The polymerization behavior and thermal properties of benzoxazine based on o-allylphenol and 4,4′-diaminodiphenyl methane

Three bifunctional benzoxazines (oAP-ddm, oC-ddm, and P-ddm) were synthesized from 4,4′-diaminodiphenyl methane, formaldehyde, and three phenols, namely o-allylphenol, o-cresol, and phenol. The polymerization temperatures and activation energies of oAP-ddm and oC-ddm are very similar and higher than those of P-ddm; however, their reaction enthalpies exhibit inverse behavior. The storage moduli of the corresponding polybenzoxazines, PoAP-ddm, PoC-ddm, and PP-ddm, are approximately 2.1, 3.2, and 2.9 GPa at 25 °C, respectively, and their glass transition temperatures are 139, 166, and 198 °C, respectively. The thermal stabilities of PoAP-ddm and PoC-ddm are similar and lower than that of PP-ddm. The results indicate that polybenzoxazines based on ortho-substituted phenols provide higher flexibility than their counterparts prepared from unsubstituted phenol.     

Chain‐extended polyurethanes—Synthesis and characterization

Chain‐extended polyurethanes (PUs) were prepared using castor oil and different diisocyanates such as toluene‐2,4‐diisocyanate and 4,4′‐methylene bis(phenylisocyanate) as a crosslinker and different aromatic diamines like 4,4′‐diaminodiphenyl methane and 4,4′‐diaminodiphenyl sulphone as chain extenders. The effect of aromatic diamines on the swelling and thermal degradation behavior of PU have been discussed. A thermogravimetric analyzer (TGA) curve shows that all the chain‐extended PUs are stable up to 194°C and that maximum weight loss occurs at 490°C. The TGA thermograms show that the thermal degradation of the PUs was found to proceed in two steps. The average molecular weight between crosslinks (M?_c) was determined by swelling studies. The properties imparted by the aromatic chain extenders are explained on the basis of groups present in the diamines. © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 84: 359–369, 2002; DOI 10.1002/app.10347     

Preparation of novel benzoxazine monomers containing ferrocene moiety and properties of polybenzoxazines

Novel benzoxazine monomers containing ferrocene were prepared, one monomer was monofunctional benzoxazine ferrocenylmethyl-3,4-dihydro-2H-1,3-benzoxazine (pC-fcma), and the other was bifunctional benzoxazine, bis(ferrocenylmethyl-3,4-dihydro-2H-1,3-benzoxazinyl)isoprapane (BA-fcma). Followed by thermal cure of monomers, metallopolybenzoxazines with ferrocene moiety in the polymer networks were obtained. The chemical structures of the novel monomers were confirmed by IR, ¹H NMR and elemental analysis. The cure behaviors of the monomers, pC-fcma and BA-fcma were studied by DSC. The thermograms of BA-fcma showed multiple peaks, which were resulted from the quickly forming network and the bulkiness factor of ferrocene moiety. In addition, the first peak temperature was much decreased by nearly 70°°C than that of typical B-a benzoxazine, which was mainly due to the electron-donating effect of N-ferrocen group stability of zwitterionic intermediates. TGA suggested that thermal stability of metallopolybenzoxazines was improved, in particular, the weight loss temperature of 5% for polyBA-fcma was increased by almost 100 °C than that of PB-a, and the char yield even reached 60% at 800 °C under N₂. Cyclic voltammetry studies of pC-fcma and BA-fcma showed that the species underwent one reversible and one-electron redox coupling.     

Dynamic mechanical analysis on highly thermally stable polybenzoxazines with an acetylene functional group

Dynamic mechanical analysis is performed on polybenzoxazines from acetylene-terminated benzoxazine monomers, and glass transition temperatures of these polybenzoxazines are found in the range of 329–368°C. It has been identified that the high glass transition temperature and high thermal stability are due to polymerization of the acetylene terminal group, in addition to oxazine ring polymerization through a comparison study with analogous polybenzoxazines that are obtained from monomers without an acetylene functional group. © 1999 John Wiley & Sons, Inc. J Appl Polym Sci 73: 857–862, 1999     

