Sesamol-based polybenzoxazines for ultra-low-k, high-k and hydrophobic coating applications

Sesamol-based polybenzoxazines, their dielectric behavior, and superhydrophobic properties for microelectronic insulation applications.

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.

Selective photocatalytic oxidation of sulfides with dioxygen over carbazole-fluorene conjugated microporous polymers

One sustainable concept emerges to implement the selective oxidation of sulfides with dioxygen (O₂) at ambient conditions and has received increasing attention. As such, three donor-acceptor (D-A) type conjugated microporous polymers (CMPs) were connected via robust CC bonds prepared from FeCl₃-promoted polymerization of monomers of 3,6-di(9H-carbazol-9-yl)-9H-fluorene with the 9H position of the fluorene moiety occupied by 1,1'-biphenyl-, difluoro-, or keto- group, furnishing 9,9'-(9,9'-spirobi[fluorene]-2,7-diyl)-bis-9H-carbazole-CMP (SFC-CMP), 9,9'-(9,9-difluoro-9H-fluorene-2,7-diyl)bis(9H-carbazole)-CMP (FFC-CMP), and 2,7-di(carbazol-9-yl)-fluoren-9-one-CMP (OFC-CMP), respectively. These three carbazole-fluorene CMPs could implement blue light-driven highly selective oxidation of sulfides into sulfoxides with O₂ in methanol (CH₃OH). Intriguingly, the SFC-CMP imparted the best photocatalytic activity for selective oxidation of sulfides in a broad scope. Besides, the SFC-CMP photocatalyst could be fully recovered even outperforming the fresh one. This work highlights that the properties of CMPs could be regulated by the D-A units like carbazole-fluorene to execute selective chemical transformations ambiently.

Synthesis of Spiro[benzo[d][1,3]oxazine-4,4'-isoquinoline]s via [4+1+1] Annulation of N-Aryl Amidines with Diazo Homophthalimides and O2

Synthesis of spiro[benzo[d][1,3]oxazine-4,4'-isoquinoline]s through a unique [4+1+1] annulation of N-aryl amidines with diazo homophthalimides and O₂ is presented. This unprecedented spirocyclization reaction features readily obtainable substrates, structurally and pharmaceutically attractive products, a cost-free and clean oxygen source, sustainable reaction medium, tolerance of a broad spectrum of functional groups, and an interesting reaction mechanism based on sequential C(sp²)-H/C(sp³)-H bond cleavage and oxygen insertion.

Novel self-promoted phthalonitrile monomer with siloxane segments: synthesis, curing kinetics, and thermal properties

In the study, we synthesize a novel auto-catalytic phthalonitrile monomer containing siloxane segments and secondary amino groups. The phthalonitrile monomer has good processability. And the new polymer shows a higher Tg.

Synthesis and thermal properties of phenol- and amine-capped main-chain benzoxazine oligomers with multiple methyl substitutions

A series of main-chain benzoxazine oligomers with different methyl substitutions are successfully synthesized. Chemical structures are analyzed by Fourier transform infrared spectroscopy, proton nuclear magnetic resonance spectroscopy, and gel permeation chromatography. Effects of methyl substitutions on chemical shifts of protons in oxazine ring and thermal properties, including glass transition temperature, thermal stability, and char yield, are discussed. The influences of methyl substitutions on different positions are demonstrated: (i) substitution on phenols induces obvious increase in curing temperature while substitution on amine does not show apparent impact; (ii) substitution at different positions results in T g variation, following the sequence of none-substitution > substitution at end-capping > substitution on diamines in main-chain > substitution on bisphenols in main-chain; and (iii) substitution at end-capping would cause apparent deterioration in thermal stability while substitution on diamines in main-chain would benefit thermal stability and char yield. Experimental results and related explanations are provided in detail.

Novel Routes in Transformation of Lignocellulosic Biomass to Furan Platform Chemicals: From Pretreatment to Enzyme Catalysis

The constant depletion of fossil fuels along with the increasing need for novel materials, necessitate the development of alternative routes for polymer synthesis. Lignocellulosic biomass, the most abundant carbon source on the planet, can serve as a renewable starting material for the design of environmentally-friendly processes for the synthesis of polyesters, polyamides and other polymers with significant value. The present review provides an overview of the main processes that have been reported throughout the literature for the production of bio-based monomers from lignocellulose, focusing on physicochemical procedures and biocatalysis. An extensive description of all different stages for the production of furans is presented, starting from physicochemical pretreatment of biomass and biocatalytic decomposition to monomeric sugars, coupled with isomerization by enzymes prior to chemical dehydration by acid Lewis catalysts. A summary of all biotransformations of furans carried out by enzymes is also described, focusing on galactose, glyoxal and aryl-alcohol oxidases, monooxygenases and transaminases for the production of oxidized derivatives and amines. The increased interest in these products in polymer chemistry can lead to a redirection of biomass valorization from second generation biofuels to chemical synthesis, by creating novel pathways to produce bio-based polymers.

