Synthesis Of Benzoxazine Research Articles

Synthesis of benzoxazine from eugenol and its co-polymerization with a gallic acid-based epoxy resin for flame retardant application

Synthesis of benzoxazine from eugenol and its co-polymerization with a gallic acid-based epoxy resin for flame retardant application

The Performance and Synthesis of Alkynyl-Functionalized Benzoxazine Containing Phthalide Side Groups and Cyano Groups with Different Molecular Weights.

Benzoxazine resins are widely employed in a variety of applications due to their exceptional heat resistance and treatment properties. However, traditional benzoxazine resins still confront hurdles in today's engineering applications, such as their inability to provide long-term service in high-temperature settings and their inadequate toughness. In this study, four alkyne-functionalized benzoxazines with phthalide side groups and cyano groups of varying molecular weights were produced. Fourier transform infrared spectroscopy (FT-IR) and hydrogen nuclear magnetic resonance spectroscopy (1H-NMR) were used to characterize the resin structure, and differential scanning calorimetry (DSC) was used to investigate the thermal curing kinetics at different warming rates. The apparent activation energy was 116.9 kJ/mol. In-situ FT-IR was used to investigate the cure mechanism. Dynamic mechanical analysis (DMA) was used to evaluate the gelation time of BOZ series resins at various temperatures, and the curing process was designed by combining the results with DSC. The Tg of the composites made using BOZ-1N21 as the matrix was 336 °C, which was much higher than the Tg of the BP-a resin made with aniline, phenolphthalein, and formaldehyde (Tg = 251 °C). As a result, the resin system is expected to be employed in applications requiring high-temperature resistance and toughness.

Preparation and exploration of multifunctional wood coating based on an interpenetrating network system of CO2-polyurethane and natural bio-based benzoxazine

In this study, we synthesized CO2-based polyurethane (PU) as a wood coating through the reaction of CO2-polyol with isocyanate and explored its properties such as heat resistance, acid and alkali resistance, hydrophobicity, and flame retardancy. From the results, the modulus of rupture (MOR) and modulus of elasticity (MOE) of PU wood coatings are 150.60 and 2524.45 MPa, respectively, and the hydrophobic angle is 115°, but they do not have good acid/alkali and salt resistance. At the same time, the flame retardant effect is also poor with the limiting oxygen indexes (LOI) of 24.5 %. Therefore, PU was modified after the synthesis of bio-based benzoxazine (BZ) to prepare PU/BZ 3D interpenetrating network system, which is versatile and practical as wood coatings. In contrast, the PU/BZ wood coatings exhibited a higher value of MOR and MOE of 2979.01 and 176.63 MPa and exhibited a super-hydrophobicity of 150°. They are also stronger than PU coatings in terms of acid/alkali and aging resistance. At the same time, it endows the coating with flame retardant properties, and the LOI is 30.1 due to the existence of BZ. Therefore, the interpenetrating network system of PU/BZ has an innovative impact on the preparation of wood coatings.

Chemoselective hydrosilylation of carboxylic acids using a phosphine-free ruthenium complex and phenylsilane

A highly chemoselective hydrosilylation of carboxylic acids was achieved using a bench-stable, phosphine-free Ru-complex tethered with hemi-labile thiophene ligands as the catalyst, employing phenylsilane as the reducing agent. The methodology was further elaborated towards the one-pot synthesis of indole and benzoxazine via tandem reduction/cyclization of acid and nitro group.

Design, synthesis, flame retardancy and dielectric properties of novel aromatic hyperbranched benzoxazine

Two kinds of novel aromatic hyperbranched benzoxazines (HBs), HB-Tppa1 and HB-Tppa2, were designed and prepared by using 1,1,1-tris(4-hydroxyphenyl)ethane (THPE), p-phenylenediamine (PPA), paraformaldehyde and phenol through two different synthetic routes via Mannich condensation reaction. Fourier transform infrared (FTIR) and nuclear magnetic resonance (1H and 13C NMR) spectroscopy were employed to characterize the featured structures of these (HB-Tppa)s. HB-Tppa1 exhibits greater molecular weight than HB-Tppa2, owing to a priority of forming the hyperbranched structure for preparing HB-Tppa1 without adding capped phenol in the first step. The greater reaction enthalpy (ΔH) value of HB-Tppa1 has been provided by differential scanning calorimeter (DSC), indicating that the mass fraction of benzoxazine rings in HB-Tppa1 is higher than that of HB-Tppa2. The thermal and flame retardancy properties of poly(HB-Tppa1) superior to poly(HB-Tppa2) are affected by these mentioned factors. Besides the high glass transition temperature (Tg, ≥ 320 °C), the low total heat release (THR) and heat release capacity (HRC) values of poly(HB-Tppa)s in the range of 5.4–11.7 kJ/g and 41.5–50.5 J/(g K), respectively, suggest that they are potential nonignitable materials. Moreover, the poly(HB-Tppa)s exhibit low dielectric constants (2.27 ≥ k ≥ 2.15) in the high-frequency range of 2 to 18 GHz, which may perform well in next-generation integrated circuits.

