repeated cycles of the patterning method, several independent patterns that contained different color particles were fabricated. In addition, a thermosensor array was also fabricated, which was constructed with independent patterns containing colored NIPAM gel having different color‐changing temperatures. The patterning method studied here is considered to have strong potential to extend the application field of the smart light‐modulation gels. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 102: 5351–5357, 2006     

Uses of electron‐beam irradiation to prepare pH‐ and temperature‐sensitive hydrogels from reactive poly(vinyl alcohol) grafts

Thermosensitive poly(vinyl alcohol)‐graft‐(maleic anhydride), PVA‐MA, and poly(vinyl alcohol)‐graft‐(N‐isopropylacrylamide maleic anhydride) (PVA‐MA‐NIPAAm) copolymers containing carboxyl groups were prepared using electron beam irradiation at dose 80 kGy. The swelling ratios of the cross‐linked gels were measured at various temperatures. The LCST values were measured using DSC technique. The temperature dependence of the swelling ratios of the cross‐linked copolymers and terpolymers were measured at different temperatures. The swelling ratios of copolymers increased with increasing temperature up to 25–38°C, then decreased. The swelling behavior of both copolymers and terpolymers was referred to formation of hydrogen bonds between amide group of NIPAAm moieties and carboxyl group in MA moieties and to hydrophobic interaction due to methyl groups of NIPAAm. The swelling behaviors of these gels were analyzed in buffer solution at various pH. Swelling ratios of all gels were relatively high and they showed reasonable sensitive to pH. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2008     

Organosoluble and light‐colored fluorinated polyimides based on 2,2‐bis[4‐(4‐amino‐2‐trifluoromethylphenoxy)phenyl]propane and aromatic dianhydrides

A novel fluorinated diamine monomer, 2,2‐bis[4‐(4‐amino‐2‐trifluoromethylphenoxy)phenyl]propane (2), was prepared through the nucleophilic substitution reaction of 2‐chloro‐5‐nitrobenzotrifluoride with 2,2‐bis(4‐hydroxyphenyl)propane in the presence of potassium carbonate, followed by catalytic reduction with hydrazine and Pd/C. Polyimides were synthesized from diamine 2 and various aromatic dianhydrides 3a–f via thermal imidization. These polymers had inherent viscosities ranging from 0.73 to 1.29 dL/g. Polyimides 5a–f were soluble in amide polar solvents and even in less polar solvents. These films had tensile strengths of 87–100 MPa, elongations to break of 8–29%, and initial moduli of 1.7–2.2 GPa. The glass transition temperatures (T_g) of 5a–f were in the range of 222–271°C, and the 10% weight loss temperatures (T₁₀) of them were all above 493°C. Compared with polyimides 6 series based on 2,2‐bis[4‐(4‐aminophenoxy)phenyl]propane (BAPP) and polyimides 7 based on 2,2‐Bis[4‐(4‐aminophenoxy)phenyl]hexafluoropropane (6FBAPP), the 5 series showed better solubility and lower color intensity, dielectric constant, and lower moisture absorption. Their films had cutoff wavelengths between 363 and 404 nm, b* values ranging from 8 to 62, dielectric constants of 2.68–3.16 (1 MHz), and moisture absorptions in the range of 0.04–0.35 wt %. © 2004 Wiley Periodicals, Inc. J Appl Polym Sci 95: 922–935, 2005     

Syntheses and properties of polyimides derived from diamines containing 2,5‐disubstituted pyridine group

A series of novel homo‐ and copolyimides containing pyridine units were prepared from the heteroaromatic diamines, 2,5‐bis (4‐aminophenyl) pyridine and 2‐(4‐aminophenyl)‐5‐aminopyridine, with pyromelltic dianhydride (PMDA), and 3,3′, 4,4′‐biphenyl tertracarboxylic dianhydride (BPDA) via a conventional two‐step thermal imidizaton method. The poly(amic acid) precursors have inherent viscosities of 1.60–9.64 dL/g (c = 0.5 g/dL in DMAC, 30°C) and all of them can be cast and thermally converted into flexible and tough polyimide films. All of the polyimides show excellent thermal stability and mechanical properties. The polyimides have 10% weight loss temperature in the range of 548–598°C in air. The glass transition temperatures of the PMDA‐based samples are in the range of 395–438°C, while the BPDA‐based polyimides show two glass transition temperatures (T_g1 and T_g2), ranging from 268 to 353°C and from 395 to 418°C, respectively. The flexible films possess tensile modulus in the range of 3.42–6.39 GPa, strength in the range of 112–363 MPa and an elongation at break in the range of 1.2–69%. The strong reflection peaks in the wide‐angle X‐ray diffraction patterns indicate that the polyimides have a high packing density and crystallinity. The polymer films are insoluble in common organic solvents exhibiting high chemical resistance. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 102: 1844–1851, 2006     

Syntheses and properties of novel polyimides derived from 2‐(4‐Aminophenyl)‐5‐aminopyrimidine

