Mechanical,thermal, electrical,and interfacial properties of high‐performance bisphthalonitrile/polyarylene ether nitrile/glass fiber composite laminates

Bisphthalonitrile (BAPh)/polyarylene ether nitrile end‐capped with hydroxyl groups (PEN‐OH) composite laminates reinforced with glass fiber (GF) have been fabricated in this article. The curing behaviors of BAPh/PEN‐OH prepolymers have been characterized by differential scanning calorimetry and dynamic rheological analysis. The results indicate that with the introduction of PEN‐OH the curing temperature of BAPh has decreased to 229.6–234.8°C and BAPh/PEN‐OH prepolymers exhibit large processing windows with relatively low melt viscosity. The BAPh/PEN‐OH/GF composite laminates exhibit tensile strength (272.4–456.5 MPa) and modulus (4.9–10.0 GPa), flexural strength (507.1–560.9 MPa), and flexural modulus (24.0–30.4 GPa) with high thermal (stable up to 538.3°C) and thermal stabilities (stable up to 475.5°C). The dielectric properties of BAPh/PEN‐OH/GF composite laminates have also been investigated, which had little dependence on the frequency. Meanwhile, scanning electron microscopy results show that the BAPh/PEN‐OH/GF composite laminates display excellent interfacial adhesions between the matrix and GFs. Herein, the BAPh/PEN‐OH matrix can be a good matrix for high‐performance polymeric materials and the advanced BAPh/PEN‐OH/GF composite laminates can be used under high temperature environment. POLYM. COMPOS., 34:2160–2168, 2013. © 2013 Society of Plastics Engineers     

Curing behavior and processability of BMI/3‐APN system for advanced glass fiber composite laminates

The prepolymers containing bismaleimide (BMI) and 3‐aminophenoxyphthalonitrile (3‐APN) were prepared through simple solution prepolymerization, and the corresponding curing behaviors and processability were investigated by differential scanning calorimetry and dynamic rheological analysis. The results showed that the processability of the prepolymers could be controlled by temperature and time on processing, also depended on the relative content of 3‐APN and BMI. The possible curing reactions of the prepolymers were studied by Fourier transform infrared spectroscopy, which involved the Michael addition between BMI and 3‐APN and self‐polymerization of BMI or 3‐APN. The resulting polymers displayed high thermo‐oxidative stabilities (T_5% > 425 °C) and good adhesion capability. Furthermore, BMI/3‐APN systems were employed to prepare BMI/3‐APN/glass fiber (GF) composite laminates and their morphological, mechanical, and electrical stable properties were also investigated. The BMI/3‐APN/GF laminates exhibited the improvement of the mechanical properties (the maximum flexural strength is 633.5 MPa and flexural modulus is 38.7 GPa) compared with pristine BMI/GF laminates because of the strong interfacial adhesions between GF and matrices, which was confirmed with SEM observations. This study provides a concise strategy for diversifying the preparation of BMI/3‐APN prepolymers to obtain advanced GF composite laminates with various properties which have potential applications in industrial manufacture or electronic circuit, and so on. © 2016 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2016 , 133, 43640.     

Effect of polyarylene ether nitriles on processing and mechanical behaviors of phthalonitrile‐epoxy copolymers and glass fiber laminated composites

A series of copolymers and glass fiber composites were successfully prepared from 2,2‐bis [4‐(3,4‐dicyanophenoxy) phenyl] propane (BAPh), epoxy resins E‐44 (EP), and polyarylene ether nitriles (PEN) with 4,4′‐diaminodiphenyl sulfone as curing additive. The gelation time was shortened from 25 min to 4 min when PEN content was 0 wt % and 15 wt %, respectively. PEN could accelerate the crosslinking reaction between the phthalonitrile and epoxy. The initial decomposition temperatures (T_i) of BAPh/EP copolymers and glass fiber composites were all more than 350°C in nitrogen. The T_g of 15 wt % PEN glass fiber composites increased by 21.2°C compared with that of in comparison with BAPh/EP glass fiber composite. The flexural strength of the copolymers and glass fiber composites reached 119.8 MPa and 698.5 MPa which increased by 16.6 MPa and 127.3 MPa in comparison with BAPh/EP composite, respectively. © 2012 Wiley Periodicals, Inc. J. Appl. Polym. Sci., 2013     

