High performance benzoxazine monomers and polymers containing furan groups

Furan‐containing benzoxazine monomers, 3‐furfuryl‐3,4‐dihydro‐2H‐1,3‐benzoxazine (P‐FBz) and bis(3‐furfuryl‐3,4‐dihydro‐2H‐1,3‐benzoxazinyl)isopropane (BPA‐FBz), were prepared using furfurylamine as a raw material. The chemical structures of P‐FBz and BPA‐FBz were characterized with FTIR, ¹H NMR, elemental analysis, and mass spectrometry. Formation of furfurylamine Mannich bridge networks in the polymerizations of P‐FBz and BPA‐FBz increased the cross‐linking densities and thermal stability of the resulting polybenzoxazines. P‐FBz‐ and BPA‐FBz‐based polymers also exhibited high glass transition temperatures above 300 °C, high char yields, and low flammability with limited oxygen index values of 31. The dielectric (D_k = 3.21–3.39) and mechanical properties (high storage modulus of 3.0–3.9 GPa and low coefficient of thermal expansion of 37.7–45.4 ppm) of the P‐FBz‐ and BPA‐FBz‐based polymers were superior or comparable to other polybenzoxazines. © 2005 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 43: 5267–5282, 2005     

Preparation and properties of novel benzoxazine and polybenzoxazine with maleimide groups

A benzoxazine compound with a maleimide group, 3‐phenyl‐3,4‐dihydro‐2H‐6‐(N‐maleimido)‐1,3‐benzoxazine (HPM‐Ba), was prepared from N‐(4‐hydroxyphenyl)maleimide, formaldehyde, and aniline. The chemical structure of HBM‐Ba was identified by FT‐IR, ¹H‐NMR, and elemental analysis. HPM‐Ba showed a melting point of 52–55 °C and good solubility in common organic solvents. HPM‐Ba showed a two‐stage process of thermal polymerization. The first stage arose from the polymerization of maleimide groups, and the second one was the ring‐opening reaction of benzoxazine groups. Fusible polymaleimides with a Tg of around 100 °C could be obtained by thermally polymerizing HPM‐Ba at 130 °C. Further polymerizing the polymaleimides at 240 °C resulted in a completely cured resin showing a Tg at 204 °C. Good thermal stability and self‐extinguishing behavior was observed with the cured polybenzoxazine resins. © 2004 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 42: 5954–5963, 2004     

Synthesis of a benzoxazine with precisely two phenolic OH linkages and the properties of its high‐performance copolymers

A phenolic OH‐containing benzoxazine ( F‐ap ), which cannot be directly synthesized from the condensation of bisphenol F, aminophenol, and formaldehyde by traditional procedures, has been successfully prepared in our alternative synthetic approach. F‐ap was prepared by three steps including (a) condensation of 4‐aminophenol and 5,5'‐methylenebis(2‐hydroxybenzaldehyde) (1) , (b) reduction of the resulting imine linkage by sodium borohydride, and (c) ring closure condensation by formaldehyde. The key starting material, (1) , was prepared from 2‐hydroxybenzaldehyde and s‐trioxane in the presence of sulfuric acid. F‐ap is structurally similar to bis(3,4‐dihydro‐2H‐3‐phenyl‐1,3‐benzoxazinyl)methane ( F‐a, a commercial benzoxazine based on bisphenol F/aniline/formaldehyde) except for two phenolic OHs. The phenolic OHs can provide reaction sites with epoxy and 1,1'‐(methylenedi‐p‐phenylene)bismaleimide (BMI). The structure–property relationships between the thermosets of F‐ap /epoxy, F‐a /epoxy, F‐ap /BMI, and F‐a /BMI were discussed. Experimental data showed that thermosets based on F‐ap /epoxy and F‐ap /BMI provided much better thermal properties than those based on F‐a /epoxy and F‐a /BMI. © 2013 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2013, 51, 2686–2694     

Synthesis and characterization of fluid 1,3‐benzoxazine monomers and their thermally activated curing

