Reaction-Induced Liquid Crystalline Polybenzoxazine Bearing Aromatic Amide Side Branches.

In this study, a nematic phase structure is incorporated into polybenzoxazine to increase its thermal conductivity. A simple route for the synthesis of a thermally conductive polybenzoxazine containing liquid crystalline (LC) structure by grafting oligomeric p-sulfophenylene-terephthalamide (PSTA) is offered. Benzoxazine monomer of pHBA-da is synthesized via Mannich reaction of p-hydroxy benzoic acid, p-formaldehyde, and dodecyl amine. After ring-opening polymerization, the oligomer benzoxazine of OBZ─COOH is obtained. The OBZ─COOH/PSTA mixture is prepared by mixing PSTA with OBZ─COOH. Afterward, the grafted copolymer is named OBZ─PSTA copolymer. The liquid crystalline behavior of OBZ─COOH/PSTA is studied by polarized optical microscopy and small angle X-ray scattering analysis. The results show that the OBZ─PSTA forms the LC structure during isothermal and non-isothermal curing. The LC structure displays a floral textured nematic phase. The phase formation is induced by an amidation reaction. Due to the grafts of LC PSTA, the thermal conductivity of OBZ─PSTA is 0.296 W m-1 K-1 , which is 26% greater than OBZ─COOH. The glass transition temperature (Tg ) of OBZ─PSTA is 241 °C. The 5% (Td5 ) and 10% weight loss temperatures (Td10 ) of OBZ─PSTA are 346 and 362 °C, respectively.

Tunable Syngas Formation at Industrially Relevant Current Densities via CO2 Electroreduction and Hydrogen Evolution over Ni and Fe-derived Catalysts obtained via One-Step Pyrolysis of Polybenzoxazine Based Composites.

Simultaneous electroreduction of CO2 and H2O to syngas can provide a sustainable feed for established processes used to synthesize carbon-based chemicals. The synthesis of MOx/M-N-Cs (M = Ni, Fe) electrocatalysts reported via one-step pyrolysis that shows increased performance during syngas electrosynthesis at high current densities with adaptable H2/CO ratios, e.g., for the Fischer-Tropsch process. When embedded in gas diffusion electrodes (GDEs) with optimized hydrophobicity, the NiOx/Ni-N-C catalyst produces syngas (H2/CO = 0.67) at -200 mA cm-2 while for the FeOx/Fe-N-C syngas production occurs at ≈-150 mA cm-2. By tuning the electrocatalyst's microenvironment, stable operation for >3 h at -200 mA cm-2 is achieved with the NiOx/Ni-N-C GDE. Post-electrolysis characterization revealed that the restructuring of the catalyst via reduction of NiOx to metallic Ni NPs still enables stable operation of the electrode at -200 mA cm-2, when embedded in an optimized microenvironment. The ionomer and additives used in the catalyst layer are important for the observed stable operation. Operando Raman measurements confirm the presence of NiOx during CO formation and indicate weak adsorption of CO on the catalyst surface.

Highly Thermally Stable, Reversible, and Flexible Main Chain Type Benzoxazine Hybrid Incorporating Both Polydimethylsiloxane and Double-Decker Shaped Polyhedral Silsesquioxane Units through Diels-Alder Reaction.

This work synthesizes a new bifunctional furan derivative (PDMS-FBZ) through a sequence of hydrosilylation of nadic anhydride (ND) with polydimethylsiloxane (PDMS), reaction of the product with p-aminophenol to form PDMS-ND-OH, and its subsequent Mannich reaction with furfurylamine and CH2 O. Then, the main chain-type copolymer PDMS-DABZ-DDSQ is prepared through a Diels-Alder (DA) cycloaddition of PDMS-FBZ with the bismaleimide-functionalized double-decker silsesquioxane derivative DDSQ-BMI. Fourier transform infrared (FTIR) and nuclear magnetic resonance (NMR) spectroscopy confirm the structure of this PDMS-DABZ-DDSQ copolymer; differential scanning calorimetry (DSC), thermogravimetric analysis (TGA), and dynamic mechanical analysis (DMA) reveal it to have high flexibility and high thermal stability (Tg = 177 °C; Td10 = 441 °C; char yield = 60.1 wt%); contact angle measurements reveal a low surface free energy (18.18 mJ m-2 ) after thermal ring-opening polymerization, because the inorganic PDMS and DDSQ units are dispersed well, as revealed using scanning electron microscopy (SEM) and transmission electron microscopy (TEM). This PDMS-DABZ-DDSQ copolymer possesses reversible properties arising from the DA and retro-DA reactions, suggesting its possible application as a functional high-performance material.

