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In this study, we designed and synthesized a series of norbornene‐furan functionalized benzoxazine monomers (HPAP‐fa, HPAMP‐fa, and HPTM‐fa) by regulating the bridge length in benzoxazine structure in order to improve the comprehensive performance of norbornene‐furan functionalized benzoxazine system. This research systematically examined the impact of flexible segments on the structural information, polymerization behaviors, thermal stability, and flame retardancy of resulting polybenzoxazines. Initially, the structural characteristics of benzoxazine were confirmed through nuclear magnetic resonance, Fourier‐transform infrared (FT‐IR), and HR‐MS. Subsequently, the polymerization mechanisms of each benzoxazine monomer were investigated utilizing differential scanning calorimeter and in situ FT‐IR analyses. Finally, the thermal stability and flame‐retardant properties were investigated by TGA and micro‐combustion calorimetry measurements. Consequently, HPAP‐fa exhibited the lowest polymerization temperature and the corresponding poly(HPAP‐fa) showed very high thermal stability (Td5 of 392°C and Td10 of 437°C) as well as excellent flame retardancy (HRC of 83.7 J g−1 K−1), which shows a significant improvement compared to poly(HPTM‐fa). As a result, the modulation of bridge segments within the monomer represents a viable approach towards enhancing the holistic efficacy of norbornene‐furan functionalized benzoxazine systems. [ABSTRACT FROM AUTHOR]

Cancer remains a severe global health problem, with its incidence constantly increasing.. Among many varieties of cancer, breast cancer persists as a prevalent global health concern, with its occurrence continually ascending. Among women, breast cancer is a significant cause of illness and death globally. This study examined the antioxidant and anticancer effects of two resynthesized benzoxazine derivatives, OBOP‐01 and OBOP‐02, on human breast cancer cells. The chemicals investigated had intense antioxidant action against DPPH, H2O2, and ABTS free radicals. Furthermore, we evaluated cell viability by converting yellow MTT (3‐(4,5‐dimethylthiazol‐2‐yl)‐2,5‐diphenyl tetrazolium bromide) into purple formazan, dependent on mitochondrial function. Both compounds had IC50 values of 1.52±0.02 mM and 1.72±0.02 mM respectively. Moreover, toxicity predictions using the ProTox‐III webserver showed that the benzoxazines studied have lower LD50 values compared to doxorubicin, suggesting greater safety. We also used Density Functional Theory (DFT) to analyze OBOP‐01 and OBOP‐02′s electrical interactions and properties. Gaining insight into these interactions is essential for understanding the compounds′ potential applications and properties. According to theoretical studies using molecular docking, the derivatives may interact with estrogen receptor alpha (ERα) (ID: 7NDO), a key target molecule in the development of breast cancer. Additionally, the complex OBOP‐01 – ERα′s molecular dynamics simulations were conducted for 100 nanoseconds. These simulations revealed essential details regarding the complex's dynamic behavior in a physiological system. [ABSTRACT FROM AUTHOR]

In the present study, fully bio-based photocurable trifunctional benzoxazines derived from resveratrol were designed and characterized for multi-dimensional applications. The molecular structure was confirmed using ATR-FTIR and 1H-NMR spectral techniques. The curing temperature and thermal stability were thoroughly studied using differential scanning calorimetry (DSC) and thermogravimetric analysis (TGA) respectively. Notably, in DSC analysis RE-dda exhibited the lowest curing temperature of 191 °C among the synthesised benzoxazines. All the synthesised polybenzoxazines exhibited good thermal stability and start degrading after 263°C. Under UV irradiation, intriguing photoisomerization phenomena was observed in the case of RE-ffa and RE-lee based benzoxazines. The photoluminescence behavior of the UV irradiated benzoxazines was studied using fluorescence spectroscopy and RE-oda displayed a Stokes shift value of 318. Further benzoxazines were reinforced with cashew nut shell cake ash (CNSA) with a view to attain a low value of dielectric constant and to enhance the thermal stability of the composites. An incorporation of 10 wt% CNSA contributes to a reduction in the value of dielectric constant to 1.66, accompanied with a minimal value of dielectric loss of 0.0017. Furthermore, the hydrophobic behavior of the polybenzoxazines, composites and poly(RE-ole) coated cotton fabric was evaluated using water contact angle measurement. Poly(RE-ole) exhibited an impressive water contact angle value of 146°. Moreover, poly(RE-ole) coated cotton fabric displayed enhanced value of water contact angle close to superhydrophobic value of 151°. Data obtained from different studies infer the developed benzoxazines can be considered for water repellent and microelectronics insulation applications. [ABSTRACT FROM AUTHOR]

The article focuses on the diverse range of organizations exhibiting at CAMX 2024, including the American Composites Manufacturers Association, Across International, AcXys Technologies, and Additive Engineering Solutions, each showcasing their contributions to composites.

This paper presents a study of the flammability and thermal decomposition products of glass fiber-reinforced epoxy resin (GFRER) with the addition of cardanol-based phosphorus-containing benzoxazine monomer (CBz) and graphene and their combinations in different proportions (up to 20 wt.%). The addition of CBz alone or in combination with graphene resulted in an increase in the limiting oxygen index (LOI) and self-extinguishing in the UL-94 HB test. The flame-retardant samples had better tensile mechanical properties than the sample without additives. The differential mass-spectrometric thermal analysis (DMSTA) of the thermal decomposition products of GFRER without additives and with the addition of CBz and graphene was carried out. CBz addition promoted the thermal decomposition of high-molecular-weight products of epoxy resin decomposition in the condensed phase and at the same time decreased the time of release of low-molecular-weight thermal decomposition products into the gas phase. Graphene addition resulted in an increase in the relative intensities of high-molecular-mass peaks compared to GFRER without additives. [ABSTRACT FROM AUTHOR]

Covalent polymerization of organic molecules into crystalline one‐dimensional (1D) polymers is effective for achieving desired thermal, optical, and electrical properties, yet it remains a persistent synthetic challenge for their inherent tendency to adopt amorphous or semicrystalline phases. Here we report a strategy to synthesize crystalline 1D covalent organic frameworks (COFs) composing quasi‐conjugated chains with benzoxazine linkages via the one‐pot Mannich reaction. Through [4+2] and [2+2] type Mannich condensation reactions, we fabricated stoichiometric and sub‐stoichiometric 1D covalent polymeric chains, respectively, using doubly and singly linked benzoxazine rings. The validity of their crystal structures has been directly visualized through state‐of‐the‐art cryogenic low‐dose electron microscopy techniques. Post‐synthetic functionalizations of them with a chiral MacMillan catalyst produce crystalline organic photocatalysts that demonstrated excellent catalytic and recyclable performance in light‐driven asymmetric alkylation of aldehydes, affording up to 94 % enantiomeric excess [ABSTRACT FROM AUTHOR]

Sugarcane bagasse is one of the greatest biomass residues obtained from fuel industry, and the lignin present in sugarcane fibers is rich in phenolic compounds, which can be used to replace petroleum-derived phenols in the formulation of adhesives, phenolic resins, plasticizers, paints, among others. This work presents an alternative for synthesizing and applying bio-oil based benzoxazine resins in the fabrication of "green" medium density fiberboard. In this new concept, the wood fiber is substituted by the sugarcane bagasse fiber, and the fossil-based resin is substituted by the bio-based benzoxazine resin. To produce the bio-oil resin, 200.0 g of bio-oil, 64.9 mL of formaldehyde, 39.4 mL of aniline, and 80.0 mL of butanone were added along the different process stages. Three concentrations of bio-oil resin were used to produce fiberboards, 25, 30, and 35%. The results of characterizations were compared with fiberboards made with regular urea–formaldehyde resin, in the same concentrations. Results indicated that bio-oil can be used successfully for the development of a thermosetting resin (BO-resin), as observed by thermal and spectroscopic analysis. All BO-resin MDF formulations had densities according to international standards, between 651 and 800 kg m-3, and reached the required thickness swelling when applied in concentration of 35% resin. The modulus of rupture (MOR) showed elevated values (around 15 MPa), similar to fiberboards made from urea–formaldehyde resins. These results indicate the promising potential of using sugarcane bagasse for the full development of novel bio-based materials with technological application. [ABSTRACT FROM AUTHOR]

