Synthesis and curing behavior of a benzoxazine based on phenolphthalein and its high performance polymer

A pure benzoxazine synthesized from phenolphthalein through Mannich reaction, 3,3′-bis(3,4-dihydro-3-phenyl-2H-1,3-benzoxazinyl)-1(3H)-isobenzofuranone (Boz-BP), was characterized by FTIR and ¹H NMR. Its curing behavior was different with that of 2,2′-bis(4-phenyl-3,4-dihydro-2H-1,3-benzoxazinyl)isopropane (Boz-BA) because Boz-BP possesses highly steric and inactivated phenol rings. During curing period, the reactivity of ortho position of phenolic hydroxyl group was retarded and the addition of -CH₂- group generated in ring-opening reaction preferred to taking place on para position of aniline ring, which is beneficial for better thermal properties. Furthermore, additional hydrogen bonding would be formed between carbonyl groups on phthalide structure and hydroxyl groups in Boz-BP based polymer (P(Boz-BP)). Compared with the analogous polymer from Boz-BA (P(Boz-BA)), P(Boz-BP) displayed higher glass transition temperature, better thermal stability, better dimensional stability and flame-retardant properties.     

Synthesis and characterization of new thermosetting polybenzoxazines with other functional groups in the network

In this work, novel thermosetting systems of high performance based on multi-functional benzoxazines were developed. First, 3-(2-hydroxyethyl)-3,4-dihydro-2H-1,3-benzoxazine (BzOH) and bis(3-(2-hydroxyethyl)-3,4-dihydro-2H-1,3- benzoxazinyl) isopropane (BzPOH) monomers were synthesized by reaction between phenol or bisphenol A, paraformaldehyde, and ethanolamine. Then, BzOH and BzPOH were functionalized with maleic anhydride using a stoichiometric ratio of oxazine: maleic anhydride (1:1) to produce low molar mass species with carboxylic acid groups, named BzFA and BzPFA. The products were characterized by Nuclear Magnetic Resonance (NMR), Size-Exclusion Chromatography (SEC), and Fourier Transform Infrared Spectroscopy (FTIR). BzFA and BzPFA exhibited weight-average molecular weights of 5000 g.mol^?1and 50,000 g.mol^?1, respectively. Mixtures between the new precursors and the conventional benzoxazine (BzBA) derived from bisphenol A and aniline [bis(3-phenyl-3,4-dihydro-2H-1,3benzoxazinyl) isopropane] were prepared. The curing process was studied by FTIR and Differential Scanning Calorimetry (DSC), and viscoelastic, mechanical, thermal, and morphological properties of the materials were also evaluated. Materials obtained exhibited better thermal, viscoelastic and mechanical properties than conventional polybenzoxazine. Scanning Electron Microscope (SEM) measurements indicated homogeneous material surfaces.     

Synthesis and characterization of polyhedral oligomeric silsesquioxane (POSS) with multifunctional benzoxazine groups through click chemistry

We prepared a new class of polybenzoxazine-POSS nanocomposites with network structures through thermal curing of multifunctional benzoxazine groups of POSS (OBZ-POSS), which was synthesized from octa-azido functionalized POSS (OVBN₃-POSS) with 3,4-dihydro-3-(prop-2-ynyl)-2H-benzoxazine (P-pa) via a click reaction. Incorporation of the silsesquioxane core into the polybenzoxazine matrix could significantly enhance the thermal stability of these hybrid materials. For these nanocomposites, the POSS nanoparticles in the hybrids were improved their thermal properties with 2,2-bis(3,4-dihydro-3-methyl-2H-1,3-benzoxazine)propane (BA-m) and P-pa polybenzoxazine, analyzed via TGA analyses. In addition, the incorporation of the POSS led to the formation of an inorganic protective layer on the nanocomposite’s surface. Contact angle data provided positive evidence to back up this hypothesis that the incorporation of the POSS units would decrease the surface energy property. In addition, the low glass transition temperature of poly(4-vinyl pyridine) and polycarbonate thin films, which lack liquid resistance, could possess low surface free energy after modification with OBZ-POSS due to low temperature curing of this new compound.     

