Mannich Condensation Reaction Research Articles

Evaluation of optical, thermal and hydrophobic properties of sustainable stilbene-based benzoxazines for high-performance utilization

Currently there is a growing interest in the field of photosensitive benzoxazines synthesized from sustainable raw materials. An attempt has been made to synthesize nine structurally different benzoxazines through Mannich condensation reaction. The formation of the expected structure of the synthesized benzoxazine monomers were ascertained using spectroscopic methods. The ring-opening polymerization of benzoxazines was studied using DSC and found that THS-imp benzoxazine monomer exhibits the lowest value of curing temperature (Tp) of 179oC than the rest of the benzoxazine monomers. Thermal stability of polybenzoxazines were analyzed using thermogravimetric analyzer. Among the different polybenzoxazines studied, poly(THS-a) possesses the higher thermal stability with char yield of 53% than that of other benzoxazines. The band gap values of benzoxazines calculated from optical studies are ranged between 3.92-4.71 eV. The hydrophobic behavior of the polybenzoxazines assessed using the water contact angle obtained from goniometer for both neat polymer matrix and benzoxazine coated cotton fabric. Results from the water contact angle infer that the benzoxazines coated cotton fabric exhibited 152o, which shows the superhydrophobic behavior. The corrosion resistant properties of all the polybenzoxazines coated over MS specimen has been tested. Among them poly(THS-pfsa) and poly(THS-imp) have higher Icorr value and corrosion inhibition efficiency of 99%. Data obtained from different studies indicate that the benzoxazines developed from sustainable stilbene can be utilized in the form of coatings, adhesives, sealants, and matrices for composites for wide range of industrial and engineering applications, where high thermal stability and are required.

Synthesis and molecular structure exploration of novel piperidin-4-one imine derivatives combined with DFT and X-ray: A new class of antioxidant and anti-inflammatory agents

Inflammation is one of the pertinent responses of the body, depending mainly on the process and factors involved in combating the oxidative species produced either by any infection or failure of the antioxidant pathways. In search of new compounds to exhibit antioxidant and anti-inflammatory activity here, we have successfully reported the synthesis of three novel compounds of Piperidin-4-one skeleton by adopting simple and convenient methods. Compound 1, (3, 3-dimethyl-2, 6-bis(3,4,5-trimethoxyphenyl) piperidin-4-one) was synthesized by one-pot Mannich condensation reaction having good yield (88 %). Furthermore in the next step highly functionalized imine derivatives, Compound 2 (3,3-dimethyl-2,6-bis (3,4,5-trimethoxyphenyl) piperidine-4-one) hydrazine carbothioamide) and Compound 3 (3,3-dimethyl-2,6-bis(3,4,5-trimethoxyphenyl) piperidin-4-one oxime) were prepared by the condensation reaction with thiosemicarbazide and hydroxylamine hydrochloride with compound 1, respectively. The structure of the compounds has been deduced by the combined use of modern spectroscopic and single crystal x-ray diffraction (XRD) techniques. in-silico ADMET studies predict pharmacokinetic properties and showed that compounds are non toxic on vital organs. The optimized geometry and reactivity parameters of compounds were further calculated based on the B3LYP/6-31G (d, p) density functional theory (DFT). The negative values of chemical potential follow the trend as 2 (−0.2101) >3 (−0.2198) >1(-0.2233) signifies that all compounds are reactive in nature as evident from in-vitro antioxidant and anti-inflammatory response were determined by using the DDPH assay and protein denaturation methods respectively. Compounds possess good radical scavenging activity having IC 50 values 30.392 μM (2), 37.802 (1) μM, and 72.285 (3) μM, and anti-inflammatory response in same manner indicating that 2 (71.3 %) is more active than compound 1 (43.5 %) and 3 (39.3 %) marking them as a potential antioxidant and anti-inflammatory agents.

Construction of Benzoxazine-linked One-Dimensional Covalent Organic Frameworks Using the Mannich Reaction.

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.

Construction of Benzoxazine‐linked One‐Dimensional Covalent Organic Frameworks Using the Mannich Reaction

AbstractCovalent 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

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.

Development of NIR light-responsive shape memory composites based on bio-benzoxazine/bio-urethane copolymers reinforced with graphene.

