Reaction kinetics and thermal properties of epoxidised cresol novolac/4,4′‐diglycidyl (3,3′,5,5′‐tetramethylbiphenyl) epoxy resin composite cured with aromatic diamine

A series of novel composites based on different ratios of epoxidised cresol novolac (ECN) and 4,4′‐diglycidyl(3,3′,5,5′‐tetramethylbiphenyl) epoxy resin (TMBP) have been prepared with the curing agent 4,4′‐methylenediamine (DDM) and 4,4′‐diaminodiphenylsulfone (DDS), respectively. The investigation of cure kinetics was performed by differential scanning calorimetry using an isoconversional method. The high thermal stabilities of the cured samples were also studied by thermogravimetric analysis. In addition, no phase separation was observed for cured ECN/DDM and ECN/DDS blending with different amounts of TMBP by dynamic mechanical analysis and scanning electron microscopy. Moreover, the cured systems also exhibited excellent impact properties and low moisture absorption. All the results indicate that the ECN/TMBP/DDM and ECN/TMBP/DDS systems are promising materials in electronic packaging. Copyright © 2011 Society of Chemical Industry     

Novel adamantane‐containing epoxy resin

A novel adamantane‐containing epoxy resin diglycidyl ether of bisphenol‐adamantane (DGEBAda) was successfully synthesized from 1,3‐bis(4‐hydroxyphenyl)adamantane by a one‐step method. The proposed structure of the epoxy resin was confirmed with Fourier transform infrared, ¹H‐NMR, gel permeation chromatography, and epoxy equivalent weight titration. The synthesized adamantane‐containing epoxy resin was cured with 4,4′‐diaminodiphenyl sulfone (DDS) and dicyandiamide (DICY). The thermal properties of the DDS‐cured epoxy were investigated with differential scanning calorimetry and thermogravimetric analysis (TGA). The dielectric properties of the DICY‐cured epoxy were determined from its dielectric spectrum. The obtained results were compared with those of commercially available diglycidyl ether of bisphenol A (DGEBA), a tetramethyl biphenol (TMBP)/epoxy system, and some other associated epoxy resins. According to the measured values, the glass‐transition temperature of the DGEBAda/DDS system (223°C) was higher than that of the DGEBA/DDS system and close to that of the TMBP/DDS system. TGA results showed that the DGEBAda/DDS system had a higher char yield (25.02%) and integral procedure decomposition temperature (850.7°C); however, the 5 wt % degradation temperature was lower than that of DDS‐cured DGEBA and TMBP. Moreover, DGEBAda/DDS had reduced moisture absorption and lower dielectric properties. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci 2007     

Studies on crosslinking and thermal behavior of phthalonitrile end‐capped imide monomer in presence of aromatic amines

This paper describes the synthesis and characterization of a bisphthalonitrile monomer having an imide linkage prepared by reacting 4,4′‐(hexafluoroisopropylidene) diphthalic anhydride with 4‐(4‐aminophenoxy) phthalonitrile. The structure of the monomer was confirmed by Fourier transform infrared, ¹H‐NMR, and ¹³C‐NMR spectroscopy. The curing behavior of bisphthalonitrile monomer was investigated in the absence or presence of different diamines using differential scanning calorimetry. Diamines 4,4′‐diaminodiphenyl ether (DDE) and 4,4′‐diaminodiphenylsulfone (DDS) were used to investigate the effect of the structure of diamines on the curing behavior of bisphthalonitrile monomer. An exothermic transition due to curing was observed in the DSC scan, and the curing temperature was found to be dependent on the nucleophilicity of the amine. DDE was found to be more reactive than DDS. The thermal stability of the cured resins was evaluated using thermogravimetry in nitrogen atmosphere. All of the cured samples were stable up to 400 °C and leave behind 62% char residue at 800 °C, which was found to be dependent on the structure of the diamine used for curing as well as on the curing conditions. © 2018 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2018 , 135, 46151.     

