Imide Oligomers Research Articles

Manufacturing of Thermoset Polyimide Composites by Laser Sintering

Selective Laser Sintering (SLS) is an additive manufacturing technique that builds 3D models layer by layer using a laser to selectively melt cross sections in powdered polymeric materials, following sequential slices of the computer-aided design (CAD) model. SLS generally uses thermoplastic polymeric powders such as polyamides. The resultant 3D-printed objects are often weaker in their strength compared to traditionally processed materials, due to their higher porosity. This paper described the process development of using melt-processable imide oligomers terminated with reactive 4-phenylethynylphthalic anhydride (4-PEPA) to conduct laser sintering (LS). The first successful 3D-printing of high temperature RTM370 thermoset polyimide carbon fiber composite was further post-cured to promote additional crosslinking for achieving higher temperature (Tg = 370°C) capability. Another novel imide oligomer, RTM385-SLS, formulated with a complex melt viscosity [h*] of ~104-105 poise is also suitable for LS. RTM385-SLS resin powder was mixed with 20-25% of hexagonal boron nitride (h-BN) and subjected to LS to print out “Green” specimens which could be further post-cured to afford a thermally conductive but electrically insulating composites with high Tg of 385°C. The cured composite specimens were then subjected to mechanical testing, thermal conductivity and porosity evaluation as well as SEM characterization.

Phenylethynyl-Terminated Imide Oligomer-Based Thermoset Resins.

Phenylethynyl-terminated imide (PETI) oligomers are highly valued for their diverse applications in films, moldings, adhesives, and composite material matrices. PETIs can be synthesized at varying molecular weights, enabling the fine-tuning of their properties to meet specific application requirements. Upon thermal curing, these oligomers form super-rigid network structures that enhance solvent resistance, increase glass-transition temperatures, and improve elastic moduli. Their low molecular weights and melt viscosities further facilitate processing, making them particularly suitable for composites and adhesive bonding. This review examines recent advancements in developing ultra-high-temperature PETIs, focusing on their structure-processing-properties relationships. It begins with an overview of the historical background and key physicochemical characteristics of PETIs, followed by a detailed discussion of PETIs synthesized from monomers featuring noncoplanar configurations (including kink and cardo structures), fluorinated groups, flexible linkages, and liquid crystalline mesogenic structures. The review concludes by addressing current challenges in this research field and exploring potential future directions.

Curing Kinetics of Ultrahigh-Temperature Thermosetting Polyimides Based on Phenylethynyl-Terminated Imide Oligomers with Different Backbone Conformations

Curing Kinetics of Ultrahigh-Temperature Thermosetting Polyimides Based on Phenylethynyl-Terminated Imide Oligomers with Different Backbone Conformations

Synthesis and optical properties of fluorinated polyurethaneimide electro-optic waveguide polymer

Fluorinated polyurethaneimide (PUI) electro-optic waveguide polymer with polyurethane and polyimide chain segment structures was synthesized by stepwise polymerization using the synthesized amino ester oligomer pu and imide oligomer pi as monomers. Since the main chain structure of the synthesized PUI had the functionality of both polyurethane and polyimide chain segment structures, it combines the excellent thermal and film-forming properties of polyurethanes and polyimides, as well as lower optical transmission loss in the near-infrared wavelength band. The glass transition temperature (Tg) of PUI was 182 °C, and the 5% heat loss decomposition temperature was 325 °C. The PUI had good optical properties with an optical propagation loss of 1.10 dB/cm and an electro-optic (EO) coefficient (γ33) of 86 pm/V at a wavelength of 1550 nm. A Mach-Zehnder interferometric polymer waveguide EO modulator had been designed and fabricated by using the PUI as a waveguide electro-optic core layer. The prepared polymer waveguide EO modulator showed a good electro-optic modulation response at a wavelength of 1550 nm under an applied 1 kHz sinusoidal modulation signal. The results showed that the synthesized PUI met the performance requirements for the preparation of polymer optical waveguide devices and was a polymer electro-optic waveguide material with good overall performance.

Colorless Polyimides Derived from 5,5'-bis(2,3-norbornanedicarboxylic anhydride): Strategies to Reduce the Linear Coefficients of Thermal Expansion and Improve the Film Toughness.

