Heat-resistant adhesive resins derived from bismaleimides and bisnadimides containing amide linkages

A novel class of bismaleimides and bisnadimides containing amide linkages in their backbones were synthesized and characterized. The synthesis of these polymer precursors was carried out by reacting a diamine containing amide linkages with maleic/nadic anhydride. They were alternatively prepared by reacting the monomaleamic/monoadiamic acid of an aromatic diamine (1 mol) with terephthaloyl chloride (0.5 mol) and subsequent cyclodehydration. The latter new preparation method circumvented the hydrogeneration necessary in the first method of synthesis. The monomers were characterized by infrared (IR) and proton nuclear magnetic resonance (¹H-NMR) spectroscopy. Differential thermal analysis (DTA) of monomers showed that bisnadimide and bismethylnadimide were polymerized at lower temperatures than the corresponding bismaleimide. Thermogravimetric analysis (TGA) in nitrogen and air atmosphere revealed that all polymers were stable up to 321–363°C. Their char yield at 800°C under anaerobic conditions was 49–67%.     

Addition polyimide adhesives containing various end groups

Addition polyimide oligomers have been synthesized from 3,3′,4,4′-benzophenone tetracarboxylic acid dianhydride and 3,3′-methylenedianiline using a variety of latent crosslinking groups as end-caps. The nominal 1300 molecular weight imide prepolymers were isolated and characterized for solubility in amide, chlorinated and ether solvents, melt-flow and cure properties, glass transition temperature, and thermal stability on heating in an air atmosphere. Adhesive strengths of the polyimides were obtained both at ambient and elevated temperatures before and after aging at 232°C. Properties of the novel addition polyimides were compared to a known nadic end-capped adhesive, LARC-13.     

Synthesis and photodegradation behavior of polyethylene containing side-chain keto ether groups

The synthesis and photochemical behavior of the polymers obtained by grafting diazoacetophenones and p-substituted diazoacetophenones onto an ethylene–vinyl alcohol copolymer were studied. Photodegradation proceeds through a primary process with generation of acetophenone (or the p-substituted acetophenone) and “in chain” keto groups. A secondary photochemical process sensitized by these two units leads to oxidative photodegradation. The degradation leads to lowering of the molecular weight in prevalence to crosslinking. The effect of the p-substitution on the acetophenone with electron-withdrawing substituent has little effect on the degradation rate.     

Synthesis of thermosetting poly(phenylene ether) containing allyl groups

New thermosetting poly(2-allyl-6-methylphenol-co-2,6-dimethylphenol)s (3) have been developed by oxidative coupling copolymerization of 2-allyl-6-methylphenol (1) with 2,6-dimethylphenol (2), followed by thermal curing. Copolymerization was conducted in nitrobenzene in the presence of copper(I) chloride and pyridine as the catalyst under a stream of oxygen, producing high molecular weight copolymers (M_n∼50,000) with broad molecular weight distributions (M_w/M_n∼35). The structure of resulting copolymers 3 was characterized by IR, ¹H, and ¹³C NMR spectroscopy. Cross-linking reactions of copolymers were carried out by thermal treatment in the absence or presence of a peroxide (3 wt%, 2,5-dimethyl-2,5-di(tert-butylperoxy)-3-butane). The 10% weight loss and glass transition temperatures of the cured copolymers were 436 °C in nitrogen and 235 °C, respectively after curing at 70 °C for 1 h and 300 °C for 1 h. The average refractive index of the cured copolymer (3b) film was 1.5407, from which the dielectric constant (ε) at 1 MHz was estimated as 2.6. The ε and dissipation factor of copolymer-films at 1 MHz were directly measured from their capacitances as 2.5-2.6 and 0.0015-0.0019, respectively.     