Phosphorus-Containing Polybenzoxazine Aerogels with Efficient Flame Retardation and Thermal Insulation.

Bisphenol A type benzoxazine (Ba) monomers and 10-(2, 5-dihydroxyphenyl)-10- hydrogen-9- oxygen-10- phosphine-10- oxide (DOPO-HQ) were employed to prepare flame retardant and heat insulated polybenzoxazine (PBa) composite aerogels. The successful preparation of PBa composite aerogels was confirmed by Fourier transform infrared (FTIR), X-ray photoelectron spectroscopy (XPS), and scanning electron microscopy (SEM). The thermal degradation behavior and flame-retardant properties of the pristine PBa and PBa composite aerogels were investigated with thermogravimetric analysis (TGA) and cone calorimeter. The initial decomposition temperature of PBa decreased slightly after incorporating DOPO-HQ, increasing the char residue amount. The incorporation of 5% DOPO-HQ into PBa led to a decrease of 33.1% at the peak of the heat-release rate and a decrease of 58.7% in the TSP. The flame-retardant mechanism of PBa composite aerogels was investigated by SEM, Raman spectroscopy, and TGA coupled with infrared spectrometry (TG-FTIR). The aerogel has advantages such as a simple synthesis procedure, easy amplification, lightweight, low thermal conductivity, and good flame retardancy.

Microporous Carbon and Carbon/Metal Composite Materials Derived from Bio-Benzoxazine-Linked Precursor for CO2 Capture and Energy Storage Applications.

There is currently a pursuit of synthetic approaches for designing porous carbon materials with selective CO2 capture and/or excellent energy storage performance that significantly impacts the environment and the sustainable development of circular economy. In this study we prepared a new bio-based benzoxazine (AP-BZ) in high yield through Mannich condensation of apigenin, a naturally occurring phenol, with 4-bromoaniline and paraformaldehyde. We then prepared a PA-BZ porous organic polymer (POP) through Sonogashira coupling of AP-BZ with 1,3,6,8-tetraethynylpyrene (P-T) in the presence of Pd(PPh3)4. In situ Fourier transform infrared spectroscopy and differential scanning calorimetry revealed details of the thermal polymerization of the oxazine rings in the AP-BZ monomer and in the PA-BZ POP. Next, we prepared a microporous carbon/metal composite (PCMC) in three steps: Sonogashira coupling of AP-BZ with P-T in the presence of a zeolitic imidazolate framework (ZIF-67) as a directing hard template, affording a PA-BZ POP/ZIF-67 composite; etching in acetic acid; and pyrolysis of the resulting PA-BZ POP/metal composite at 500 °C. Powder X-ray diffraction, thermogravimetric analysis, scanning electron microscopy, transmission electron microscopy, and Brunauer-Emmett-Teller (BET) measurements revealed the properties of the as-prepared PCMC. The PCMC material exhibited outstanding thermal stability (Td10 = 660 °C and char yield = 75 wt%), a high BET surface area (1110 m2 g-1), high CO2 adsorption (5.40 mmol g-1 at 273 K), excellent capacitance (735 F g-1), and a capacitance retention of up to 95% after 2000 galvanostatic charge-discharge (GCD) cycles; these characteristics were excellent when compared with those of the corresponding microporous carbon (MPC) prepared through pyrolysis of the PA-BZ POP precursors with a ZIF-67 template at 500 °C.

Enhanced CO2 capturing over ultra-microporous carbon with nitrogen-active species prepared using one-step carbonization of polybenzoxazine for a sustainable environment.