Benzoxazine dimers are a group of compounds with a variety of properties, such as anticancer properties and good chelating behaviors. The modification of the benzoxazine dimers can be carried out on the OH groups as well as the benzene moiety. There are several works reported on the property adjustment involving the use of different substituent groups on the benzene ring. Only a few works described the properties and crystallographic studies of the OH-modified benzoxazine dimer. The repulsion forces between two bulky benzoyl groups push them to be more distant compared to the unmodified benzoxazine dimer. According to the crystallographic information, the C—H···O, C—H···π, and π···π interactions hold neighbor molecules together, which consequently stabilize the crystal structure. Thermal analyses (TGA and DSC) reveal that the synthesized benzoated benzoxazine dimer is stable up to 175 °C. Hirshfeld surface analysis confirmed the presence of the C—H···O and C—H···π interactions as seen from the high contributions of the following contacts: H···H (60.6%), H···C/C···H (25.1%), and H···O/O···H (12.3%). Moreover, the observed π···π interaction is supported by the shape-index property of the corresponding Hirshfeld surface. For the solid-state photoluminescence of the di-benzoated benzoxazine dimer recorded at the excitation wavelength range from 265 to 320 nm, the emission peak at 490 nm is observed together with another peak or shoulder in the range of 440–480 nm. For all the excitation wavelengths studied, the di-benzoated dimer emits the fluorescence in the blue color shades (CIE coordinate of x at 0.137–0.142 and y at 0.200–0.262). The photoluminescence property is found to originate by the benzoate modification of the benzoxazine dimer. [ABSTRACT FROM AUTHOR]

Conventional cellulosic packaging materials lack the ability to resist the penetration of water, mineral oil, and harmful chemicals. These poor barrier properties of the conventional cardboard packaging materials make them ineffectual in various industrial applications. Hence, the present work focuses on the development of hydrophobic polybenzoxazine coated cellulose paper with improved tensile strength for the replacement of existing cardboard packaging materials. The trifunctional polybenzoxazines have been synthesized and coated on cellulose paper for the hydrophobic packaging material application. A new type of series of tri-functional polybenzoxazines were synthesized using leucoaurin with paraformaldehyde and separately with five different aliphatic amines of varying chain length (i.e.) butylamine (ba), hexylamine (ha), ethylhexylamine (eha), dodecylamine (dda) and octadecylamine (oda) through Mannich condensation. In the present work, the influencing effect of aliphatic chain length present in the skeleton of polybenzoxazines has been studied and the hydrophobic behavior was exploited for water-proof packaging application by coating polybenzoxazines on normal cellulosic printable paper-75 GSM (CP) and Wattman paper (WP) through spray coatings. The hydrophobic behavior of leucoaurin based benzoxazines coated cellulose paper was tested using goniometer and the coated cellulosic paper possesses good hydrophobic behavior with value of water contact angle above 125º. Among the polybenzoxazines synthesized, the leucoaurin with octadecylamine benzoxazine coated on cellulosic WP paper shows better water repellent property (water contact angle 136 ± 2º) than that of others. In addition to that, the value of tensile strength of leucoaurin based polybenzoxazines coated papers was tested using UTM and the results obtained were compared with that of non-coated papers. The tensile strength of the coated papers was found to be 2 to 3 times higher than that of non-coated paper with the value of 21 MPa and 18 MPa for LA-PBZ coated copier paper and Wattman paper respectively. The obtained results suggest that the leucoaurin based polybenzoxazines coated papers can be considered for effective utilization for water-proof packaging applications. [ABSTRACT FROM AUTHOR]

This study aims to explore new flame-retardant composites based on a phosphorus-functionalized cellulose derivative and epoxy/benzoxazine thermosetting resins in order to broaden the use of natural fibers in advanced applications. The study involved the phosphorylation of microcrystalline cellulose followed by its characterization through employing various analytical methods to corroborate the accomplishment of its functionalization. The curing behavior of composites based on the polybenzoxazine/epoxy copolymer reinforced with (1 and 5 wt.%) modified microcrystalline cellulose was hereafter considered. The thermal behavior of these composites was correspondingly investigated using thermogravimetric analysis, where improved thermal stability and the limiting oxygen index were stressed. Flame retardancy tests using the vertical burning test UL 94 and heat of combustion analysis utilizing an oxygen bomb calorimeter were also carried out to deeply examine the possible flame retardancy ability of the considered composites. [ABSTRACT FROM AUTHOR]

Traditional polybenzoxazine thermosets cannot be reprocessed or recycled due to the permanent crosslinked networks. The dynamic exchangeable characteristics of imine bonds can impart the networks with reprocessabilities and recyclabilities. This study reported a weldable, reprocessable, and water‐resistant polybenzoxazine vitrimer (C‐ABZ) crosslinked by dynamic imine bonds. It was synthesized through a condensation reaction between an aldehyde‐containing benzoxazine oligomer (O‐ABZ) and 1,12‐dodecanediamine. The resulting C‐ABZ was able to be welded and reprocessed due to the dynamic exchange of imine bonds. The tensile strengths of the welded C‐ABZ and the reprocessed C‐ABZ after three cycles of hot‐pressing were 76.7, 81.3, 70.8, and 58.1 Mpa, with corresponding tensile strength recovery ratios of 74.1 %, 78.6 %, 68.4 %, and 56.1 %, respectively. Furthermore, the polybenzoxazine backbone significantly improved the water resistance of the imine bonds. After immersing in water for 30 days at room temperature, the weight gain of C‐ABZ was less than 1 % with corresponding tensile strength and tensile strength retention ratio of 59.5 Mpa and 57.5 %, respectively. Although the heat resistance of C‐ABZ decreased slightly with increased hot‐pressing cycles, a glass transition temperature (Tg, tanδ) of 150 °C was retained after the third hot‐pressing. Overall, these findings demonstrate that the C‐ABZ possesses excellent comprehensive performances. [ABSTRACT FROM AUTHOR]

This study presents a promising method for creating high-performance supercapacitor electrodes. The approach involves crafting a unique composite material—nickel-cobalt-layered double hydroxides (NiCo-LDH) grown on carbon nanoballs (CNBs). This is achieved by first creating a special carbon material rich in oxygen and nitrogen from a polybenzoxazine source. At first, eugenol, ethylene diamine and paraformaldehyde undergo Mannich condensation to form the benzoxazine monomer, which undergoes self-polymerization in the presence of heat to produce polybenzoxazine. This was then carbonized and activated to produce CNBs containing heteroatoms. Then, through a hydrothermal technique, NiCo-LDH nanocages are directly deposited onto the CNBs, eliminating the need for complicated templates. The amount of CNBs used plays a crucial role in performance. By optimizing the CNB content to 50%, a remarkable specific capacitance of 1220 F g−1 was achieved, along with excellent rate capability and impressive cycling stability, retaining 86% of its capacitance after 5000 cycles. Furthermore, this NiCo-LDH/CNB composite, when combined with active carbon in a supercapacitor configuration, delivered outstanding overall performance. The exceptional properties of this composite, combined with its simple and scalable synthesis process, position it as a strong contender for next-generation sustainable energy storage devices. The ease of fabrication also opens doors for its practical application in advancing energy storage technologies. [ABSTRACT FROM AUTHOR]