Trifunctional quinoxaline-based maleimide and its polymer alloys with benzoxazine: Synthesis,characterization, and properties

Novel quinoxaline-based trismaleimide (2,3-di[3-maleimido]phenyl-6- maleimidoquinoxaline, namely TQMI) and its polymer alloys with 3-phenyl-3,4-dihydro-2H-1,3-benzoxazine (P-a) were successfully prepared and characterized. Differential scanning calorimetry investigation of TQMI exhibited distinct double exothermic peaks, which implied that the curing behavior of different type of maleimide group was discrepant. The curing temperature of P-a/TQMI prepolymers was lower than that of both neat TQMI and P-a monomer. The temperatures at 5% (T₅) and 10% (T₁₀) weight loss and the char yield (Y_c) of cured TQMI at 800°C reached 513°C, 524°C, and 63.5%, respectively, which were much higher than the record of traditional 4,4′-bismaleimideodiphenylmethane (BMDPM) resin as well as most of other reported bismaleimide resins. Moreover, the addition of TQMI enhanced thermal stability, glass transition temperature (T_g), and limiting oxygen index of benzoxazine resin dramatically. Attractively, the T_g value of P-a/TQMI copolymer at 30 wt% TQMI loadings was approximately 20°C higher than that of P-a/BMDPM copolymer owing to the bulky quinoxaline group.     

Polybenzoxazine/clay hybrid nanocomposites: influence of preparation method on the curing behavior and properties of polybenzoxazines

Several types of polybenzoxazine/clay hybrid nanocomposites have been prepared from organically modified montmorillonite (OMMT) and mono- or bifunctional benzoxazine, 3-phenyl-3,4-dihydro-2H-1,3-benzoxazine (Pa) or bis(3-phenyl-3,4-dihydro-2H-1,3-benzoxazinyl) isopropane (Ba), respectively. OMMT was prepared by a cation exchange of montmorillonite (MMT) with ammonium salts of amines such as tyramine, phenylethylamine, aminolauric acid, and dodecyl amine. Polybenzoxazine/clay nanocomposites were prepared by two different methods, namely melt method and solvent method. Melt method employs the blending of benzoxazine and OMMT above the melting point of benzoxazine without solvent. In the solvent method, OMMT was dispersed in an organic solvent and then blended with benzoxazine. XRD measurements of the polybenzoxazine/clay hybrid nanocomposites showed that the blending method and the kind of solvent play crucial roles in the dispersion of OMMT in the polybenzoxazine matrix. DSC showed that the inclusion of any type of OMMT significantly lowered the curing exotherm of benzoxazines. The hybrid nanocomposites exhibited higher T_g values than the pristine resins. Dynamic and isothermal TGA clearly showed that the thermal stability was improved by the inclusion of clay.     

Effects of thermal history on the polymerisation mechanism and network development in aromatic polybenzoxazines

The effect of heating rate (2, 8 and 15 K min^-1) during the initial stages of cure of 2,2-bis(3,4-dihydro-3-phenyl-2H-1,3-benzoxazine)propane is examined. The rate of heating has a marked effect on the observed modulus, measured by DMTA, with the higher heating rate giving rise to an increase in storage modulus of ca. 1000 MPa, although this is not accompanied by an increase in glass transition temperature. The thermal stability of the resulting polybenzoxazines also differs with the slower heating rate giving rise to less thermally stable structures. Data obtained from Raman spectroscopy (when combined with principal components analysis) suggest subtle changes in the mechanism during the early stages of reaction associated C–N–C and C–O moieties, some of which persist following a higher temperature postcure step leading to a crosslinked network with higher aliphatic character.     

Synthesis,Characterization and Anti-Breast Cancer Activity of New 4-Aminoantipyrine-Based Heterocycles