Synthesis of novel allylamine-fluorene based benzoxazine and its copolymerization with typical benzoxazine: curing behavior and thermal properties

Poly(t-BF-sa-a) showed much better thermal properties and glass transition temperatures than traditional fluorene-based benzoxazine monomers.

Curing kinetics of phenolphthalein based polyphosphazene towards thermal stability and flame retardancy of polybenzoxazine

Phenolphthalein type polyphosphazene (PZPT) microspheres were synthesized by an ultrasound assisted precipitation polymerization method, and their structures were confirmed by scanning electron microscopy (SEM) and Fourier transform infrared (FTIR) spectroscopy. Benzoxazine/PZPT (Ba/PZPT) hybrid materials were fabricated and cured to prepare polybenzoxazine/PZPT (PBa/PZPT) composites. The effects of PZPT microspheres on the curing kinetics and behaviors of Ba were systematically analyzed and supported by differential scanning calorimetry (DSC) and in situ FTIR. The thermogravimetric (TGA) results demonstrated good thermal stability of the PBa composites incorporating PZPT. The peak of heat release rate and total heat release values of PBa/PZPT-5% composites obviously deceased by 57.8% and 17.3% compared to those of the pristine PBa. Moreover, the smoke released from the PZPT/PBa system significantly reduced with the loading of microspheres. Finally, the dynamical mechanical analysis results demonstrated that the T g of PBa flame retardant composites was approximately 210 °C, not affecting further applications of PBa composites.

Synthesis and characterization of siloxane-containing benzoxazines with high thermal stability

To understand the influence of phenyl substituents on silicon and to improve the glass transition temperature ( T g) and thermal stability, phenol/bis ( p-aminophenoxyl) dimethylsiloxane-based benzoxazine (P-adms), phenol/bis ( p-aminophenoxyl) methylphenylsiloxane-based benzoxazine (P-amps), and phenol/bis ( p-aminophenoxyl) diphenylsiloxane-based benzoxazine (P-adps) were designed and synthesized. The structure of the siloxane-containing benzoxazines were confirmed by proton and carbon nuclear magnetic resonance imaging and Fourier transform infrared spectra. The curing reaction of the obtained benzoxazines was studied by differential scanning calorimetry (DSC) and in situ infrared spectra. The influence of the aromatic content on the T g and thermal stability were investigated by modulated DSC and thermogravimetric analysis. Compared to aminopropylsiloxane-based benzoxazines, the bis ( p-aminophenoxyl) siloxane-based benzoxazines possessed relatively higher T g about 140°C due to the replacement of flexible propyl chain by phenoxyl chain. With increasing phenyl substituents on silicon, the polybenzoxazines possessed lower T g and higher thermal stability. It is notedthat the phenol/bis ( p-aminophenoxyl) diphenylsiloxane-based benzoxazine (P-adps) still has low viscosity despite high aromatic content due to the flexible ether linkage (Ar–O–Si).

Synthesis of Eugenol-Based Silicon-Containing Benzoxazines and Their Applications as Bio-Based Organic Coatings

In this work, several bio-based main-chain type benzoxazine oligomers (MCBO) were synthesized from eugenol derivatives via polycondensation reaction with paraformaldehyde and different diamine. Afterwards, their chemical structures were confirmed by Fourier Transform Infrared Spectroscopy (FT-IR) and Nuclear Magnetic Resonance Spectroscopy (1H-NMR). The curing reaction was monitored by Differential Scanning Calorimetry (DSC) and FT-IR. The polybenzoxazine films were prepared via thermal ring-opening reaction of benzoxazine groups without solvent, and their thermodynamic properties, thermal stability, and coating properties were investigated in detail. Results indicated that the cured films exhibited good thermal stability and mechanical properties, showing 10% thermal weight loss (Td10%) temperature as high as 408 °C and modulus at a room temperature of 2100 MPa as well as the glass transition temperature of 123 °C. In addition, the related coatings exhibited high hardness, excellent adhesion, good flexibility, low moisture absorption, and outstanding solvent resistance.

Synthesis of a Bisbenzylideneacetone-Containing Benzoxazine and Its Photo- and Thermally Cured Thermoset