Mechanical and thermal enhancements of benzoxazine‐based GF composite laminated by in situ reaction with carboxyl functionalized CNTs

An easy and efficient approach by using carboxyl functionalized CNTs (CNT‐COOH) as nano reinforcement was reported to develop advanced thermosetting composite laminates. Benzoxazine containing cyano groups (BA‐ph) grafted with CNTs (CNT‐g‐BA‐ph), obtained from the in situ reaction of BA‐ph and CNT‐COOH, was used as polymer matrix and processed into glass fiber (GF)‐reinforced laminates through hot‐pressed technology. FTIR study confirmed that CNT‐COOH was bonded to BA‐ph matrices. The flexural strength and modulus increased from 450 MPa and 26.4 GPa in BA‐ph laminate to 650 MPa and 28.4 GPa in CNT‐g‐BA‐ph/GF composite, leading to 44 and 7.5% increase, respectively. The SEM image observation indicated that the CNT‐COOH was distributed homogeneously in the matrix, and thus significantly eliminated the resin‐rich regions and free volumes. Besides, the obtained composite laminates showed excellent thermal and thermal‐oxidative stabilities with the onset degradation temperature up to 624°C in N₂ and 522°C in air. This study demonstrated that CNT‐COOH grafted on thermosetting matrices through in situ reaction can lead to obvious mechanical and thermal increments, which provided a new and effective way to design and improve the properties of composite laminates. © 2013 Wiley Periodicals, Inc. J. Appl. Polym. Sci., 2013     

Effect of processing conditions on physical properties of 3‐aminophenoxyphthalonitrile/epoxy laminates

To develop high performances of polymer composite laminates, differential scanning calorimetry and dynamic rheological analysis studies were conducted to show curing behaviors of 3‐aminophenoxyphthalonitrile/epoxy resin (3‐APN/EP) matrix and define cure parameters of manufacturing processes. Glass fiber reinforced 3‐APN/EP (GF/3‐APN/EP) composite laminates were successfully prepared through different processing conditions with three parameters such as pressures, temperatures, and time. Based on flexure tests, dynamic mechanical analysis, thermal gravimetric analysis, and scanning electron microscope, the complementary catalytic effect of the three processing parameters is investigated by studying mechanical behavior, thermomechanical behavior, thermal behavior, and fracture morphology of GF/3‐APN/EP laminates. The 50/50 GF/3‐APN/EP laminates showed a significant improvement in flexural strength, glass transition temperature (T_g), and thermal stability with favorable processing parameters. It was also found that the T_g and thermal stability were significantly improved by the postheated treatment method. The effect of manufacturing process provides a new and simple route for the polymer–matrix composites application, which indicates that the composites can be manufactured at low temperatures. But, they can be used in a high temperature environment. © 2013 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2014 , 131, 39746.     

Effect of ortho‐diallyl bisphenol A on the processability of phthalonitrile‐based resin and their fiber‐reinforced laminates

Sluggish and narrow process window of phthalonitrile resin has tremendously limited their wide applications. In this work, a novel phthalonitrile containing benzoxazine (4,4′‐(((propane‐2,2‐diylbis (2H‐benzo [e] [1,3]oxazine‐6,3 (4H)‐diyl) bis(3,1‐phenylene))bis(oxy)) diphthalonitrile, BA‐ph) with ortho‐diallyl bisphenol A (DABPA) was investigated. The processing window of the BA‐ph/DABPA blends were found from 50°C to 185°C, which was significantly broader than that of the pure BA‐ph (120–200°C). The composites were prepared through a curing process involving sequential polymerization of allyl moieties, ring‐opening polymerization of oxazine rings and ring‐forming polymerization of nitrile groups. BA‐ph/DABPA/GF(glass fiber) composite laminates were prepared in this study, and the composite laminate with BA‐ph/DABPA molar ratio of 2/2 showed an outstanding flexural strength and modulus of 560 MPa and 37 GPa, respectively, as well as a superior thermal and thermo‐oxidative stability up to 408 and 410°C. These outstanding properties suggest that the BA‐ph/DABPA/GF composites are suitable candidates as matrices for high performance composites. POLYM. ENG. SCI., 56:150–157, 2016. © 2015 Society of Plastics Engineers     