In this paper, novel colorless polyimides (PIs) derived from 5,5'-bis(2,3-norbornanedicarboxylic anhydride) (BNBDA) were presented. The results of single-crystal X-ray structural analysis using a BNBDA-based model compound suggested that it had a unique steric structure with high structural linearity. Therefore, BNBDA is expected to afford new colorless PI films with an extremely high glass transition temperature (Tg) and a low linear coefficient of thermal expansion (CTE) when combined with aromatic diamines with rigid and linear structures (typically, 2,2'-bis(trifluoromethyl)benzidine (TFMB)). However, the polyaddition of BNBDA and TFMB did not form a PI precursor with a sufficiently high molecular weight; consequently, the formation of a flexible, free-standing PI film via the two-step process was inhibited because of its brittleness. One-pot polycondensation was also unsuccessful in this system because of precipitation during the reaction, probably owing to the poor solubility of the initially yielded BNBDA/TFMB imide oligomers. The combinations of (1) the structural modification of the BNBDA/TFMB system, (2) the application of a modified one-pot process, in which the conditions of the temperature-rising profile, solvents, azeotropic agent, catalysts, and reactor were refined, and (3) the optimization of the film preparation conditions overcame the trade-off between low CTE and high film toughness and afforded unprecedented PI films with well-balanced properties, simultaneously achieving excellent optical transparency, extremely high Tg, sufficiently high thermal stability, low CTE, high toughness, relatively low water uptake, and excellent solution processability.

High performance imide oligomers and thermosets derived from 9,9-bis (3,4-dicarboxyphenyl)fluorene dianhydride

In this work, a new class of imide oligomers and thermosets with improved overall properties was developed by exploiting the steric effects of 9,9-bis(3,4-dicarboxyphenyl)fluorene dianhydride (BPAF). First, a model compound was prepared from BPAF and aniline. This model compound possessed a twisted architecture, with two dihedral angles between fluorene ring and phthalimide segments of around 75°. Then, an array of phenylethynyl-endcapped imide oligomers was synthesized from BPAF, 4-phenylethynyl phthalic anhydride (4-PEPA), and aromatic diamines (4,4′-oxydianiline (4,4′-ODA), 2,2′-bis(trifluoromethyl)benzidine (TFMB), m-phenylenediamine (m-PDA)). The BPAF-derived imide oligomers exhibited improved organic solvents solubility and higher melt viscosity compared to those based on 2,3,3′,4′-biphenyltetracarboxylic dianhydride (3,4′-BPDA), due to their bulky, twisted, and sterically hindered cardo architectures. The imide oligomers under pressure were converted into thermosets by the thermal crosslinking of phenylethynyl at 370 °C for 2 h. The BPAF-derived thermosets exhibited much higher glass transition temperature (Tg) (＞ 404 °C), 5% weight-loss temperature (T5%) (＞ 549 °C) in an air environment, and more excellent high-frequency dielectric properties from 30 to 45 GHz (dielectric constant as low as 2.85 and dielectric loss factor as low as 0.0037) while possessing comparable or even better mechanical properties relative to the 3,4′-BPDA-derived polymers. Therefore, these polymers based on BPAF may have potential applications as matrix resins for heat-resistant, structural and functional composites.

Soluble imide oligomers containing benzoxazole structures

A series of soluble thermosetting polyimide resins containing benzoxazole structure were synthesized by two-step polymerization using 4-phenylethynylphthalic anhydride (4-PEPA) as the end-capping reagent, 2-(4-aminophenyl)-5-aminobenzoxazole (BOA) and 3,4′-diaminodiphenyl ether (3,4′-ODA) as the aromatic diamines, and 4,4′-(hexafluoroisopropylidene) diphthalic anhydride (6FDA) as the aromatic dianhydride. The imide oligomers were characterized by employing Fourier transform infrared spectroscopy (FTIR), differential scanning calorimetry (DSC), solubility tests and rheological measurements. Thermosetting polyimides derived from the imide oligomers were then produced via a thermal cross-linking reaction of the phenylethynyl group. The thermal and mechanical properties of the thermosets were studied using thermogravimetric analysis (TGA), dynamic mechanical thermal analysis (DMA), and mechanical property measurements. The effects of chemical architectures and molecular weights of the imide oligomers on processability, thermostability and mechanical properties were systematically investigated. The results showed that all the copolymerized imide oligomers possessed good solubility in organic and low melt viscosity, and the corresponding thermosets exhibited high glass transition temperature (up to 401°C) and 5% weight-loss temperature (up to 533°C) in an air atmosphere while excellent mechanical properties (flexural strength up to 217 MPa and elongation at break up to 11.2%). With the increase of the concentration of the benzoxazole group, the imide oligomers of PI-X-2 (-O-, -BO-, -B-) exhibited less solubility and higher minimum melt viscosity but improved glass transition temperature after curing and mechanical properties of their thermosets.