Dual‐curing thermosetting monomer containing both propargyl ether and phthalonitrile groups

Novel self‐curing monomer containing two thermosetting groups, namely propargyl ether and phthalonitrile (PN) in a molecular structure, is synthesized and investigated. The study of catalyzed and uncatalyzed curing is performed and high heat release during curing is observed. This disadvantage can be adjusted by catalysis of propargyl ether polymerization with Ni (II), Co (II), and Cu (II) salts. The cured monomer possesses high thermal properties featured to phthalonitrile matrices (Heat deflection temperature, HDT = 428 °C, T_5% = 499 °C) and moderate mechanical properties (E = 4.9 ± 0.65 GPa, G_IC = 106 ± 26 J/m²), it can be applied as a high temperature matrix for carbon fiber reinforced plastics (CFRP). Low melt viscosity (223 mPa s at 120 °C) of the monomer provides a possibility to consider its application for composite material formation by vacuum infusion or resin transfer molding (RTM) techniques, which are exceptionally rarely applied for matrices with HDT > 300 °C but allow to obtain composites of complex shape with minimal joining parts. © 2017 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2017 , 133, 44786.     

Structure–property relationship of polyimide fibers containing ether groups

The copolyimide (co‐PI) fibers with outstanding mechanical properties were prepared by a two‐step wet‐spinning method, derived from the design of combining 4,4′‐oxydianiline (ODA) with the rigid 3,3′,4,4′‐biphenyltetracarboxylic dianhydride (BPDA)/p‐phenylenediamine (p‐PDA) backbone. The mechanical properties of PI fibers were drastically improved with the optimum tensile strength of 2.53 GPa at a p‐PDA/ODA molar ratio of 5/5, which was approximately 3.7 times the tensile strength of BPDA/p‐PDA PI fibers. Two‐dimensional wide‐angle X‐ray diffraction indicated that the highly oriented structures were formed in the fibers. Two‐dimensional small‐angle X‐ray scattering revealed the existence of the needle‐shaped microvoids aligned parallel to the fiber axis, and the introduction of ODA led to the reduction in the size of the microvoids. As a result, the significantly improved mechanical properties of PI fibers were mainly attributed to the gradually formed homogeneous structures. The co‐PI fibers also exhibited excellent thermal stabilities of up to 563°C in nitrogen and 536°C in air for a 5% weight loss and glass transition temperatures above 279°C. © 2015 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2015 , 132, 42474.     

Synthesis and properties of novel polyamides containing sulfone‐ether linkages and xanthene cardo groups

In order to obtain polyamides with enhanced solubility and processability, as well as good mechanical and thermal properties, several novel polyamides containing sulfone‐ether linkages and xanthene cardo groups based on a new diamine monomer, 9,9‐bis[4‐(4‐aminophenoxy)phenyl]xanthene (BAPX), were investigated. The BAPX monomer was synthesized via a two‐step process consisting of an aromatic nucleophilic substitution reaction of readily available 4‐chloronitrobenzene with 9,9‐bis(4‐hydroxyphenyl)xanthene in the presence of potassium carbonate in N,N‐dimethylformamide, followed by catalytic reduction with hydrazine and Pd/C. Four novel aromatic polyamides containing sulfone‐ether linkages and xanthene cardo groups with inherent viscosities between 0.98 and 1.22 dL g^?1 were prepared by low‐temperature polycondensation of BAPX with 4,4′‐sulfonyldibenzoyl chloride, 4,4′‐[sulfonyl‐bis(4‐phenyleneoxy)]dibenzoyl chloride, 3,3′‐[sulfonyl‐bis(4‐phenyleneoxy)]dibenzoyl chloride and 4,4′‐[sulfonyl‐bis(2,6‐dimethyl‐1,4‐phenyleneoxy)]dibenzoyl chloride in N,N‐dimethylacetamide (DMAc) solution containing pyridine. All these new polyamides were amorphous and readily soluble in various polar solvents such as DMAc and N‐methylpyrrolidone. These polymers showed relatively high glass transition temperatures in the range 238–298 °C, almost no weight loss up to 450 °C in air or nitrogen atmosphere, decomposition temperatures at 10% weight loss ranging from 472 to 523 °C and 465 to 512 °C in nitrogen and air, respectively, and char yields at 800 °C in nitrogen higher than 50 wt%. Transparent, flexible and tough films of these polymers cast from DMAc solution exhibited tensile strengths ranging from 78 to 87 MPa, elongations at break from 9 to 13% and initial moduli from 1.7 to 2.2 GPa. Primary characterization of these novel polyamides shows that they might serve as new candidates for processable high‐performance polymeric materials. Copyright © 2010 Society of Chemical Industry     