Synthesis,characterization, and properties of low viscosity tetra‐functional epoxy resin N,N,N′,N′‐ tetraglycidyl‐3,3′‐diethyl‐4,4′‐diaminodiphenylmethane

Tetra‐functional epoxy resin N,N,N′,N′‐tetraglycidyl‐3,3′‐diethyl‐4,4′‐diaminodiphenylmethane (TGDEDDM) was synthesized and characterized. The viscosity of TGDEDDM at 25°C was 7.2 Pa·s, much lower than that of N,N,N′,N′‐tetraglycidyl‐4,4′‐diaminodiphenylmethane (TGDDM). DSC analysis revealed that the reactivity of TGDEDDM with curing agent 4,4′‐diamino diphenylsulfone (DDS) was significantly lower than that of TGDDM. Owing to its lower viscosity and reactivity, TGDEDDM/DDS exhibited a much wider processing temperature window compared to TGDDM/DDS. Trifluoroborane ethylamine complex (BF₃‐MEA) was used to promote the curing of TGDEDDM/DDS to achieve a full cure, and the thermal and mechanical properties of the cured TGDEDDM were investigated and compared with those of the cured TGDDM. It transpired that, due to the introduction of ethyl groups, the heat resistance and flexural strength were reduced, while the modulus was enhanced. © 2013 Wiley Periodicals, Inc. J. Appl. Polym. Sci., 2014 , 131, 40009.     

Curing of epoxy resin using imide‐amines

The curing behavior of diglycidyl ether of bisphenol‐A (DGEBA) was investigated by differential scanning calorimetry, using varying molar ratios of imide‐amines and 4,4′‐diaminodiphenyl sulfone (DDS). The imide‐amines were prepared by reacting 1 mol of pyromellitic dianhydride (P) with excess (2.5 mol) of 4,4′‐diaminodiphenyl ether (E), 4,4′‐diaminodiphenyl methane (M), or 4,4′‐diaminodiphenyl sulfone (S) and designated as PE, PM, PS. Structural characterization was done using FTIR, ¹H NMR, ¹³C NMR spectroscopic techniques and elemental analysis. The mixture of imide‐amines and DDS at ratio of 0 : 1, 0.25 : 0.75, 0.5 : 0.5, 0.75 : 0.25, and 1 : 0 were used to investigate the curing behavior of DGEBA. The multiple heating rate method (5, 10, 15, and 20°C/min) was used to study the curing kinetics of epoxy resins. The peak exotherm temperature was found to be dependent on the heating rate, structure of imide‐amine, and also on the ratio of imide‐amine : DDS used. Activation energy was highest in case of epoxy cured using a mixture of DDS : imide‐amine of a ratio of 0.75 : 0.25. Thermal stability of the isothermally cured resins was also evaluated in a nitrogen atmosphere using dynamic thermogravimetry. The char yield was highest in case of resins cured using mixture of DDS : PS (0.25 : 0.75; EPS‐3), DDS : PM (0.25 : 0.75; EPM‐3), and DDS : PE (0.75 : 0.25; EPE‐1). © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 101: 3502–3510, 2006     

Improving the curing process and thermal stability of phthalonitrile resin via novel mixed curing agents

High curing temperature (including post‐curing temperature) and long curing time of phthalonitrile resins make them thermally stable but difficult to process. In this paper, novel mixed curing agents (CuCl/4,4′‐diaminodiphenylsulfone (DDS) and ZnCl₂/DDS) were firstly designed for solving these problems. Bisphenol‐based phthalonitrile monomer (BP‐Ph; melting point: 228–235 °C) was synthesized and used as the curing precursor. Differential scanning calorimetry results indicated that BP‐Ph cured with CuCl/DDS and ZnCl₂/DDS exhibited curing temperatures close to the melting point of BP‐Ph with curing ending temperatures of 225.4 and 287.1 °C, respectively. Rheologic investigations demonstrated obvious curing reactions of BP‐Ph occurred with the mixed curing agents at 220 °C. Thermogravimetric analysis showed that BP‐Ph cured by CuCl/DDS or ZnCl₂/DDS maintained 95% mass at 573 or 546 °C, respectively, at a post‐curing temperature of 350 °C for 2 h. Reasonable long‐term thermo‐oxidative stability was also demonstrated. When the post‐curing temperature decreased to 290 °C, char yield at 800 °C of BP‐Ph cured by CuCl/DDS was 77.0%, suggesting the curing procedure can be milder when using mixed curing agents. © 2017 Society of Chemical Industry     