Resveratrol and 2‐thiophenemethylamine have been employed in the synthesis of a novel tri‐functional benzoxazine (RES‐th) to develop the bio‐benzoxazine monomer. The chemical structure of the synthesized monomer is confirmed by various characterization technics. The polymerization behavior is monitored by in situ Fourier transform infrared spectroscopy (FTIR) and differential scanning calorimetry (DSC). The in situ FTIR results reveal distinct reaction mechanisms for the three oxazine rings presented in RES‐th, with both ether and phenolic Mannich bridge structures observed in the products. The activation energy values of RES‐th are calculated to be 119.05, 120.97, and 119.44 kJ mol−1 by Kissinger, Ozawa, and Starink methods, respectively, which are all based on the heat flow curves at various heating temperatures. The thermal stability and flame retardancy of the resulting polybenzoxazine (poly(RES‐th)) are investigated by thermogravimetric analysis (TGA) and microscale combustion calorimeter (MCC). The values of Td5 and Td10 of polybenzoxazine are found to be 356 °C and 399 °C, respectively, with a char yield of 66.3% at 800 °C. The prepared polybenzoxazine also demonstrates nonflammability characteristics with the values of heat release capacity (HRC) and total heat release rate (THR) of 18.65 J (g K)−1 and 2.69 kJ g−1, respectively. These findings suggest that the thermoset, poly(RES‐th), is a promising candidate for fire‐resistant applications. [ABSTRACT FROM AUTHOR]

Purpose: This study aims to synthesize two different benzoxazines (Bz) monomers using bio-based and petroleum-based primary amines, respectively, and they have been compared to study their thermal and mechanical performances. Design/methodology/approach: A bio-based bisphenol, Divanillin (DiVa), was formed by reacting two moles of vanillin with one mole of ethylenediamine (EDA) which was then reacted firstly with paraformaldehyde and EDA to form the benzoxazine DiVa-EDA-Bz, and secondly with paraformaldehyde and furfuryl amine (FFA) to form the benzoxazine DiVa-FFA-Bz. The molecular structure and thermal properties of the benzoxazines were characterized by fourier transform infrared spectroscopy and nuclear magnetic resonance (1H,13C) spectroscopies, differential scanning calorimetry (DSC) and thermogravimetric analysis (TGA), respectively. The benzoxazines were further coated on mild steel panels to evaluate their mechanical properties and chemical resistance. Findings: The DSC results of DiVa-FFA-Bz showed two exothermic peaks related to crosslinking compared to the one in DiVa-EDA-Bz. The DiVa-FFA-Bz also showed a higher heat of polymerization than DiVa-EDA-Bz. The TGA results showed that DiVa-FFA-Bz exhibited higher thermal stability with a residual char of 54.10% than 43.24% for DiVa-EDA-Bz. The chemical resistance test results showed that DiVa-FFA-Bz showed better chemical resistance and mechanical properties due to its higher crosslinking density. Originality/value: This study shows the use of bio-based materials, vanillin and FFA, for synthesizing a benzoxazine resin and its application at high temperatures. [ABSTRACT FROM AUTHOR]

Two bio‐based polybenzoxazine coatings, cardanol/3‐aminopropyltriethoxysilane‐based polybenzoxazine (PC‐aptes) and cardanol/stearylamine‐based polybenzoxazine (PC‐s), were prepared for corrosion protection on mild steel. The structures of polybenzoxazines were characterized by differential scanning calorimetry (DSC) and Fourier transform infrared spectroscopy (FT‐IR). Due to the presence of long hydrocarbon chains and hydrogen bond networks, the PC‐aptes and PC‐s coatings showed high hydrophobicity, with static water contact angles of 106.0 ± 0.6° and 104.8 ± 1.6°, respectively. It was noted that the silane‐functionalized PC‐aptes coating had a dual‐crosslinked network of polybenzoxazine and polysiloxane, which could effectively inhibit the penetration of corrosive media. The results of electrochemical impedance spectroscopy (EIS) indicated that the PC‐aptes coating with higher crosslinking density exhibited superior corrosion resistance compared to the PC‐s coating. [ABSTRACT FROM AUTHOR]

An iron-mediated bromination/cyclization for the synthesis of bromobenzoxazines from olefinic amides has been successfully developed. In this protocol, the simple iron salt FeBr3 was employed as a bromination reagent, giving the bromobenzoxazine products in moderate to excellent yields. This methodology features good functional group tolerance, gram-scale synthesis, and green reaction conditions by the use of air as the terminal oxidant. Preliminary mechanistic studies suggest that a free radical pathway is involved. [ABSTRACT FROM AUTHOR]

In this study, we succesfully synthesized bio‐benzoxazine resins using eugenol, a bio‐based phenolic compound, in combination with three distinct functional amines: ethanamine, aniline, and hexane‐1,6‐diamine. Characterization of the resulting bio‐benzoxazine resins, namely E‐ea (eugenol, ethanamine), E‐a (eugenol, aniline), and E‐dh (eugenol, hexane‐1,6‐diamine), was performed through 1H NMR spectroscopy, FTIR spectroscopy, high‐resolution mass spectrometry, and elemental analysis. Thermal properties were investigated using thermogravimetric analysis (TGA) for both the eugenol‐derived bio‐benzoxazines (E‐ea, E‐a, E‐dh) and their corresponding polybenzoxazines (PE‐ea, PE‐a, PE‐dh). Notably, all eugenol‐based polybenzoxazines exhibited excellent thermal stability with very similar characteristics. Our findings suggest that the presence of allyl groups in eugenol promoted a more cross‐linked network structure compared to other functional groups on amines. As a result, eugenol‐derived bio‐benzoxazines demonstrated superior thermal properties, illustrated by their impressive char yields: PE‐ea; 45.6%, PE‐a; 45.1%, and PE‐dh; 44.1%. [ABSTRACT FROM AUTHOR]

To alleviate the environmental hazard and minimize the practice of utilizing fossil fuel‐based precursors in the production of benzoxazines, sustainable bio‐phenol precursors namely magnolol and bio‐based amine furan‐2yl‐methanamine have been utilized to synthesize bio‐benzoxazine and was cured and characterized. The curing temperature of the synthesized bio‐benzoxazine monomer was found to be 216°C. Utilizing the carbon obtained from two different bio‐sources namely, chicken feather and cashew nut shell cake bio‐polybenzoxazine composites were prepared. The char yield of bio‐carbon reinforced bio‐polybenzoxazine composites was enhanced to 65% compared to that of neat polybenzoxazine (60%). The value of the dielectric constant of neat polybenzoxazine was found to be 5.52 which was further improved to a maximum of 8.9 and 7.8 on reinforcement of 15 wt% chicken feather carbon and 15 wt% cashew nut shell cake carbon respectively. The prepared bio‐polybenzoxazine composites exhibit a near superhydrophobic nature with the value of water repulsive angle at 150° than that of neat matrix (143°). From the obtained results, it is suggested that the sustainable bio‐carbon reinforced bio‐based benzoxazine will be a promising material for thermally stable, high dielectric, and water‐repellent applications. Highlights: Eco‐friendly, sustainable magnolol‐based bio‐benzoxazine was synthesized.Waste valorization for bio‐carbon—poultry, and agricultural wastes were utilized.Bio‐carbon reinforcement marginally increases the thermal stability of composites.Bio‐carbon reinforced composites exhibit close to superhydrophobic nature.Incorporation of bio‐carbon enhances the value of dielectric constant. [ABSTRACT FROM AUTHOR]

Polypropylene (PP) is a commonly used material in medical supplies. However, its lack of antibacterial properties has led to a frequent occurrence of healthcare-associated infections that need to be addressed. This study extensively investigates the antibacterial effects of bisphenol A-type benzoxazine (BA-a), revealing a relationship between the curing degree of BA-a and its antibacterial performance. A lower degree of curing corresponds to stronger antibacterial activity. At the processing temperature of 170 °C, the curing degree of BA-a reached only 14.6%, and it had strong antibacterial activity. Based on this relationship, a melt blending method at 170 °C is determined to prepare PP/BA-a composite material, aiming to enhance the antibacterial properties. The antibacterial performance of PP/BA-a is evaluated by plate coating method. The results demonstrate that PP/0.8BA-a exhibits an antibacterial rate as high as 99.99% against E. coli and S. aureus. Migration experiments confirm the stability of the antibacterial effect. The extracts from PP/BA-a show no toxicity towards mouse fibroblast cells (L929). Furthermore, compared to pure PP, the addition of BA-a improves the thermal stability of PP/BA-a, with an increase of 56 °C in the onset thermal decomposition temperature (T5%), enabling PP to better adapt to the high-temperature environment of moist heat sterilization. This study presents a novel method for obtaining highly antibacterial medical polymer materials (PP/BA-a) with broad application prospects. [ABSTRACT FROM AUTHOR]

