Synthesis and characterization of benzimidazole‐based low CTE block copolyimides

A series of block and random copolyimide films were synthesized from various molar ratios of two diamines, rigid 2‐(4‐aminophenyl)‐5‐aminobenzimidazole (APBI) and flexible 4,4′‐oxydianiline (ODA) by polycondensation with dianhydride 3,3′,4,4′‐biphenyltetracarboxylic dianhydride. The contents of APBI ranged from 10 to 60 mol % in copolyimides. The copolyimide films obtained by thermal imidization of poly(amic acid) solutions, were characterized by TMA, DMA, TGA, DSC, wide‐angle X‐ray diffraction, FTIR, tensile testing, water uptake (WU), and dielectric constant measurements. Rigid heterocyclic diamine APBI with interchain hydrogen bonding capability, led to low coefficient of thermal expansion (CTE), high T_g, high thermal stability and better mechanical properties. Increasing the APBI mol % caused a gradual decrease in the CTE and increase in T_g, thermal stability and tensile strength properties of the copolyimides films. Moreover, significantly enhanced thermal and mechanical properties of the block copolyimides were also found as compared to random copolyimides. The block copolyimide with APBI content of 60 mol %, achieved excellent properties, that is, a low CTE (4.7 ppm/K), a high T_g at 377°C, 5% weight loss at 562°C and a tensile strength at 198 MPa. This can be interpreted because of comparatively higher degree of molecular orientation in block copolyimides. These copolyimides also exhibited better dielectric constant and WU. This combination of properties makes them attractive candidates for base film materials in future microelectronics. © 2013 Wiley Periodicals, Inc. J. Appl. Polym. Sci., 2013     

Synthesis and characterization of copolyimides with high solubility

A series of copolyimides were prepared from various diamines (polysiloxane and isophorone units) with aromatic tetracarboxylic dianhydrides via a two‐step (thermal imidization) method. The monomers and polymers were produced in high yields, and the copolyimides containing Si? O? C bonds and asymmetric meta catenation in the polymer backbone exhibited good solubility. The glass‐transition temperatures (T_g's) of all the copolyimides were found to be 201–262 and 215–258°C by differential scanning calorimetry (DSC) and dynamic mechanical analysis, respectively. Thermogravimetric analyses indicated that the polymers were fairly stable up to 502–578°C (10 wt % loss in N2) and 490–574°C (10 wt % loss in air). The char yields at 800°C in N2 and air atmospheres were 26–59 and 20–53%, respectively. The copolymerization results, determined with 1H‐NMR and DSC, indicated a random copolymer. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 88: 1963–1970, 2003     

Synthesis and characterization of novel borosiloxane‐containing aromatic copolyimides with excellent thermal stability and low coefficient of thermal expansion

The properties of borosiloxane‐containing copolyimides with borosiloxane in the main chain and in the side chain were studied. Two series of borosiloxane‐containing copolyimides were synthesized by the reaction of 3,3′,4,4′‐biphenyltetracarboxylic dianhydride (s‐BPDA ) and 2,3′,3,4′‐biphenyltetracarboxylic dianhydride (a‐BPDA ) with p ‐phenylenediamine (PDA ), 4,4′‐oxydialinine (4,4′‐ODA ) and different borosiloxane diamine monomers (BSiAs ). The synthesized borosiloxane‐containing copolyimides exhibited better solubility than borosiloxane‐free copolyimides and showed high glass transition temperatures (320–360 °C), excellent thermal stability (570–620 °C for T ₁₀), great elongation at break (10% ? 14%) and a low coefficient of thermal expansion (14–24 ppm °C^?1). More specifically, the copolyimides containing BSiA‐2 formed nano‐scale protrusions and the copolyimides containing BSiA‐1 formed micro‐scale protrusions. The contact angles of the copolyimides increased from 72° for neat copolyimide to 96° for 5% of borosiloxane in the main chain of the copolymer up to 107° for 10% of borosiloxane in the side chain of the copolymer. © 2017 Society of Chemical Industry     

Synthesis and characterization of ternary‐copolymer of soluble fluorinated polyimides based on 1,4‐bis (4‐amino‐2‐trifluoromethylphenoxy) benzene