Preparation and thermal properties of novel phthalonitrile oligomer containing biphenyl ethernitrile/bisphthalonitrile blends

A kind of novel n = 2 phthalonitrile oligomer containing biphenyl ethernitrile (2PEN‐BPh) had been firstly synthesized from 2,6‐dichlorobenzonitrile, 4,4′‐biphenol and 4‐nitrophthalonitrile via solution reaction, and the 2PEN‐BPh was characterized by FTIR, ¹H‐NMR spectra which exhibited that cyano groups and ethernitrile linkages existed in the backbone of 2PEN‐BPh. The 2PEN‐BPh oligomer was blended with bisphthalonitrile monomer, the curing reaction behaviors of the blends were studied by FTIR, DSC, and rheological analysis. The thermal and thermo‐oxidative stabilities of the 2PEN‐BPh/BPh polymers were investigated by TGA, and the results showed that the completely cured polymers could achieve char yields up to 78% at 800°C in nitrogen, above 11% at 800°C in air. The whole research indicated that the 2PEN‐BPh/BPh blends could efficiently improve the processability of BPh monomer without scarifying other desirable high temperature properties. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2011     

Studies on the curing kinetics and thermal stability of diglycidyl ether of bisphenol‐A using mixture of novel,environment friendly sulphur containing amino acids and 4,4′‐diaminodiphenylsulfone

This article describes the curing behavior of diglycidyl ether of bisphenol‐A using Cysteine (A)/ Methionine (B)/Cystine (C)/ mixture of 4,4′‐diaminodiphenyl sulfone (DDS) and Cysteine/DDS and Methionine/DDS and Cystine in various molar ratios as curing agent. Differential scanning calorimetry was used to study the cure kinetics by recording the DSC scans at heating rates of 5, 10, 15, and 20°C/min. The peak exotherm temperature was found to be dependent on the heating rate, structure of the amino acids and on the DDS/amino acids molar ratio. A broad exotherm was observed in the temperature range of 150–245°C (EA), 155–240°C (EB), and 190–250°C (EC). Curing of DGEBA with mixture of amino acids and 4, 4′‐diaminodiphenyl sulfone (DDS) resulted in a decrease in characteristic curing temperatures. Activation energy of curing reaction is determined in accordance to Ozawa's method and was found to be dependent on the structure of the amino acids and on the ratio of 4,4′‐diaminodiphenyl sulfone (DDS) to amino acid. Thermal stability of the isothermally cured resins was evaluated using dynamic thermogravimetry in nitrogen atmosphere. No significant change has been observed in the char yield of all the samples, but it was highest in the system cured using either Cystine alone (EC‐1) or a mixture of DDS/Cystine (EC‐2, EC‐3, and EC‐4). © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2009     

Synthesis,characterization, thermal and optical properties of soluble polyimides derived from an unsymmetrical diamine