2‐(4‐Aminophenyl)‐5‐aminopyrimidine (4) is synthesized via a condensation reaction of vinamidium salts and amidine chloride salts, followed by hydrazine palladium catalyzed reduction. A series of novel homo‐ and copolyimides containing pyrimidine unit are prepared from the diamine and 1,4‐phenylenediamine (PDA) with pyromellitic dianhydride (PMDA) or 3,3′,4,4′‐biphenyl tertracarboxylic dianhydride (BPDA) via a conventional two‐step thermal imidization method. The poly(amic acid) precursors had inherent viscosities of 0.97–4.38 dL/g (c = 0.5 g/dL, in DMAc, 30°C) and all of them could be cast and thermally converted into flexible and tough polyimide films. All of the polyimides showed excellent thermal stability and mechanical properties. The glass transition temperatures of the resulting polyimides are in the range of 307–434°C and the 10% weight loss temperature is in the range of 556–609°C under air. The polyimide films possess strength at break in the range of 185–271 MPa, elongations at break in the range of 6.8–51%, and tensile modulus in the range of 3.5–6.46 GPa. The polymer films are insoluble in common organic solvents, exhibiting high chemical resistance. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 102: 5871–5876, 2006     

Soluble and light‐colored polyimides from 2,3,2′,3′‐oxydiphthalic anhydride and aromatic diamines

A series of polyimides were prepared from 2,3,2′,3′‐oxydiphthalic anhydride (3,3′‐ODPA) with various aromatic diamines via three different synthetic procedures. The one‐step and two‐step methods with the thermal imidization of poly(amic acids) (PAAs) yielded polyimides with a relatively low inherent viscosity; these produced brittle films. The polyimides prepared by the two‐step method via the chemical imidization of PAA precursors exhibited a higher inherent viscosity and afforded tough and creaseable films. All the 3,3′‐ODPA based polyimides had a significantly higher solubility than the corresponding polyimides from 3,4,3′,4′‐oxydiphthalic anhydride. The films cast from 3,3′‐ODPA polyimides also showed high optical transparencies and less color, with an ultraviolet–visible absorption edge of 370–397 nm and low yellowness index values of 11.3–29.8. These polyimides exhibited glass‐transition temperatures in the range 211–289°C and showed no significant decomposition below 500°C under nitrogen or air atmospheres. © 2005 Wiley Periodicals, Inc. J Appl Polym Sci 97: 1352–1360, 2005     

Polyimides derived from 1,4‐bis [3‐oxy‐(N‐aminophthalimide)] benzene

A novel diamine, 1,4‐bis [3‐oxy‐(N‐aminophthalimide)] benzene (BOAPIB), was synthesized from 1,4‐bis [3‐oxy‐(N‐phenylphthalimide)] benzene and hydrazine. Its structure was determined via IR, ¹H NMR, and elemental analysis. A series of five‐member ring, hydrazine‐based polyimides were prepared from this diamine and various aromatic dianhydrides via one‐step polycondensation in p‐chlorophenol. The inherent viscosities of these polyimides were in the range of 0.17–0.61 dL/g. These polymers were soluble in polar aprotic solvents and phenols at room temperature. Thermogravimetric analysis (TGA) showed that the 5% weight‐loss temperatures of the polyimides were near 450°C in air and 500°C in nitrogen. Dynamic mechanical thermal analysis (DMTA) indicated that the glass‐transition temperatures (T_gs) of these polymers were in the range of 265–360°C. The wide‐angle X‐ray diffraction showed that all the polyimides were amorphous. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2009     

Organosoluble and light‐colored fluorinated polyimides derived from 5,5′‐bis[4‐(4‐amino‐2‐trifluoromethylphenoxy) phenyl]‐4,7‐methanohexahydroindan

A novel bis(ether amine) monomer, 5,5′‐bis[4‐(4‐amino‐2‐trifluoromethylphenoxy)phenyl]‐4,7‐methanohexahydroindan ( 2 ), was synthesized through the nucleophilic aromatic substitution reaction of 5,5′‐bis‐(4‐hydroxyphenyl)‐4,7‐methanohexahydroindan with 2‐chloro‐5‐nitrobenzotrifluoride to yield the intermediate dinitro compound, followed by catalytic reduction with hydrazine and Pd/C. A series of polyimides were synthesized from 2 and various aromatic dianhydrides using a standard two‐stage process with chemical or thermal imidization of poly(amic acid). All of these polymer films were soluble in amide‐type solvents above 10% w/v, had tensile strengths of 97–117 MPa, and the 10% weight loss temperature was above 464 °C with their residues exceeding 46% at 800 °C in nitrogen. Compared with the non‐fluorinated polyimides, the fluorinated series were observed to have lower dielectric constants (2.92–3.28 at 1 MHz) and lower moisture absorptions (0.15–0.43 wt%) as well as lower color intensity and better solubility. Copyright © 2006 Society of Chemical Industry     