A series of novel ternary‐copolymer of fluorinated polyimides (PIs) were prepared from 1,4‐bis(4‐amino‐2‐trifluoromethylphenoxy)benzene (pBATB), commercially available aromatic dianhydrides, and aromatic diamines via a conventional two‐step thermal or chemical imidization method. The structures of all the obtained PIs were characterized with FTIR, ¹H‐NMR, and element analysis. Besides, the solubility, thermal stability, mechanical properties, and moisture uptakes of the PIs were investigated. The weight‐average molecular weight (M_w) and the number‐average molecular weight (M_n) of the PIs were determined using gel‐permeation chromatography (GPC). The PIs were readily dissolved not only in polar solvents such as DMF, DMAc, and NMP, but also in some common organic solvents, such as acetic ester, chloroform, and acetone. The glass transition temperatures of these PIs ranged from 201 to 234°C and the 10% weight loss temperatures ranged from 507 to 541°C in nitrogen. Meanwhile, all the PIs left around 50% residual even at 800°C in nitrogen. The GPC results indicated that the PIs possessed moderate‐to‐high number‐average molecular weight (M_n), ranging from 9609 to 17,628. Moreover, the polymer films exhibited good mechanical properties, with elongations at break of 8–21%, tensile strength of 66.5–89.8 MPa, and Young's modulus of 1.04–1.27 GPa, and low moisture uptakes of 0.54–1.13%. These excellent combination properties ensure that the polymer could be considered as potential candidates for photoelectric and microelectronic applications. © 2012 Wiley Periodicals, Inc. J. Appl. Polym. Sci., 2013     

Incorporating bis‐benzimidazole into polyimide chains for effectively improving thermal resistance and dimensional stability

Heteroaromatic 6,6′‐bis[2‐(4‐aminobenzene)benzimidazole] and its corresponding copolyimides were synthesized to produce high temperature resistant polyimides (PIs). Due to the rigidity and aromaticity of heterocyclic bis‐benzimidazole, and the increased hydrogen bonding interactions, these PIs were found to have a high glass transition temperature (T_g) over 457 °C, which also guarantees a better dimensional stability with a coefficient of thermal expansion (CTE) lower than 10 ppm K^?1 in a wider temperature range of 50–400 °C. In addition, the PIs exhibit excellent thermal stability (5% weight loss temperature higher than 559 °C) along with outstanding mechanical properties. This study demonstrates the viability to access PIs with ultrahigh T_g and low CTE in a wider range of temperature by the incorporation of bis‐benzimidazole moieties. © 2019 Society of Chemical Industry     

Preparation and characterization of aromatic polyimides and related copolymers

Copolyimides containing BTDA-3DDS and BTDA-4ODA units have been synthesized by solution imidization methods. The copolyimides have high T_g's (267–283°C) and high decomposition temperatures (540–575°C; nitrogen); both properties are dependent on composition. Those copolymides with low concentrations of BTDA-4ODA are generally soluble in organic solvents, whereas those copolyimides with higher BTDA-4ODA content are only partially soluble or insoluble. However, all the copolyimides prepared can be compression molded. It has also been found that segmental motion above T_g is heavily suppressed in the BTDA-4ODA homopolymer relative to that in the BTDA-3DDS homopolymer. This reduction in molecular motion may severely hinder the solubility and fusibility of the BTDA-4ODA homopolymer. © 1993 John Wiley & Sons, Inc.     

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     

Investigations on the polyimides derived from unfunctionalized symmetric cyclopentyl‐containing alicyclic cardo‐type dianhydride

This study presents an investigation on polyimides derived from a unfunctionalized symmetric cyclopentyl‐containing alicyclic cardo‐type dianhydride with ester linkage 1,1‐bis(4‐(3,4‐dicarboxylbenzoyloxy)phenyl)cyclopentylene dianhydride (BDPCP) that was readily accessed starting from cyclopentanone through two steps in high yield. Two series of polyimides, Cardo‐type series (CPI‐x) and analogous aromatic series (ArPI‐x) were prepared from condensation of BDPCP and aromatic 3,3′,4,4′‐Oxydiphthalic dianhydride with four aromatic diamines, respectively. Comparative studies revealed that CPI polymers show more favorable properties including better solubility in organic solvents, higher transparency with lower cut‐off wavelength (λ₀) ranging in 395–375 nm than 425–405 nm, lower water absorption ranging in 0.66–1.14% and surface energy 23.71–32.77 mN/m than 1.01–1.28% and 29.52–41.99 mN/m of ArPI analogs. Meanwhile, CPI series exhibit considerable mechanical properties with tensile strengths ranging in 87.6–102.9 MPa, elongations at break 6.6–8.9%. Owing to the moderate strain in cyclopentyl ring, CPI series retain good thermal properties with the glass transition temperature (T_g) in the range of 217–271°C. Dynamic dielectric measurement revealed that Cardo‐type dianhydride BDPCP endows CPI‐4 film with lower dielectric constant (ε′) 3.34 at 1 MHz and 25°C and dielectric loss (ε′′) 0.0064 at 1 kHz and 25°C than 3.49 and 0.013 for ArPI‐4 film. © 2015 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2015 , 132, 42670.     