Bismaleimides,bisnadimides, and polyaspartimides containing ether and ester linkages and pyridine

A series of bismaleimides (BMI) and bisnadimides (BNI) containing pyridine ring and flexible linkages were prepared and the structural characterization of the resins was carried out by elemental analysis, FTIR, ¹H NMR, and ¹³C NMR spectroscopy. Their curing behavior were characterized by differential scanning calorimetry and thermal stability of the cured resins were investigated by thermogravimetric analysis. In addition, a series of polyaspartimides were prepared by the polyaddition of the bismalemide with various dimaines. The polymers were characterized by FT‐IR, inherent viscosity, and molecular weight measurements. All the polyimides were soluble in many organic solvents, the glass transition temperature of the polyaspartimides are in the range of 194–231°C, 10% weight loss (T₁₀) takes place in the temperature range of 379–482°C in N₂ and char yield in the range of 44.31–53.31%. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2008     

Preparation and characterization of biscyanamide resins containing o-substituted groups or phenyl–ether linkage

New biscyanamides containing o-substituted groups or a phenyl-ether linkage were synthesized. The curing reaction behaviors of the biscyanamides were investigated. All the prepared biscyanamides began to polymerize as soon as they melted after being put on a heated plate beyond a certain temperature. The cured resins of each biscyanamides were prepared on the optimal conditions. Optimal conditions for cured resins were obtained from the curing reaction behaviors of each biscyanamide by differential scanning calorimetry (DSC). The effect of chemical structures of the biscyanamides on the thermal and mechanical properties of the cured resins such as seen by thermal gravimetric analysis (TGA), density, and flexural strength were studied. The introduction of alkyl groups into the ortho position decreased intermolecular interactions. The introduction of a long phenyl-ether linkage into the structure gave a broad exothermal peak in the DSC and good workability for the preparation of the cured resins. Moreover, the extension between cross-linkings improved the flexibility of the cured resins. The cured resins with fluorine-containing substituent groups also had better thermal stability in the air compared with hydrocarbon group resins.     

Synthesis and properties of bismaleimide resins containing ether bonds

New bismaleimides containing ether bonds were prepared. The thermal properties of the bismaleimides were investigated by differential scanning calorimetry (DSC). The effects of structure of the bismaleimides and curing conditions on the thermal and mechanical properties of the cured resins such as initial decomposition temperature (T_d), glass transition temperature (T_g), and flexural strength were studied. The introduction of ether bonds to bismaleimide resins decreased the brittleness of the resins without reductions in their heat-resistant properties.     

Synthesis and properties of polyimides containing bisphenol unit and flexible ether linkages

A series of novel polyimides was prepared from various diamines (with bisphenol units) and various aromatic tetracarboxylic dianhydrides via a two‐step (thermal imidization) method. The monomers and polymers were produced in high yields. The benzophenone series exhibited better solubility than the pyromellitic series and, especially, those with the alkyl (methyl)‐substituted ring exhibited good solubility and could be readily dissolved in polar aprotic solvents such as dimethylformamide and N,N′dimethylacetamide. The glass transition temperatures of all polyimides were found to be 235–322 and 223–332°C, respectively, by DSC and dynamic mechanical analysis. Thermogravimetric analyses indicated that the polymers were fairly stable up to 482–617°C (10 wt % loss in N₂) and 480–610°C (10 wt % loss in air). Wide‐angle X‐ray diffractograms revealed that most polyimides were predominantly amorphous. © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 87: 945–952, 2003     

Synthesis and properties of novel organosoluble aromatic poly(ether ketone)s containing pendant methyl groups and sulfone linkages