In this work, shape memory polymers (SMPs) were developed from a combination of a bio-based benzoxazine (BZ) monomer and polyurethane prepolymer (PU-prepolymer), both derived from bio-based raw materials. The bio-based BZ monomer (V-fa monomer) was synthesized through a Mannich condensation reaction using vanillin, paraformaldehyde, and furfurylamine. The bio-based PU-prepolymer was obtained by reacting palm oil polyol (MW = 1400 Da) and toluene diisocyanate (TDI). To investigate the curing behavior of poly(V-fa/urethane), with a mass ratio of 50/50, differential scanning calorimetry was employed. The structure of the resulting poly(V-fa/urethane) was confirmed using Fourier transform infrared spectroscopy. Furthermore, the synthesized V-fa/urethane copolymers with weight ratios of 70/30, 60/40, 50/50 and 40/60 were observed to exhibit shape memory behaviors induced by near-infrared irradiation (808 nm). Poly(V-fa/urethane), specifically with a mass ratio of 50/50, demonstrated superior shape memory performance. It exhibited a remarkable capacity to retain the temporary shape up to 90%, achieve 99% shape recovery, and exhibit a recovery time of 25 s. The shape memory properties were further improved with the addition of 3 wt% graphene nanoplatelets (GNPs), exhibiting an improvement in the shape fixity value to 94%, and shape recovery time value to 16 s. Moreover, our findings suggest that 60/40 poly(V-fa/urethane) reinforced with 3 wt% GNPs possesses favorable characteristics for applications as multiple SMPs, with shape fixity values of 97% and 94%, and shape recovery values of 96% and 89% for the first and second shapes, respectively.

Construction of three-dimensional porous organic polymers with enhanced CO2 uptake performance via solid-state thermal conversion from tetrahedral benzoxazine-linked precursor

Porous organic polymers (POPs) with three-dimensional (3D) linkages have drawn great interest due to their potential applications in separation, adsorption, and sensing fields. Herein, a new 3D benzoxazine (BZ)-linked porous organic polymer (TPM-BZ-Py POP) was synthesized by linking a tetrahedral benzoxazine (TPM-BZ-Br4) with tetraethynylpyrene (Py-T) via Sonogashira coupling. Specifically, the synthesis of the tetrahedral benzoxazines with four oxazine rings in a single monomer involved the utilization of Schiff base formation, NaBH4 reduction as well as Mannich condensation reactions. To confirm the chemical structure of the benzoxazine monomers and their corresponding polybenzoxazines, Fourier transform infrared (FTIR), proton nuclear magnetic resonance (1H NMR), and carbon nuclear magnetic resonance (13C NMR) spectroscopy techniques were employed. The pore volume and specific surface area of the 3D TPM-BZ-Py POP were determined through N2 adsorption/desorption isotherms, and they were found to be 0.52 cm3/g and 185 m2/g, respectively. In addition, the solid-state chemical transformation occurred during thermal ring-opening polymerization (ROP), and the resulting 3D poly(TPM-BZ-Py) POP displayed higher CO2 capture ability (1.81 mmol/g) compared with TPM-BZ-Py POP (0.60 mmol/g) at room temperature. Such enhancement observed in poly(TPM-BZ-Py) POP was proposed to be caused by the formation of phenolic units and Mannich bridges within the polymer network by taking into consideration the structural transformation during the ring-opening polymerization (ROP). The functionalities in poly(TPM-BZ-Py) have great potential to interact with CO2 molecules through strong intermolecular hydrogen bonding or acid/base interactions, which further supports the benefit of incorporating oxazine rings into POP frameworks.

Supramolecular self-assembly of EGCG-selenomethionine nanodrug for treating osteoarthritis

Osteoarthritis (OA) has emerged as a significant health concern among the elderly population, with increasing attention paid to ferroptosis-induced OA in recent years. However, the prolonged use of nonsteroidal anti-inflammatory drugs or corticosteroids can lead to a series of side effects and limited therapeutic efficacy. This study aimed to employ the Mannich condensation reaction between epigallocatechin-3-gallate (EGCG) and selenomethionine (SeMet) to efficiently synthesize polyphenol-based nanodrugs in aqueous media for treating OA. Molecular biology experiments demonstrated that EGCG-based nanodrugs (ES NDs) could effectively reduce glutathione peroxidase 4 (GPX4) inactivation, abnormal Fe2+ accumulation, and lipid peroxidation induced by oxidative stress, which ameliorated the metabolic disorder of chondrocytes and other multiple pathological processes triggered by ferroptosis. Moreover, imaging and histopathological analysis of the destabilization of the medial meniscus model in mice confirmed that ES NDs exhibiting significant therapeutic effects in relieving OA. The intra-articular delivery of ES NDs represents a promising approach for treating OA and other joint inflammatory diseases.