Synthesis,curing behavior and thermal properties of fluorene-containing benzoxazines based on linear and branched butylamines

A series of fluorene-containing benzoxazine monomers based on linear and branched butylamines were successfully synthesized in high purity and good yield through a facile one-pot procedure by the reaction of 9,9-bis-(4-hydroxyphenyl)-fluorene with paraformaldehyde and isomeric butylamines. The chemical structures of the target monomers were characterized by Fourier transform infrared (FT-IR), Elemental analysis, ¹H and ¹³C nuclear magnetic resonance (NMR). The curing behavior of benzoxazine monomers was studied by differential scanning calorimetry (DSC) and FT-IR. The thermal properties of cured polybenzoxazines were measured by DSC and thermogravimetric analysis (TGA). The results reveal that the polarity of solvent and the basicity of butylamines produce clear effects on the synthesis of the butylamine-based benzoxazine monomers. Also, the basicity and steric effect of butylamines exhibit significant effects on the curing behavior of benzoxazine monomers and the thermal properties of their polymers. The glass transition temperature and thermal stability of branched butylamine-based polybenzoxazines are higher than those of the corresponding linear butylamine-based polybenzoxazine and traditional bisphenol A-based polybenzoxazines.     

1,4-Bis(2,3-dicarboxyl-phenoxy)benzene dianhydride-based phenylethynyl terminated thermoset oligoimides for resin transfer molding applications

A series of thermoset oligoimides have been prepared by the thermal polycondensation of 1,4-bis(2,3-dicarboxyl-phenoxy)benzene dianhydride with three different aromatic diamines in the presence of 4-phenylethynylphthalic anhydride as an end capping reagent. The aromatic diamines included 4,4′-oxydianiline, 2,2′-bis(trifluoromethyl)benzidine (TFDB) and 2-phenyl-4,4′-diaminodiphenyl ether (p-ODA). Effects of the chemical structures and molecular weights of the oligoimides on their aggregated structures, melt processability as well as the thermal and mechanical properties of the cured films were then systematically investigated. X-ray diffraction results indicated that ODA series oligoimides and TFDB series oligoimides showed crystallinity; however, the asymmetrical p-ODA enables the p-ODA series oligoimides to exhibit amorphous forms. So the p-ODA based oligoimides with molecular weight of 750 g mol⁻¹ showed much lower melt viscosity at a low temperature and the melt viscosity could maintain below 1 Pa s⁻¹ after isothermal aging for 2 h at any temperature in the range of 220–280 °C by rheological measurements. © 2019 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2019 , 136, 47967.     

Flexible polybenzoxazine thermosets containing pendent aliphatic chains

The rich chemistry of polybenzoxazines allows a wide range of molecular structure design by using appropriate starting materials. A new class of polybenzoxazines has been developed from benzoxazine monomers containing pendent long aliphatic chains. The monomers have been synthesized by the reaction of phenol or bisphenol A with two different long‐chain aliphatic amines. The chemical structure of the monomers was confirmed by ¹H nuclear magnetic resonance and Fourier transform infrared spectroscopy. The polymerization behavior of the monomers studied by differential scanning calorimetry shows exothermic peaks due to the ring‐opening polymerization of benzoxazine monomers centered at 247–255 °C. Dynamic mechanical analysis indicated that the glass transition temperatures T_g were in the range 81–92 °C. The thermal stability of the polymers was also examined by thermogravimetric analysis, demonstrating that the weight loss temperatures decreased in comparison with that of traditional polybenzoxazine. Copyright © 2011 Society of Chemical Industry     

Synthesis and thermal,mechanical and gas permeation properties of aromatic polyimides containing different linkage groups