Synthesis and properties of the bio-based isomeric benzoxazine resins: Revealing the effect of the neglected short alkyl substituents

Bio-based feedstocks usually contain many isomers with similar structures, and the short alkyl substituents are generally considered as low-reactive groups in benzoxazine chemistry due to their low induction effect and chemical inertness. Therefore, little attention has been paid on their effects on the synthesis or properties of benzoxazine. In this work, two bio-based benzoxazine isomers (CAR-fbz and THY-fbz) containing methyl and isopropyl groups with interchanged positions were synthesized from the renewable carvacrol and thymol. Their synthetic process, crystal features, and curing reactions were carefully investigated. Results showed that different side reacitions and by-products were detected under the same synthese conditions. And using the similar purification method, CAR-fbz and THY-fbz with high purity were found to have different crystal features. In addition, the cured systems also indicated varied H-bonding features and thermal properties based on differential scanning calorimetric (DSC) and thermogravimetric analysis (TGA) results. With the help of density functional theory (DFT) calculation, the reasons were attributed to the different electrophilicity of phenol moiety, varied molecular symmetry and intermolecular interaction caused by the overlooked short alkyls. Summarily, the leverage of short-chain alkyl groups on benzoxazine chemistry is revealed. The result is significant for the benzoxazine synthesis, especially when the renewable compounds are taken as the starting materials for bio-based benzoxazine preparation, which often has many isomers with similar structures.

Synthesis, curing characteristics, and kinetics of tetra-functional fluorene-based benzoxazines having saturated aliphatic groups

In this paper, a novel series of tetra-functional fluorene-based benzoxazine monomers (SAMFB) were obtained by o-hydroxy-benzylamine method combining with Mannich condensation reaction. Compared with the traditional three-step method, the synthesis of asymmetric benzoxazine reduced the treatment process of the intermediate product, greatly shortened the reaction time and experimental period, improved the yield of the intermediate product, and reduced the production cost. In the traditional three-step synthesis method, the double bond reduction process took 8–12 h, but in this paper, it only took 15 min to complete this process. The curing characteristics, kinetics, thermal stabilities, and thermomechanical properties of SAMFB monomers and their polymers were analyzed. Non-isothermal curing kinetics studies showed that the polymerization process of SAMFB monomers was an autocatalytic reaction. The introduction of fluorene rings and polymerizable groups and the increase of oxazine rings in the polymer network structure can result in an obvious increase in the crosslinking density of polymers. Therefore, SAMFB polymers (poly(SAMFB)) exhibited higher glass transition temperature (Tg, 314–317 °C) and better thermal stability properties, higher than that of traditional bisphenol A-aniline-based and reported bifunctional fluorene-based polybenzoxazine resins. The TGA results showed that the T5 and T10of poly(SAMFB)were 334−368 °C and 370−414 °C, respectively, and Yc at 800 °C was 45.7–61.6 %. Moreover, the toughness of poly(SAMFB) was greatly improved due to the introduction of the flexible alkyl chain.

Synthesis and thermal properties of silicon-containing benzoxazine

A novel benzoxazine, containing silicon (Si) in the main chain and bonded to two benzene ring, was synthesized from aniline, bis( p-hydroxyphenyl)dimethylsilane, and paraformaldehyde. The structure was characterized by proton nuclear magnetic resonance and Fourier transform infrared (FTIR) spectra. The curing behavior of the benzoxazine was evaluated by differential scanning calorimeter and in situ FTIR. The thermal stability of the resulting polybenzoxazine was studied by thermogravimetric analysis under nitrogen and air atmospheres. The results indicated that the Si-containing polybenzoxazine possessed significantly higher initial degradation temperature and char yield than conventional bisphenol A/aniline-based polybenzoxazine.

