Preparation of silvered polyimide films with reflective and electrically conductive surfaces using single‐stage self‐metallization techniques and factors affecting silver particles migration

Reflective and surface conductive flexible polyimide (PI) films were prepared by the incorporation of silver(I) acetate and 1,1,1‐trifluoro‐2,4‐pentanedione into a dimethylacetamide solution of several poly(amic acid)s which were prepared from dianhydrides and diamines. Thermal curing of the silver(I)‐containing poly(amino acid)s precursor led to cycloimidization of the PI with silver(I) reduction and formation of a reflective and conductive silvered surface at about 13 wt % silver. Effects on silver particles migration and aggregation were discussed in this article. The results indicated that the PI structures with flexible chains and groups easily fabricate the silvered films, with both reflective and conductive characteristics. With the forced air condition, the evaporation rate of the solvent and water increases, which facilitates the migration of silver particles to give reflective and conductive silvered surfaces. Films were characterized by transmission electron microscopy, scanning electron microscopy, and tapping‐mode atomic force microscopy. Electrical conductivity, reflectivity, and dynamic mechanical thermal analysis were performed on the metallized films. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 102: 2218–2225, 2006.     

Reflective and electrically conductive surface silvered polyimide films and coatings prepared via unusual single-stage self-metallization techniques

Highly reflective and/or surface conductive flexible polyimide films can be prepared by the incorporation of positive valent silver compounds into solutions of poly(amic acid)s formed from a variety of dianhydrides and diamines. Thermal curing of selected silver(I)-containing poly(amic acid)s leads to cycloimidization of the polyimide precursor with concomitant silver(I) reduction and surface aggregation of the metal yielding a reflective and/or conductive silver surface similar to that of the native metal. However, not all silver(I) precursors are effective surface metallization agents and not all poly(amic acid)s metallize with equal facility. Ligand/anion and polyimide structural effects on film metallization efficacy and on physical properties on metallized films are reviewed.     

Synthesis and characterization of a positive‐working,aqueous‐base‐developable photosensitive polyimide precursor

A positive‐working, aqueous‐base‐developable photosensitive polyimide precursor based on poly(amic ester)‐bearing phenolic hydroxyl groups and a diazonaphthoquinone photosensitive compound was developed. The poly(amic ester) was prepared from a direct polymerization of 2,2′‐bis‐(3‐amino‐4‐hydroxyphenyl)hexafluoropropane and bis(n‐butyl)ester of pyromellitic acid in the presence of phenylphosphonic dichloride as an activator. Subsequently, the thermal imidization of the poly(amic ester) precursor at 300°C produced the corresponding polyimide. The inherent viscosity of the precursor polymer was 0.23 dL/g. The cyclized polyimide showed a glass‐transition temperature at 356°C and a 5% weight loss at 474°C in nitrogen. The structures of the precursor polymer and the fully cyclized polymer were characterized by Fourier transform infrared spectroscopy and ¹H‐NMR. The photosensitive polyimide precursor containing 25 wt % diazonaphthoquinone photoactive compound showed a sensitivity of 150 mJ/cm² and a contrast of 1.65 in a 3 μm film with 1.25 wt % tetramethylammonium hydroxide developer. A pattern with a resolution of 10 μm was obtained from this composition. © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 86: 352–358, 2002     

原位一步法制备表面银化的聚酰亚胺纳米复合薄膜

介绍了原位一步自金属化制备银/聚酰亚胺(PI)纳米复合薄膜的方法。以银盐为线索,评述了各种银盐/二酐/二胺体系所制得的复合薄膜的性能。采用该法可制得具有较高的表面反射率和电导率,优异的界面粘结性,并保持母体PI大部分优异性能的复合薄膜;其反射性和导电性与银含量,银的配位体或者反离子,二酐、二胺的种类及热处理工艺等因素相关。使用三氟乙酰丙酮银盐(AgTFA),银的质量分数为12％以上,进行适当的热处理,则某些体系所制薄膜的表面反射性和导电性可以达到纯银的水平,而其他的银盐体系制备的薄膜只能达到中等反射性而无导电性,但对薄膜表面进行轻微抛光可以提高反射性和导电性。     