A bis(4-hydroxybenzylidene)acetone/aniline-based benzoxazine (BHBA-a) was prepared from a bisbenzylidene-containing bisphenol, bis(4-hydroxybenzylidene)acetone (BHBA), aniline, and paraformaldehyde through Mannich condensation in a cosolvent of toluene/ethanol (2:1, v/v). The structure of BHBA-a was successfully confirmed by Fourier transform infrared and ¹H and ¹³C NMR spectra. According to the differential scanning calorimetry (DSC) thermogram of BHBA, an immediate exothermic peak after the melting peak was observed, suggesting that BHBA is thermally active. NMR data of thermally treated BHBA confirm that the immediate exothermic peak after melting of BHBA in the DSC thermogram is resulted from the curing of a double bond. UV and ¹H NMR spectra of BHBA-a show that the bisbenzylideneacetone moiety underwent dimerization through the [2π + 2π] cycloaddition. Therefore, two procedures were applied to cure BHBA-a. The first one was thermal curing of the double bond of bisbenzylideneacetone and oxazine moieties. The second one was photocuring of the bisbenzylideneacetone moiety, followed by thermal curing of the oxazine moiety. The thermal properties of thermosets were evaluated based on these two procedures. Thermosets of BHBA-a exhibit T _g as high as 318 °C for curing procedure 1 and 342 °C for curing procedure 2. These values are much higher than that of a traditional bisphenol/aniline-based benzoxazine thermoset. We conclude that the thermal curing of the double bond of bisbenzylideneacetone and photodimerization of bisbenzylideneacetone contributes to the good thermal properties.

Photo-sensitive benzoxazine II: chalcone-containing benzoxazine and its photo and thermal-cured thermoset

Chalcone-containing benzoxazine (BHP-a) was synthesized. Two procedures were applied to cure BHP-a, thermal curing of chalcone and oxazine moieties. Another one was photo curing the chalcone moiety, followed by thermal curing of the oxazine moiety.

Thermal properties of a series of tetrafunctional fluorene-based oxazines/P-a blends

A new series of aniline and aniline-mixed tetrafunctional fluorene-based oxazine monomers were synthesized using 2,7-hydroxy-9,9-bis-(4-hydroxyphenyl) fluorene, paraformaldehyde, and primary amines (including aniline or aniline mixed with n-butylamine or n-octylamine composition). Fourier transform infrared spectroscopy and proton nuclear magnetic resonance spectroscopy were used to characterize the structure of the monomers. The copolymers were obtained by adding the monomers into a typical monofunctional polybenzoxazine (phenol-aniline-based benzoxazine). Differential scanning calorimetry, thermogravimetric analysis, and dynamic mechanical analysis were performed to study the thermal properties of the copolymers. The copolymers exhibited high glass transition temperature values (164–201°C). A good thermal stability was also obtained with a 5% weight loss temperature over 355°C and high char yields at 800°C (42–50%).

Smart, Sustainable, and Ecofriendly Chemical Design of Fully Bio-Based Thermally Stable Thermosets Based on Benzoxazine Chemistry

A smart synthetic chemical design incorporating furfurylamine, a natural renewable amine, into a partially bio-based coumarin-containing benzoxazine is presented. The versatility of the synthetic approach is shown to be flexible and robust enough to be successful under more ecofriendly reaction conditions by replacing toluene with ethanol as the reaction solvent and even under solventless conditions. The chemical structure of this coumarin-furfurylamine-containing benzoxazine is characterized by FTIR, (1) H NMR spectroscopy and two-dimensional (1) H-(1) H nuclear Overhauser effect spectroscopy (2D (1) H-(1) H NOESY). The thermal properties of the resin toward polymerization are characterized by differential scanning calorimetry (DSC) and the thermal stability of the resulting polymers by thermogravimetric analysis (TGA). The results reveal that the furanic moiety induces a co-operative activating effect, thus lowering the polymerization temperature and also contributes to a better thermal stability of the resulting polymers. These results, in addition to those of natural renewable benzoxazine resins reviewed herein, highlight the positive and beneficial implication of designing novel bio-based polybenzoxazine and possibly other thermosets with desirable and competitive properties.

Synthesis of functionalized benzoxazines by copper-catalyzed C(sp3)–H bond functionalization of acetonitrile with olefinic amides

A Cu-mediated/catalyzed oxycyanomethylation reaction of olefinic amides with acetonitrile was developed for the synthesis of important benzoxazine derivatives.

A novel high performance oxazine derivative: design of tetrafunctional monomer, step-wise ring-opening polymerization, improved thermal property and broadened processing window

A novel tetrafunctional oxazine monomer containing benzoxazine and fluorene-oxazine was prepared for the first time using a Mannich condensation reaction of 2,7-dihydroxy-9,9-bis-(4-hydroxyphenyl)fluorene with paraformaldehyde and n-butylamine.

A curing system of benzoxazine with amine: reactivity, reaction mechanism and material properties

In addition to providing an acceleration effect on curing, suitable amines react with benzoxazine to form desired structures and improve the materials properties of the cured resins.

Preparation and characterization of fully renewable polybenzoxazines from monomers containing multi-oxazine rings

Fully renewable polybenzoxazines prepared from monomers with multi-oxazine rings shows reversible pH responsiveness, good thermal and mechanical performance.

Cardanol benzoxazines – interplay of oxazine functionality (mono to tetra) and properties

Cardanol, an agrowaste – solventless synthesis and processability of benzoxazine monomers. Tailoring the polymer properties as a function of oxazine functionality in the monomers.