Nitrogen-enriched porous carbon has been a promising material for CO2 capture in the recent decades. To enhance the performance of CO2 adsorption, both an N-active site and the textural properties are crucial determinants. Herein, ultra-microporous carbon with N-active species was prepared using two synthesis procedures: 1) one-step carbonization of a polybenzoxazine (PBZ) precursor at 800 °C, and 2) the CO2 activation process at 900 °C. The activated porous carbon had the higher specific surface area (943 m2/g) and a total pore volume (0.51 cm3/g) compared to un-activated porous carbon (335 m2/g and 0.19 cm3/g, respectively). In addition, the presence of N-active species such as pyridine-N, secondary-N, pyridone-N, and oxide-N in the carbon structures could be clearly observed in the high-resolution XPS spectra. The CO2 adsorption measurement was performed at 30 and 50 °C under a wide range of pressures (1-7 bar). The maximum amount of CO2 uptake was ca. 3.59 mmol/g for the activated porous carbon operated at 30 °C and a CO2 pressure of 7 bar, which was due to the high specific surface area and the large micropore volume. Specifically, carbon with a 3D interconnected pore structure, derived from the sol-gel process of the PBZ precursor, exhibited good structural stability and consequently led to better absorption capability under the high atmospheric pressure of CO2. The enhanced CO2 adsorption capability for the as-prepared porous carbon was based on two mechanisms: physisorption as a result of textural properties and chemisorption as a result of the acid-base interaction between the basic N functionality and the acidic CO2 gas. All results suggested that ultra-microporous carbon with N-active species prepared from polybenzoxazine is a promising adsorbent for CO2 capture and storage, which can be used at a wide range of pressures and in many applications e.g. flue gas adsorption and natural gas production.

Synthesis of self-curable polysulfone containing pendant benzoxazine units via CuAAC click chemistry.

Synthesis, characterization, and properties of new thermally curable polysulfone containing benzoxazine moieties in the side chain were investigated. First, chloromethylation and subsequent azidation processes were performed to form polysulfone containing pendant clickable azide groups. Independently, antagonist 3,4-dihydro-3-(prop-2-ynyl)-2H-benzoxazine was prepared by using paraformaldehyde, phenol and propargylamine. The following copper(I) catalyzed azide-alkyne cycloaddition click reaction was applied to obtain self-curable polysulfone with pendant benzoxazine units. The polymer and intermediates at various stages were characterized by 1H-NMR, 13C-NMR and FT-IR spectroscopies. The thermal properties and curing behavior of final polymer were investigated by differential scanning calorimetry and thermal gravimetric analysis. Compared to the neat polysulfone, the obtained polymers exhibited thermally more stable polymers.

Powder Catalyst Fixation for Post-Electrolysis Structural Characterization of NiFe Layered Double Hydroxide Based Oxygen Evolution Reaction Electrocatalysts.

Highly active electrocatalysts for the oxygen evolution (OER) reaction are in most cases powder nanomaterials, which undergo substantial changes upon applying the high potentials required for high-current-density oxygen evolution. Owing to the vigorous gas evolution, the durability under OER conditions is disappointingly low for most powder electrocatalysts as there are no strategies to securely fix powder catalysts onto electrode surfaces. Thus reliable studies of catalysts during or after the OER are often impaired. Herein, we propose the use of composites made from precursors of polybenzoxazines and organophilically modified NiFe layered double hydroxides (LDHs) to form a stable and highly conducting catalyst layer, which allows the study of the catalyst before and after electrocatalysis. Characterization of the material by XRD, SEM, and TEM before and after 100 h electrolysis in 5 m KOH at 60 °C and a current density of 200 mA cm-2 revealed previously not observed structural changes.

Advanced Electrochemical Monitoring of Carbendazim Fungicide in Foods Using Interfacial Superassembly of NRPC/NiMn Frameworks.

A simple, sensitive and reliable sensing system based on nitrogen-rich porous carbon (NRPC) and transition metals, NRPC/Ni, NRPC/Mn and NRPC/NiMn was developed and successfully applied as electrode materials for the quantitative determination of carbendazim (CBZ). The synergistic effect of NRPC and bimetals with acceptable pore structure together with flower-like morphology resulted in producing a highly conductive and interconnected network in NRPC/NiMn@GCE, which significantly enhanced the detection performance of CBZ. The electrochemical behavior investigated by cyclic voltammetry (CV) showed improved CBZ detection for NRPC/NiMn, due to the controlled adsorption/diffusion process of CBZ by the NRPC/NiMn@GCE electrode. The influences of various factors such as pH, NRPC/NiMn concentration, CBZ concentration and scan rate were studied. Under optimal conditions, 0.1 M phosphate-buffered saline (PBS) with a pH of 7.0 containing 30 µg/mL NRPC/NiMn, a favourable linear range detection of CBZ from 5 to 50 µM was obtained. Moreover, a chronoamperometric analysis showed excellent repeatability, reproducibility and anti-interfering ability of the fabricated NRPC/NiMn@GCE sensor. Furthermore, the sensor showed satisfactory results for CBZ detection in real samples with acceptable recoveries of 96.40-104.98% and low RSD values of 0.25-3.45%.

Research progress on polybenzoxazine aerogels: Preparation, properties, composites and hybrids fabrication, applications.