Bimetallic Al(III) Compounds as Catalysts for the Synthesis of Biodegradable Polyesters and Polycarbonates

AbstractEthylenediamine bridged benzoxazine proligands were synthesized by a modified Mannich condensation reaction. The reaction of the proligands with two equivalents of AlMe3 resulted in the formation of dinuclear Al(III) compounds in high yield and purity. When the ligand binds to the Al(III) center, it forms two separate six‐membered N,O‐chelates with the two Al atoms that resembles the N‐alkylated salan moiety. Each aluminum atom adopts a distorted tetrahedral geometry as revealed from the single‐crystal X‐ray diffraction studies of 1. The catalytic activity of these aluminum compounds was investigated towards the ROP of rac‐LA and ROCOP of epoxides (PO, CHO, tBuGE) and phthalic anhydride and ROCOP of CHO with CO2. These aluminum compounds showed notable catalytic activity towards the ROP and ROCOP reactions in the absence of cocatalyst.

Synthesis of Bio-Based Polybenzoxazine and Its Antibiofilm and Anticorrosive Activities.

Candida albicans are highly widespread pathogenic fungi in humans. Moreover, its developed biofilm causes serious clinical problems, leading to drug failure caused by its inherent drug tolerance. Hence, the inhibition of biofilm formation and virulence characteristics provide other means of addressing infections. Polymer composites (PCs) derived from natural products have attracted increasing interest in the scientific community, including antimicrobial applications. PCs are a good alternative approach to solving this challenge because of their excellent penetration power inside biofilms. The main objectives of this study were to synthesize a novel curcumin-based polybenzoxazine polymer composite (poly(Cu-A) PC) using Mannich condensation reaction and evaluate their potency as an antibiofilm and anticorrosive candidate against C. albicans. In addition, their anticorrosive efficacy was also explored. PC exhibited significant antibiofilm efficacy versus C. albicans DAY185 by the morphologic changing of yeast to hyphae, and>90% anticorrosive efficacy was observed at a higher dose of PC. These prepared PC were safe in vivo against Caenorhabditis elegans and Raphanus raphanistrum. The study shows that a polybenzoxazine polymer composite has the potential for controlling biofilm-associated fungal infections and virulence by C. albicans, and opens a new avenue for designing PCs as antifungal, anticorrosive agents for biofilm-associated fungal infections and industrial remediation.

Synthesis of bio‐diamine derived main‐chain type benzoxazine resins with low surface free energy

AbstractA series of bio‐based fluorin‐free main‐chain type benzoxazine precursors were synthesized via bisphenol A/bisphenol F/diallyl bisphenol A, Priamine 1074 and paraformaldehyde by Mannich condensation reaction. Chemical structures of these obtained main‐chain type precursors were characterized by FT‐IR and NMR spectroscopies. The polymerization processes were studied by differential scanning calorimeter (DSC) and in situ FT‐IR analysis. Besides, the contact angle and surface free energy of polybenzoxazine coatings were measured by water contact angle instrument. Moreover, the thermal performance of the resulting polybenzoxazine thermosets were evaluated by dynamic mechanical analyzer (DMA) and thermogravimetric analysis (TGA). Through the above various measurements, the newly developed bio‐based main‐chain type polybenzoxazine resins show good thermal stability and low surface free energy, suggesting great potential for applications as high‐performance resin matrix.

Photosensitive Benzoxazines Derived from Divanillidene Cyclopentanone/Cyclohexanone for Hydrophobic and Optical Applications

AbstractAn attempt is made to synthesize two series of photosensitive benzoxazines using a divanillidene cyclopentanone/divanillidene cyclohexanone (DVCP/DVCH) core containing structurally different amines such as aniline, cyclohexylamine, 4‐aminobenzonitrile, furfurylamine, and stearylamine with paraformaldehyde through Mannich condensation reaction. The molecular structure of the synthesized benzoxazines is confirmed from Fourier transform infrared and proton nuclear magnetic resonance (1H‐NMR) spectroscopic analyses. The curing behavior and thermal stability of the benzoxazines are analyzed using differential scanning calorimetry and thermogravimetric analysis, respectively. Both DVCP and DVCH core benzoxazines are cured by thermal and photocuring methods. Cyclopentanone core containing benzoxazines exhibit higher thermal stability when compared with that of most of the cyclohexanone core containing benzoxazines. The DVCP and DVCH core benzoxazines exhibit excellent hydrophobic behavior and good self‐extinguishing properties. The photolysis of DVCP‐ and DVCH‐based benzoxazines indicates that the α,β‐unsaturated ketone moiety in the main chain dimerizes through 2π+2π cycloaddition reaction to form a cyclobutane derivative and leads to crosslinking. The photosensitivity of the benzoxazine decreases with an increase in the size of the cycloalkanone ring. The band gap energy (Eg) calculated from absorption spectra is found between 3.0 and 3.29 eV.