4-Aminoantipyrine was utilized as key intermediate for the synthesis of pyrazolone derivatives bearing biologically active moieties. The newly synthesized compounds were characterized by IR, ¹H- and ¹³C-NMR spectral and microanalytical studies. The compounds were screened as anticancer agents against a human tumor breast cancer cell line MCF7, and the results showed that (Z)-4-((3-amino-5-imino-1-phenyl-1H-pyrazol-4(5H)-ylidene)methylamino)-1,5-dimethyl-2-phenyl-1,2-dihydropyrazol-3-one 5, 3-(4-bromophenyl) -1-(1,5-dimethyl-3-oxo-2-phenyl-2,3-dihydro-1H-pyrazol-4-yl)-4-oxo-2-thioxo-1,2,3,4-tetrahydropyrimidine-5-carbonitrile 13, 1-(1,5-dimethyl-3-oxo-2-phenyl-2,3-dihydro-1-Hpyrazol- 4-yl)-3-(4-iodophenyl)-4-oxo-2-thioxo-1,2,3,4-tetrahydropyrimidine-5-carbonitrile 14, 3,3′-(4,4′-sulfonylbis(4,1-phenylene))bis(1-(1,5-dimethyl-3-oxo-2-phenyl-2,3-dihydro-1H-pyrazol- 4-yl)-4-oxo-2-thioxo-1,2,3,4-tetrahydropyrimidine-5-carbonitrile) 16, (Z)-1-(1,5-dimethyl-3-oxo-2-phenyl-2,3-dihydro-1H-pyrazol-4-yl)-2-hydrazono-4-oxo-3-phenyl-1,2,3,4-tetrahydropyrimidine-5-carbonitrile 17, (Z)-1-(1,5-dimethyl-3-oxo-2-phenyl-2,3-dihydro-1H-pyrazol-4-yl)-4-oxo-3-phenyl-2-(2-phenylhydrazono)-1,2,3,4-tetrahydro pyrimidine-5-carbonitrile 18, and (Z)-4-(3-amino-6-hydrazono-7-phenyl-6,7-dihydro pyrazolo[3,4-d]pyrimidin-5-yl)-1,5-dimethyl-2-phenyl-1,2-dihydropyrazol-3-one 19 were the most active compounds with IC₅₀ values ranging from 30.68 to 60.72 μM compared with Doxorubicin as positive control with the IC₅₀ value 71.8 μM.     

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.     

The influence of montmorillonite concentration and solvent polarity on the synthesis of benzoxazine monomers in the presence of montmorillonite

The synthesis of 3,3′-(hexane-1,6-diyl)bis-(3,4-dihydro-2H-1,3-benzoxazine) was done in the absence and in the presence of 10, 30, 50 and 100 wt.% montmorillonite (MMT). The MMT exhibits a significant catalytic effect on the ring-opening reaction of the benzoxazine monomer, increasing of MMT amount influences the oligomeric structures in the polybenzoxazine precursor composition according to ¹H NMR, ¹³C NMR and SEC data. The influence of solvent polarity and temperature was also studied especially in correlation with possible interactions between solvent and MMT. The influence of the polybenzoxazine precursor composition on the polymerization behaviour was investigated by DSC. The thermostability of the obtained polybenzoxazines was studied by TGA and DMA method was involved to determine the glass transition temperature.     

The synthesis,characterization, and structure of a series of 4H-thieno[3,4-c]pyrroles and their corresponding pyrrolium cyanoborohydride salts

A general, convenient route toward N-substituted 5,6-dihydro-4H-thieno[3,4-c]pyrroles was accomplished by the reductive amination of 2,5-dimethylthiophene-3,4-dicarbaldehyde with various primary amines in a solution of sodium cyanoborohydride and methanol/acetic acid (80–88% yield). For the N-alkyl cases, the product isolated was the cyanoborohydride salt of the desired product, 1,3-dimethyl-5-alkyl-5,6-dihydro-4H-thieno[3,4-c]-5-pyrrolium cyanoborohydride. For the aryl case employing aniline, the desired free pyrrole, 1,3-dimethyl-5-phenyl-5,6-dihydro-4H-thieno[3,4-c]pyrrole, was isolated. X-ray crystallographic analysis of both the N-propyl and N-phenyl trials confirmed the salt and free amine nature of the products.     

Novel organic-inorganic hybrids prepared from polybenzoxazine and titania using sol-gel process

Novel organic-inorganic hybrids were prepared from polybenzoxazine and titania using sol-gel process by blending titanium isopropoxide as a precursor for titania with a typical benzoxazine monomer, bis(3-phenyl-3,4-dihydro-2H-1,3-benzoxazinyl)isopropane (Ba). Deep red brown and transparent hybrid materials were obtained after thermal cure at 200 °C. DSC indicated that, in the presence of titania precursor, the onset and maximum temperature of the exothermic peak due to the ring opening polymerization of Ba decreased by ca. 30 and 70 °C, respectively. Viscoelastic analyses revealed that the glass transition temperatures (T_g) of the polybenzoxazine-titania hybrids shifted to higher temperature than the neat polybenzoxazine. The storage moduli below T_g for the hybrids increased with the increase of the titania content, and the storage moduli were maintained constant up to higher temperature than the neat resin. TGA results confirmed that the thermal stability and char yield of polybenzoxazine increased by hybridization with titania.     