Preparation of Nanoporous Polyimide Films from Poly(urethane‐imide) by Thermal Treatment

Nanoporous polyimide films were prepared in two steps. The first step is the preparation of poly(urethane‐imide) films by casting blend solutions containing various weight percentages of poly(amic acid) and phenol blocked polyurethane prepolymer (from 1,6‐hexamethylene diisocyanate and poly(ethylene glycol)). Three poly(amic acid)s were obtained from biphenyltetracarboxylic dianhydride (or) 2,2‐bis(3,4‐dicarboxyphenyl)hexafluoropropane dianhydride with 1,4‐phenylenediamine (or) 2,5‐dimethyl‐1,4‐phenylenediamine. Poly(urethane‐imide) films were characterized by density and surface energy measurements, AFM, DSC, TMA, mechanical properties and TGA. In the second step, these films were thermally treated above 300 °C to give nanoporous polyimide films. During thermal treatment, less thermally stable urethane domains decomposed, leaving porous polyimide films. The presence of pores was confirmed by scanning electron microscopy (SEM). The dielectric constant of the polyimide film was found to decrease with increasing amounts of urethane content.

A nanoporous polyimide film.     

Novel phenylethynyl‐endcapped polyimide oligomers: Synthesis and characterization

A series of novel phenylethynyl‐endcapped polyimide oligomers were prepared by polycondensation of an aromatic diamine mixture of 1,3‐bis(4‐aminophenoxy) benzene (1,3,4‐APB) and 3,4′‐oxydianiline (3,4′‐ODA) with different aromatic dianhydrides including 3,3′,4,4′‐biphenyltetracarboxylic dianhydride (BPDA), 4,4′‐(hexafluoro isopropylidene)diphthalic anhydride (6FDA), 4,4′‐oxydiphthalic anhydride (ODPA), and 4,4′‐[2,2,2‐trifluoro‐1‐(3′,5′‐bis‐(trifluoro‐methyl)phenyl)ethylidene]diphthalic anhydride (9FDA) in the presence of 4‐phenyl‐ethynylaniline (PEA) as endcapping agent in aprotic solvent at elevated temperature. The chemical structures, thermal behavior, and melt rheological properties of the synthesized polyimide oligomers were investigated. Experimental results indicated that the fluorinated polyimide oligomers derived from 6FDA (PI‐2) and 9FDA (PI‐4) are amorphous solid resins and exhibited lower melt viscosities than those prepared from the unfluorinated aromatic dianhydrides such as BPDA and ODPA. The BPDA‐based polyimide oligomers with a molar ratio of 1,3,4‐APB/3,4′‐ODA = 50:50 (PI‐5) showed lower melt viscosity than those derived from a mixture of 1,3,4‐APB and 3,4′‐ODA with molar ratios of 75:25 and 100:0, respectively. In addition, the melt viscosity of the polyimide oligomers increased obviously with increasing of the polymer calculated molecular weights. POLYM. ENG. SCI., 2008. © 2008 Society of Plastics Engineers     

A novel positive‐type photosensitive polyimide based on soluble block copolyimide showing low dielectric constant with a low‐temperature curing process