Synthesis and characterization of new quinolinyl phenol based polybenzoxazine: thermal stability, hydrophobicity and corrosion resistant properties

A new class of quinolinyl phenol-based benzoxazines (QP-a, QP-cha, QP-2eha) were synthesized by using quinolinyl phenol [4-(6-chloro-4-phenylquinoline-2-yl)phenol] with three structurally distinct amines, namely aniline (a), cyclohexylamine (cha), and 2-ethylhexylamine (2eha) through Mannich condensation reaction using an appropriate solvent and reaction conditions. By using FTIR and 1H-NMR spectroscopy methods, the molecular structures of the benzoxazines QP-a, QP-cha, and QP-2eha were identified. From the differential scanning calorimetry (DSC) analysis, the exothermic peak maximum of benzoxazine monomers viz., QP-a, QP-cha, QP-2eha were observed at 218, 202 and 187 °C respectively. The thermogram obtained from TGA studies the amount of char yield obtained for poly(QP-a), poly(QP-cha) and poly(QP-2eha) were found to be 45, 24, and 32%, respectively. The value of limiting oxygen index (LOI) for polybenzoxazines was calculated using the value of percentage char yield obtained from TGA studies infer that these benzoxazines exhibit good flame-retardant characteristics. Data from water contact angle studies ascertain that these samples possess good hydrophobic properties in the range of 129–138°. Results from corrosion studies infer that the mild steel specimens coated with these benzoxazines were found to be more stable and offer better surface protection against corrosion under the conditions studied.

Simultaneously improving the fire safety and mechanical properties of epoxy resin with iron phosphonated grafted polyethylenimine

Endowing epoxy resins with enhanced flame retardancy, toughness and strength as well as glass transition temperature (Tg) simultaneously is a big challenge in academia and industry fields. Herein, a hyperbranched multifunctional additive (PEIP-Fe) was designed, which was prepared through a Mannich condensation reaction of polyethyleneimine and phosphorous acid and followed by combining with ferric. When 3 wt% of PEIP-Fe was incorporated into epoxy resin, the impact strength, tensile strength, flexural strength and Tg were all enhanced due to the multiple toughening mechanisms, good compatibility and the increased cross-linking density. Simultaneously, fire safety such as flame retardancy, smoke suppression and toxicity were all improved. The flame-retardant mechanism was verified in both condensed-phase and gas-phase by catalytic charring and free radical scavenging, forming compact and continuous char layer and releasing phosphorus-containing species respectively. This work provides new thinking for the design of multifunctional and high efficiency additives for epoxy resin.

Synthesis and characterization of chalcone based benzoxazine-magnetite nanocomposites

Here, we proposed an approach to develop magnetic chalcone based benzoxazine using different contents of magnetite nanoparticles. A chalcone containing benzoxazine was prepared from 3-(4-hydroxyphenyl)-1-phenylprop-2-en-1-one), stearyl amine and paraformaldehyde through Mannich condensation reaction in a cosolvent of ethanol/toluene (1/1)(v/v). The chemical structure of the prepared benzoxazine monomer was confirmed by FTIR and 1H NMR. Both monomer and monomer mixed with different contents of magnetite were exposed to UV irradiation to induce dimerization via [2p + 2p] cycloaddition followed by thermal curing of oxazine moiety. The crystal structure of magnetite nanoparticles was studied by X-ray diffraction (XRD) analysis. Scanning electron microscope (SEM) was used to examine the surface morphology of the resulted materials. The average size of magnetite nanoparticles was determined by transmission electron microscope (TEM) to be 30–40 nm. The magnetization properties of these materials were measured by vibrating sample magnetometer (VSM). The thermal properties of thermosets were evaluated and compared with nanocomposites using TGA and DSC. The thermosets exhibited good thermal stability and improved with increasing the magnetite contents in the feed.

Renewable biomass resources to access halogen- and phosphorus-free flame retardant thermosets with ultra-low heat release capacity

Developing high-performance thermosets with outstanding anti-flammability from sustainable resources has attracted increasing attention due to both safety and environmental concerns. Herein, a novel bio-based bis-benzoxazine thermosetting resin has been successfully synthesized via Mannich condensation reaction from paraformaldehyde and natural renewable resources, aesculetin and furfurylamine. Detailed information of the chemical structure for this bio-benzoxazine is analyzed by nuclear magnetic resonance (NMR) and Fourier transform infrared (FT-IR) spectroscopies, elemental analysis and high-resolution mass spectrometry (HR-MS). In addition, the resin polymerization behavior is investigated by differential scanning calorimetry (DSC) and in situ FT-IR analyses. Notably, the fully polymerized bio-thermoset shows high thermal stability with Td10 of 407 °C and Tg of 261 °C, and extremely low flammability with heat release capacity (HRC) value of 2.51 J·g−1·K−1 and total heat release (THR) value of 0.78 kJ·g−1. Overall, the current work provides a facile and sustainable synthetic route access to a series of halogen- and phosphorus-free nonflammable bio-thermosets based on smart benzoxazine chemistry.