Study of the characterization and curing of a phenyl benzoxazine using 15N solid-state nuclear magnetic resonance spectroscopy

A difunctional 1,3-benzoxazine compound, 2,2′-(3-phenyl-4-dihydro-1,3,2-benzoxazine)propane ( B-a ), derived from bisphenol-A, ¹⁵N-enriched aniline, and formaldehyde was synthesized and characterized using ¹⁵N-NMR and ¹³C-NMR spectroscopies. The observed resonances in the solid-state ¹⁵N- and ¹³C-NMR spectra showed good agreement with the calculated chemical shifts which are based on the chemical structure. The B-a samples were cured at 150 and 200°C. The polymerization inspired peak intensity changes and line-width broadenings in the NMR spectra. © 1998 John Wiley & Sons, Inc. J. Appl. Polym. Sci. 70: 1401–1411, 1998     

Study of the characterization and curing of benzoxazines using 13C solid-state nuclear magnetic resonance

Benzoxazines derived from bisphenol-A, formaldehyde, and primary amines were characterized using ¹³C solid-state NMR spectroscopy. The two 1,3-benzoxazines studied in this work are 2,2′-(3-methyl-4-dihydro-1,3,2-benzoxazine)propane, ( B-m ) and 2,2′-(3-phenyl-4-dihydro-1,3,2-benzoxazine)propane ( B-a ). Solid-state ¹³C-NMR spectra were obtained for B-m and B-a and the observed peak positions were noted. These resonances agreed well with chemical shifts calculated based on the chemical structure. Samples of B-m and B-a were cured at two different temperatures: 150 and 200°C. The polymerizations induced spectral changes including new resonances, intensity changes, and line-width broadenings. Kinetic analysis of the curing data gave different kinetic parameters for the two cure temperatures, which is expected since the first cure temperature is below the material's glass transition temperature (T_g) while the second cure temperature is above the T_g. © 1998 John Wiley & Sons, Inc. J. Appl. Polym. Sci. 70: 1413–1425, 1998     

ELECTROCHEMICAL SYNTHESIS AND PROPERTIES OF POLYBENZOXAZINE

A new kind of polybenzoxazine, poly(3-(p-methyl) benzyl-3,4-dihydro-6-methyl-2H-1,3-benzoxazine), has been synthesized by an electrochemical method in acetonitrile/alkali aqueous solution. The obtained film shows good heat resistance properties. The structure of the obtained film is characterized using Fourier Transform Infrared (FTIR) spectroscopy.     

Research on curing mechanism and thermal property of bis-allyl benzoxazine and N,N′-(2,2,4-trimethylhexane-1,6-diyl) dimaleimide blend

A blend of 2,2′-bis(8-allyl-3-phenyl-3,4-dihydro-2H-1,3-benzoxazinyl) propane (Bz-allyl) and N,N′-(2,2,4-trimethylhexane-1,6-diyl) dimaleimide (TBMI) was prepared. The curing mechanism and thermal property of the cured blend were studied with Differential scanning calorimetry (DSC), Fourier transform infrared (FT-IR) and Dynamic mechanical analysis (DMA). It was found that in BzT11 the thermal polymerization reaction of TBMI, the reaction of TBMI catalyzed by Bz-allyl, Ene reaction between TBMI and allyl groups occurred at a low temperature (160 °C) simultaneously. About 20% of TBMI was consumed by Ene reaction. Besides, seldom oxzine ring of Bz-allyl polymerized at a low temperature (160 °C) and most oxzine ring of Bz-allyl reacted at a high temperature (over 160 °C). The T_g of cured blends was increased with the increment of the proportion of TBMI in the blends.     

Electrochemical synthesis and properties of polybenzoxazine

A new kind of polybenzoxazine, poly(3-(p-methyl) benzyl-3,4-dihydro-6-methyl-2H-1,3-benzoxazine), has been synthesized by an electrochemical method in acetonitrile/alkali aqueous solution. The obtained film shows good heat resistance properties. The structure of the obtained film is characterized using Fourier Transform Infrared (FTIR) spectroscopy.     