The High‐Pressure Characterization of Energetic Materials: 2‐Methyl‐5‐Nitramino‐2H‐Tetrazole

The isothermal structural properties, equation of state, and vibrational dynamics of 2MNT were studied under high‐pressure using synchrotron XRD and optical Raman and IR microspectroscopy. Analysis of the XRD patterns revealed no indication of a phase transition to near 15 GPa and the pressure‐volume isotherm remained smooth to 15 GPa. Near 15 GPa, significant sample damage was observed from the X‐ray beam which precluded the acquisition of patterns above this pressure. XRD and Raman spectroscopic measurements showed the monoclinic ambient condition phase of 2MNT remains the dominant phase to near 20 GPa, although a shift of the NO₂ IR active vibrational modes to lower frequencies suggested a subtle geometry modification not reflected in the XRD data.     

Synthesis and characterization of Schiff‐base‐containing polyimides

Benzyl bisthiosemicarbazone and its complexes with nickel (NiLH₄) and copper (CuLH₄) were used as diamine monomers for the synthesis of new Schiff‐base polyimides. The solution polycondensation of these monomers with the aromatic dianhydrides afforded metal‐containing Schiff‐base polyimides with inherent viscosities of 0.98–1.33 dL/g (measured in N‐methyl‐2‐pyrrolidone at 25°C). The polyimides were generally soluble in a wide range of solvents such as N,N‐dimethylformamide, N,N‐dimethylacetamide, tetrahydrofuran, dimethyl sulfoxide, tetrachloroethane, hexamethylene phosphoramide, N‐methyl‐2‐pyrrolidone, ethyl acetate, and pyridine at room temperature. The initial degradation temperatures of the resultant polyimides fell in the range of 220–350°C in nitrogen with char yields ranging from 36 to 64% at 700°C. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2010     

Organosoluble,low‐dielectric‐constant fluorinated polyimides based on 9,9‐bis[4‐(4‐amino‐2‐trifluoromethyl‐ phenoxy)phenyl]xanthene

A new trifluoromethylated bis(ether amine) monomer, 9,9‐bis[4‐(4‐amino‐2‐trifluoromethylphenoxy)phenyl]xanthene (BATFPX), was prepared through the nucleophilic aromatic substitution reaction of 2‐chloro‐5‐nitrobenzotrifluoride and 9,9‐bis(4‐hydroxyphenyl)xanthene in the presence of potassium carbonate, followed by catalytic reduction with hydrazine and Pd/C in ethanol. A series of novel fluorinated polyimides were synthesized from BATFPX with various commercially available aromatic tetracarboxylic dianhydrides by one‐step polycondensation in m‐cresol. The resulting polyimides were readily soluble in many organic solvents such as N,N‐dimethylacetamide and tetrahydrofuran, and afforded transparent, flexible and strong films with low moisture absorption (0.28–0.51%), low dielectric constant (2.85–3.26 at 1 MHz) and good optical transparency with UV‐visible absorption cut‐off wavelengths at 352–410 nm. All the polyimides were amorphous and exhibited high thermal stability, with glass transition temperatures of 282–330 °C, 5% weight loss temperatures above 520 °C in nitrogen or air and char yields higher than 55% at 800 °C in nitrogen. Also, these polyimides had good mechanical properties with tensile strengths of 93–118 MPa, elongations at break of 9–16% and initial moduli of 2.07–2.58 GPa. Copyright © 2011 Society of Chemical Industry     

Studies on novel semi‐2‐IPNs from polyetherimide and citraconimide

A series of novel semi‐2‐interpenetrating polymeric networks (semi‐2‐IPNs) were prepared through blending in solution using two different polyimides, biscitraconamic acid as a precursor of biscitraconimide (MBMI) with various proportions of polyetherimide (PEI) to achieve optimum properties. Biscitraconamic acid was prepared by reacting citraconic anhydride (CA), 3,3',4,4'‐benzophenone tetracarboxylic dianhydride (BTDA) and bis(3‐aminopropyl)phenyl phosphine (BAPPP) and it was characterized by differential scanning calorimetry (DSC), FTIR, and ¹H‐NMR spectroscopy. Both biscitraconamic acid and PEI were blended in N,N‐dimethylacetamide (DMAc) solution, casted and thermally cured up to 300°C to give semi‐2‐IPNs. The MBMI/PEI semi‐IPN systems were characterized by UV‐Vis spectroscopy, FTIR spectroscopy and thermal techniques. The phase morphology, isothermal aging, and water uptake of semi‐IPN systems have also been studied. The morphological studies on phase distribution were investigated by scanning electron microscopy (SEM). Thermal performance of MBMI/PEI semi‐IPN systems were evaluated by DSC and thermo gravimetric analysis (TGA). All the compositions of semi‐IPN polyimide system were stable up to 400°C and their thermal stability increased with increase in the content of PEI. Isothermal aging studies done at 300°C for various time periods showed good thermo‐oxidative stability. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2011