Synthesis and properties of 6FDA‐BisAAF‐PPD copolyimides for microelectronic applications

In this work, fluorine‐containing copolyimides were synthesized from 6FDA dianhydride and different ratios of BisAAF and PPD diamines. Properties, such as composition, viscosity, dielectric constant, glass‐transition temperature, thermal decomposition temperature, tensile characteristics, and transmittance, were investigated by using elemental analysis, viscometry, Fourier transform infrared spectrometry, differential scanning calorimetry, a thermogravimetric analyzer, a tensile tester, and UV–visible spectrophotometry. After curing at 300°C for 1 h, imidization was observed, as indicated the appearance of an absorption peak of the carbonyl of the imide at 1780 cm^?1 (C?O asymmetry stretching). The inherent viscosity increased with an increasing PPD mole fraction, from 0.40 dL/g of pure 6FDA‐BisAAF to 0.84 dL/g of pure 6FDA‐PPD. The dielectric constant decreased with increasing fluorine content. The glass‐transition temperature increased with an increasing PPD mole fraction; the values increased from 317°C with pure 6FDA‐BisAAF polyimide to 364°C with pure 6FDA‐PPD polyimide. The 5% weight loss temperature (T_d) of the copolyimides was around 530°C in air and 540°C in a nitrogen atmosphere. The tensile modulus and tensile strength gradually increased with an increasing PPD molar fraction. The transmittance of 6FDA‐BisAAF‐PPD copolyimides was greater than 90% at wavelengths above 500 nm. © 2005 Wiley Periodicals, Inc. J Appl Polym Sci 98: 2064–2069, 2005     

Thermosetting Polyetherimides: The Influence of Reactive Endgroup Type and Oligomer Molecular Weight on Synthesis,Network Formation,Adhesion Strength and Thermal Properties

The influence of the reactive endgroup on the synthesis, cure behavior and network properties of thermosetting polyetherimides was investigated. Reactive phenylethynyl, ethynyl and maleimide terminated etherimide oligomers were prepared and characterized. Optimal reaction conditions were established to produce fully endcapped oligomers with imidized structures and controlled molecular weight. The phenylethynyl and ethynyl endcapped systems were synthesized by ester-acid methods. The maleimide endcapped system utilized an amic-acid route. Phenylethynyl endcapped oligomers had good processibility and were thermally cured at high temperatures (350–380°C). The networks exhibited good thermal and hydrolytic stability and good adhesion strength, and are candidates for “primary'' bonding adhesives. In contrast, more reactive ethynyl and maleimide endcapped systems were prepared as “secondary'' bonding materials, which could be cured at temperatures lower than that of the T _g of the primary structure. Lap shear test results obtained from NMP-cast/methanol-extracted scrim-cloth-supported precursors confirmed that good adhesion to titanium at both room temperature and at 177°C was achieved when cured at 250°C-280°C. High glass transition temperatures and good thermal stability were achieved as determined by thermal analysis (DSC, TGA and DMA). Solvent extraction measurements confirmed that very high gel fractions were obtained, which is consistent with good chemical resistance.

The influence of molecular weight between crosslinks (Mc) on thermal and mechanical behavior was also investigated for 2,3,5,7 and 10k initial M _n values. Lower molecular weight oligomers exhibited lower T _g and cure temperatures, but higher cured network crosslink densities afforded higher T _g and higher gel fractions, but with reduced toughness.     

Synthesis and properties of poly(ether imide)s derived from 2,5‐bis(3,4‐dicarboxyphenoxy)biphenyl dianhydride and aromatic ether–diamines

A series of poly(ether imide)s (PEIs) with light colors and good mechanical properties were synthesized from 2,5‐bis(3,4‐dicarboxyphenoxy)biphenyl dianhydride and various aromatic ether–diamines via a conventional two‐step polymerization technique that included ring‐opening polyaddition at room temperature to poly(amic acid)s (PAAs) followed by thermal imidization. The precursor PAAs had inherent viscosities ranging from 0.71 to 1.19 dL/g and were solution‐cast and thermally cyclodehydrated to flexible and tough PEI films. All of the PEI films were essentially colorless, with ultraviolet–visible absorption cutoff wavelengths between 377 and 385 nm and yellowness index values ranging from 10.5 to 19.9. These PEIs showed high thermal stabilities with glass‐transition temperatures of 206–262°C and decomposition temperatures (at 10% weight loss) higher than 478°C. They also showed low dielectric constants of 3.39–3.72 (at 1 MHz) and low water absorptions below 0.85 wt %. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2009     