A new unsymmetrical diamine monomer, 2,4‐diaminophenyl [4′‐(2′′,6′′‐diphenyl‐4′′‐pyridyl)phenyl]ether, was successfully synthesized by nucleophilic substitution of 1‐chloro‐2,4‐dinitrobenzene with 4‐(2′,6′‐diphenyl‐4′‐pyridyl) phenol. The diamine monomer was characterized by FTIR, ¹H and ¹³C NMR, and elemental analysis techniques and used for the preparation of novel polyimides (PIs) by reaction with commercially available tetracarboxylic dianhydrides such as pyromellitic dianhydride, 3,3′,4,4′‐benzophenone tetracarboxylic dianhydride, and bicyclo[2.2.2]‐oct‐7‐ene‐2,3,5,6‐tetracarboxylic dianhydride. These PIs with inherent viscosities ranged from 0.43 to 0.48 dL/g were readily soluble in many organic solvents and afforded tough and flexible films by solution casting. These polymers exhibited T_gs between 237 and 294°C, and 10% weight loss temperatures in excess of 500°C with up to 56% char yield at 600°C in air. Their maximum fluorescence emission in dilute (0.2 g/dL) NMP solution appeared at 450 nm. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2010     

Poly(aryl ether ketone)s with bromomethyl groups: Synthesis and quaternary amination

A series of bromomethylated poly(arylene ether ketone)s (PAEKs) with different contents of bromine tethered to the benzyl groups were successfully synthesized and characterized in this work. For this purpose, poly(arylene ether ketone) with 3,3′,5,5′‐tetramethyl‐4,4′‐dihydroxybipheny moiety (PAEK‐TM) was prepared by the aromatic nucleophilic polycondensation, and then the PAEK‐TM has benzylic methyl groups that were converted to bromomethyl groups by a radical reaction using N‐bromosuccinimide. Then, the bromomethylbenzyl groups in the membrane was converted to quaternary ammonium moieties in TMPAEK‐NOH. ¹H‐NMR measurements were used to characterize and confirm the structures of the resulting PAEK‐x‐BrTM and TMPAEK‐NBr derivatives (x refers to the molar percentage of bromine introduced per repeating units). TGA analysis showed that PAEK‐x‐BrTM exhibited a very low‐decomposition temperature at about 200°C corresponding to the C Br bond cleavage. The hydroxide conductivity of TMPAEK‐NOH membrane was 8 mS cm⁻¹ at room temperature, while the water uptake of TMPAEK‐NOH membrane was 22.3% at 20°C and 32.6% at 60°C. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2011     

Preparation and characterization of high char yield polybenzoxazine/polyarylacetylene blends for resin‐transfer molding

Benzoxazine precursors (BOZP), 6,6′‐bis(2,3‐dihydro‐3‐(3‐ethynylphenyl)‐4H‐1,3‐ benzoxazinyl)ketone and 6,6′‐bis(2,3‐dihydro‐3‐(3‐ethynylphenyl)‐4H‐1,3‐benzoxazinyl)ether were synthesized and characterized by Proton nuclear magnetic resonace (¹H‐NMR) and Fourier transform infrared spectroscopy (FTIR). The polyarylacetylene (PAA) was synthesized through thermal polymerization of diethynylbenzene, and characterized by ¹H‐NMR, FTIR, and Differential Scanning Calorimetry (DSC). The BOZP/PAA blends were prepared with different contents of PAA, and their viscosity was measured using NDJ‐79 rotating visometer. The curing behavior of BOZP/PAA blends was characterized by DSC. The thermal stability of cured BOZP/PAA blends was studied using Thermogravimetric Analysis, the results show char yield at 800°C was in the range of 78–84%. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2009     

Synthesis and properties of a novel bismaleimide resin containing 1,3,4‐oxadiazole moiety and the blend systems thereof with epoxy resin