Novel mono‐ and difunctional aliphatic oxyalcohol‐based benzoxazines have been synthesized and characterized in detail. Molecular structures of the monomers were investigated by spectral analysis. The obtained benzoxazine monomers exhibit fluidic behavior, which makes them particularly useful for many applications compared to other traditional benzoxazines. Differential scanning calorimetry was used to monitor the thermal crosslinking behavior of synthesized monomers. Mono‐ and bifunctional benzoxazine monomers exhibited low curing exhothermic peak with the onset around 173 and 180 °C, respectively. Relatively, low ring‐opening polymerization temperature was due to the hydroxyl groups present in the structure of the monomers. The hydrogen bonding of hydroxyl groups may cause alignment of the monomers in the liquid state. Thermal stabilty of the polybenzoxazines was studied by thermogravimetric analysis. © 2009 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2009     

Concerted reactions of aldehyde groups during polymerization of an aldehyde‐functional benzoxazine

Polymerization reactions of a new aldehyde‐functional benzoxazine (4HBA‐a) were investigated in detail. The curing behavior of 4HBA‐a was studied by differential scanning calorimetry (DSC) and Fourier transform infrared (FTIR) methods. The results indicate that the disappearance of the aldehyde group from 4HBA‐a and the ring‐opening reaction of 4HBA‐a occur simultaneously. Gases evolved during the curing process of 4HBA‐a were analyzed by thermogravimetric analyzer interfaced with FTIR spectra. The elimination of CO₂ is attributed to the oxidation and decarboxylation of the aldehyde groups. In addition, the crosslink sites of the aldehyde groups in the polymer structure are confirmed by model reactions. A possible reactive position should be sited in ortho position of phenol rather than ortho and/or para positions of N‐phenyl ring. Finally, the crosslinked structures of polymerized 4HBA‐a have been proposed. © 2011 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2011     

Synthesis and characterization of nanomagnetite thermosets based on benzoxazines

Nanomagnetite thermosets were obtained by thermally activated ring opening copolymerization of benzoxazine groups coated on the surface of the nanomagnetite with bare benzoxazine. For this purpose, carboxylic acid containing 1,3‐benzoxazine was synthesized and covalently bonded on magnetite nanoparticles by postcoating method. The average size of benzoxazine coated nanoparticles was 40–100 nm as determined by Dynamic Light Scattering (DLS), Atomic Force Microscopy (AFM) and Transmission Electron Microscopy (TEM) measurements. The crystal structure of benzoxazine coated nanoparticles was shown to be magnetite by X‐ray diffraction (XRD) analysis. Thermally activated curing behavior of nanomagnetite‐benzoxazines has also been studied by differential scanning calorimetry (DSC). Magnetic and thermal properties of the cured samples were investigated. It was shown that the precursor nanomagnetite benzoxazine and cured samples exhibited typical ferromagnetic character with low coercivities between 1.5 and 2.5 Oe. The cured samples showed high thermal stability. © 2008 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 46: 6780–6788, 2008     

Thermally curable benzoxazine monomer with a photodimerizable coumarin group

A new monomer, 4‐methyl‐9‐p‐tolyl‐9,10‐dihydrochromeno[8,7‐e][1,3]oxazin‐2(8H)‐one, possessing both benzoxazine and coumarin rings in its structure was synthesized by the reaction of 4‐methyl‐7‐hydroxycoumarin, paraformaldehyde, and p‐toluidine in methanol at 40 °C and characterized with spectral analysis. Upon photolysis around 300 nm, this monomer underwent dimerization via the [2πs+2πs] cycloaddition reaction. Photodimerization reactions were investigated with UV and ¹H NMR spectroscopy measurements. The thermal ring‐opening reaction of the benzoxazine ring was demonstrated with differential scanning calorimetry measurements. The thermal behavior of the cured product was also investigated with thermogravimetric analysis. © 2007 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 45: 1670–1676, 2007     

Preparation and properties of novel low dielectric constant benzoxazole‐based polybenzoxazine