The unremitting pursuit of high-performance and multifunctional materials has consistently propelled modern industries forward, stimulating research and motivating progress in related fields. In such materials, polybenzoxazine (PBz) aerogel, which combines the virtues of PBz and aerogel, has attracted salient attention recently, emerging as a novel research focus in the realm of advanced materials. In this review, the preparation scheme, microscopic morphology, and fundamental characteristics of PBz aerogels are comprehensively summarized and discussed in anticipation of providing a clear understanding of the correlation between preparation process, structure, and properties. The effective strategies for enhancing the performance of PBz aerogels including composite fabrication and hybridization are highlighted. Moreover, the applications of PBz-based aerogels in various domains such as adsorption (including wastewater treatment, CO2 capture, and microwave adsorption), thermal insulation, energy storage as well as sensors are covered in detail. Furthermore, several obstacles and potential directions for subsequent research are delineated with a view to surmounting the prevailing constraints and achieving a realization of the shift from experimental exploration to practical applications.

Partially Bio-Based Benzoxazine Monomers Derived from Thymol: Photoluminescent Properties, Polymerization Characteristics, Hydrophobic Coating Investigations, and Anticorrosion Studies.

In this work, four thymol-based benzoxazines were synthesized using four primary amines with different chain lengths, namely methylamine, ethylamine, 1-propylamine, and 1-butylamine, which are then named T-m, T-e, T-p, and T-b, respectively. The optical properties of the synthesized thymol-based benzoxazines were examined via the photoluminescent study of their solutions in acetone. The results show that all the prepared benzoxazines emitted blue light with the maximum wavelengths from 425 to 450 nm when irradiated by the excitation wavelengths from 275 to 315 nm. The maximum excitation wavelengths are found to be 275 nm. The polymerization of the thymol-based benzoxazines is triggered by heat treatments with different conditions (160, 180, and 200 °C for 1 h). According to the FTIR results, the heat-curing process introduces a presence of the OH peak, of which intensity increases as the curing temperature increases. Thermal decompositions of thymol-based benzoxazines regarding TGA analyses reveal the enhancement of thermal stability of the benzoxazines with respect to the N-substituent chain length, as significantly observed the change in the first thermal decomposition at temperature ranged from 253 to 260 °C. Synthesized benzoxazine derivatives are further employed to coat the substrate, e.g., the glass slides. The investigation of the water contact angle shows that the coating of the benzoxazines onto the surface improves the hydrophobicity of the substrate, resulting in the enlargement of the contact angle from 25.5° to 93.3°. Moreover, the anticorrosion performance of the polybenzoxazine coatings is examined using potentiodynamic polarization techniques. The results illustrate the anticorrosion efficiency of the thymol-based polybenzoxazine up to 99.99%. Both hydrophobic and electrochemical studies suggest the feasibility for employing benzoxazines in anticorrosion coating applications.

High-Performance Supercapacitor Electrodes from Fully Biomass-Based Polybenzoxazine Aerogels with Porous Carbon Structure.

In recent years, polybenzoxazine aerogels have emerged as promising materials for various applications. However, their full potential has been hindered by the prevalent use of hazardous solvents during the preparation process, which poses significant environmental and safety concerns. In light of this, there is a pressing need to explore alternative methods that can mitigate these issues and propel the practical utilization of polybenzoxazine aerogels. To address this challenge, a novel approach involving the synthesis of heteroatom self-doped mesoporous carbon from polybenzoxazine has been devised. This process utilizes eugenol, stearyl amine, and formaldehyde to create the polybenzoxazine precursor, which is subsequently treated with ethanol as a safer solvent. Notably, the incorporation of boric acid in this method serves a dual purpose: it not only facilitates microstructural regulation but also reinforces the backbone strength of the material through the formation of intermolecular bridged structures between polybenzoxazine chains. Moreover, this approach allows ambient pressure drying, further enhancing its practicability and environmental friendliness. The resultant carbon materials, designated as ESC-N and ESC-G, exhibit distinct characteristics. ESC-N, derived from calcination, possesses a surface area of 289 m2 g-1, while ESC-G, derived from the aerogel, boasts a significantly higher surface area of 673 m2 g-1. Furthermore, ESC-G features a pore size distribution ranging from 5 to 25 nm, rendering it well suited for electrochemical applications such as supercapacitors. In terms of electrochemical performance, ESC-G demonstrates exceptional potential. With a specific capacitance of 151 F g-1 at a current density of 0.5 A g-1, it exhibits superior energy storage capabilities compared with ESC-N. Additionally, ESC-G displayed a more pronounced rectangular shape in its cyclic voltammogram at a low voltage scanning rate of 20 mV s-1, indicative of enhanced electrochemical reversibility. The impedance spectra of both carbon types corroborated these findings, further validating the superior performance of ESC-G. Furthermore, ESC-G exhibits excellent cycling stability, retaining its electrochemical properties even after 5000 continuous charge-discharge cycles. This robustness underscores its suitability for long-term applications in supercapacitors, reaffirming the viability of heteroatom-doped polybenzoxazine aerogels as a sustainable alternative to traditional carbon materials.