Several novel aromatic poly(ether ketone)s containing pendant methyl groups and sulfone linkages with inherent viscosities of 0.62–0.65 dL/g were prepared from 2‐methyldiphenylether and 3‐methyldiphenylether with 4,4′‐bis(4‐chloroformylphenoxy)diphenylsulfone and 4,4′‐bis (3‐chloroformylphenoxy)diphenylsulfone by electrophilic Friedel–Crafts acylation in the presence of N,N‐dimethylformamide with anhydrous AlCl₃ as a catalyst in 1,2‐dichloroethane. These polymers, having weight‐average molecular weights in the range of 57,000–71,000, were all amorphous and showed high glass‐transition temperatures ranging from 160.5 to 167°C, excellent thermal stability at temperatures over 450°C in air or nitrogen, high char yields of 52–57% in nitrogen, and good solubility in CHCl₃ and polar solvents such as N,N‐dimethylformamide, dimethyl sulfoxide, and N‐methyl‐2‐pyrrolidone at room temperature. All the polymers formed transparent, strong, and flexible films, with tensile strengths of 84.6–90.4 MPa, Young's moduli of 2.33–2.71 GPa, and elongations at break of 26.1–27.4%. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci, 2008     

Synthesis and properties of organosoluble polynaphthalimides bearing ether linkages and phthalide cardo groups

A series of organic‐soluble polynaphthalimides (PNI) bearing flexible ether links and phthalide cardo group were synthesized from 1,4,5,8‐naphthalenetetracarboxylic dianhydride (NTDA) with 3,3‐bis[4‐(4‐aminophenoxy)‐3‐methylphenyl]phthalide (BAMP) and its equimolar mixtures with other dietheramines by high‐temperature solution polycondensation in m‐cresol. The PNIs had moderate to high inherent viscosities in the range of 1.24–2.25 dL/g and could afford flexible and tough films with tensile strengths of 97–138 MPa by casting their m‐cresol solutions. These PNIs exhibited high thermal stability, with glass transition temperature of 291°C–321°C, 10% weight‐loss temperatures above 542°C, and char yields at 800°C in nitrogen higher than 56%. In comparison with PNIs without the BAMP component, these BAMP‐modified PNIs revealed an enhanced solubility and film‐forming capability. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci 104: 1104–1109, 2007     

Preparation and characterization of novel polyimide films containing amide groups

A novel diamine monomer 4-amino-N-(4-amino-phenyl)-benzamide (DABA) containing amide group was introduced to modify the polyimide of pyromellitic dianhydride (PMDA) and 4, 4′-oxydianiline (ODA) by copolymerization. A series of homo- and co-polyamic acid were synthesized by DABA and ODA in different molar ratio with PMDA, and polyimide films were obtained by thermal imidization. The films were characterized by tensile testing, dynamic mechanical analysis (DMA), thermal gravimetry analysis (TGA), fourier transform infrared (FTIR) and wide x-ray diffraction (WAXD). All of the obtained polyimide films show excellent mechanical properties and thermal stability. With the content of DABA increasing from 0% to 100%, the tensile strength and initial modulus are highly improved from 124.72 MPa and 4.70 GPa to 286.46 MPa and 22.06 GPa respectively. The polyimides have 5% weight loss temperature in the range of 530.0–555.5 °C. The glass transition temperatures are in the range of 387.90–409.16 °C and the tanδ values decrease from 0.3721 to 0.08316. The results of WAXD and FTIR indicate that the introduction of DABA containing amide group can improve the order degree of macromolecule and form hydrogen bonds between the main chains, which results in the improvement of mechanical properties.     

Synthesis and characterization of polyetherimides containing multiple ether linkages and pendent pentadecyl chains