Sulphur-containing phenylethynyl terminated polyimide via chemical crosslinking method for excellent thermal properties and antibacterial performance

Thermal stability and antibacterial property of polyimide have emerged as two significant property parameters when used in the aerospace field. In this work, sulphur-containing linkage is introduced into the polyimide by using phenylethynyl terminated imide oligomers (PETI) and sulphur agent. The curing properties of this new type of thermosetting polyimide were studied by Fourier transform infrared (FTIR) and Raman spectra, X-ray photoelectron spectroscopy (XPS), X-ray diffraction (XRD), differential scanning calorimetry (DSC), and thermogravimetric analyzer (TGA). The sulphur-containing polyimide shows a unique thermoplastic-like glass transition behavior rather than typical thermoset behavior. Its film material shows the tensile strength and modulus of 59.46 MPa and 1767 MPa respectively, which have increased to 187.68% and 155.16% when compared with the control sample cured at 381 °C. And the mechanical retention rates of tensile strength and modulus reach 96.8% and 82.1% respectively after 371 °C/100 h aging. In addition, it shows potential value in the fabrication of carbon fiber reinforced composite and antibacterial materials. Though the curing temperature of PETI oligomer decreases from 381 °C to 300 °C, the prepared PI/CF composite shows excellent mechanical performance, and the interlaminar shear strength, the flexural strength, and the flexural modulus reach 104.53 MPa, 1846.71 MPa and 129.24 GPa, respectively. Also, the novel polyimide shows excellent antibacterial performance, with antibacterial retention rate to negative E. coli and positive S. aureus of 90.4% and 89.1%, respectively.

Design and synthesis of anhydride-terminated imide oligomer containing phosphorus and fluorine for high-performance flame-retarded epoxy resins

Challenges remain in the design and construction of robust epoxy thermosets with concurrently improved flame retardancy, thermal, mechanical and dielectric properties.In this work, a novel method has been exploited to synthesize anhydride-terminated imide oligomer containing phosphorus and fluorine (FPI) in the mixed solvents consisting of benzoic acid and acetic acid by single-step reaction. Compared to the ones synthesized by the conventional methods, FPI possessed a much higher content of anhydride groups, and was more suitable to be used as co-curing and flame-retarded agents for epoxy resins. With multifunctional groups, FPI can endow epoxy thermosets with a series of excellent properties. At the loading of 28.5 wt% FPI (only 0.87 wt% phosphorus), the epoxy thermoset (EP/FPI-3) passed the UL-94 V-0 test with the limiting oxygen index (LOI) value of 31.1%. Instead of the reduction in other properties of most polymeric materials after being flame-retarded, the overall performance of EP/FPI-3 was improved, hereinto, the glass transition temperature, heat deflection temperature, 5 wt% mass loss temperature (under N2) and Young’s modulus were increased by 37.2 °C, 42.4 °C, 10.2 °C, 50.6%, respectively, and the dielectric constant, dielectric loss and water adsorption were decreased by 9.9% (100 MHz), 33.3% (100 MHz), 16.2%, respectively, compared to those of the original epoxy thermoset. This work provides a simple and practical way to prepare the flame-retarded epoxy thermosets with improved overall properties by the bespoke multifunctional imide oligomers used as co-curing and flame-retarded agents, and the resulting epoxy thermosets are highly competitive as the advanced electrical materials.

Design of Imide Oligomer-Mediated MOF Clusters for Solar Cell Encapsulation Systems by Interface Fusion Strategy.

Dielectric encapsulation materials are promising for solar cell areas, but the unsatisfactory light-management capability and relatively poor dielectric properties restrict their further applications in photovoltaic and microelectronic devices. Herein, an interface fusion strategy to engineer the interface of MOF (UiO-66-NH2 ) with anhydride terminated imide oligomer (6FDA-TFMB) is designed and a novel MOF cluster (UFT) with enhanced forward scattering and robust porosity is prepared. UFT is applied as an optical and dielectric modifier for bisphenol A epoxy resin (DGEBA), and UFT epoxy composites with high transmittance (>80%), tunable haze (45-58%) and excellent dielectric properties can be prepared at low UFT contents (0.5-1 wt%), which delivers an optimal design for dielectric encapsulation systems with efficient light management in solar cells. Additionally, UFT epoxy composites also show excellent UV blocking, and hydrophobic, thermal and mechanical properties. This work provides a template for the synthesis of covalent bond-mediated nanofillers and for the modulation of haze and dielectric properties of dielectric encapsulation materials for energy systems, semiconductors, microelectronics, and more.