KINETIC MODELING OF MAIN-CHAIN BENZOXAZINE POLYMER SYNTHESIS STUDIED USING POLYMATH: CASE STUDY

This study reports kinetics of benzoxazine synthesis of main chain type benzoxazine polymer (MCBP(BA-a)), which was derived using Mannich condensation reaction of bisphenol-A with formaldehyde and aniline. The chemical structural of MCBP(BA-a) was confirmed by Fourier-transform infrared (FTIR) and proton nuclear magnetic resonance spectroscopy (1H NMR). Kinetics of benzoxazine (BZ) synthesis was theoretically studied using Polymath Software. The synthesis of BZ precursors consist of two main reactions. Reaction of amine with formaldehyde, and then followed by the reaction of phenolic compound with the intermediate component of the first reaction. Therefore, the effect of the reaction constant ratio (

Synthesis, Characterization and anti-corrosion property of GPTMS functionalized mesoporous silica (F-SBA-15) incorporated aliphatic chain containing polybenzoxazine nanocomposites

ABSTRACT The (F-SBA-15) dispersed aliphatic chain containing polybenzoxazine nanocomposite coating materials having better corrosion resistance property has been developed. The new aliphatic chain containing polybenzoxazines is synthesized from n-octylamine, bisphenol-A and paraformaldehyde involving mannich condensation reaction. The structure of polymer and monomer was examined with the help of proton magnetic resonance1NMR spectroscopy and Fourier transform IR spectroscopy. The polybenzoxazine composites were prepared n-octylamine, bisphenol-A and paraformaldehyde and using varying percentages (1, 5, 10 wt%) of GPTMS functionalized mesoporous silica (F-SBA-15) through in situ polymerization process. The polybenzoxazine nanocomposites were characterized using X-ray powder diffraction and scanning electron microscopy. In addition Surface treated (F-SBA-15) dispersed polybenzoxazine nanocomposites has been prepared and studied for their N2 adsorption/desorption, water contact angle, dielectric behavior and anticorrosive properties. The polymer nanocomposites subjected to the highest water contact angle noted at 115° was attained for 10 wt% (F-SBA-15). The value of dielectric constant for neat, 1, 5, 10 wt% (F-SBA-15) incorporated polymer nanocomposites was noted as 4.7, 3.8, 2.9, and 2.1, respectively. The corrosion resistant capacity of BZ/(F-SBA-15), on mild steel specimens, was noticeably higher than that of conventional polybenzoxazine due to the hydrophobic aliphatic chain segments and porous structure of (F-SBA-15).

Structural and thermal analysis of bio-based polybenzoxazine derived from liquefied empty fruit bunch (EFB) via solventless method

A bio-based polybenzoxazine demonstrating excellent thermal properties was synthesized using phenolic and its derivatives derived from liquefaction of empty fruit bunch (EFB) fibres to fulfill green chemistry principles. The liquefied EFB was reacted with furfurylamine and paraformaldehyde through a Mannich condensation reaction. For comparison purposes, a guaiacol polybenzoxazine was synthesized using guaiacol as a phenolic component reacted with similar amine and aldehyde. Both types of polybenzoxazine synthesized from liquefied EFB and guaiacol were named L-fa and G-fa, respectively. The structural analysis was performed using Fourier-Transform Infrared (FTIR) and proton Nuclear Magnetic Resonance (1H NMR). It was observed that the synthesis of benzoxazine groups for both types of polybenzoxazine was successful with the formation of the oxazine ring. Thermal stability showed that liquefied EFB polybenzoxazine (L-fa) has higher thermal stability above 360 °C compared to guaiacol-polybenzoxazine (G-fa), which is higher is 280 °C due to the complex structure of the lignin derivative in the liquefied EFB. For polymerization behavior, L-fa exhibit two exothermic peaks compared to three peaks on G-fa, indicating that L-fa is more reactive due to additional polymerizable sites present in L-fa. This work widens the synthesis route for the preparation of bio-based benzoxazine derived from oil palm waste which will perpetuate outstanding evolution towards the sustainable development of the bio-based polymeric industry.

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

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