A novel benzoxazine monomer containing a benzoxazole group was synthesized using a nonsolvent method and then named DAROH‐a. The structure of DAROH‐a was confirmed by FTIR, ¹H NMR, elemental analysis, and mass spectrometry. The curing reaction activation energy was calculated at 140 kJ/mol. Its corresponding crosslinked polybenzoxazines, poly(DAROH‐a), displayed a higher glass transition temperature at 402 °C, a 9% weight loss at the said temperature, and a high char yield of 42 wt % (800 °C, in nitrogen). Moreover, the dielectric constants of poly(DAROH‐a) were low and changed only slightly at different temperatures. Furthermore, the dielectric constants and dielectric loss of poly(DAROH‐a) at the same frequency barely changed from room temperature to 150 °C. The photophysical properties of poly(DAROH‐a) film were also investigated. Poly(DAROH‐a) showed an absorption peak at 280 nm. The photoluminescent emission spectrum of poly(DAROH‐a) film displayed predominant emission peaks at 521 nm. It might have potential application as high‐performance materials because of its excellent dielectric constants stability and thermal stability under high temperature. © 2012 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2012     

Polysiloxane‐containing benzoxazine moieties in the main chain

Polysiloxanes containing thermally curable benzoxazine units in the main chain have been synthesized. For this purpose, first the diallyl functional benzoxazine monomer is synthesized through the Mannich and respective ring closing reactions of 4,4′‐isopropylidenediphenol (bisphenol A), formaldehyde, and allyamine. Subsequent hydrosilylation reaction of the resulting allylic monomer (B‐ala) with 1,1,3,3‐tetramethyldisiloxane (TMDS) in the presence of Pt catalyst yields the corresponding oligo(B‐ala‐tetramethyldisiloxane)s (OBTMDS). Using the anionic polymerization route, OBTMDS was then converted to poly(bisbenzoxazinedimethylsiloxane)s (PBDMSs) by reacting with readily available cyclic oligomer octamethylcyclotetrasiloxane (D4) or decamethylcyclopentasiloxane (D5) in the presence of tetrabutylammonium hydroxide as catalyst. The structures of the precursor diallyl monomer, the intermediate oligomer, and the resulting polymers are confirmed by Fourier transform infrared and ¹H NMR analysis. Curing behavior of the products at various stages has also been studied by differential scanning calorimetry. Flexible transparent films of the PBDMSs are obtained by solvent casting. Thermal properties of the cured polymers are also investigated by thermogravimetric analysis. © 2010 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2010     

Nanocomposites based on crosslinked polyacrylic latex/silver nanoparticles for waterborne high‐performance antibacterial coatings

Functional polymer/AgNPs nanocomposites have been prepared. Silver nanoparticles (NPs) were synthesized to which polyacrylamide, PAAm, was covalently bound. PAAm was synthesized via a RAFT reaction and carried thiol and carboxylic acid end groups. Thiol was used to bind the polymer to the metal surface and carboxyl for further reactions. The AgNPs were used in a post‐crosslinking reaction with a separately synthesized poly(butyl acrylate‐co‐methyl methacrylate)/polyglycidyl methacrylate core/shell latex bearing epoxy functional groups. Dynamic mechanical analysis showed that the functional AgNPs effectively crosslinked the latex polymer, and that the final product had excellent mechanical strength. Antibacterial tests revealed that the nanocomposite films had strong antibacterial activity against all types of the bacteria and the immobilization of silver NPs by crosslinking retarded the release of silver in comparison to the uncrosslinked ones. With the presented method, it is possible to obtain ductile antibacterial nanocomposites to be used as waterborne functional coatings. © 2014 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2014 , 52, 1435–1447     

Resorcinol‐based benzoxazine with low polymerization temperature

The industrial applications of benzoxazines are limited due to their high curing temperatures. This drawback can be overcome by more reactive precursor compared to conventional benzoxazines or by application of efficient initiators. We report the synthesis of a new resorcinol‐based benzoxazine and its cationic polymerization with thermolatent super acids, namely organic sulfonium hexafluoroantimonates. This combination of a reactive precursor and an efficient initiator results in a curing temperature below 100 °C (differential scanning calorimetry onset) which is up to now one of the lowest polymerization temperatures for benzoxazine systems. Furthermore, the thermal stability of the formed polybenzoxazine has not been influenced by the applied initiators. © 2014 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2014 , 52, 1693–1699     

High‐Tg and low‐dielectric epoxy thermosets based on a propargyl ether‐containing phosphinated benzoxazine