A new bismaleimide monomer, 2‐((4‐maleimidophenoxy)methyl)‐5‐(4‐maleimidophenyl)‐1,3,4‐oxadiazole (Mioxd), was designed and synthesized. The chemical structure of the monomer was confirmed by means of Fourier transform infrared (FTIR) spectroscopy, proton nuclear magnetic resonance (¹H NMR) spectroscopy and elemental analysis, and its thermal properties were characterized using differential scanning calorimetry (DSC) and thermogravimetric analysis (TGA). Mioxd as a reactive modifier was blended with epoxy resin based on bisphenol A diglycidyl ether (DGEBA) in weight ratio of 5, 10, and 15%, using 4,4′‐diaminodiphenyl sulfone (DDS) as hardener. The effect of Mioxd addition on the cure behavior and thermal properties of the blend resins was studied by DSC, TGA, and dynamic mechanical analysis (DMA). DSC investigations showed that the main exothermic peak temperature (T_p) of the blend systems did not obviously shift with increasing Mioxd content whereas a new shoulder appeared and gradually grew on the high temperature side of the exothermic peak. The results of DMA measurements exhibited the glassy storage modulus (G') and glass transition temperatures (T_g) increased as the Mioxd content was increased, the cured blends investigated were miscible and no phase separation occurred. Further, the thermal decomposition temperature first decreased and then increased, but the char yield at 600°C increased with an increase in Mioxd content. POLYM. ENG. SCI., 2011. © 2011 Society of Plastics Engineers     

Synthesis and characterization of high‐performance epoxy resin based on disiloxane and 4,4′‐oxybis(benzoic acid) ester

Epoxy‐terminated siloxane‐contained resin (BCDS/OBBA‐ETS) with high tensile strength and lap shear strength as well as good thermal stability was synthesized and characterized by ¹H‐NMR and Fourier transform infrared spectroscopy. Carboxy‐capped disiloxane‐4,4′‐oxybis (benzoic acid) ester oligomer (BCDS/OBBA) was firstly prepared from the reaction between 1,3‐bis(chloromethyl)‐1,1,3,3‐tetramethyl‐disiloxane and 4,4′‐oxybis(benzoic acid) (OBBA) in N,N‐dimethylformamide in the presence of triethylamine. Then, the BCDS/OBBA oligomer was reacted with epichlorohydrin to obtain the title BCDS/OBBA‐ETS resin. Cured with liquid polyamide L‐651, or diethylenetriamine, the mechanical and thermal properties as well as the lap shear strength of the BCDS/OBBA‐ETS resin were evaluated. The results indicated that the BCDS/OBBA‐ETS resin exhibited good thermal stability below 200°C, and the glass transition temperature (T_g) was about 64°C after cured with L‐651. The tensile strength of same cured BCDS/OBBA‐ETS resin was 27.46 MPa with a stain at break of 42.11%, and the lap shear strength for bonding stainless steel was 18.59 MPa. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2012     

Phosphorus‐containing epoxy resins: Thermal characterization

Three novel aromatic phosphorylated diamines, i.e., bis N,N′‐{3‐[(3‐aminophenyl)methyl phosphinoyl] phenyl} pyromellitamic acid (AP), 4,4′‐oxo bis N,N′‐{3‐[(3‐aminophenyl)methyl phosphinoyl] phenyl}phthalamic acid (AB) and 4,4′‐hexafluoroisopropylidene‐bis N,N′‐{3‐[(3‐aminophenyl)methyl phosphinoyl] phenyl}phthalamic acid (AF) were synthesized and characterized. These amines were prepared by solution condensation reaction of bis(3‐aminophenyl)methyl phosphine oxide (BAP) with 1,2,4,5‐benzenetetracarboxylic acid anhydride (P)/3,3′,4,4′‐benzophenonetetracarboxylic acid dianhydride (B)/4,4′‐(hexafluoroisopropylidene)diphthalic acid anhydride (F), respectively. The structural characterization of amines was done by elemental analysis, DSC, TGA, ¹H‐NMR, ¹³C‐NMR and FTIR. Amine equivalent weight was determined by the acetylation method. Curing of DGEBA in the presence of phosphorylated amines was studied by DSC and curing exotherm was in the temperature range of 195–267°C, whereas with conventional amine 4,4′‐diamino diphenyl sulphone (D) a broad exotherm in temperature range of 180–310°C was observed. Curing of DGEBA with a mixture of phosphorylated amines and D, resulted in a decrease in characteristic curing temperatures. The effect of phosphorus content on the char residue and thermal stability of epoxy resin cured isothermally in the presence of these amines was evaluated in nitrogen atmosphere. Char residue increased significantly with an increase in the phosphorus content of epoxy network. © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 84: 2235–2242, 2002     