Polybenzoxazines (PBz) are a new type of resin belonging to the category of phenolic resins. As polybenzoxazines are addition-curable polymers, this obviates many of the shortcomings associated with conventional phenolic resins while endowing them with excellent thermal, physical, and thermo-physical properties and surpass the features of many conventional and state-of-the-art polymers. They even possess excellent design flexibility. In this study, a benzoxazine monomer was successfully synthesized from eugenol (Eu), ethylenediamine, and paraformaldehyde utilizing a solventless approach. The synthesized benzoxazine resin was characterized for its structural elucidation via FTIR, 1H, and 13C NMR spectroscopy and was used for crosslinking a petroleum-based epoxy and a gallic acid-based epoxy. The effects of the presence of benzoxazine on the thermal and flame retardant properties of the films were evaluated using TGA and DSC analysis and the LOI and UL 94 tests, respectively. It was found that the benzoxazine in the epoxy systems led to an increase in thermal stability and flame retardancy. The gallic acid-based epoxy system showed better thermal and flame retardant properties compared to the petroleum-based epoxy system, thus showing potential to replace the petroleum-based epoxy for high-performance applications. [ABSTRACT FROM AUTHOR]

An overview of bionanocomposites of polybenzoxazine, which is a highly promising material, is presented in this review paper along with an update on the current developments in this material. With an enormous range of applications, polybenzoxazines are emerging as a latest set of phenolic resins. Its favorable features make it an excellent replacement for many current polymers due to its simplicity in structure design, synthetic process, and polymerization reactions. Problematic aspects of petro‐based raw materials are their nonrenewable nature, toxicity, and rising expense. Hence, the advent of sustainable benzoxazines is promising since it enables the synthesis of monomers without the need for solvents and the processing of these monomers to create extremely thermally stable thermoset resins. This is particularly true when the monomer is derived from naturally occurring, agro‐waste cardanol. A platform for additional structural alterations to expand the uses of cardanol benzoxazine in adhesives, composites, and energy storage devices is provided by its intrinsic properties. There are numerous articles are available for biobased polybenzoxazine, and hence, the focus of the present review is dedicated to (1) nanomaterails loaded bio‐based polybenzoxazines, and (2) bio‐derived nanomaterials loaded polybenzoxazines. [ABSTRACT FROM AUTHOR]

The article discusses the polymerization scheme of benzoxazine monomer based on 4,4′‐diaminodiphenylmethane (P‐ddm) and the chemical structure of polybenzoxazine based on it poly(P‐ddm). The polymerization behavior of benzoxazine P‐ddm is studied using differential scanning calorimetry (DSC). Solid‐state 13C MAS NMR is used to determine the chemical structure of poly(P‐ddm). It is revealed that the сhemical structure of poly(P‐ddm) predominantly consists not of phenolic Mannich bridges, as expected, but of methylene bridges, which indicates the process of deamination of phenolic Mannich bridges. However, no weight loss associated with the expected release of free amine during this process is detected. This may indicate the incorporation of a diamine moiety into the polymer chain through the formation of imine bonds, the signal of which is detected in the 13C MAS NMR and FTIR spectra of the poly(P‐ddm), and on the 1H and 13C NMR spectra of model polybenzoxazine based on p‐cresol and 4,4′‐diaminodiphenylmethane poly(pC‐ddm). Based on the data obtained, a hypothesis is put forward about the formation of a network polymer, the structure of which consists mainly of methylene and imine units. [ABSTRACT FROM AUTHOR]

The first example of intramolecular nucleophilic addition of 1,4-diazabutatriene to ester is disclosed. This approach provides a facile and versatile synthesis for functionalized 2H-1,4-benzoxazines under metal-, reagent-, and solvent-free conditions. Experimental and computational studies revealed the pivotal role of 1,5-acyl migration as the self-catalytic step in the reaction selectivity. [ABSTRACT FROM AUTHOR]

Two series of unsymmetrical hybrid benzoxazines were separately synthesized using combinations of natural bio-phenolic materials, namely cardanol (C) with eugenol (E), vanillin (V), and guaiacol (G) using diaminodiphenylmethane (ddm)/diaminodiphenyl ether (dde) through the well-known Mannich reaction. The synthesized hybrid benzoxazines have a cure temperature between 229 °C and 269 °C. Compared to previous synthesized benzoxazines, vanillin-based benzoxazines (C-dde-V and C-ddm-V) have a lower cure temperature. TGA results show that poly(C-ddm-V) and poly(C-dde-V), two hybrid polybenzoxazines, have superior thermal stability than the other hybrid polybenzoxazines. In order to develop polybenzoxazine composites, different wt% of GPTMS functionalized vermiculite was incorporated with poly(C-ddm-V). The properties of these composites were examined and contrasted with those of a neat matrix. The hybrid polybenzoxazines and composites water contact angle values vary from 136° to 144°, suggesting that all of the hybrid polybenzoxazines and composites have good hydrophobic behavior. On increasing the concentration of vermiculite, the dielectric constant value significantly decreased to a low dielectric constant. [ABSTRACT FROM AUTHOR]

Data on the synthesis methods, chemical transformations, and biological activity of 4H-3,1-benzoxazines and their dihydro derivatives, including coordination compounds of the dihydro derivatives with transition metals, are systematized and analyzed. [ABSTRACT FROM AUTHOR]

Benzoxazines, renowned for their self-curing properties, high glass transition temperature, and exceptional thermal stability, have faced environmental and biotoxicity concerns despite their remarkable performance. Combining high-performance, ecofriendly and degradable benzoxazines remains a challenge. In this work, we synthesized an entirely bio-based benzoxazine resin, 2,6-bis(3-(furan-2-ylmethyl)-8-methoxy-2-phenyl-3,4-dihydro-2H-benzo[e][1,3]oxazin-6-yl)tetrahydro-[1,3]dioxino[5,4-d][1,3]dioxine (VE-BZ), from natural raw materials, including vanillin, erythritol, furfurylamine, and natural benzaldehyde. The presence of the bis(acetal) structure, furanic structure, and benzene ring-branched chain structure in the resin confers favorable adhesive strength, high carbon residue, self-extinguishing ability, and outstanding thermal stability to VE-BZ. Moreover, VE-BZ can undergo dual-site curing and complete degradation through the synergistic effects of acid and heat, enabling its reuse in benzoxazine synthesis. The acid used for both synthesis and degradation is bio-based citric acid, eliminating non-biobased catalysts or additives from the entire process. This approach embodies a comprehensive green chemistry closed-loop process. In essence, this research offers valuable perspectives on seamlessly combining exceptional performance with eco-friendly attributes in the realm of benzoxazine resin materials. [ABSTRACT FROM AUTHOR]