High temperature phenylethynyl-terminated imide oligomers derived from asymmetric diphenyl ether diamines for resin transfer molding

Resin transfer molding (RTM) require phenylethynyl-terminated imide oligomers (PETIs) to exhibit low melt temperatures and better melt stability. To decrease the melt temperatures of PETIs and improve their resin transfer moldable processability, asymmetric 4,4′-diaminodiphenyl ether substituted by fluorine (F-ODA), trifluoromethyl group (3F-ODA) or phenyl group (p-ODA) were introduced. Asymmetric molecular structure and substituent groups decrease the melt temperatures of PETIs, endowing PETIs with the wider processing temperature windows and low minimum melt viscosity (<1 Pa s). These polyimides show pot lives of 30–60 min at 260–280 °C. Furthermore, the effects of backbone structure on melt fluidity of imide oligomers were discussed by the calculation of viscous activation energy (Ea,η) and analysis of Molecular Dynamics. PETI-3F and PETI-P based on 3F-ODA and p-ODA exhibit low and stable melt viscosities (<1 Pa s) at 250–270 °C and 260–270 °C for 4 h respectively, enabling the successful fabrication of carbon fiber reinforced polyimide composites via RTM process. After cured at 380 °C, the thermosets of PETI-3 and PETI-4 show high Tg of 412 °C and 402 °C and good thermal stability (Td5>550 °C). Cured PETI-3 and PETI-4 also show good mechanical properties (tensile strength >50 MPa). In comparison with p-ODA, 3F-ODA could provide PETIs with superior resin transfer moldable processability and higher heat-resistance and is more suitable to synthesize PETIs for RTM application, because of better balance between polymer segmental mobility and polymer chain packing.

Preparation and Properties of Modified Phenylethynyl Terminated Polyimide with Neodymium Oxide.

Modified phenylethynyl terminated polyimides (PIs) were successfully prepared by using neodymium oxide (Nd2O3) via high-speed stirring and ultrasonic dispersion methods. In addition, the structure and properties of the Nd2O3-modified imide oligomers as well as the thermo-oxidative stability of the modified polyimides (PI/Nd2O3 hybrid) and its modification mechanism were investigated in detail. The thermogravimetric analysis (TGA) results indicated that the 5% decomposition temperature (Td5%) of the PI/Nd2O3 hybrids improved from 557 °C to 575 °C, which was also verified by the TGA-IR tests. Meanwhile, the weight loss rate of the PI/Nd2O3 hybrids significantly decreased by 28% to 31% compared to that of pure PI under isothermal aging at 350 °C for 450 h when the added content of Nd2O3 was between 0.4 wt% and 1 wt%, showing outstanding thermo-oxidative stability. Moreover, the mechanism of the enhanced thermo-oxidative stability for the modified PIs was analyzed by scanning electron microscopy (SEM) and X-ray diffraction (XRD).

Improved Melt Processabilities of Thermosetting Polyimide Matrix Resins for High Temperature Carbon Fiber Composite Applications.

With the goal of improving processability of imide oligomers and achieving of high temperature carbon fiber composite, a series of Thermosetting Matrix Resin solutions (TMR) were prepared by polycondensation of aromatic diamine (3,4′-oxybisbenzenamine, 3,4-ODA) and diester of biphenylene diacid (BPDE) using monoester of 4-phenylethynylphthalic acid (PEPE) as end-capping agent in ethyl alcohol as solvent to afford phenylethynyl-endcapped poly(amic ester) resins with calculated molecular weight (Calc’d Mw) of 1500–10,000. Meanwhile, a series of reactive diluent solutions (RDm) with Calc’d Mw of 600–2100 were also prepared derived from aromatic diamine (4,4′-oxybisbenzenamine, 4,4-ODA), diester of asymmetrical biphenylene diacid (α-BPDE) and monoester of 4-phenylethynylphthalic acid (PEPE) in ethyl alcohol. Then, the TMR solution was mixed with the RDm solution at different weight ratios to afford a series of A-staged thermosetting blend resin (TMR/RDm) solutions for carbon fiber composites. Experimental results demonstrated that the thermosetting blend resins exhibited improved melt processability and excellent thermal stability. After being thermally treated at 200 °C/1 h, the B-staged TMR/RDm showed very low melt viscosities and wider processing window. The minimum melt viscosities of ≤50 Pa·s was measured at ≤368 °C and the temperature scale at melt viscosities of ≤100 Pa·s were detected at 310–390 °C, respectively. The thermally cured neat resins at 380 °C/2 h showed a great combination of mechanical and thermal properties, including tensile strength of 84.0 MPa, elongation at breakage of 4.1%, and glass transition temperature (Tg) of 423 °C, successively. The carbon fiber reinforced polyimide composite processed by autoclave technique exhibited excellent mechanical properties both at room temperature and 370 °C. This study paved the way for the development of high-temperature resistant carbon fiber resin composites for use in complicated aeronautical structures.