Curing behaviors and properties of novolac/bisphthalonitrile blends

Bisphthalonitrile (BAPh) monomer was blended with novolac resins to achieve good processing resin blends. The curing behaviors of the novolac/BAPh (novolac/BAPh) blends were studied by differential scanning calorimetry (DSC) and dynamic rheological analysis. The results indicated that the blends had large processing windows (98–118°C), and they can copolymerize without any other curing additives. The novolac/BAPh copolymers were obtained by short curing times and low curing temperatures. Thermal and thermal-oxidative stabilities of the copolymers were investigated by thermal gravimetric analysis, and the char yields up to 74 and 35% by weight at 800°C were achieved under nitrogen and air atmosphere, respectively. These postcured copolymers exhibited a 5% weight loss temperature of 502°C in air. These results revealed that the copolymers exhibited excellent thermal and thermal-oxidative stabilities. Dynamic mechanical properties of the copolymers were systematically evaluated by dynamic mechanical analysis. The copolymers exhibited higher glass transition temperatures (T_g) as the BAPh content increased. Mechanical properties of the copolymers were investigated, and these data showed that flexural strength and flexural modulus of the 50 : 50 novolac/BAPh copolymers were 91 MPa and 5.78 GPa, respectively. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2012     

Preparation and properties of halogen‐free flame‐retarded phthalonitrile–epoxy blends

Halogen‐free flame‐retarded blends composed of 2,2‐bis[4‐(3,4‐dicyanophenoxy) phenyl] propane (BAPh) and epoxy resin E‐44 (EP) were successfully prepared with 4,4′‐diaminodiphenyl sulfone as a curing additive. The structure of the copolymers was characterized by Fourier transform infrared spectroscopy, which showed that epoxy groups, a phthalocyanine ring, and a triazine ring existed. The limiting oxygen index values were over 30, and the UL‐94 rating reached V‐0 for the 20 : 80 (w/w) BAPh/EP copolymers. Differential scanning calorimetry and dynamic rheological analysis were employed to study the curing reaction behaviors of the phthalonitrile/epoxy blends. Also, the gelation time was shortened to 3 min when the prepolymerization temperature was 190°C. Thermogravimetric analysis showed that the thermal decomposition of the phthalonitrile/epoxy copolymers significantly improved with increasing BAPh content. The flexible strength of the 20:80 copolymers reached 149.5 MPa, which enhanced by 40 MPa compared to pure EP. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2012     

Heat‐distortion temperature of unidirectional polyethylene–glass fiber–PMMA hybrid composite laminates

Unidirectional (UD) composite laminates based on high‐performance polyethylene fibers (PEF) and glass fibers (GF) and their hybrids were prepared with partially polymerized methyl methacrylate (MMA) at room temperature, followed by heating at 55°C (well below the softening point of PEF, 147°C) for 2 h. The heat distortion temperatures (HDT) of the composites were measured and analyzed. The dependency of the HDT correlated with the wettability of the fibers, measured from the contact angle. The HDT of the composites increased with increasing GF content but decreased when PEF was used. An optimum combination of different properties was obtained by using PEF/GF/PMMA hybrid composites, with GF ply/plies on the lower tension side of the UD laminates. © 1999 John Wiley & Sons, Inc. J Appl Polym Sci 71: 541–545, 1999     

Crosslinking behavior of polyarylene ether nitrile terminated with phthalonitrile (PEN‐t‐Ph)/1,3,5‐Tri‐(3,4‐dicyanophenoxy) benzene (TPh) system and its enhanced thermal stability