Aromatic polyimides have attracted wide attentions in fields of aerospace, microelectronics and defense applications due to their outstanding thermal and mechanical performances. However, the rigidity originating from the imide structure attached with an aromatic ring causes difficulties in processing. In this study, we synthesized two ortho-phthalimide functional benzoxazine monomers with additional cross-linkable groups (including both furan and alkynyl). An ortho-phthalimide functional phenol, 2-(2-hydroxyphenyl) isoindole-1,3-dione (oPP), was obtained by reacting o-aminophenol and phthalic anhydride in acetic acid. Two monofunctional ortho-phthalimide containing benzoxazine monomers (oPP-fa and oPP-pa) were then synthesized using the Mannich reaction based on raw materials of oPP, furfurylamine/propargylamine and paraformaldehyde in toluene. The structures of benzoxazine monomers were confirmed by FT-IR and 1H NMR spectroscopies. We also investigated effects of cross-linkable functionalities on curing behaviors as well as their corresponding polymerization mechanisms. The activation energies of oPP-fa and oPP-pa were calculated by Kissinger and Ozawa equations based on DCS measurements with different heating rates. It demonstrates that the exothermic peak temperature of oPP-pa is located at 178.5 °C, which is much lower than that of oPP-fa (223.3 °C). The alkyne group in oPP-pa plays a catalytic effect role in reducing the ring-opening polymerization temperature of the oxazine ring. Moreover, the thermogravimetric analyzer (TGA) was used to evaluate thermal properties of the obtained polybenzoxazine thermosets. Both thermosets exhibited improved thermal stability compared with some other reported monobenzoxazine-derived polybenzoxazines. [ABSTRACT FROM AUTHOR]

Corrosion is a major issue in steel applications for industrial purposes and other fields. In order to combat this, extensive research has been done on anti-corrosive materials, resulting in the development of various types of precursors. This work presents a polyurethane-based material that uses benzoxazine as a monomer. The synthesized monomer has been characterized extensively and systematically using NMR, UV-visible, and FT-IR spectroscopic methods. The monomer's electronic properties have been explained by DFT analysis, including FMO's analysis and molecular mapping studies. Moreover, three different ratios of polyurethane precursor have been used to create an anti-corrosive co-polymer material. The hygroscopic nature and gel formation of the synthesized polymer have been tested, demonstrating superior results. Additionally, the Tafel experiment was used to test the coated polymer's activity, and the results showed that it was more active than bare mild steel. [ABSTRACT FROM AUTHOR]

We report new nanocomposites with poly(benzoxazine-co-epoxy) matrix reinforced with 1 wt% graphene. Curabox 24-111, a benzoxazine resin was copolymerised with Epilok 60-566, a mixture of epoxy resins. Copolymerisation was also carried out in the presence of different graphene powders, namely, Nanene-001 and Nanene-002, used as single fillers and as mixture (relative weight ratio 70:30 or 30:70). DSC results showed the addition of either single filler caused a delay in polymerisation and an increase in the exothermic peak temperature of the curing reaction with a related reduction in ΔH Total. compared to the neat copolymer. Copolymerisation showed a 38% reduction and 24% increase in tensile modulus (E) compared to the neat polybenzoxazine and epoxy polymer, with a respective 18% and 30% reduction in tensile strength (TS). Nanocomposites with 0.7wt% Nanene-002 + 0.3 wt% Nanene-001 showed the highest increase of 35% in TS, a 1.6% reduction in E and 36% increase in elongation at break (EB) compared to the neat copolymer matrix. Samples with 1 wt% Nanene-001 showed the largest reduction of 21% in E, a 27% increase in TS and a 45% increase in EB. Additionally, TGA thermographs showed a 22°C increase in the onset of degradation (300°C–322°C) improving the materials thermal stability. [ABSTRACT FROM AUTHOR]

BackgroundDrugs taken during pregnancy can affect maternal and child health outcomes, but few studies have compared the safety and virological efficacy of different antiretroviral therapy (ART) regimens. We report the primary safety outcomes from enrolment up to 50 weeks post partum and a secondary virological efficacy outcome at 50 weeks post partum of three commonly used ART regimens for HIV-1.MethodsIn this multicentre, open-label, randomised, controlled, phase 3 trial, we enrolled pregnant women aged 18 years or older with confirmed HIV-1 infection at 14-28 weeks of gestation. Women were enrolled at 22 clinical research sites in nine countries (Botswana, Brazil, India, South Africa, Tanzania, Thailand, Uganda, the USA, and Zimbabwe). Participants were randomly assigned (1:1:1) to one of three oral regimens: dolutegravir, emtricitabine, and tenofovir alafenamide; dolutegravir, emtricitabine, and tenofovir disoproxil fumarate; or efavirenz, emtricitabine, and tenofovir disoproxil fumarate. Up to 14 days of antepartum ART before enrolment was permitted. Women with known multiple gestation, fetal anomalies, acute significant illness, transaminases more than 2·5 times the upper limit of normal, or estimated creatinine clearance of less than 60 mL/min were excluded. Primary safety analyses were pairwise comparisons between ART regimens of the proportion of maternal and infant adverse events of grade 3 or higher up to 50 weeks post partum. Secondary efficacy analyses at 50 weeks post partum included a comparison of the proportion of women with plasma HIV-1 RNA of less than 200 copies per mL in the combined dolutegravir-containing groups versus the efavirenz-containing group. Analyses were done in the intention-to-treat population, which included all randomly assigned participants with available data. This trial was registered with ClinicalTrials.gov, NCT03048422.FindingsBetween Jan 19, 2018, and Feb 8, 2019, we randomly assigned 643 pregnant women to the dolutegravir, emtricitabine, and tenofovir alafenamide group (n=217), the dolutegravir, emtricitabine, and tenofovir disoproxil fumarate group (n=215), and the efavirenz, emtricitabine, and tenofovir disoproxil fumarate group (n=211). At enrolment, median gestational age was 21·9 weeks (IQR 18·3-25·3), median CD4 count was 466 cells per μL (308-624), and median HIV-1 RNA was 903 copies per mL (152-5183). 607 (94%) women and 566 (92%) of 617 liveborn infants completed the study. Up to the week 50 post-partum visit, the estimated probability of experiencing an adverse event of grade 3 or higher was 25% in the dolutegravir, emtricitabine, and tenofovir alafenamide group; 31% in the dolutegravir, emtricitabine, and tenofovir disoproxil fumarate group; and 28% in the efavirenz, emtricitabine, and tenofovir disoproxil fumarate group (no significant difference between groups). Among infants, the estimated probability of experiencing at least one adverse event of grade 3 or higher by postnatal week 50 was 28% overall, with small and non-statistically significant differences between groups. By postnatal week 50, 14 infants whose mothers were in the efavirenz-containing group (7%) died, compared with six in the combined dolutegravir groups (1%). 573 (89%) women had HIV-1 RNA data available at 50 weeks post partum: 366 (96%) in the dolutegravir-containing groups and 186 (96%) in the efavirenz-containing group had HIV-1 RNA less than 200 copies per mL, with no significant difference between groups.InterpretationSafety and efficacy data during pregnancy and up to 50 weeks post partum support the current recommendation of dolutegravir-based ART (particularly in combination with emtricitabine and tenofovir alafenamide) rather than efavirenz, emtricitabine, and tenofovir disoproxil fumarate, when started in pregnancy.FundingNational Institute of Allergy and Infectious Diseases, the Eunice Kennedy Shriver National Institute of Child Health and Human Development, and the National Institute of Mental Health.

[Display omitted] Iodocyclization of N -(2-alkenylphenyl)carboxamides with acetoxybenziodoxolone/NaI system gives 4-iodomethyl- 4 H -3,1-benzoxazines with high efficiency. The process is triggered by the oxidation of NaI with acetoxybenziodo- xolone to afford iodine cation which is added to alkene moiety to form iodonium species, and the ultimate intra- molecular nucleophilic addition generates the final products. [ABSTRACT FROM AUTHOR]

BackgroundTreatment and prophylaxis options for neonatal HIV are limited. This study aimed to develop a population pharmacokinetic model to characterize the disposition of maraviroc in neonates to inform dosing regimens and expand available options.MethodsUsing maraviroc concentrations from neonates who received either a single dose or multiple doses of 8 mg/kg of maraviroc in the first 6 weeks of life, a population pharmacokinetic model was developed to determine the effects of age, sex, maternal efavirenz exposure and concomitant ARV therapy on maraviroc disposition. The final model was used in Monte Carlo simulations to generate expected exposures with recommended dosing regimens.ResultsA total of 396 maraviroc concentrations, collected in the first 4 days of life, at 1 week, at 4 weeks and at 6 weeks, from 44 neonates were included in the analysis. After allometrically scaling for weight, age less than 4 days was associated with a 44% decreased apparent clearance compared with participants 7 days to 6 weeks of life. There were no differences identified in apparent clearance or volume of distribution from ages 7 days to 6 weeks, sex, maternal efavirenz exposure or concomitant nevirapine therapy. Monte Carlo simulations with FDA-approved weight band dosing resulted in the majority of simulated patients (84.3%) achieving an average concentration of ≥75 ng/mL.ConclusionsWhile maraviroc apparent clearance is decreased in the first few days of life, the current FDA-approved maraviroc weight band dosing provides maraviroc exposures for neonates in the first 6 weeks of life, which were consistent with adult maraviroc exposure range. Maraviroc provides another antiretroviral treatment option for very young infants.