A propargyl ether‐containing benzoxazine (4) was prepared from a potassium carbonate‐catalyzed nucleophilic substitution of propargyl bromide and a phenolic OH‐containing benzoxazine (3) , which was prepared from 1‐(4‐hydroxyphenyl)‐1‐(4‐aminophenyl)‐1‐(6‐oxido‐6H ‐dibenz <c,e><1,2> oxaphosphorin‐6‐yl)ethane (1) by a three‐step procedure. The curing reactions of (4) were monitored by IR and DSC. A reaction mechanism was proposed based on the observation. Benzoxazines (3) and (4) were applied as epoxy curing agents. The microstructure and the structure‐property relationship of the resulting thermosets are discussed. The double‐strand structure in (4) ‐cured epoxy thermosets afforded higher crosslinking density, and led to higher thermal properties. In addition, the (4) ‐cured epoxy thermosets possess half the amount of highly polar hydroxyl groups than those of the (3) ‐cured epoxy thermosets, resulting in a lower dielectric constant, dissipation factor, and water absorption. © 2014 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2014 , 52, 1359–1367     

Preparation,characterization, and properties of fluorene‐containing benzoxazine and its corresponding cross‐linked polymer

A benzoxazine compound (FDP‐FBz), which possesses a fluorene group and two terminal furan groups, and its corresponding cross‐linked polymer (CR‐FDP‐FBz) have been prepared using 4,4′‐(9‐fluorenylidene)diphenol (FDP), furfurylamine, and formaldehyde as precursors. The chemical structure of FDP‐FBz has been characterized with Fourier‐transform infrared and ¹H nuclear magnetic resonance spectroscopies. FDP‐FBz displays a melting point at about 173 °C and a processing window of 52 °C as well as good solubility in common organic solvents. As a result, FDP‐FBz can be fabricated in both molten and solution processes. Under an excitation at 365 nm, FDP‐FBz exhibits a photoluminescent (PL) emission at about 445 nm. The PL intensity of FDP‐FBz is as high as sixfolds of the intensity recorded with FDP. CR‐FDP‐FBz displays a glass transition temperature of 215 °C, a high storage modulus of 3.1 GPa, a 10% weight loss at 384 °C, and a high char yield of 56 wt % (900 °C, in nitrogen). Moreover, CR‐FDP‐FBz has a high refractive index of about 1.65 as a result of incorporating fluorene groups to its structure. © 2010 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 48: 4020–4026, 2010     

Bifunctional benzoxazines: Synthesis and polymerization of resorcinol based single isomers

Aside from their outstanding properties such as thermal and chemical stability and excellent mechanical performance, benzoxazines suffer from high polymerization temperatures. Isomeric mixtures of bifunctional benzoxazines based on resorcinol proved already to be highly reactive monomers enabling polymerizations at lower temperatures. This contribution describes the polymerization behavior of single benzoxazine isomers and furthermore the influence of different substituents at the aniline moiety on the curing temperature. Single isomers of bifunctional benzoxazines are now accessible in a straightforward one‐pot synthesis starting from resorcinol and the appropriate N‐phenyl functionalized aniline component. The asymmetric benzoxazine monomers bearing no (R‐a: T_peak = 179 °C) or electron‐donating substituents in meta position to N (R‐3,5dma: T_peak = 183 °C) succeed in lowering the polymerization temperature. Additionally, the impact of several initiating systems was studied resulting in a decrease of the polymerization temperature for all studied resorcinol derived benzoxazine isomers (down to 144 °C). © 2015 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2016 , 54, 1243–1251     

Synthesis of high thermal stability polybenzoxazoles via ortho‐imide‐functional benzoxazine monomers

We report our work for preparing cross‐linked polyimide via a series of imide functional benzoxazine resins as precursors. The structures of synthesized monomers have been confirmed by ¹H NMR and FT‐IR. Among this class of benzoxazine monomers, the ortho‐imide functional benzoxazine resins show useful features both in the synthesis of benzoxazine monomers and the properties of the corresponding thermosets. For the cross‐linked polyimides based on ortho‐imide functional benzoxazine, an additional route is adopted to form a more thermally stable cross‐linked polybenzoxazole with the release of carbon dioxide. The ortho‐imide functional benzoxazine resins show the possibility to form high performance and even super high performance thermosets with low cost and easy processability. The thermal properties are evaluated by DSC and TGA. © 2015 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2015 , 53, 1330–1338     

High performance thermosets from a curable Diels–Alder polymer possessing benzoxazine groups in the main chain