Two series of aromatic polyimides containing various linkage groups based on 2,7‐bis(4‐aminophenoxy)naphthalene or 3,3′‐dimethyl‐4,4′‐diaminodiphenylmethane and different aromatic dianhydrides, namely 4,4′‐(4,4′‐isopropylidenediphenoxy)bis(phthalic anhydride), 4,4′‐(hexafluoroisopropylidene)bis(phthalic anhydride), 3,3′,4,4′ benzophenonetetracarboxylic dianhydride, 9,9‐bis[4‐(3,4‐dicarboxyphenoxy)phenyl]fluorene dianhydride and 4,4′‐(4,4′‐hexafluoroisopropylidenediphenoxy)bis(phthalic anhydride), were synthesized and compared with regard to their thermal, mechanical and gas permeation properties. All these polymers showed high thermal stability with initial decomposition temperature in the range 475–525 °C and glass transition temperature between 208 and 286 °C. Also, the polymer films presented good mechanical characteristics with tensile strength in the range 60–91 MPa and storage modulus in the range 1700–2375 MPa. The macromolecular chain packing induced by dianhydride and diamine segments was investigated by examining gas permeation through the polymer films. The relationships between chain mobility and interchain distance and the obtained values for gas permeability are discussed. © 2014 Society of Chemical Industry     

Synthesis and characterization of new thermally stable aromatic copoly(ester–amide)s from diester‐dicarboxylic acids

Two new aromatic diester‐dicarboxylic acids containing furan rings, namely, benzofuro[2,3‐b]benzofuran‐2,9‐dicarboxyl‐bis‐pyridyl ester‐4,4′‐dicarboxylic acid and benzofuro[2,3‐b]benzofuran‐2,9‐dicarboxyl‐bis‐phenyl ester‐4,4′‐dicarboxylic acid were synthesized by the reaction of benzofuro[2,3‐b]benzofuran‐2,9‐dicarbonyl chloride with 6‐hydroxynicotinic acid and 4‐hydroxybenzoic acid, respectively. These monomers were converted to aromatic copoly(ester–amide)s by reaction with various aromatic diamines via direct polycondensation. Polymers were characterized by FTIR and ¹H NMR spectroscopy, thermogravimetry, viscosity and solubility tests. The inherent viscosity of the polymers was in the range 0.23–0.46 dl g^?1 in dimethyl sulfoxide at 30 °C. They dissolved readily in polar solvents at room temperature. They possess a glass‐transition temperature in the range 210–260 °C and exhibit excellent thermal stability. Copyright © 2004 Society of Chemical Industry     

Synthesis and characterization of 4,4′‐diaminodiphenyl methane‐based benzoxazines and their polymers

A series of diamine‐based benzoxazine precursors have been prepared using 4,4′‐diaminodiphenyl methane, formaldehyde, and different phenol derivatives including phenol, p‐cresol, and 2‐naphthol. Their chemical structures were identified by FTIR, ¹H NMR, and elemental analysis. The curing reactions of those precursors were monitored by FTIR and DSC. The obtained materials exhibited higher glass transition temperature and char yields than the corresponding bisphenol‐A based polybenzoxazines. The polybenzoxazine prepared from phenol showed the highest char yields of 65% and thermal stability with 5 and 10% weight‐loss temperatures at 346 and 432°C, respectively. The polybenzoxazine prepared from 2‐naphthol exhibited the highest glass transition temperature at 244°C. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci 2007     

Ultrasound‐assisted synthesis of benzoxazine monomers: thermal and mechanical properties of polybenzoxazines

A series of benzoxazine monomers (P‐aea2–P‐aea8) were prepared from appropriate aromatic diamines containing linear aliphatic ether chains with phenol and formaldehyde through the Mannich reaction under ultrasonication and conventional methods. Based on the reaction performance, the ultrasonication method has been found to be more facile and convenient for the synthesis of benzoxazine monomer than the conventional method. The synthesized monomers undergo curing at a lower temperature than that of conventional benzoxazine (Ba‐A) monomer as evidenced from differential scanning calorimetric analysis. The presence of an aliphatic ether core in the benzoxazine monomer aids in lowering the curing temperature, which seems to vary linearly with chain length. Thermally polymerized benzoxazine (poly(P‐aea_s)) shows an enhanced tensile and flexural strength. Copyright © 2012 Society of Chemical Industry     

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.     