A new type of benzoxazine resin has been synthesized using a natural phenol source, guaiacol, and a biomass amines, furfuramine. The synthesis conditions were optimized; when the reaction molar ratio of guaiacol, furfuramine, and polyformaldehyde was 1:1:4, the highest synthetic yield was reached. The product was characterized via testing using transform infrared spectroscopy (FT-IR), gel permeation chromatography (GPC), mass spectrogram (MS), and nuclear magnetic resonance (1H-NMR) to confirm its molecular structure. A differential scanning calorimetry (DSC) test was conducted to analyze the thermodynamic properties of the product, and the results showed that the product decomposed and evaporated at around 180 °C, making it impossible to achieve self-curing. However, the prepared guaiacol-furfuramine benzoxazine resin (GFZ) can be blended and cured in certain proportions with bisphenol A-aniline oxazine resin (BAZ) as a GFZ/BAZ binary system (5:95, 10:90, 20:80, and 40:60). Dynamic mechanical analysis (DMA) test results showed that when the content of GFZ was 10%, the storage modulus of the copolymer resin was greatly improved. After conducting impact strength tests on the copolymer resin, it was found that the toughness of the copolymer resin had improved, and the maximum impact strength had increased by nearly three times. This indicates that the flexible long-chain structure in GFZ can effectively improve the toughness of the cured copolymer system. The reaction of active groups on benzoxazine molecules with other resins can not only improve the mechanical properties of their cured products, but also has important significance in the preparation of low-cost and environmentally friendly sustainable composite materials with excellent comprehensive performance. [ABSTRACT FROM AUTHOR]

A method has been developed for the synthesis of new fused 1,4-benzoxazine monoadducts of fullerene C60 by the reaction with 2-aminophenols (2-aminophenol, 2-amino-4-methylphenol, 3-amino-[1,1′-bi-phenyl]-4-ol) in the presence of LiOH and Pb(OAc)4. A probable reaction mechanism has been proposed. [ABSTRACT FROM AUTHOR]

The bifunctional phenol (BBC) was derived from a sustainable resource, viz., cardanol, which is utilized to prepare benzoxazines using five structurally different amines with paraformaldehyde through Mannich condensation. The molecular structure of the synthesized benzoxazines were confirmed by FTIR and 1H-NMR spectral analyses. The curing behavior of the benzoxazines was studied using DSC and among all the synthesized benzoxazines, BBC-imp exhibits lower curing temperature of 224 °C than that of others. The thermal stability of all the polybenzoxazines were analyzed using TGA and poly(BBC-a) was found to be better thermally stable than that of other polybenzoxazines. Poly(BBC-tfma) showed the highest value of water contact angle of 152° and the lowest value of dielectric constant of 4.50. All the synthesized BBC-based polybenzoxazines possess good anti-corrosion property with a protection efficiency of 99%. Data obtained from different studies suggest that the polybenzoxazines developed in the present work can be considered for possible use in the form of sealants, encapsulants, adhesives and coatings for microelectronics and other industrial applications for better performance. [ABSTRACT FROM AUTHOR]

Polybenzoxazines (Pbzs) are advanced forms of phenolic resins that possess many attractive properties, including thermal-induced self-curing polymerization, void-free polymeric products and absence of by-product formation. They also possess high Tg (glass transition temperature) and thermal stability. But the produced materials are brittle in nature. In this paper, we present our attempt to decrease the brittleness of Pbz by blending it with polyvinylalcohol (PVA). Benzoxazine monomer (Eu-Ed-Bzo) was synthesized by following a simple Mannich condensation reaction. The formation of a benzoxazine ring was confirmed by FT-IR and NMR spectroscopic analyses. The synthesized benzoxazine monomer was blended with PVA in order to produce composite films, PVA/Pbz, by varying the amount of benzoxazine monomer (1, 3 and 5 wt. % of PVA). The property of the composite films was studied using various characterization techniques, including DSC, TGA, water contact angle analysis (WCA) and SEM. WCA analysis proved that the hydrophobic nature of Pbz (value) was transformed to hydrophilic (WCA of PVA/Pbz5 is 35.5°). These composite films could play the same role as flexible electrolytes in supercapacitor applications. For this purpose, the composite films were immersed in a 1 M KOH solution for 12 h in order to analyze their swelling properties. Moreover, by using this swelled gel, a symmetric supercapacitor, AC//PVA/Pbz5//AC, was constructed, exhibiting a specific capacitance of 170 F g−1. [ABSTRACT FROM AUTHOR]

Lignin is an abundant and sustainable resource that exhibits numerous attractive functional properties as a reinforcing agent for benzoxazine‐based composites, due to its stiffness, thermal stability, and high carbon content. However, the low quality of lignin particles dispersions associated with the weak particles‐matrix interactions reduces the reinforcement capability. In this work, hybrid lignin/silica (NaLS/SiO2) nanoparticles were obtained from sodium lignosulfonate (NaLS) and tetraethylorthosilicate (TEOS) under basic conditions. The particles were characterized by transmission electron microscopy (TEM) confirming their spherical morphology and narrow nanometric‐size distributions. The hybrid particles were incorporated into conventional benzoxazine (BA‐a) and a difuran biobased benzoxazine (SA‐dfda) to prepare nanocomposites with different mass compositions (3, 5, and 10 wt%). Morphological, mechanical, dynamo‐mechanical, and thermal properties of the obtained composites were assessed. All the materials exhibited a homogenous filler dispersion that contributed to improve the reinforcement properties. Hybrid nanoparticles proved to be an interesting alternative as a filler in the benzoxazine matrix to prepare high‐performance thermosetting composites. [ABSTRACT FROM AUTHOR]

The objective of this study was to enhance the mechanical properties of 3D printed specimens in commercial photosensitive resin (PS‐resin) through blend‐thermosets using a benzoxazine monomer based on bisphenol A and a commercially available resin. Specifically, a benzoxazine‐based bisphenol A compound, 6,6‐(propane‐2,2‐diyl)bis(3‐cyclohexyl‐3,4‐dihydro‐2H‐benzo[e][1,3]oxazine), was successfully synthesized via the Mannich reaction. The synthesis involved paraformaldehyde, bisphenol A, and cyclohexylamine in a molar ratio of 4:1:2, respectively. To prepare the blend‐thermosets, a stereolithography 3D printer (SLA) was utilized, combining the PS‐resin with varying amounts of the benzoxazine (ranging from 0 to 8 parts per hundred of resin, phr). The printed specimens were then subjected to a polymerization process by heating them at various temperatures ranging from 120 to 160°C in a hot air oven for 2 h, allowing the benzoxazine to undergo ring‐opening reaction and form the thermoset structure. Characterization of all the materials obtained, including the PS‐resin, benzoxazine, and the blend‐thermosets before and after heating, was conducted using techniques such as FT‐IR and DSC. This work also showcased a sample technique for verifying the ring‐opening of the benzoxazine ring. Additionally, the mechanical properties of the blend‐thermosets were evaluated through tests for tensile strength, elongation at break, modulus, and hardness. The addition of merely 2 phr of benzoxazine monomers and subsequent curing at 120°C resulted in a notable improvement in the mechanical properties. [ABSTRACT FROM AUTHOR]