A high‐molecular‐weight polymer (PBz) possessing reactive benzoxazine groups in the main chain was prepared through the Diels–Alder reaction using bis(3‐furfuryl‐3,4‐dihydro‐2H‐1,3‐benzoxazinyl)isopropane (BPA‐FBz) and bismaleimide (BMI) as monomers. The chemical structure of PBz is characterized with FTIR and ¹H NMR. The polymer PBz was further thermally reacted with a high performance polymer (PBz‐R) through the ring‐opening addition reaction of benzoxazine groups and the addition reaction of maleimide groups. PBz‐R exhibit a high glass transition temperature of 242 °C, good thermal stability, high flame retardancy, high mechanical strength, and great flexibility. Another crosslinked polymer (PBz‐BR) curing from the mixture of BPA‐FBz and BMI was also prepared. The properties of PBz‐BR are also attractive but, however, not as good as what observed with PBz‐R. © 2008 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 46: 6509–6517, 2008     

Synthesis of networked polymer based on ring‐opening addition reaction of 1,3‐benzoxazine with resorcinol

A highly efficient ring‐opening addition reaction of benzoxazine at ambient temperature has been developed with 2‐methylresorcinol as a nucleophilic reagent. In this reaction, 2‐methylresorcinol reacted with two equivalent amount of benzoxazine to give the corresponding 1:2 adduct, demonstrating its potential as a bifunctional nucleophile. Based on this reaction, a new crosslinking system consisting of a polymer bearing benzoxazine moieties in the side chains and 2‐methylresorcinol as a crosslinker has been performed to obtain the corresponding networked polymer. © 2012 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2012     

A novel benzimidazole moiety‐containing benzoxazine: Synthesis,polymerization, and thermal properties

A novel benzoxazine‐containing benzimidazole moiety (P‐PABZ) was synthesized from 2‐(4‐aminophenyl)‐1H‐benzimidazole‐5‐amine and characterized. With the aid of differential scanning calorimetry and in situ Fourier transform infrared, we found the thermal polymerization of P‐PABZ in bulk started around 140 °C and its favored polymerization pathway. Compared to the benzoxazine derived from 4,4′‐diamine diphenyl methane (P‐MDA), P‐PABZ exhibited lower processing temperature, and the corresponding polymers had higher glass transition temperature and enhanced thermal stability. © 2011 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2011     

Synthesis and characterization of sulfone containing main chain oligobenzoxazine precursors

The preparation of soluble and processable polybenzoxazine precursors capable of forming high performance networks is an important field of research with a broad spectrum of application. This study demonstrates an approach that utilizes aromatic sulfonediamine, bisphenol‐A, and formaldehyde in Mannich‐type polycondesation to prepare polybenzoxazine precursor. The structure of the oligomeric precursor (M_n = 2600) was confirmed by FTIR and ¹H NMR spectral analysis. The precursor contained both sulfone and benzoxazine ring structures in the backbone. It was shown that small amount of ring‐opened phenolic groups were also present. Thermally activated self‐curing behavior of precursor in the absence of catalyst was studied by differential scanning calorimetry. Thermal properties of the cured polymers were also investigated by thermo gravimetric analysis. © 2011 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2011     

Synthesis and crosslinking behavior of a novel linear polymer bearing 1,2,3‐triazol and benzoxazine groups in the main chain by a step‐growth click‐coupling reaction

The click‐coupling reaction was applied to polycondensation, to synthesize a high‐molecular weight prepolymer having benzoxazine moieties in the main chain. For the polycondensation, a bifunctional N‐propargyl benzoxazine was synthesized from bisphenol A, propargylamine, and formaldehyde. The propargyl group was efficiently used for the copper(I)‐catalyzed alkyne‐azide “click” reaction with p‐xylene‐α,α′‐diazide, to give the corresponding linear polycondensate having 1,2,3‐triazole junctions. The polycondensation proceeded in N,N‐dimethylformamide (DMF) at room temperature. By this highly efficient “click‐” polycondensation reaction, the benzoxazine ring in the monomer was successfully introduced into the polymer main chain without any side reaction. The obtained polymer (=prepolymer) underwent thermal crosslinking to afford the corresponding product, which was insoluble in a wide range of organic solvents and exhibited higher thermal stability than the polymer before crosslinking. © 2008 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 46: 2316–2325, 2008