A soluble block copolyimide (Bco‐PI) was prepared by direct one‐pot polycondensation of 2,2‐bis‐(3‐amino‐4‐hydroxyphenyl)hexafluoropropane, 2,2‐bis[4‐(4‐aminophenoxy)phenyl]hexafluoropropane, and cyclohexane‐tetracarboxylic dianhydride in the presence of γ‐valerolactone and a pyridine catalyst system using γ‐butyrolactone as the solvent. The thermal transmission temperature (T_g) of Bco‐PI was 282°C. By having the curing process occur at 250°C, which was below the T_g, colorless and transparent films could be obtained. The film showed excellent optical characteristics. Such properties could not be attained by the conventional high‐temperature thermal imidization process of poly(amic acid). The hydroxy groups in the polyimide backbone gave the Bco‐PI the potential to become alkaline. To the Bco‐PI was added 15 wt % ester of 2,3,4‐trihydroxybenzophenone with 1,2‐naphthoquinone‐(2) diazide‐5‐sulfonic acid (NT200) as the photoreactive compound. The system worked as a positive‐type photosensitive polyimide (PSPI). The sensitivity and contrast of the PSPI system were 220 mJ/cm² and 1.27, respectively, when exposed to UV light, followed by development with a 5% tetramethylammonium hydroxide (TMAH) aqueous solution at room temperature. After curing at 250°C for 1 h, the average refractive index of Bco‐PI with and without NT200 was 1.5543 and 1.5563, and the optically estimated dielectric constant of the polyimides was 2.66 and 2.67, respectively. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 100: 4240–4246, 2006     

X‐Ray reflectivity study of polyimide thin films swollen by 1,3‐butadiene and n‐butane

X‐ray reflectivity measurements were performed on two different polyimide thin films synthesized from 2,2‐bis(3,4‐carboxyphenyl)hexafluoropropane dianhydride (6FDA) in 1,3‐butadiene and n‐butane. In 1,3‐butadiene at 2.3 atm, the film thickness increased by 24–30%. However, the film thickness increased by only 10% in n‐butane at 2.3 atm. Excessive increases in film thickness were shown in 1,3‐butadiene, but the decreases in film density were minor. The probability of the condensation of 1,3‐butadiene in the films is indicated. © 2000 John Wiley & Sons, Inc. J Appl Polym Sci 78: 1818–1825, 2000     

Synthesis and properties of low‐color polyimide/silica hybrid films

A series of polyimide precursors, poly(amic acid)s, containing propyltrimethoxysliane at two chain ends were prepared from 4,4′‐bis(4‐amino‐2‐trifluoromethylphenoxy)biphenyl ( I ) with six commercially available dianhydrides, followed by end‐capping with 3‐aminopropyltrimethoxysilane (APrTMOS). A new class of fluorine‐containing polyimide/silica composite films ( III ) with chemical bonds between the fluorinated polyimide backbone and the silica network has been synthesized from the APrTMOS‐terminated precursors with tetramethoxysilane via the sol‐gel process and thermal cyclodehydration. The resultant hybrid films were light‐colored, flexible, and tough. They had high levels of thermal stability associated with high glass‐transition temperatures (>251°C), 10% weight‐loss temperatures in excess of 527°C, and char yields at 800°C in nitrogen higher than 60%. For a comparative study, the analogous nonfluorinated polyimide/silica hybrid films ( III′ ), based on 4,4′‐bis(4‐aminophenoxy)biphenyl ( I′ ), and the neat fluorinated polyimide films ( IV ), based on diamine I , were also synthesized and characterized. The hybrid films of the fluorinated series III showed a higher transparency and less color intensity when compared with the nonfluorinated III′ analogs. They also revealed a lower refraction index and birefringence than pure polyimides ( IV ). © 2007 Wiley Periodicals, Inc. J Appl Polym Sci 104: 4046–4052, 2007     