A novel polyarylene ether nitrile terminated with phthalonitrile (PEN‐t‐Ph) was synthesized by a simple solution polycondensation of biphenyl and hydroquinone with 2,6‐dichlorobenzonitrile, followed by termination with 4‐nitrophthalonitrile. The PEN‐t‐Ph/1,3,5‐Tri‐(3,4‐dicyanophenoxy) benzene (TPh) system was prepared by cure treatment. The phthalonitrile on PEN‐t‐Ph were thermally crosslinked with TPh in the presence of diamino diphenyl sulfone through cure treatment up to 280–340°C, which led to the transformation from thermoplastic polymers to thermosetting polymers. This is because the phthalonitrile on the PEN‐t‐Ph can react with TPh by forming phthalocyanine ring. The glass transition temperatures of the PEN‐t‐Ph/TPh system increased from 152.4°C to 194.7°C, and the initial decomposition temperature (ranging from 475.3°C to 544.0°C) increased by 68°C after thermal curing. Therefore, their thermal properties can be greatly enhanced by crosslinking. © 2013 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 130: 1363‐1368, 2013     

Synthesis and characterization of bis(4‐cyanato‐3,5‐dimethylphenyl)anisylmethane/epoxy/glass fiber composites

Bis(4‐cyanato‐3,5‐dimethylphenyl)anisylmethane was prepared by treating CNBr with bis(4‐hydroxy‐3,5‐dimethylphenyl)anisylmethane and blended with commercial epoxy resin in different ratios and cured at 120°C for 2 h, 180°C for 1 h, and postcured at 220°C for 1 h using diamino diphenyl methane as curing agent. Castings of neat resin and blends were prepared and characterized. The composite laminates were also fabricated with glass fiber using the same composition. The tensile strength of the composites increased with increase in cyanate content (3, 6, and 9%) from 322 to 355 MPa. The fracture toughness values also increased from 0.7671 kJ/m², for neat epoxy resin, to 0.8615 kJ/m², for 9% cyanate ester‐modified epoxy system. The 10% weight loss temperature of pure epoxy (358°C) was increased to 390°C by the incorporation of cyanate ester resin. The incorporation of cyanate ester up to 9% in the epoxy resin increases the T_g from 143 to 147°C. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2009     

Low Temperature‐Based Flexural Properties of Carbon Fiber/Epoxy Composite Laminates Incorporated with Carbon Nanotube Sheets

This study introduces carbon nanotube buckypaper (CNTBP) into the easily fractured sites of [0°]₁₆ and [0°/90°]_4S composite laminates, and comparatively explores how the CNTBP affects the flexural properties of the laminates at 25, ?15, and ?55 °C. Compared to the base [0°]₁₆ and [0°/90°]_4S laminates at the same temperature, improvements of the flexural strengths in the order of 4.0–15.3% and 6.5–31.0% are respectively obtained from the corresponding CNTBP‐reinforced [0°]₁₆ and [0°/90°]_4S laminates. Importantly, the lower the temperature is, the higher the strength improves. In fact, the CNTBP has little effect on the flexural moduli of the studied laminates, although there is an increasing trend with decreased temperature. Moreover, the introduced CNTBP would significantly change the fracture mechanism of the laminates at low temperature. The present work reveals that the CNTBP exhibits more positive reinforcing capability to the polymer matrix‐based composite laminates at relatively low temperatures.     

Design of the phthalonitrile‐based composite laminates by improving the interfacial compatibility and their enhanced properties

Phthalonitrile containing benzoxazine (BA‐ph) and cyanate ester (CE) were chosen as the thermosetting matrix and the glass fiber (GF) reinforced laminates formed at low temperature were designed. The polyarylene ether nitriles containing pendent carboxyl groups (CPEN) was selected to modify the interfacial interaction between the resin matrix and GFs. Two methods of introducing CPEN were compared and the effects of CPEN on curing behaviors and properties of the composites were investigated. Results showed that with the CPEN, exothermic peaks shifted to lower temperature and curing temperatures of BA‐ph/CE decreased slightly. The mechanical and thermal properties of GF‐reinforced composites were discussed and the results indicated that the composites of modified GFs with CPEN exhibited outstanding mechanical properties, higher glass transition temperature (T_g > 290 °C) than that of composites composed of CPEN mixed with BA‐ph/CE. Moreover, GF‐reinforced composites showed stable dielectric constants (3.8–4.5) and low dielectric loss (0.005–0.01), which were independent of the frequency. In sum, the various methods of the introduction of CPEN in the GF‐reinforced composites may provide a new route to prepare improved composites, meanwhile, composites with outstanding processability and excellent mechanical and thermal properties are expected to be widely applied in the fields of high‐performance structural materials. © 2017 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2018 , 135, 45881.     