Fluorinated anhydride-terminated imide oligomers toward high-performance epoxy thermosets enabled by hydroxyl elimination and low dielectric polarizability strategy

In this paper, for the first time, a novel fluorinated anhydride-terminated imide oligomer 6FDA-ODA was prepared with a facile and one-step route, and used as the multifunctional co-curing agent of methylhexahydrophthalic anhydride (MHHPA) for commercial bisphenol A epoxy resin (DGEBA). For the epoxy thermoset containing 30 phr of 6FDA-ODA, 6FDA-ODA-30 exhibited a high glass transition temperature (Tg) of 151.6 ℃ and an initial degradation temperature of 382.5 ℃, and also showed a 211%, 134% and 11.8% increase in impact strength (20.5 kJ/m2 vs. 6.6 kJ/m2), char yield (in N2) (15.2% vs. 6.5%) and tensile strength (71.3 MPa vs. 63.8 MPa), respectively, compared with the pure epoxy thermoset (6FDA-ODA-0). Moreover, 6FDA-ODA-30 possessed a low dielectric constant of 3.23 at 1 MHz and high water resistance (water absorption = 0.52%) due to the introduction of bulky trifluoromethyl (-CF3) and imide moieties. This paper provides a facile design strategy and new opportunity for synthesizing anhydride-terminated imide oligomer, possessing high potential for the utilization in advanced matrix materials for microelectronic and aerospace industries.

Phenylethynyl-terminated Imide Oligomers Modified by Reactive Diluent for Resin Transfer Molding Application

Phenylethynyl-terminated Imide Oligomers Modified by Reactive Diluent for Resin Transfer Molding Application

Interpenetrating polymer networks derived from ethynyl-terminated imide oligomers and cyanate ester

Interpenetrating polymer networks derived from ethynyl-terminated imide oligomers and cyanate ester

Charge transfer properties of imide-functionalized thiazole-based oligomers: Roles of oligomer length, thiophene donor, and fluorine-substitution

Three series of oligomers containing functionalized imide and thiophene rings, namely the acceptor type bisthiazole imide oligomer with different length (PBTzIn, n = 1–8), the donor-acceptor type derivatives by introducing three electron donating thiophene rings into BTzI (PBTzI3Tm, m = 1–4), and derivatives by substituting the two hydrogen of center thiophene in PBTzI3Tm with fluorine (PBTzI3T-2Fm, m = 1–4), were designed based on some experimentally synthesized oligomers to clarify the roles of oligomer length, thiophene donor, and fluorine-substitution on the charge transfer properties. The charge transfer properties of these imide-functionalized thiazole-based oligomers were systematically studied using density functional theory and traditional Marcus theory in term of geometric structures, frontier molecular orbitals, ionization potentials (IP), electron affinities (EA), reorganization energies, charge transfer integrals, crystal packing models, and charge transfer mobilities. The IP/EA decreased/increased with increasing oligomer length in PBTzIn, rendering long PBTzIn oligomers showing both p- and n-type characteristic of organic semiconductors. The orbital energy level and mobility show saturation characteristics for n = 6.PBTzI8 shows high and balanced hole/electron mobility of 1.089/0.249 cm2 V−1s−1 and thus is good ambipolar semiconductor. The introduced three thiophene rings in PBTzI3Tm (m = 1–4) enhances the backbone conjugate property and reduces the hole injection barrier. Substituting thiophene H atoms with F further enhances the interaction between the non-covalent bond N…S and S…F and thus increases the molecular planarity, rendering PBTzI3T-2Fm (m = 1–4) being better semiconductor. PBTzI3T3 is ambipolar organic semiconductor with hole/electron mobility of 11.760/1.396 cm2V−1s−1, while PBTzI3T-2F3 and PBTzI3T-2F4 show better ambipolar organic semiconductor performance with much larger hole/electron mobility of 16.325/3.674 cm2V−1s−1 and 60.019/5.086 cm2V−1s−1.