Synthesis and characterization of a novel silicon‐containing polytriazole resin

4,4′‐Diazidomethylbiphenyl (DAMBP) and poly(dimethylsilylene‐ethynylenephenyleneethynylene) (PDMSEPE) were thermally polymerized to form a novel silicon‐containing polytriazole resin (PDMSEPE‐DAMBP) by 1,3‐dipolar cycloaddition. Differential scanning calorimetry, FTIR, and ¹³C‐NMR were used to characterize the curing behaviors of PDMSEPE‐DAMBP resins. The results indicated that the resins could cure at temperatures as low as 80°C. Dynamic mechanical analysis showed that there was a glass transition at 302°C for the cured PDMSEPE‐DAMBP resin. The carbon fiber (T700) reinforced PDMSEPE‐DAMBP composites exhibited excellent mechanical properties at room temperature and high property retention at 250°C. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2009     

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     

Organosoluble polyimides derived from asymmetric 2‐substituted‐and 2,2′,6‐trisubstituted‐4,4′‐oxydianilines

We report a new method for the preparation of asymmetric diamines using 4,4′‐oxydianiline (4,4′‐ODA) as the starting material. By controlling the equivalents of bromination agent, N‐bromosuccinimide, we were able to attach bromide and phenyl substituents at the 2‐ or 2,2′,6‐positions of 4,4′‐ODA. Thus, four new asymmetric aromatic diamines, 2‐bromo‐4,4′‐oxydianiline (6), 2,2′,6‐tribromo‐4,4′‐oxydianiline (7), 2‐phenyl‐4,4′‐oxydianiline (8) and 2,2′,6‐triphenyl‐4,4′‐oxydianiline (9), were synthesized by this method. Their structural asymmetry was confirmed using ¹H NMR spectroscopy. Asymmetric polyimides (PI10–PI13) were prepared from these diamines and three different dianhydrides (pyromellitic dianhydride (PMDA), 3,3′,4,4′‐biphenyltetracarboxylic dianhydride and 2,2‐bis(3,4‐dicarboxyphenyl)hexafluoropropane dianhydride) in refluxing m‐cresol. The formed polyimides, except PI10a derived from 6 and PMDA, were all soluble in m‐cresol without premature precipitation during polymerization. These polyimides with inherent viscosity of 0.41–0.96 dL g^?1, measured at a concentration of 0.5 g dL^?1 in N‐methyl‐2‐pyrrolidone at 30 °C, can form tough and flexible films. Because of the structural asymmetry, they also exhibited enhanced solubility in organic solvents. Especially, polyimides PI11a and PI13a derived from 7 and 9 with rigid PMDA were soluble in various organic solvents at room temperature. The structural asymmetry of the prepared polyimides was also evidenced from ¹H NMR spectroscopy. In the ¹H NMR spectrum of PI11a, the protons of pyromellitic moiety appeared in an area ratio of 1:2:1 at three different chemical shifts, which were assigned to head‐to‐head, head‐to‐tail and tail‐to‐tail configurations, respectively. These polyimides also exhibited good thermal stability. Their glass transition temperatures ranged from 297 to 344 °C measured using thermal mechanical analysis. © 2013 Society of Chemical Industry     

Synthesis and curing behavior of a novel benzoxazine‐based bisphthalonitrile monomer