Fabrication and Characterization of Glass Fiber Reinforced Composites from 2,3‐Epoxypropyl 3‐(2‐Furyl)acrylate and Acrylonitrile

The present paper comprises synthesis and characterization of 2,3‐epoxypropyl 3‐(2‐furyl)acrylate (EPFA) from 3‐(2‐furyl)acrylic acid (FAA) and epichlorohydrin, and its subsequent copolymerization with acrylonitrile (AN) by varying the ratio of EPFA:AN and time using benzoyl peroxide as initiator at 80°C in toluene. The resultant pre‐polymers were characterized by epoxy equivalent weight (EEW), viscosity measurement, gel permeation chromatography (GPC), and infrared (IR) spectral studies. The prepolymers were cured by employing two different curing agents viz. chlorosulfonic acid (ClSO₃H) and maleic anhydride/triethanolamine (MAN : TEA). The curing study was performed isothermally at 120 and 160°C, respectively, for the agents employed. Differential scanning calorimetry (DSC) was also employed to study the curing behavior on dynamic runs. The cured samples were analyzed by thermogravimetry for their thermal stability. The glass fiber reinforced composites (GFRC) were fabricated from selected resin samples and were characterized for their mechanical properties, electrical properties and chemical resistance.     

Effect of different aromatic amines on the crosslinking behavior and thermal properties of phthalonitrile oligomer containing biphenyl ethernitrile

To find a proper amine to promote the processability of phthalonitrile‐based composites, three different aromatic amines: 4‐aminophenoxyphthalonitrile (APN), 2,6‐bis (4‐diaminobenzoxy) benzonitrile (BDB) and 4,4′‐diaminediphenyl sulfone (DDS) were used as curing agents to investigate the crosslinking behavior and thermal decomposition behavior of phthalonitrile oligomer containing biphenyl ethernitrile (2PEN‐BPh). Differential scanning calorimeter (DSC) and dynamic rheological analysis were employed to study the curing reaction behavior of the phthalonitrile/amine blends and prepolymers. The studies revealed that BDB was the preferred curing agent and the preferred concentration of BDB was 3 wt %. The thermal properties of the 2PEN‐BPh polymers were monitored by TGA, and the results indicated that all the completely cured 2PEN‐BPh polymers maintained good structure integrity upon heating to elevated temperatures and these polymers could thermal stabilize up to over 550°C in both air and nitrogen atmospheres. Dynamic mechanical analysis (DMA) showed the glass transition temperature (T_g) exceeded 450°C when the 2PEN‐BPh polymer post cured at 375°C for 8 h. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2011     

A novel bio‐based phthalonitrile resin derived from catechin: synthesis and comparison of curing behavior with petroleum‐based counterpart

The development of bio‐based thermosetting resins with good thermal stability can potentially afford sustainable polymers as replacements for petroleum‐based polymers. We report a practical route to a novel catechin‐based phthalonitrile resin precursor (CA‐Ph), which contains free phenolic hydroxyl groups that result in ‘self‐curing’ at elevated temperatures to afford a thermostable polymer. Comparison of the performance of this CA‐Ph resin with that of a conventional petroleum‐based bisphenol A phthalonitrile resin (BPA‐Ph; containing 5 wt% of the curing agent 4,4′‐diaminodiphenylsulfone) revealed that CA‐Ph exhibits a lower melting point and curing temperature. Cured CA‐Ph resin retains 95% of its weight at 520 °C under a nitrogen atmosphere, which compares favorably with results obtained for BPA‐Ph resin that retains 95% of its weight at a lower temperature of 484 °C. Kinetic results indicated that the curing reactions of both CA‐Ph and BPA‐Ph systems follow an autocatalytic mechanism. These results suggest that catechin is a useful bio‐based feedstock for the preparation of self‐curing and thermally stable phthalonitrile resins for advanced technological applications. © 2017 Society of Chemical Industry     