4‐(4‐(4‐(4‐Aminophenoxy)‐2‐pentadecylphenoxy)phenoxy)aniline (APPPA) was synthesized starting from cashew nut shell liquid‐derived bisphenol, i.e. 4‐(4‐hydroxyphenoxy)‐3‐pentadecylphenol, by nucleophilic substitution reaction with 4‐chloronitrobenzene followed by reduction of the formed 4‐(4‐nitrophenoxy)‐1‐(4‐(4‐nitrophenoxy)phenoxy)‐2‐pentadecylbenzene. Three new polyetherimides containing multiple ether linkages and pendent pentadecyl chains were synthesized by one‐step high‐temperature solution polycondensation of APPPA in m‐cresol with three aromatic dianhydrides, i.e. 3,3′,4,4′‐oxydiphthalic anhydride, 4,4′‐(hexafluoroisopropylidene)diphthalic anhydride and 3,3′,4,4′‐biphenyltetracarboxylic dianhydride. Inherent viscosities and number‐average molecular weights of the polyetherimides were in the ranges 0.66–0.70 dL g^?1 and 17 100–29 700 g mol^?1 (gel permeation chromatography, polystyrene standards), respectively, indicating the formation of reasonably high molecular weight polymers. The polyetherimides were soluble in organic solvents such as chloroform, dichloromethane, tetrahydrofuran, pyridine, m‐cresol, N,N‐dimethylformamide, N,N‐dimethylacetamide, N‐methylpyrrolidone and dimethylsulfoxide, and could be cast into transparent, flexible and tough films from their solutions in chloroform. The polyetherimides exhibited glass transition temperatures (T_g) in the range 113–131 °C. The lowering of T_g could be attributed to the combined influence of flexibilizing ether linkages and pentadecyl chains which act as ‘packing‐disruptive’ groups. The temperature at 10% weight loss (T₁₀), determined from thermogravimetric analysis in nitrogen atmosphere, was in the range 460–470 °C demonstrating good thermal stability. The virtues of solubility and large gap between T_g and T₁₀ mean that the polyetherimides containing pendent pentadecyl chains have possibilities for both solution as well as melt processability. © 2015 Society of Chemical Industry     

Trehalose‐based thermosetting resins. I. Synthesis and thermal properties of trehalose vinylbenzyl ether

Trehalose vinylbenzyl ether was synthesized from trehalose and p‐chloromethylstyrene (CMS) in DMSO in the presence of powdered NaOH. The structure of the product was characterized by IR and ¹H NMR spectroscopy. Degree of substitution (DS) on a trehalose unit calculated from the ¹H NMR spectrum varied from 2.4 to 3.2 by changing the feed ratio of p‐chloromethylstyrene to trehalose. Thermal properties of the resin were analyzed by differential scanning calorimetry (DSC). DSC analysis revealed that the resin DS 2.4 has one exothermal peak at 132°C, whereas the resins DS 2.8 and 3.0 have two exothermal peaks. Furthermore, the resin DS 3.2 was found to have only one exothermal peak at 191°C. Dynamic mechanical analysis (DMA) and thermomechanical analysis (TMA) revealed that the cured resin has one transition, implying a glass transition. Biodegradability was assayed by the BOD method, and several percent of the cured resin was found to be degraded with activated sludge for 50 days. Further degradation, however, was not observed. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 91: 46–51, 2004     

Synthesis and properties of lyotropic liquid crystalline copolyamides containing phthalazinone moiety and ether linkages

A series of aromatic copolyamides containing phthalazinone moiety and ether linkages were prepared from 1,2-dihydro-2-(4-aminophenyl)-4-[4-(4-(aminophenoxyl)phenyl)](2H)phthalazin-1-one (DHPZ-DA), p-phenylenediamine (PPD), 4,4′-diaminodiphenylether (DAPE) and terephthaloyl dichloride (TPC) by low temperature solution polycondensation. The copolyamides had relatively high inherent viscosities, ranging from 1.86 to 5.30 dl/g. The copolyamides showed T_g values between 297 and 351 °C. Solubility of these copolyamides was improved in NMP, DMAc, NMP (1 wt% LiCl) and DMAc (1 wt% LiCl) by introducing phthalazinone moiety and ether linkages into the main chain. And they had good thermal stability, associated with 5 and 10% weight loss temperatures in the range of 480-516 and 501-532 °C in nitrogen, respectively. WAXD measures indicated these copolyamides were semicrystalline in nature. Some of these copolyamides exhibited lyotropic liquid crystalline behavior in concentrated H₂SO₄, NMP (1 wt% LiCl), and even in NMP solutions, as evidenced by polarizing light microscopy.     