Synthesis and properties of aromatic polyimide,poly(benzoxazole imide), and poly(benzoxazole amide imide)

Two series of heterocyclic aromatic polymers were synthesized from 4,4′‐(4,4′‐isopropylidenediphenoxy)bis(phthaltic anhydride) and 2,2′‐bis(3,4‐dicarboxyphenyl)hexafluoropropane dianhydride by two‐step method. The inherent viscosities were in the range of 24–45 cm³/g. The effects of the rigid benzoxazole group in the backbone of copolymer on the thermal, mechanical, and physical properties were investigated. These polymers exhibit good thermal stability. The temperatures of 5% weight loss (T₅) of these polymers are in the range of 403–530°C in air and 425–539°C in nitrogen. The chard yields of these polymers are in the range of 15–24% in air and 54–61% in nitrogen. These polymers also have high glass‐transition temperatures and a low coefficient of thermal expansion and good mechanical properties. The poly(benzoxazol imide) has a higher tensile strength and modulus than those of neat polyimide. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2009     

Polyamide derived from 4,4′-thiobis(methylene)dibenzoyl chloride and aliphatic diamine: interfacial synthesis and characterization

A series of processable semi-aromatic polyamides containing thioether and methylene units were synthesized through the reaction of 4,4′-thiobis(methylene)dibenzoyl chloride and aliphatic diamine by the method of interfacial polycondensation. These polyamides had excellent thermal properties with glass transition temperatures (T _g) of 104.3–130.6 °C, melting temperatures (T _m) of 300.3–303.8 °C, and initial degradation temperatures (T _d) of 405.2–410.3 °C. They had wider processing windows than traditional semi-aromatic polyamides (such as PA6T can not be processed by melting) and can be processed by melting method. They had better tensile strengths of 57.6–64.1 MPa, low-temperature mechanical properties, low water absorption of 0.19–0.27 %, low dielectric constants of 3.11–3.95 at 100 kHz, and better melt flowability properties of 232–60.7, 301.9–78.8, and 423.1–83.6 Pa s under a shear rate ranging from 20 to 1,170 s^?1, respectively. In addition, these polyamides showed good corrosion resistance, they did not dissolve in solvents such as NMP, DMSO, hydrochloric acid (6 mol/l), and solution of NaOH (1 mol/l) and so on.     

Improvement in Low Temperature Izod Impact Strength of SAN/ASA/HNBR Ternary Blends Considering Competing Effects of Glass Transition Temperature and Compatibility

The competing effects of glass transition temperature (T_g) and compatibility on the low temperature Izod impact toughness of styrene–acrylonitrile copolymer/acrylonitrile–styrene‐acrylate terpolymer (SAN/ASA, 75/25, w/w) blends were investigated by using a series of hydrogenated nitrile butadiene rubbers (HNBRs) with different acrylonitrile (AN) contents. The results showed that the HNBR with AN mass content ranging from 21% to 43% had good compatibility with polymer matrix and exhibited dramatic toughening effect at 25°C. Owing to their low T_gs, only the HNBRs (AN = 21% and 25%) remained favorable toughening effect at 0 and ?30°C, respectively. Furthermore, the HNBR with 0% AN content was represented by butadiene rubber (BR). Although, BR has an extremely low T_g (?94.5°C), it is incompatible with polymer matrix, and then could not toughen the material at three temperatures (?30, 0, and 25°C, respectively). Various characterizations including solubility parameters, scanning electron microscopy (SEM), dynamic mechanical thermal analysis (DMTA), Fourier transform infrared (FTIR) spectroscopy, and so on were carried out to elucidate the toughening mechanism. J. VINYL ADDIT. TECHNOL., 25:225–235, 2019. © 2018 Society of Plastics Engineers     

2,6‐Diamino‐4‐phenylphenol (DAPP) copolymerized polyimides: synthesis and characterization