Water‐sorption behavior of P‐phenylene diamine–based polyimide thin films

Four different p‐PDA–based polyimide thin films were prepared from their respective poly(amic acid)s through thermal imidization at 400°C: poly(p‐phenylene pyromellitimide) (PMDA‐PDA); poly(p‐phenylene biphenyltetra carboximide) (BPDA‐PDA); poly(p‐phenylene 3,3′,4,4′‐oxydiphthalimide) (ODPA‐PDA); and poly(p‐phenylene 4,4′‐hexafluoroisopropylidene diphthalimide) (6FDA‐PDA). Water‐sorption behaviors of polyimide films were gravimetrically investigated at 25°C and 22–100% relative humidity by using the modified electromicrobalance (Thin Film Diffusion Analyzer). The diffusion coefficients of water for the polyimides varies in the range of 1.6 to 10.5 × 10⁻¹⁰ cm²/s, and are in the increasing order: BPDA‐PDA < PMDA‐PDA ∼ ODPA‐PDA < 6FDA‐PDA. The water uptakes of polyimides vary from 1.46 to 5.80 wt %, and are in the increasing order: BPDA‐PDA < ODPA‐PDA < 6FDA‐PDA < PMDA‐PDA. The water‐sorption behaviors for the p‐PDA–based polyimides are closely related to the morphological structure; specifically, the diffusion coefficients in p‐PDA–based polyimide thin films are closely related to the in‐plane orientation and mean intermolecular distance, whereas the water uptakes are affected by the packing order. © 2000 John Wiley & Sons, Inc. J Appl Polym Sci 76: 1315–1323, 2000     

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     

Thermal and electrical behavior of polyimide/silica hybrid thin films

Silica‐containing polyimide films were prepared by sol‐gel technique using a poly(amic acid) and tetraethoxysilane. The poly(amic acid) was synthesized by solution polycondensation reaction of 4,4′‐oxydiphthalic anhydride with 2,6‐bis(3‐aminophenoxy)benzene and an aminosilane coupling agent, 3‐aminopropyltriethoxysilane. The properties of these films, such as water vapors sorption capacity, dynamic contact angles and contact angle hysteresis, thermal, and electrical behavior have been evaluated with respect to their structure. The polymer films exhibited good thermal stability having the initial decomposition temperature above 450°C, glass transition temperature in the range of 223?228°C, and low‐dielectric constant in the range of 2.64?3.16. Two subglass transitions, γ and β, were evidenced by dynamic mechanical analysis and dielectric spectroscopy. The surface morphology and the roughness were investigated by atomic force microscopy and scanning electron microscopy. POLYM. ENG. SCI., 2010. © 2009 Society of Plastics Engineers     

Preparation of thermally stable,low dielectric constant,pyridine‐based polyimide and related nanofoams

Reaction of 6‐chloronicotinoyl chloride with p‐phenylene diamine resulted in preparation of a dichloro diamide compound. Subsequently, chloro displacement of this compound with 4‐amino phenoxy groups led to production of a new pyridine‐based ether diamine named as N,N′‐(1,4‐phenylene)bis(6‐(4‐aminophenoxy) nicotinamide). Novel polyimide was prepared through polycondensation reaction of the diamine with hexafluoroisopropylidene diphthalic anhydride (6‐FDA) via two‐step imidization method. In addition, new nanoporous polyimide films were produced through graft copolymerization of polyimide as the continuous phase with a thermally labile poly (propylene glycol) oligomer as the labile phase. The grafted copolymers were synthesized using reaction of the diamine and 6‐FDA in the presence of poly (propylene glycol) 2‐bromoacetate as thermally labile constituent via a poly(amic acid) precursor process. The labile block was decomposed via thermal treatment to release inert molecules that diffused out of the matrix to leave pores with diameters between 30 and 60 nm. The structures and properties of polyimide and polyimide nanofoams were characterized by different techniques including ¹H‐NMR, FTIR, TGA, DMTA, SEM, TEM, dielectric constant, and tensile strength measurement. © 2012 Wiley Periodicals, Inc. J. Appl. Polym. Sci., 2013     

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     

Preparation and solubility of water–methanol mixtures in sulfonated poly(etherketone) containing a cardo‐ring structure