Preparation and properties of 4,4′‐(hexafluoroisopropylidene) diphenol cured 2,2‐bis(4‐cyanatophenyl) propane

A novel easily curing system of 2,2‐bis(4‐cyanatophenyl) propane(BACY) was prepared by employing 4,4′‐(Hexafluoroisopropylidene) Diphenol (BPAF) as modifier. The curing efficiency of BPAF was evaluated by means of differential scanning calorimetry (DSC) and Fourier translation infrared spectroscopy analysis (FTIR). It was found that the exothermic peak temperature (T_p) was 168 °C when the content of BPAF/BACY was 15/85 by weight, while the temperature of BACY was 215 °C under the same conditions when trace of cobalt(III) acetylacetonate(CoAt(III)) was added. Besides, BPAF/BACY system owned outstanding properties including excellent curing characteristics, high shear strength, remarkable dielectric properties and high thermal stability in contrast to BACY, 4,4′‐(1‐methylethylidene) bisphenol(BPA)/BACY, and nonylphenol(NoP)/BACY systems. Moreover, the properties of cured BPAF/BACY modified by different proportions of BPAF were studied in detail. It was shown that moderate BPAF was conducive to most properties of polycyanurate, and the optimal proportion of BPAF/BACY was 15/85 by weight. © 2016 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2017 , 134, 44518.     

Designing a low-temperature curable phenolic/benzoxazine-functionalized phthalonitrile copolymers for high performance composite laminates

A low-temperature curable phenolic/benzoxazine-functionalized phthalonitrile (SH/BZ-CN) copolymer system with well processability is designed and applied in high performance glass fiber (GF) composite laminates. Differential scanning calorimetry (DSC) results showed that plenty of phenolic hydroxyl groups on SH could catalyze the oxazine ring-opening and triazine/phthalonitrile ring-forming reaction of BZ-CN. The ring-opening peak and ring-forming peak of SH/BZ-CN systems are reduced by 47.1 °C and 17.0 °C than those of BZ-CN, respectively. The processability of SH/BZ-CN copolymers were improved and could be controlled by tuning SH content, processing temperature and time. These parameters provided ground for preparing SH/BZ-CN/GF composite laminates under a relatively mild condition. All SH/BZ-CN/GF composite laminates exhibit excellent flexural strength more than 500 MPa and flexural modulus over 22.0 Gpa. SH/BZ-CN/GF composites showed immiscible structures and double Tgs, and they could stand high temperature up to 350 °C. Low temperature curing, short processing time and low processing pressure are beneficial to large-scale manufacturing and application of SH/BZ-CN/GF composites.     

Fabrication of electrically conductive polymer composites for bipolar plate by two‐step compression molding technique

Electrically conductive polymer composites for bipolar plate were fabricated by two‐step compression molding technique. Raw materials consisted of natural graphite flakes (G), expanded graphite (EG), carbon black (CB), and phenol resin (PF). The G/EG/CB/PF composites were first compressed at a temperature lower than curing point (100°C) and then cured at a high temperature above curing point (150°C) and high pressure (10 MPa). Results showed that G and EG are oriented in the direction parallel to the composite plate surface. CB is dispersed not only in the phenol resin matrix but also in the packing and porous space of G and EG. The addition of EG and CB significantly increases number of the electrical channels and thus enhances the electrical conductivity of the composite. Under optimal conditions, electrical conductivity and flexural strength of the composite were 2.80 × 10⁴ S/m and 55 MPa, respectively, suggesting that the dipolar plates prepared by two‐step compression molding technique are adequate to meet the requirement of proton exchange membrane fuel cells. © 2013 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 130: 2296–2302, 2013     

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