Adapting benzoxazine chemistry for unconventional applications

Polybenzoxazines, as a kind of phenolics, are high performance thermosets with a range of features and overcoming some drawbacks of resole and novolac type phenolics. Most of the polybenzoxazines exhibit high Tg, high char yield, flame resistance, low water absorption, low shrinkage and also limited or no release of by-products during curing, they have good mechanical performance and are effective contender of high performance polymers such as bismaleimide resins. Thus, the interest in polybenzoxazines is continuously increasing in the polymer science as reflected by the number of scientific publications and patents. In this mini review, an overview about polybenzoxazines is reported highlighting the current advances and progress in the synthesis of benzoxazine based materials for unconventional uses that can be considered as smart applications ranging from self-healing materials to electrochromic devices.

BF3·OEt2‐Mediated Synthesis of 2‐Arylthio‐ and (N‐Aryl‐2,5‐dioxopyrrolidin‐3‐yl)‐Substituted 1,4‐Benzoxazine Derivatives

1,4‐Benzoxazines have been explored as versatile precursors for the synthesis of novel benzoxazine and benzoxazinone derivatives. 2‐Hydroxy‐1,4‐benzoxazines and 1,4‐benzoxazinones have been functionalized with thiols and N‐arylmaleimides, respectively, in the presence of BF3·OEt2 as a promoter. All the products were obtained in moderate to excellent yields. The Michael reactions of the benzoxazinones with maleimides furnished diastereomeric mixtures of adducts, which were characterized by standard spectroscopic methods.

Ionic liquid functionalized cellulose as an efficient heterogeneous catalyst for the facile and green synthesis of benzoxazine, pyrazine and quinoxaline derivatives in aqueous media

Immobilization of acidic ionic liquid, 1-methyl-3-(3-trimethoxysilylpropyl) imidazolium hydrogen sulfate on cellulose (Cell-[pmim]HSO4) as an efficient heterogenous catalyst for the simple and environmentally benign synthesis of benzoxazine, pyrazine and quinoxaline derivatives in aqueous media at room temperature is described. The catalyst was characterized by FTIR spectroscopy and X-ray diffraction pattern. This method provides several advantages such as mild reaction conditions, environmentally friendly catalyst, good to excellent yields and simple work-up procedure.

Sustainable Bis-benzoxazines from Cardanol and PET-Derived Terephthalamides

This paper deals with the preparation of sustainable benzoxazines that exhibit enormous potential to compete with the existing petro-based advance performance thermosets. The phenolic component used for the synthesis of benzoxazine is derived from naturally occurring cardanol, which is obtained from cashew nut tree, Anacardium occidentale. Polyethylene terephthalate (PET) was chosen as a sustainable feedstock for the amine fraction used to prepare the benzoxazine monomer containing amide linkages. Microwave-assisted aminolysis of PET was performed to obtain bis(amino-ethyl) terephthalamide (BAET) and α,ω-aminoligo(ethylene terephthalamide) (AOET), which were employed as the difunctional amine for the preparation of bis-benzoxazines. In comparison to the traditional method, microwave-assisted aminolysis of PET was found to be significantly faster, and the reaction completion time could be brought down appreciably. Mannich-like condensation of cardanol with PET-derived terephthalamides and paraformaldehyde ...

A Double Activation Method for the Conversion of Vinyl Epoxides into vic-Amino Alcohols and Chiral Benzoxazine/Quinoxaline Derivatives.

A new method for the synthesis of 1,2-syn-vic amino alcohols (with double inversion of configuration) from vinyl epoxides, by the amination of a π-allyl palladium-borate complex generated by using Pd(0) and phenyl-o-phenylene borate (a double activation technique), is reported. Further, this new method with broad functional group compatibility was extended to a one-pot/two-step synthesis of chiral benzoxazine and quinoxaline derivatives.

Innovative approach for the synthesis of benzoxazine-modified montmorillonite

The synthesis of a benzoxazine (BZ) monomer inside the montmorillonite (MT) layers was done using a diamino-modified MT as the amine component, phenol, and formaldehyde. The formation of the BZ rings within the MT layers was investigated by thermogravimetric analysis, X-ray photoelectron spectroscopy, proton nuclear magnetic resonance spectroscopy, and X-ray diffraction, this being enhanced when dioxane was used as the solvent. The morphology of the hybrid BZ monomer was investigated by scanning electron microscopy.