Synthesis and Antimicrobial Evaluation of Some Novel Bis-α,β-Unsaturated Ketones,Nicotinonitrile, 1,2-Dihydropyridine-3-carbonitrile,Fused Thieno[2,3-b]pyridine and Pyrazolo[3,4-b]pyridine Derivatives

The title compounds were prepared by reaction of 1,1′-(5-methyl-1-phenyl-1H-pyrazole-3,4-diyl)diethanone (1) with different aromatic aldehydes 2a–c, namely Furfural (2a), 4-chlorobenzaldehyde (2b) and 4-methoxybenzaldhyde (2c) to yield the corresponding α,β-unsaturated ketones 3a–c. Compound 3 was reacted with malononitrile, 2-cyanoacetamide or 2-cyanothioacetamide yielded the corresponding bis[2-amino-6-(aryl)nicotinonitrile] 4a–c, bis[6-(2-aryl)-2-oxo-1,2-dihydropyridine-3-carbonitrile] 5a–c or bis[6-(2-aryl)-2-thioxo-1,2-dihydropyridine-3-carbonitrile] 6a,b, respectively. The reaction of compound 6a with each of 2-chloro-N-(4-bromophenyl) acetamide (7a), chloroacetamide (7b) in ethanolic sodium ethoxide solution at room temperature to give the corresponding 4,4′-(5-methyl-1-phenyl-1H-pyrazole-3,4-diyl)bis-6-(2-furyl)thieno[2,3-b]pyridine-2-carboxamide] derivatives 9a,b. While compound 6a reacted with hydrazine hydrate yielded the 4,4′-(5-methyl-1-phenyl-1H-pyrazole-3,4-diyl)bis[6-(2-furyl)-1H-pyrazolo[3,4-b]pyridin-3-amine] 11. The structures of the products were elucidated based on their spectral properties, elemental analyses and, wherever possible, by alternate synthesis. Antimicrobial evaluation of the products was carried out.     

A dinuclear copper(II) complex and a zigzag chain iron(II) polymer based on the 4-antipyrine derived Schiff base ligands: The hydroxylation and redox occurred under the solvothermal conditions

A new dinuclear copper(II) compound, [Cu₂(L1-O)₂] (1) (L1 = (4E)-4-(2-hydroxybenzylideneamino)-1,2-dihydro-2,3-dimethyl-1-phenylpyrazol-5-one), and zigzag chain polymer, {[FeCl₂(L2)]}_n (2) (L2 = 1,5-dimethyl-2-phenyl-4-{[(1E)-pyridine-4-ylmethylene]amino}-1,2-dihydro-3H-pyrazol-3-one), were synthesized by solvothermal reactions and structurally characterized. The methyl group hydroxylation and the redox have been observed in the preparation of 1 and 2, respectively.     

Aromatic diamine-based benzoxazines and their high performance thermosets

Four high-purity aromatic diamine-based benzoxazines (13-16), which could not easily be synthesized by traditional approaches, were successfully synthesized by a facile, widely useful three-step synthetic method using four typical aromatic diamines - 4,4′-diamino diphenyl methane (1), 4,4′-diamino diphenyl sulfone (2), 2,2-bis(4-(4-aminophenoxy)phenyl)propane (3), and bis(4-(4-aminophenoxy)phenyl)ether (4), respectively, as starting materials. The structures of the monomers (5-16) were confirmed by ¹H, ¹³C, ¹H-¹H and ¹H-¹³C NMR spectra. Their high performance thermosets, P(13-16), were obtained by thermal curing of benzoxazines (13-16), and their properties were studied and compared with polymer derived from bis(3,4-dihydro-2H-3-phenyl-1,3-benzoxazinyl)methane (F-a), a typical aromatic biphenol-based benzoxazine. Among the benzoxazines, 13 and F-a are constitutional isomers, but the T_g value and 5% decomposition temperature of P(13) are 53 and 111 °C, respectively, higher than those of P(F-a), demonstrating the power of the molecule-approach to enhance the thermal properties. Because of the large varieties of aromatic diamines, this approach can increase the molecule-design flexibility of benzoxazines.     

A rapid and high efficient microwave promoted multicomponent domino reaction for the synthesis of spirooxindole derivatives

A simple, efficient and rapid method has been developed for synthesis of 6,6-dimethyl-4-phenyl-6,7-dihydro-1H-spiro[furo[3,4-b]quinoline-9,3′-indoline]1,2′,8(3H,4H,5H)-trione derivatives. These heterocycles were prepared through domino one-pot and multicomponent condensation reactions of isatins, dimedone, and anilinolactones in the presence of alum (15 mol%) as an inexpensive, nontoxic, convenient, and available Lewis acid catalyst under microwave irradiation. The corresponding products have been obtained in excellent isolated yields between 78% and 90%, with high purity, in short reaction times about 10–12 min and easy work up.