To minimize the possible usage of petroleum resources in the field of production of benzoxazines, the sustainable biological monomer magnolol has been utilized to synthesize bio-polybenzoxazines. Magnolol-based bio-thermosetting benzoxazines were synthesized using four different bio-amines, which were characterized for hydrophobicity, anti-microbial activity, cytotoxicity and anti-corrosion activity. Structural characterisation of synthesized bio-polybenzoxazines was carried out by ATR-FTIR and 1H-NMR spectral analyzes. The polymerization behavior and thermal stability of synthesized magnolol-based monomers were studied by DSC and TGA analyzes, respectively. The TGA results indicate that poly(M-ffa) possesses excellent thermal stability with a char yield of 60% compared to that of other bio-thermosets. Anti-microbial studies suggest that M-oda exhibits the highest anti-microbial activity with inhibition zones of 25 and 20 mm against Staphylococcus aureus and Escherichia coli, respectively. As reported by an MTT assay, synthesized polybenzoxazines did not show any significant toxic effects on cell line 3T3-L1. It was observed that M-oda exhibits the least toxicity of 91.2% on 3T3-L1 cells at a minimum dosage of 5 μg mL−1. All synthesized bio-polybenzoxazines exhibit excellent hydrophobicity with values of water contact angle ranging from 143 to 148°. A poly(M-oda)-coated cotton fabric retains significant durability even after repeated washing. All synthesized bio-thermosets showed an outstanding anti-corrosion property with a protection efficiency of over 95%. Using data obtained from different studies, it is suggested that magnolol-based thermoset polybenzoxazines could potentially be used as coatings to protect structures under marine environments and in other medically related uses due to their inherent characteristics to resist the growth of pathogens, low toxic nature, close to superhydrophobic behavior, and corrosion-resistant properties. [ABSTRACT FROM AUTHOR]

This work describes the preparation of thermally curable benzoxazine-modified polyurethanes with pendant carboxylic acid moieties, which have potential as organic coatings with enhanced thermal stability and electrical insulation properties. Thermoplastic poly(urethane-co-benzoxazine)s (PUBs) were synthesized via the polyaddition reaction of a benzoxazine diol chain extender with isocyanate-terminated urethane oligomers made from poly(tetramethylene ether)glycol at various molecular weights, dimethylol propionic acid, and toluene diisocyanate. Spectroscopic methods were utilized to characterize the proposed structures of the starting materials and final polymeric coatings and confirmation of co-presence of urethane bonds and benzoxazine rings. The curing temperature of the cross-linked PUBs (XPUBs) was evaluated using differential scanning calorimetry analysis. A catalytic effect of free carboxylic acids was observed, resulting in a lowering of the curing temperature by up to 30 °C. The XPUBs exhibited excellent thermal stability and reduced flammability compared to common polyurethane due to the formation of phenolic cross-linked linkages. The tensile strength and modulus of the XPUBs were also improved, while the extensibility of the polymeric coatings was mostly preserved. The key parameters that determine the possible application of these materials as electrical insulator coatings were very promising. The XPUBs displayed high dielectric strength of up to 38 kV/mm, low dielectric constant of less than 3, and a dissipation factor of approximately 6. [ABSTRACT FROM AUTHOR]

With the rapid development of ultra‐large‐scale integrated circuits and aerospace, the demand for materials with excellent overall performances is on the rise. In this study, we have successfully synthesized novel main‐chain benzoxazine precursors ((BPA‐AD/dd1)main) containing both cycloaliphatic and aliphatic structures by employing adamantanediamine and Priamine 1074 for the first time, and their chemical structures and polymerization behaviors were characterized using Fourier transform infrared spectroscopy (FT‐IR), NMR spectroscopy (1H‐NMR) and differential scanning calorimetry (DSC). The results showed that the exothermic onset of the (BPA‐AD/dd1)main shifted to lower temperatures with an increasing molar ratio of Priamine 1074. Furthermore, the thermal properties, dielectric properties, surface hydrophobicity, and tensile properties of P(BPA‐AD/dd1)main films were explored via dynamic mechanical analysis (DMA), thermogravimetric analysis (TGA), contact angle measuring instrument, an impedance analyzer and universal testing machine. The molar ratio of Priamine 1074 and 1,3‐Bis(4‐anilino)‐adamantane (AD) significantly influenced the thermal properties, dielectric properties, and surface hydrophobicity of P(BPA‐AD/dd1)main. P(BPA‐AD 0.75)main exhibited a high Tg of 296.8°C, excellent dielectric properties (Dk = 2.58 and Df = 0.0055 @ 10 MHz), and large water contact angle as high as 105.8°, qualifying it as a potential candidate for interlayer materials in ultra‐large‐scale integrated circuits and resin matrix in high‐performance composites. [ABSTRACT FROM AUTHOR]

In an attempt to make polybenzoxazines more sustainable, a novel bio-based benzoxazine monomer namely Q-Bz was synthetized via the Mannich condensation reaction utilizing Quercetin, paraformaldehyde and aniline. The chemical structure of the monomer was confirmed by 1H nuclear magnetic resonance (1H NMR) and Fourier transform infrared spectroscopies (FTIR). The curing behaviour was studied by differential scanning calorimetry (DSC) and the polymerization process was investigated by FTIR. The obtained results showed very low melting and polymerization temperatures (73 and 183°C, respectively) and the disappearance of the oxazine ring absorption bands due to the ring opening polymerization of the monomers. Afterwards, the cured bio-based thermoset, referred to as PQ-Bz, was obtained and its thermal stability and thermo-mechanical properties were also assessed by DSC and thermogravimetric analysis (TGA). As expected the newly developed thermoset exhibited high thermal stability along with excellent processability. Indeed, the results showed that PQ-Bz had a relatively high Tg of approximately 280°C, with a 53% char yield at 800°C, 5% and 10% weight reduction temperature (T5% and T10%) values of 349 and 373°C, respectively. These findings demonstrate the potential of the novel bio-based benzoxazine monomer as a sustainable alternative to traditional petroleum-based thermosets in high performance applications. [ABSTRACT FROM AUTHOR]

As a new type of thermosetting resin, polybenzoxazine resin (PBz) has the advantages of flexible molecular design, excellent thermal stability, and mechanical properties. It has application potential in many fields such as aerospace, hydrophobic flame retardant, anti‐corrosion, antibacterial, and electronic communication. Unlike traditional thermosetting resins, PBz can be made with natural renewable resources in addition to petrochemical raw materials. At present, PBz has synthesized monomers from renewable resources and made breakthroughs in raw material sources and performance improvement. In this work, the preparation methods and research progress of bio‐based benzoxazine (BOZ) with different phenol sources and amine sources in the past 10 years are reviewed. The existing shortcomings and improvement methods of PBz functional materials are analyzed, and the future research direction of bio‐based PBz is prospected. [ABSTRACT FROM AUTHOR]

Herein, an evaluation of the initial step of benzoxazine polymerization is presented by mass spectrometry, with a focus on differentiating the phenoxy and phenolic products formed by distinct pathways of the cationic ring opening polymerization (ROP) mechanism of polybenzoxazine formation. The use of infrared multiple photon dissociation (IRMPD) and ion mobility spectrometry (IMS) techniques allows for differentiation of the two pathways and provides valuable insights into the ROP mechanism. The results suggest that type I pathway is favored in the initial stages of the reaction yielding the phenoxy product, while type II product should be observed at later stages when the phenoxy product would interconvert to the most stable type II phenolic product. Overall, the findings presented here provide important information on the initial step of the benzoxazine polymerization, allowing the development of optimal polymerization conditions and represents a way to evaluate other multifunctional polymerization processes. [ABSTRACT FROM AUTHOR]