Effects of 3,4′-oxydianiline on the structures and properties of a novel aromatic polyimide foam

Aiming at the low volumetric shrinkage, a novel aromatic polyimide foam is successfully prepared from polymethane polyphenyl isocyanate (PAPI) and a poly(amic-acid) precursor which has been synthesized from 3,4′-oxydianiline (3,4′-ODA) and pyromellitic dianhydride (PMDA). In this research, five polyimide foams, with different contents of 3,4′-ODA, are comparatively studied including structural, thermal, mechanical, shrink, and degradation properties. The results indicate that the content of 3,4′-ODA has minor influence on chemical structures, but significant influence on cell structures of the foams. With the increase of 3,4′-ODA, the volumetric shrinkages, apparent densities and the compressive and flatwise tensile strengths of the materials decrease. The glass transition temperatures (T_g) decrease from 301°C to 279°C, and the 5% weight loss temperatures (T_5%) increase from 323°C to 340°C. Through TG-FTIR analysis, we can observe that the addition of 3,4′-ODA has no influence on the pyrolysis mechanism of polyimide foams. © 2012 Wiley Periodicals, Inc. J Appl Polym Sci, 2012     

High-performance polymer films. III. Preparation and characterization

A series of polyimide and copolyimide films were prepared by film casting, drying, and thermal imidization from the respective precursor poly(amic acid) (PAA) and copoly(amic acid) solutions derived from two dianhydrides, pyromellitic dianhydride (PMDA) and 3,3′,4,4′-benzophenonetetracarboxylic dianhydride (BTDA), and two diamines, 4,4′-oxydianiline (ODA) and a proprietary aromatic diamine (PD) as monomers. Depending on the solution's inherent viscosity value (molecular weight) and the nature of the polymer chains (derived from rigid or flexible monomers), precursor poly(amic acid) and copoly(amic acid) solution concentrations of 8–12% (w/w) were found to be suitable for the preparation of good quality polyimide/copolyimide films. The recovery of film toughness and creasability from the brittleness at the intermediate temperature of the cure cycle depended not only on the molecular weight of the precursor poly(amic acids)/copoly(amic acids) but also on their chain flexibility. The poly(amic acid) derived from both rigid dianhydride and diamine practically gave rise to a brittle film of polyimide even after curing to 360°C. The resulting polyimide and copolyimide films were compared with Du Pont's Kapton H film. The density of the films was in the range 1.39–1.42 g/cm³. The thickness of most of the films was in the range 20–30 μm. The HPF 3 film, based on PMDA–PD, appeared to be highly colored (reddish brown), and the HPF 2 film, based on BTDA–ODA, had the lightest yellow coloring among the films in this investigation, including Kapton H film. HPF 2, HPF 6, and HPF 8 films were more amorphous than the other films. © 2001 John Wiley & Sons, Inc. J Appl Polym Sci 82: 976–988, 2001     

Synthesis of liquid crystalline epoxy and its mechanical and electrical characteristics—curing reaction of LCE with diamines by DSC analysis

An aromatic liquid crystalline epoxy monomer based on biphenyl mesogen was synthesized and cured with three different aromatic diamines. The curing reaction characteristics were analyzed by DSC, and the data were introduced to the Kissinger equation to attain the kinetic parameters. Diglycidyl ether of 4,4′‐biphenyl (DGEBP)/4,4′‐diaminobiphenyl (DABP), and DGEBP/4,4′‐methylenediamine (MDA) systems showed an exotherm curing reaction after comelting of the monomers; the DGEBP/p‐phenylenediamine (PDA) system's curing reaction took place in the solid state without melting of monomers. The activation energy and preexponential factor for the DGEBP/DABP system were 55.6 kJ/mol and 4.0 × 10⁶ min^?1, respectively. Those values for DGEBP/MDA and DGEBP/PDA systems were 55.1 kJ/mol and 1.0 × 10⁶ min^?1 and 148.8 kJ/mol and 7.7 × 10¹⁹ min^?1, respectively. The rate constant at 100°C for DGEBP/PDA is 2 times higher than those for DGEBP/DABP and DGEBP/MDA, which have almost the same values. Strictly speaking, the rate constant of DGEBP/DABP is a little higher than that of DGEBP/MDA, and these results are in good agreement with the DSC curves. © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 83: 2419–2425, 2002     