Novel soluble copolyimides containing phenyl and hydroxyl pendant groups were synthesized from pyromellitic dianhydride (PMDA) and two diamines, 2,6‐diamino‐4‐phenylphenol (DAPP) and 4,4′‐oxydianiline (ODA), in various ratios via thermal imidization. The structures and physical properties of the copolyimides were characterized by FTIR, elemental analysis, DSC, dynamic mechanical analysis (DMA), TGA, a universal testing machine for stress–strain behaviour, and a dielectric analyzer to study the effect of DAPP on the physical properties of the modified polymers. Copolyimides containing more than 40 mol% DAPP were soluble in hot N‐methyl‐2‐pyrrolidone (NMP), dimethylacetamide (DMAc) and dimethylformamide (DMF), and possessed a high glass transition temperature (358 °C) and a high modulus (3.9 GPa). Introduction of the diamine DAPP could also reduce the dielectric constant. A segment of imide linkages could convert to benzoxazole linkages by decarboxylation at temperatures higher than 420 °C under vacuum. Although the heat‐treated polybenzoxazoles (PBOs) exhibited many good properties, they were found to be too rigid and brittle to be processable for microelectronic applications. Copyright © 2005 Society of Chemical Industry     

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     

Modification of bismaleimide with allyl compound and N‐phenylmaleimide

Three different formulas with low‐cost resins, made up of N,N′‐bismaleimidephenylmethane (BMI), O,O′‐diallybisphenol A(BA), and N‐phenylmaleimide (NPMI) were developed. The properties of prepolymers, such as activation energies, enthalpy, and constants of reaction rate, were obtained by a kinetic programmer on DSC. Thermal and mechanical properties of neat resins were also studied. The results showed that the systems had low melting point and low viscosity. All cured resins presented excellent thermal and good mechanical properties. The mechanical properties could be affected by the quantity of NPMI and postcuring process. The water absorption is ≤1.98%; heat deflection temperature (HDT) is ≥250°C after aging for 100 h in distilled water of 90°C. The data indicate that the BMI can be effectively improved by adding BA and NPMI, while its heat resistance and hot/wet mechanical properties can be fairly retained. © 2001 John Wiley & Sons, Inc. J Appl Polym Sci 80: 2518–2522, 2001     

Poly(arylene ether nitrile) copolymers containing pendant phenyl: Synthesis and properties

A series of poly(arylene ether nitrile) copolymers (PENAPs) were synthesized with bisphenol A (BP-A), bisphenol AP (BP-AP) and 2,6-Dichlorobenzonitrile (DCBN) via a nucleophilic substitution polycondensation reaction. FTIR and ¹H-NMR were used to confirm the structure of PENAPs. Glass transition temperature (T_g) of PENAPs determined by differential scanning calorimetry (DSC) ranged from 154.2 to 200.8°C. The 5% weight lost temperature (T_5%) of PENAPs were 418.9–447.7°C. The tensile and DMA test indicated that PENAPs possessed excellent mechanical properties with tensile strength more than 92.8 MPa and storage modulus more than 1.0 GPa at about 150°C. The melt flowability was measured by rheology properties testing ranging from 80 to 1639 GPa at 290°C and under shear frequency 100 Hz, which indicated the copolymers had good flowability and thermal stability. Additionally, PENAPs could be dissolved in many solutions, which meant PENAPs had good solubility and can be processed by solution method.     

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     

Polyarylene ether nitrile/divinyl siloxane-bisbenzocyclobutene composite films: Curing reaction and thermal/mechanical/dielectric properties

Polymer dielectrics, are commonly used as insulating materials for electronic products. Light weight, good mechanical properties and high thermal conductivity are important properties. However, electrical and thermal parameters are interrelated, and it is challenging to have a dielectric polymer that is also resistant to high temperatures and high thermal conductivity. Hence, high-performance composite films were prepared by the method of post-solid phase chemical reaction using polyarylene ether nitrile (PEN) and divinyl siloxane-bisbenzocyclobutene (BCB) as raw materials. First, parameters of the curing reaction were determined by rheological and activation energy calculations. Then, through adjusting the content of BCB resin and treatment temperature, the performance of PEN/BCB composites could be tuned. Thermal properties have been studied by differential scanning calorimetry, dynamic mechanical analysis, thermal gravimetric analysis, and hot-disk method. Here, the PEN/BCB composite electric insulating materials with outstanding thermal performance (T_g: 208–400°C, T_5%: 469–544°C, thermal conductivity: 1.270–2.215 W/m K). Besides, its mechanical and dielectric properties were investigated in detail. It is noteworthy that the tensile strength of composite film can exceed a maximum of 130 MPa, which is 23.19% higher compared to the untreated one. Also, PEN/BCB composites own low dielectric constant (2.27–4.08 at 1 KHz), and the relationship between frequency or a wide temperature range and dielectric constant/loss is stable. Thus, it has a greater potential for applications in electronics in high-temperature environments.