Bio-based thermosetting bismaleimide resins using eugenol,bieugenol and eugenol novolac

5,5′-Bieugenol (BEG) and eugenol novolac (EGN) were synthesized by the oxidative coupling reaction of eugenol (EG) and the addition–condensation reaction of EG with formaldehyde, respectively. The EG, BEG and EGN were prepolymerized with 4,4′-bismaleimidediphenylmethane (BMI) at 180 °C and then compression-molded at finally 250 °C for 6 h to produce cured EG/BMI (EB), BEG/BMI (BB) and EGN/BMI (NB) resins with eugenol/maleimide unit ratios of 1/1, 1/2 and 1/3. The FT-IR analysis of EBs and ¹³C NMR analysis of the model reaction product of EG/N-phenylmaleimide (PMI) 1/3 at 200 °C for 12 h suggested that the ene reaction and subsequent Diels-Alder/ene reactions mainly occurred for EBs. The FT-IR analyses of BBs and NBs supported the occurrence of ene reaction and subsequent thermal addition copolymerization in a similar manner to the well-known curing reaction of 2,2′-diallylbisphenol A and BMI. The glass transition temperature (T_g) and 5% weight loss temperature (T₅) of the cured resin increased with increasing BMI content, and EB 1/3 showed the highest T_g 377 °C and T₅ 475 °C. The flexural strengths and moduli of EBs and NBs were higher than those of BBs, and EB 1/2 showed the most balanced flexural strength and modulus (84.5 MPa and 2.75 GPa). The FE-SEM analysis revealed that there is no phase separation for all the cured resins.     

Relationship between gas transport properties and fractional free volume determined from dielectric constant in polyimide films containing the hexafluoroisopropylidene group

The dielectric constant and gas transport properties (i.e., permeability, diffusivity, and solubility) in 2,2′‐bis(3,4‐dicarboxyphenyl)hexafluoropropane dianhydride (6FDA)‐based polyimides were systematically investigated in terms of their polymer fractional free volumes (FFVs) at 30°C. The permeability and diffusion coefficients of the 6FDA‐based polyimide films to hydrogen, oxygen, nitrogen, methane, and carbon dioxide were correlated with their FFVs estimated using van Krevelen's group contribution method. There appeared, however, small linear correlation coefficients. Linear correlations were also observed between the gas transport properties and dielectric constant of these polyimides. This study described FFVas a function of the dielectric constant based on the Clausius‐Mossotti equation. It was found that the gas permeability and diffusion coefficients of these 6FDA‐based polyimide films increased as their dielectric constant‐based FFV increased. A better linear relationship was observed between the gas transport properties and the FFV determined from the polymer dielectric constant in comparison to that estimated using the group contribution method. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci 2008     

Preparation and adsorption properties of the chelating resins containing carboxylic,sulfonic, and imidazole groups

The crosslinked poly(1‐vinylimidazole‐co‐acrylic acid), P(VIm‐co‐AA), and poly(1‐vinylimidazole‐co‐2‐acrylamido‐2‐methyl‐1‐propane sulfonic acid) P(VIm‐co‐APSA) were synthesized by radical polymerization and tested as adsorbents under competitive and noncompetitive conditions for Cu(II), Cd(II), Hg(II), Zn(II), Pb(II), and Cr(III) by batch equilibrium procedure. The resin–metal ion equilibrium was achieved before 1 h. The resin P(VIm‐co‐AA) showed a maximum retention capacity (MRC) value for Pb(II) at pH 3 and Hg(II) at pH 1 of 1.1 and 1.2 mEq/g, respectively, and the resin P(VIm‐co‐AA) showed at pH 3 the following MRC values: Hg(II) (1.5 mEq/g), Cd(II) (1.9 mEq/g), Zn(II) (2.7 mEq/g), and Cr(III) (2.8 mEq/g). The recovery of the resin was investigated at 25°C with 1 M and 4 M HNO₃ and 1 M and 4 M HClO₄. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 89: 2852–2856, 2003