Weldable, Reprocessable, and Water-resistant Polybenzoxazine Vitrimer Crosslinked by Dynamic Imine Bonds.

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.

High-Performance Supercapacitors Using Compact Carbon Hydrogels Derived from Polybenzoxazine.

Polybenzoxazine (PBz) aerogels hold immense potential, but their conventional production methods raise environmental and safety concerns. This research addresses this gap by proposing an eco-friendly approach for synthesizing high-performance carbon derived from polybenzoxazine. The key innovation lies in using eugenol, ethylene diamine, and formaldehyde to create a polybenzoxazine precursor. This eliminates hazardous solvents by employing the safer dimethyl sulfoxide. An acidic catalyst plays a crucial role, not only in influencing the microstructure but also in strengthening the material's backbone by promoting inter-chain connections. Notably, this method allows for ambient pressure drying, further enhancing its sustainability. The polybenzoxazine acts as a precursor to produce two different carbon materials. The carbon material produced from the calcination of PBz is denoted as PBZC, and the carbon material produced from the gelation and calcination of PBz is denoted as PBZGC. The structural characterization of these carbon materials was analyzed through different techniques, such as XRD, Raman, XPS, and BET analyses. BET analysis showed increased surface of 843 m2 g-1 for the carbon derived from the gelation method (PBZGC). The electrochemical studies of PBZC and PBZGC imply that a well-defined morphology, along with suitable porosity, paves the way for increased conductivity of the materials when used as electrodes for supercapacitors. This research paves the way for utilizing heteroatom-doped, polybenzoxazine aerogel-derived carbon as a sustainable and high-performing alternative to traditional carbon materials in energy storage devices.

Flexible Composite Hydrogels Based on Polybenzoxazine for Supercapacitor Applications.

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.

Polymer Composite Hydrogel Based on Polyvinyl Alcohol/Polyacrylamide/Polybenzoxazine Carbon for Use in Flexible Supercapacitors.

Polymer gels are cross-linked polymer networks swollen by a solvent. These cross-linked networks are interconnected to produce a three-dimensional molecular framework. It is this cross-linked network that provides solidity to the gel and helps to hold the solvent in place. The present work deals with the fabrication of polybenzoxazine carbon (PBzC)-based gels that could function as a solid electrode in flexible supercapacitors (SCs). With the advantage of molecular design flexibility, polybenzoxazine-based carbon containing different hetero-atoms was synthesized. A preliminary analysis of PBzC including XRD, Raman, XPS, and SEM confirmed the presence of hetero-atoms with varying pore structures. These PBz-carbons, upon reaction with polyvinyl alcohol (PVA) and acrylamide (AAm), produced a composite polymer hydrogel, PVA/poly (AAm)/PBzC. The performance of the synthesized hydrogel was analyzed using a three-electrode system. PVA/poly (AAm)/PBzC represented the working electrode. The inclusion of PBzC within the PVA/poly (AAm) matrix was evaluated by cyclic voltammetry and galvanostatic charge/discharge measurements. A substantial increase in the CV area and a longer charge/discharge time signified the importance of PBzC inclusion. The PVA/poly (AAm)/PBzC electrode exhibited larger specific capacitance (Cs) of 210 F g-1 at a current density of 0.5 A g-1 when compared with the PVA/poly (AAm) electrode [Cs = 92 F g-1]. These improvements suggest that the synthesized composite hydrogel can be used in flexible supercapacitors requiring light weight and wearability.

Molecular dynamics simulations of hydrogen-bonded network structures of polybenzoxazines in the gas phase and aqueous solution.