Effect of phenol on the synthesis of benzoxazine

The kinetic parameters of benzoxazine synthesis approximately equaled those of phenol consumption revealing that phenol was the key starting material.

H3PW12O40 catalyzed synthesis of benzoxazine and quinazoline in aqueous media

A heteropolyacid efficiently catalyzed the cyclocondensation reaction of 2-aminobenzamide and salicylamide with aldehydes and ketones to afford good yields of benzoxazine and quinazoline ring systems in an aqueous medium. The method gives clean reactions, has simple workup procedure, and uses environment friendly conditions.

Synthesis of Silsesquioxane-Contained Benzoxazine and the Thermal Properties of its High Performance Polymer

A new kind of high performance benzoxazine (BOZ) was synthesized from p-aminophenol functionalized chloropropyl polyhedral oligomeric silsesquioxane (AP-POSS), aniline and paraformaldehyde through a solvent-free process. Fourier transform infrared spectroscopy (FTIR) was employed to characterize the structure of the new BOZ resin contained POSS (POSS-BOZ). The differential scanning calorimeter (DSC) was chosen to research the curing behavior of the new resin, and the thermo gravimetric analysis (TGA) was chosen to research the thermal properties. The results show that the POSS-BOZ is successfully synthesized, and the POSS-BOZ also exhibits better thermal performance in comparison with bisphenol-A benzoxazine (bA-BOZ).

Synthesis, polymerization, and thermal properties of benzoxazine based on p-aminobenzonitrile

The 6,6′-bis(3-benzonitrile-3,4-dihydro-2H-benzo[e][1,3]oxazinyl) isopropane (BA-PABN) was synthesized from bisphenol-A, p-aminobenzonitrile and paraformaldehyde via solventless method. The chemical structure of BA-PABN was confirmed by 1H and 13C nuclear magnetic resonance (NMR) spectroscopy, Fourier transform infrared (FTIR) spectroscopy, and elemental analysis, and the polymerization of BA-PABN was investigated by FTIR, solid-state 13C NMR, and differential scanning calorimetry. BA-PABN undergoes the oxazine ring-opening polymerization and the cyclotrimerization of cyano groups with the formation of the corresponding polybenzoxazine (PBA-PABN). Dynamic mechanical analysis results show the storage modulus of PBA-PABN at 25°C is about 2.7GPa, and the glass transition temperature is 190°C. The 5% and 10% weight loss temperatures of PBA-PABN are 300 and 325°C in both air and nitrogen, respectively. The char yield is about 43% at 800°C in nitrogen, whereas almost no degradation residue is remained at 750°C in air.

Synthesis, polymerization, and thermal properties of benzoxazine based on bisphenol-S and allylamine

A bifunctional benzoxazine monomer, 6,6′-bis(3-allyl-3,4-dihydro-2H-benzo[e][1,3]oxazinyl) sulfone (BS-ala), was synthesized from bisphenol-S, allylamine and formaldehyde via a solution method. The chemical structure of BS-ala was confirmed by 1H and 13C nuclear magnetic resonance (NMR) spectroscopy, Fourier transform infrared (FTIR) spectroscopy, and elemental analysis. The polymerization behavior of BS-ala was investigated by FTIR, solid-state 13C NMR, and differential scanning calorimetry (DSC). The oxazine ring opening polymerization is prior to the addition polymerization of allyl group, and the exothermic peaks corresponding to the two reactions appear partially overlapped in the DSC curve. The storage modulus of the resultant polybenzoxazine at 25°C is about 3.9 GPa, and the glass transition temperature is 254°C. The 5% and 10% weight loss temperatures of the polybenzoxazine are about 335°C and 361°C in both air and nitrogen, respectively. The char yield is about 58% at 800°C in nitrogen, whereas almost no residue is remained at 700°C in air. Copyright © 2012 John Wiley & Sons, Ltd.

ChemInform Abstract: Synthesis of Benzoxazine and 1,3‐Oxazine Derivatives via Ligand‐Free Copper(I)‐Catalyzed One‐Pot Cascade Addition/Cyclization Reaction.

AbstractA new synthetic methodology for benzoxazine and 1,3‐oxazine derivatives via readily available starting materials and relatively mild conditions is presented.