A novel bisphthalonitrile containing benzoxazine units (BZ‐BPH) was synthesized via a solventless method from 4,4′‐dihydroxybiphenyl, paraformaldehyde, and 4‐aminophenoxylphthalonitrile. The chemical structure of BZ‐BPH was confirmed by ¹H‐NMR and ¹³C‐NMR analyses. The curing behavior was investigated with DSC, FTIR, TGA, and rheology techniques. The monomer manifested a two‐stage thermal polymerization pattern. The first stage was attributed to the ring‐opening polymerization of benzoxazine moiety, and the second to the polymerization of phthalonitriles. Study about the effect of the catalysts including 4,4′‐diaminodiphenylsulfone and FeCl₃ on the polymerization of BZ‐BPH was performed, and the result indicated that the addition of these agents could increase the curing rate and lower the curing temperature. Additionally, the cured product showed excellent thermal and thermo‐oxidative stability, the high char yield was 76.0% by weight at 800°C in nitrogen atmosphere and 81.2% by weight at 600°C in air, and temperature at 5% weight loss (T_5%) in nitrogen and air was 477.9°C and 481.7°C, respectively. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2010     

Synthesis and characterization of poly(acrylate amic acid) and its application as negative‐tone photosensitive polyimides

The dianhydride monomer 3,3′,4,4′‐benzophenone tetracarboxylic acid dianhydride and two diamine monomers, 4,4′‐diamino‐3,3′‐biphenyldiol (HAB) and 2,4‐diaminophenol dihydrochloride (DAP), were used to synthesize a series of poly(hydroxyl amic acid). Further functionalization by grafting acrylate groups yields the corresponding poly(acrylate amic acid) that underwent a crosslinking reaction on exposure to UV‐light and was used as a negative‐tone photosensitive polyimide (PSPI). The analysis of chemical composition and molecular weight of these poly(amic acid)s determined by nuclear magnetic resonance (NMR) spectroscopy, Fourier transform infrared spectroscopy, and gel permeation chromatography revealed that the molecular weight of the poly(hydroxyl amic acid) increased with the molar content of HAB in the feedstock, because HAB exhibited higher polymerization reactivity than DAP. Moreover, the degree of grafting acrylate groups onto poly(hydroxyl amic acid) was determined by ¹H‐NMR spectroscopy. The photoresist was formulated by adding 2‐benzyl‐2‐N,N‐dimethylamino‐1‐(4‐morpholinophenyl) butanone (IRG369) and isopropylthioxanthone as a photoinitiator, tetra(ethylene glycol) diacrylate as a crosslinker, and tribromomethyl phenyl sulfone as a photosensitizer. The PSPI precursor exhibited a photosensitivity of 200 mJ/cm² and a contrast of 1.78. A pattern with a resolution of 10 μm was observed in an optical micrograph after thermal imidization at 300°C. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2009     

Resistive switching characteristics of polyimides derived from 2,2′‐aryl substituents tetracarboxylic dianhydrides

2,2′‐Position aryl‐substituted tetracarboxylic dianhydrides including 2,2′‐bis(biphenyl)‐4,4′,5,5′‐biphenyl tetracarboxylic dianhydride and 2,2′‐bis[4‐(naphthalen‐1‐yl)phenyl)]‐4,4′,5,5′‐biphenyl tetracarboxylic dianhydride were synthesized. A new series of aromatic polyimides (PIs) were synthesized via a two‐step procedure from 3,3′,4,4′‐biphenyl tetracarboxylic dianhydride and the newly synthesized tetracarboxylic dianhydrides monomers reacting with 2,2′‐bis[4′‐(3″,4″,5″‐trifluorophenyl)phenyl]‐4,4′‐biphenyl diamine. The resulting polymers exhibited excellent organosolubility and thermal properties associated with T_g at 264 °C and high initial thermal decomposition temperatures (T_5%) exceeding 500 °C in argon. Moreover, the fabricated sandwich structured memory devices of Al/PI‐a/ITO was determined to present a flash‐type memory behaviour, while Al/PI‐b/ITO and Al/PI‐c/ITO exhibited write‐once read‐many‐times memory capability with different threshold voltages. In addition, Al/polymer/ITO devices showed high stability under a constant stress or continuous read pulse voltage of ? 1.0 V. Copyright © 2011 Society of Chemical Industry