The preparation and solubility of water–methanol mixtures in sulfonated (1,3‐dihydro‐3‐oxoisobenzofuran‐1,1‐diyl‐1,4‐phenyleneoxy‐1,4‐phenylenecarbonyl‐1,4‐phenyleneoxy‐1,4‐phenylene) (C‐PEK) was systematically studied. The sulfonation was carried out by reacting C‐PEK with 98% sulfuric acid at 60°C. This reaction obeys a first‐order reaction mechanism up to 4 h. The sulfonic acid group was uniformly dispersed in a sulfonated C‐PEK (SC‐PEK) membrane. The introduction of sulfonic acid groups in C‐PEK could increase polymer segmental gaps because of the size of a bulky sulfonic acid group or decrease polymer segmental gaps as a result of polar interactions. The former effect is dominant for SC‐PEK with low sulfonic acid content, whereas the latter occurs for SC‐PEK with high sulfonic acid content. The uptake of pure water or an aqueous methanol solution (e.g., 3, 5, and 10 wt % methanol concentration) in the sulfonated C‐PEK membranes increases with increasing sulfonic acid group content. However, the sulfonated C‐PEK with high sulfonic acid content selectively sorbs water rather than methanol in the membrane. This suggests that the sulfonated C‐PEK membrane could prevent crossover of methanol through the membrane and has potential as a polymer electrolyte for the direct methanol fuel cell. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 100: 1113–1123, 2006     

Porous polyimide films prepared by thermolysis of porogens with hyperbranched structure

Two hyperbranched molecules, benzenetricarboxylic acid dendritic benzyl ether ester (BTRC–BE) and benzenetricarboxylic acid polyethylene glycol ester (BTRC–PEG), were prepared and tested as pore‐generating agents (porogens) for the preparation of porous polyimide. The hyperbranched molecules were thermally stable during the imidization process and completely decomposed well below the degradation temperature of polyimides, indicating that they possessed desirable thermal decomposition characteristics as porogens for the porous polyimide. From the SEM analysis dispersed domains were observed in the poly(amic acid) films containing BTRC–BE, whereas no phase separation was observed in the poly(amic acid) films containing BTRC–PEG. This may be attributable to the different polarities of the porogens because the hydrophobic BTRC–BE was phase‐separated in the hydrophilic poly(amic acid) matrix but BTRC–PEG was well mixed with poly(amic acid). The morphology developed in the poly(amic acid) film was retained after imidization and decomposition of the porogens; thus only BTRC–BE produced the porous polyimide. As the content of BTRC–BE decreased from 20 to 5 wt %, the pore size decreased from 390 ± 100 to 90 ± 50 nm and the pore density also decreased. © 2004 Wiley Periodicals, Inc. J Appl Polym Sci 93: 1711–1718, 2004     

Processable and colorless fluorinated poly(ether imide)s based on an isopropylidene‐containing bis(ether anhydride) and various aromatic bis(ether amine)s bearing trifluoromethyl groups

A series of novel organosoluble and light‐colored fluorinated poly(ether imide)s (PEIs) ( IV ) having inherent viscosities of 0.43–0.59 dL/g were prepared from 4,4′‐[1,4‐phenylenbis(isopropylidene‐1,4‐phenyleneoxy)]diphthalic anhydride ( I ) and various trifluoromethyl‐substituted aromatic bis(ether amine)s by a standard two‐step process with thermal and chemical imidization of poly(amic acid) precursors. These PEIs showed excellent solubility in many organic solvents and could be solution‐cast into transparent and tough films. These films were essentially colorless, with an UV–visible absorption edge of 361–375 nm and a very low b* value (a yellowness index) of 15.3–17.0. They also showed good thermal stability with glass‐transition temperature of 191–248°C, 10% weight loss temperature in excess of 494°C, and char yields at 800°C in nitrogen more than 39%. The thermally cured PEI films showed good mechanical properties with tensile strengths of 83–96 MPa, elongations at break of 8–11%, and initial moduli of 1.7–2.0 GPa. They possessed lower dielectric constants of 3.25–3.72 (1 MHz). In comparison with the V series nonfluorinated PEIs, the IV series showed better solubility, lower color intensity, and lower dielectric constants. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci 104: 620–628, 2007     

Inkjet printing of polyimide insulators for the 3D printing of dielectric materials for microelectronic applications