Sustainable methodologies, such as mechanochemical mixers, have revolutionized the way compounds are synthesized in minimal time and with better yields. In this work, a series of latest 4th generation benzoxazine monomers were synthesized via a facile, highly scalable, efficient mechanochemical ball-milling process, making them more viable than those synthesized via traditional synthesis route. The 4th generation benzoxazine (BZ) monomers contained 100% biosynthons (vanillin, ortho-vanillin and furfuryl amine) and were purified without strenuous separation techniques. We found that the variation in the nature of aryl substitution (with and without phenolic–OH) at the reactive oxazine C2 centre governs the polymerization temperature, volatilization of monomers, kinetics of polymerization, thermal and mechanical properties. As expected, the control monomer without inherent phenolic–OH showed a high polymerization temperature and the advantages offered by vanillin regioisomers facilitated the polymerization with minimal volatile release. The latent catalytic effect in the monomer was confirmed by both temperature-dependent NMR and SCXRD studies. Interestingly, distal phenolic–OH was found to be more labile and polymerized easily at a lower temperature than when it was present at the ortho-position. Additionally, the former monomer structure led to a well-defined polymer network with an appreciable Tg (116 °C) and thermal stability (Tmax of 348 °C and char yield of 36%). Furthermore, it also revealed an excellent storage modulus and good adhesion properties compared to many classical petroleum-based polybenzoxazines. Overall, we showcased the viability of employing the benefits of copolymerizing two generations of benzoxazines at low temperature and explored this new class of latest benzoxazine monomers as greener adhesives with improved stability to enable future designing and open up the possibility of using them in several practical and innovative applications. [ABSTRACT FROM AUTHOR]

Benzoxazine resin shows great potential as matrix for high performance composites, possessing good processabilty, dielectric property, mechanical property, and thermal properties, but its further application is limited by low crosslinking density and poor curing activity, especially for mono‐cyclic benzoxazines. In this work, melamine, a tertiary amine with a stable triazine structure, was introduced into the aldehyde‐containing mono‐cyclic benzoxazine, in order to achieve higher crosslinking density, higher curing activity, and better thermal properties. The chemical structure of prepolymers was verified by Fourier transform infrared spectroscopy (FTIR), 1H nuclear magnetic resonance (1H NMR) spectra, the curing behavior was investigated by differential scanning calorimetry, the thermal properties of polymers were studied by thermogravimetric analysis (TGA) and thermal mechanical analysis (TMA). It was found that the introduction of trifunctional melamine (MA) could lower curing temperature and promote the curing degree. Additionally, a proper amount of MA could increase the crosslinking density and thermal properties of the resultant polybenzoxazine. For example, poly(BZ‐3MA) showed the highest thermal stability with the temperature at 5% weight loss (Td5) of 415°C, carbon residue (Yc) of 67.7%, 23°C, and 2.9% higher than those of poly(BZ). Moreover, the glass transition temperature of poly(BZ‐5MA) reached 204.06°C, 36.51°C higher than that of poly(BZ). [ABSTRACT FROM AUTHOR]

A synthetic pathway to a novel 4-aryl-3,4-dihydro-2H-1,4-benzoxazine scaffold was developed and a series of compounds based on the scaffold were synthesised as potential anticancer agents. The 4-aryl-substituted compounds were prepared via Buchwald–Hartwig cross-coupling between substituted bromobenzenes and various 1,4-benzoxazines, which in turn were generated from a cascade hydrogenation and reductive amination one-pot reaction. These analogues exhibited moderate to good potency against various cancer cell lines. Structure–activity relationship analysis indicated that the inclusion of hydroxyl groups on ring A and ring B was beneficial to biological activity, while having a para-amino group on ring C significantly enhanced potency. Molecule 14f displayed the most potent anticancer activity (IC50 = 7.84–16.2 µM against PC-3, NHDF, MDA-MB-231, MIA PaCa-2, and U-87 MG cancer cell lines), indicating its potential as a lead compound for further structural optimisation. All the synthesised compounds were fully characterised with NMR, HMRS, and IR. The novel benzoxazine scaffold described in this study holds promise and deserves further in-depth studies. [ABSTRACT FROM AUTHOR]

A series of di-functional benzoxazine (BZ) monomers was synthesized, specifically the double-decker silsesquioxane (DDSQ) cage structure (DDSQ-BZ). Comparative analyses were conducted between DDSQ-BZ monomers and the most commonly utilized bisphenol A-functionalized bifunctional benzoxazine (BPA-BZ) monomer. DDSQ-BZ compounds possess better thermal properties such as high char yield and high thermal decomposition temperature (Td10) after thermal ring-opening polymerization (ROP) because the inorganic DDSQ cage nanostructure features a nano-reinforcement effect. In addition, blending inorganic DDSQ-BZ compounds with epoxy resin was explored to form organic/inorganic hybrids with enhanced thermal and mechanical properties following thermal ROP. The improvement in mechanical properties is primarily attributed to the network structure formed by the cross-linking between DDSQ-BZ and the epoxy resin during thermal ROP, as well as hydrogen bonding interactions formed between the hydroxyl groups generated during thermal ROP and the Si-O-Si bonds in the DDSQ structure. [ABSTRACT FROM AUTHOR]

The cardo tetrafunctional benzoxazines (BZ-aP-ffa, P-aP-ffa and BBA-aP-ffa) were synthesized from bis-phenols (phenolphthalein, bisphenol-Z and bisphenol-BA), paraformaldehyde, aminophenol and furfurylamine under appropriate experimental conditions. Their structural, thermal, hydrophobic, morphology and dielectric properties were characterized using modern analytical methods. Thermal studies indicate that the poly(P-aP-ffa) possesses better thermal stability (char yield 61%) than that of other two polybenzoxazines, viz. poly(BZ-aP-ffa) and poly(BBA-aP-ffa) (char yield 50 and 56%, respectively). Polybenzoxazine (P-ap-ffa) composites reinforced using varied weight percentages (10, 20, 30, 40 and 50 wt%) of GPTMS-functionalized vermiculite were prepared and the properties studied and compared with those of neat benzoxazine matrices. The values of water contact angle of neat poly(BZ-aP-ffa), poly(BBA-aP-ffa) and poly(P-aP-ffa) are found to be 142°, 141° and 142°, respectively, while that of vermiculite-reinforced poly(P-aP-ffa) composites have a water contact angle of 135° regardless of vermiculite content. A similar study indicated that the values of dielectric constant of neat polybenzoxazine matrix, 10, 20, 30, 40 and 50 wt% of GPTMS-functionalized vermiculite-reinforced poly(P-ap-ffa) composites are 3.34, 2.11, 2.01, 1.92, 1.86 and 1.84, respectively. The value of the dielectric constant is appreciably lowered to the extent of an ultra-low-k level, when vermiculite concentration increases. Results indicated that benzoxazines and composites developed in the present work can be used in the form of sealants for printed circuit boards in the field of microelectronics. [ABSTRACT FROM AUTHOR]

In the current study, an isothermal compression molding process was used to develop enhanced green composites made from alkali‐treated pine nut shell particles (TPS) reinforced in fully bio‐driven benzoxazine (VB) and epoxy (EP) copolymer. Reinforcement with varying weight percent (wt%) of bio‐filler enhanced the properties of composites. Composites showed a rise of 75.9 MPa, 5.8 GPa, and 5.1 kJ/m2 in flexural strength, modulus, and impact strength, respectively. Thermal stability shows that composites can endure higher temperatures and hence be classified as flame‐retardant materials. The dynamic mechanical analysis (DMA) confirms that composites exhibit higher storage modulus, which was elevated to 77.6% compared to the unfilled copolymer. FTIR spectroscopy analyzed the structure of copolymerized composites. Further, finite element analysis (FEA) was observed for the prepared composites. A transversely isotropic composite material model was created with the properties of composites, and stress analysis was observed. FEA outcomes are in good agreement with experimental findings. [ABSTRACT FROM AUTHOR]