Synthesis and characterization of aromatic/cycloaliphatic poly(amide‐ imide‐imide)s from bis(4‐amino‐ 3,5‐dimethylphenyl) cycloalkane derivatives

A series of novel aromatic diamines containing cycloaliphatic moieties was synthesized by the reaction of cycloalkanones like cyclohexanone and cycloheptanone with 2,6‐dimethylaniline. The tetrimide diacid was synthesized using the prepared diamine with 3,3′,4,4′‐benzophenonetetracarboxylic acid dianhydride/pyromellitic dianhydride and p‐aminobenzoic acid. The polymers were prepared by treating the tetrimide diacid with different aromatic diamines. The structures of the monomers and polymers were identified using elemental analysis and Fourier transform infrared, ¹H NMR and ¹³C NMR spectroscopy. The polymers show excellent solubility. The polymers are amorphous and have high optical transparency. They also show good thermal stability and their T_g value is found to be in the range 268–305 °C. Copyright © 2007 Society of Chemical Industry     

Synthesis and characterization of new polyamides and copolyamides containing 6,6'-sulfonediquinoline units

Summary Aromatic polyamides were obtained by the direct polycondensation reaction of a new monomer containing a 6,6'-sulfonediquinoline unit with various aromatic diamines. The polymers were characterised by elemental, infrared, wide angle X-ray diffraction and thermal analysis. The polyamides, possessed inherent viscosities in the range 0.24 – 0.43 dl g⁻¹, 10% weight loss in nitrogen and air above 410°C and glass transition temperatures in the range 170–220°C. The polyamides obtained by reaction with 4,4'-methylenedianiline and 4,4'-sulfonyldianiline were soluble on heating in N-methyl-2-pyrrolidinone and partially soluble in dimethylacetamide. Solubility and thermal properties of copolyamides, prepared from the reaction of 4,4'-oxydianiline with the new monomer and the 4,4'-dicarboxydiphenyl sulfone, were also studied. Received: 5 October 1998/Revised version: 19 April 1999/Accepted: 19 April 1999     

Synthesis of branched benzoxazine monomers with high molecular mass,wide processing window,and properties of corresponding polybenzoxazines

Four cyclotriphosphazene‐based benzoxazine monomers (I, II, III, and IV) with relatively high molecular weight were synthesized by a nucleophilic substitution reaction, and their chemical structures were confirmed by ¹H‐NMR and ³¹P‐NMR. A new term, oxazine value (OV, similar to epoxy value), was first proposed to explain the structure–property relationship of the cured polymers. The polymerization behaviors of the four monomers were studied by differential scanning calorimetry and Fourier transform infrared spectroscopy. The maximum exothermic peaks of the four monomers are in the range 244–248 °C. All monomers possess a wide processing window despite their high molecular weight. The thermal stability, glass‐transition temperature (T_g), and mechanical properties of each cured polymer were studied by thermogravimetric analysis and dynamic mechanical thermal analysis. The char yield at 850 °C, T_g, and storage moduli of PIV (polybenzoxazine obtained from monomer IV) are 60.0%, 218 °C, and 9.0 GPa, respectively. The surface property and humidity absorption character of the cured polybenzoxazines were also studied. © 2016 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2017 , 134, 44453.     

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     

Structure–property relationship in polybutadiene–polyamide multiblock copolymers

Two kinds of aromatic–aliphatic polyamide oligomers were newly prepared by the reactant pairs of 3,4′-oxydianiline–adipic acid and 3,4′-oxydianiline–azelaic acid. These oligomers were then condensed separately with α, ω-polybutadienedicarboxylic acid giving two series of polybutadiene–polyamide multiblock copolymers. Properties of four series of polybutadiene–polyamide multiblock copolymers, whose polyamide blocks consisted of not only newly prepared polyamides but also previously synthesized aromatic polyamides derived from 4,4′-oxydianiline–isophthalic acid and 3,4′-oxydianiline–isophthalic acid, were investigated on the view point of structure-property relationship. A larger extent of the T_g depression of polybutadiene phase, and higher tensile strength and modulus were observed in the block copolymers having aromatic polyamides compared with those having aliphatic ones.