Type and Size Selectivity of Single-Walled Carbon Nanotubes by Phenylethynyl Terminated Imide Oligomers

Aromatic polyimides are well-known as high-performance polymer materials which have excellent properties such as high thermal stability, strong mechanical strength, and superior chemical resistance. However, rigid backbones of oligomers and strong chain interactions result in lower processibility. Our molecular modeling suggests that the enhancement of nanotube solubilization is attributed to the formation of self-assembled intermolecular structures associated with the inclusion of curing agents, in conformity with experimental findings. On the other hand, isolation of single-walled carbon nanotubes (SWNTs) with specific chirality and diameter is critical for achieving optimum performances of SWNTs in various application. Our studies reveal that phenylethynyl terminated imide (PETi) oligomer selectively enriches metallic and semiconducting (6, 5) SWNT.

Resin Transfer Moldable Fluorinated Phenylethynyl-Terminated Imide Oligomers with High Tg: Structure-Melt Stability Relationship.

Phenylethynyl-terminated aromatic polyimides meet requirements of resin transfer molding (RTM) and exhibits high glass transition temperature (Tg) were prepared. Moreover, the relationship between the polyimide backbones structure and their melting stability was investigated. The phenylethynyl-terminated polyimides were based on 4,4′-(hexafluorosiopropylidene)-diphthalic anhydride (6FDA) and different diamines of 3,4′-oxydianiline (3,4′-ODA), m-phenylenediamine (m-PDA) and 2,2′-bis(trifluoromethyl)benzidine (TFDB) were prepared. These oligoimides exhibit excellent melting flowability with wide processing temperature window and low minimum melt viscosities (<1 Pa·s). Two of the oligoimides display good melting stability at 280–290 °C, which meet the requirements of resin transfer molding (RTM) process. After thermally cured, all resins show high glass transition temperatures (Tgs, 363–391 °C) and good tensile strength (51–66 MPa). The cure kinetics studied by the differential scanning calorimetry (DSC), 13C nuclear magnetic resonance (13C NMR) characterization and density functional theory (DFT) definitely confirmed that the electron-withdrawing ability of oligoimide backbone can tremendously affect the curing reactivity of terminated phenylethynyl groups. The replacement of 3,4′-ODA units by m-PDA or TFDB units increase the electron-withdrawing ability of the backbone, which increase the curing rate of terminated phenylethynyl groups at processing temperatures, hence results in the worse melting stability.

Effect of Blending Modifications for Phenylethynyl-terminated Polyimides

A reactive diluent (ODA-PEPA) and a flexible phenylethynyl-terminated imide oligomer (PEI-PEPA) were designed and synthesized based on the 2,3,3’,4’-diphenyl ether tetracarboxylic acid dianhydride (a-ODPA), 3,4’-oxydianiline (3,4’-ODA), and 4-phenylethynylphthalic anhydride (PEPA). Solution blended systems with the addition of 5, 10, and 15 wt% ODA-PEPA to PEI-PEPA oligomer and their cured resin systems were prepared. Results showed that ODA-PEPA is semi-crystalline in nature. The Tg values of cured resins were improved from 273 °C to 280 °C by the addition of ODA-PEPA, due to the higher crosslink densities. In addition, rheological properties of blends showed lower melt viscosity and wider processing window, revealing improved melt processabilities for potential application in making advanced composites. The isothermal viscosity in 280 °C of PEI-PEPA containing 15 wt% ODA-PEPA reactive diluent decreased by two thirds, due to the low molecular weight of ODA-PEPA. The cured blends demonstrated high thermal stability and heat resistance. 5 wt% thermal decomposition temperatures (Td5) of the cured blends were above 549 °C and 547 °C in N2 and air atmosphere, respectively. The char yield reported at 800 °C in N2 atmosphere increased from 58.8% to 63.7 % with the addition of ODAPEPA. Meanwhile, the cured polyimides blends possessed good bond strength (> 9.3 MPa).