In this article, we report the first continuous fabrication of inkjet‐printed polyimide films, which were used as insulating layers for the production of capacitors. The polyimide ink was prepared from its precursor poly(amic) acid, and directly printed on to a hot substrate (at around 160 °C) to initialize a rapid thermal imidization. By carefully adjusting the substrate temperature, droplet spacing, droplet velocity, and other printing parameters, polyimide films with good surface morphologies were printed between two conducting layers to fabricate capacitors. In this work, the highest capacitance value, 2.82 ± 0.64 nF, was achieved by capacitors (10 mm × 10 mm) with polyimide insulating layers thinner than 1 μm, suggesting that the polyimide inkjet printing approach is an efficient way for producing dielectric components of microelectronic devices. © 2016 The Authors Journal of Applied Polymer Science Published by Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2016 , 133, 43361.     

Synthesis and characterization of new cardo poly(ether imide)s derived from 9,9‐bis [4‐(4‐aminophenoxy)phenyl]xanthene

A series of new cardo poly(ether imide)s bearing flexible ether and bulky xanthene pendant groups was prepared from 9,9‐bis[4‐(4‐aminophenoxy)phenyl]xanthene with six commercially available aromatic tetracarboxylic dianhydrides in N,N‐dimethylacetamide (DMAc) via the poly(amic acid) precursors and subsequent thermal or chemical imidization. The intermediate poly(amic acid)s had inherent viscosities between 0.83 and 1.28 dL/g, could be cast from DMAc solutions and thermally converted into transparent, flexible, and tough poly(ether imide) films which were further characterized by X‐ray and mechanical analysis. All of the poly(ether imide)s were amorphous and their films exhibited tensile strengths of 89–108 MPa, elongations at break of 7–9%, and initial moduli of 2.12–2.65 GPa. Three poly(ether imide)s derived from 4,4′‐oxydiphthalic anhydride, 4,4′‐sulfonyldiphthalic anhydride, and 2,2‐bis(3,4‐dicarboxyphenyl))hexafluoropropane anhydride, respectively, exhibited excellent solubility in various solvents such as DMAc, N,N‐dimethylformamide, N‐methyl‐2‐pyrrolidinone, pyridine, and even in tetrahydrofuran at room temperature. The resulting poly(ether imide)s with glass transition temperatures between 286 and 335°C had initial decomposition temperatures above 500°C, 10% weight loss temperatures ranging from 551 to 575°C in nitrogen and 547 to 570°C in air, and char yields of 53–64% at 800°C in nitrogen. © 2012 Wiley Periodicals, Inc. J Appl Polym Sci, 2012     

Mechanical and thermal properties of polyimide/silica hybrids with imide‐modified silica network structures

A series of hybrid materials incorporating imide‐modified silica (IM‐silica) network structures into a polyimide (PI) matrix were produced with a sol–gel technique from solution mixtures of poly(amic acid) and tetraethoxysilane (TEOS) containing alkoxysilane‐terminated amic acids with various degrees of polymerization. The hybrid films, obtained by solvent evaporation, were heated successively to a maximum temperature of 300°C to carry out the imidization process and silica network formation in the PI matrix. The morphology and mechanical properties of these hybrids with IM‐silica networks were studied and compared with the properties of one in which reinforcement of the matrix was achieved with a pure silica network generated from TEOS. The introduction of longer imide spacer groups into the silica network led to a drastic decrease in the silica particle size. Improved tensile modulus was observed in such compatibilized hybrid systems. Comparative thermogravimetric measurements of these hybrids showed improved thermooxidative resistance. A PI hybrid with 30% IM‐silica had a thermal decomposition temperature nearly 260°C higher than that of the pure PI matrix. The high surface area of the interconnected silica domains and increased interfacial interaction were believed to restrict the segmental motion of the polymer and thus slow the diffusion of oxygen in the matrix, thereby slowing the oxidative decomposition of the polymer. The reinforcement of existing and new PIs by this method offers an opportunity for improving their thermooxidative stability without degrading their mechanical strength. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci, 2008