The crucial role of the amine functional group at the Mannich bridge of polybenzoxazines (PBZs) has been reported to be responsible for their hydrogen-bonded network structures. However, they have not been thoroughly studied in an aqueous solution and at the atomistic level. In this study, molecular dynamics simulations were applied to investigate the formation of hydrogen bond interactions of PBZs prepared from bisphenol A/methylamine (m-PBZ), bisphenol A/aniline-based (a-PBZ), and bisphenol A/2-(methylamino)ethylamine (e-PBZ). Based on the simulation results, the hydrogen-bonded network structures of the PBZs interfered with water molecules, leading to less compaction of the PBZ structure in the aqueous solution. The hydrogen bonding species of the m-PBZ and a-PBZ structures consisted of the -OH…N (Mannich) and -OH…O intramolecular interactions. However, for e-PBZ, the -OH…O species was not present, but the 2-(ethylamino)ethylamine substituent formed more hydrogen bonding species than those of m-PBZ and a-PBZ. Additionally, the intermolecular hydrogen bond interactions of the PBZs and water molecules were not detected in any of the aqueous solution simulations.

Effect of Fiber Characteristics on the Structure and Properties of Quartz Fiber Felt Reinforced Silica-Polybenzoxazine Aerogel Composites.

Fiber-reinforced aerogel composites are widely used for thermal protection. The properties of the fibers play a critical role in determining the structure and properties of the final aerogel composite. However, the effects of the fiber's characteristics on the structure and properties of the aerogel composite have rarely been studied. Herein, we prepared quartz fiber felt-reinforced silica-polybenzoxazine aerogel composite (QF/PBSAs) with different fiber diameters using a simple copolymerization process with the ambient pressure drying method. The reasons for the effects of fiber diameter on the structure and properties of the aerogel composites were investigated. The results showed that the pore structure of the aerogel composites was affected by the fiber diameter, which led to significant changes in the mechanical behavior and thermal insulation performance. At room temperature, pore structure and density were found to be the main factors influencing the thermal conductivity of the composites. At elevated temperatures, the radiative thermal conductivity (λr) plays a dominant role, and reducing the fiber diameter suppressed λr, thus decreasing the thermal conductivity. When the QF/PBSAs were exposed to a 1200 °C butane flame, the PBS aerogel was pyrolyzed, and the pyrolysis gas carried away a large amount of heat and formed a thermal barrier in the interfacial layer, at which time λr and the pyrolysis of the PBS aerogel jointly determined the backside temperature of the composites. The results of this study can provide valuable guidance for the application of polybenzoxazine aerogel composites in the field of thermal protection.

Recent Progress of Low Dielectric and High-Performance Polybenzoxazine-Based Composites.

With the rapid advancement of intelligent electronics, big data platforms, and other cutting-edge technologies, traditional low dielectric polymer matrix composites are no longer sufficient to satisfy the application requirements of high-end electronic information materials, particularly in the realm of high integration and high-frequency, high-speed electronic communication device manufacturing. Consequently, resin-based composites with exceptional low dielectric properties have garnered unprecedented attention. In recent years, benzoxazine-based composites have piqued the interest of scholars in the fields of high-temperature-resistant, low dielectric electronic materials due to their remarkable attributes such as high strength, high modulus, high heat resistance, low curing shrinkage, low thermal expansion coefficient, and excellent flame retardancy. This article focuses on the design and development of modification of polybenzoxazine based on low dielectric polybenzoxazine modification methods. Studies on manufacturing polybenzoxazine co-polymers and benzoxazine-based nanocomposites have also been reviewed.

Ring Opening Polymerization Used for the Production of VOC Free High-Performance Ecofriendly Novel PBZ/PDA/CeO2 Nanocomposites.

This study analyzed the fabrication and characterization of polybenzoxazine/polydopamine/ceria as tertiary nanocomposites. To this end, a new benzoxazine monomer (MBZ) was fabricated based on the well-known Mannich reaction of naphthalene-1-amine, 2-tert-butylbenzene-1,4-diol and formaldehyde under ultrasonic-assisted process. Polydopamine (PDA) was used as dispersing polymer nanoparticles and surface modifier for CeO2 by in-situ polymerization of dopamine with the assistance of ultrasonic waves. Then, nanocomposites (NC)s were manufactured by in-situ route under thermal conditions. The FT-IR and 1H-NMR spectra confirmed the preparation of the designed MBZ monomer. The FE-SEM and TEM results showed the morphological aspects of prepared NCs and illustrated the distribution of CeO2 NPs in the polymer matrix. The XRD patterns of NCs showed the presence of crystalline phases of nanoscale CeO2 in an amorphous matrix. The TGA results reveal that the prepared NCs are classified as thermally stable materials.