Synthesis and Characterization of Partially Fluorinated Polybenzoxazine Resins Utilizing Octafluorocyclopentene as a Versatile Building Block

Modifying Polyvinylidene Chloride Resin with Fluorine Monomer and Cross-Linking Monomers

Modified polyvinylidene chloride (PVDC) resin was prepared using octafluoropentyl methacrylate and trimethylolpropane trimethacrylate as modifying monomers through seeded emulsion polymerization. The successful incorporation of octafluoropentyl methacrylate into the PVDC resin was confirmed by Fourier transform infrared spectroscopy (FTIR) and X-ray photoelectron spectroscopy (XPS) analyses. Scanning electron microscopy (SEM), energy dispersive spectroscopy (EDS) and XPS were utilized to investigate the element distribution in the modified monomer emulsion and the mechanism of monomer modification. The results demonstrated that the fluorine monomer was reacted in the resin, and mainly concentrated on the surface of the resin. The addition of octafluoropentyl methacrylate and trimethylolpropane trimethacrylate improved the water resistance of the resin. Compared to unmodified PVDC resin, the contact angle of the modified PVDC resin increased from 89.46° to 109.51°, and the water resistance at room temperature increased from 120 to 500 h. Furthermore, the modified resin exhibited excellent mechanical properties, thermal stability, and storage stability.

A New Polycyclic Naphthoxazine Resin: Facile Synthesis, Characterization, Polymerization, and Thermal Properties of Its Corresponding Thermosets

A novel polycyclic naphthoxazine resin (NSA-thiq) is synthesized via N, O-acetal forming reaction between o-hydroxyl naphthaldehyde and 1,2,3,4-tetrahydroisoquinoline. The chemical structure of the monomer is investigated and confirmed by 1H and 13C NMR, Fourier-transform infrared (FT-IR) spectroscopy, and high-resolution mass spectrometry. Besides, the ring-opening polymerization behavior similar to ordinary benzoxazine resins is observed by differential scanning calorimetry (DSC) and in situ FT-IR analyses, leading to the formation of the phenolic cross-linked network. Notably, DSC thermograms indicate that the newly obtained polycyclic naphthoxazine resin exhibits much lower polymerization temperatures compared to many other reported benzoxazine or naphthoxazine resins. Moreover, the corresponding polybenzoxazine (poly(NSA-thiq)) shows comparable thermal stability in comparison with thermosets derived from monobenzoxazine resins. As a consequence of these unique performances, NSA-thiq is applied as a property modifier for a commercialized benzoxazine resin (BA-a). The glass transition temperature of copolymeric thermosets is enhanced without sacrificing too much thermal stability and heat resistance. Here, another series of naphthoxazine thermosetting resin is explored, which can provide more examples for constructing composites based on thermoset polymers.

Intelligent perceptual textiles based on ionic-conductive and strong silk fibers

Endowing textiles with perceptual function, similar to human skin, is crucial for the development of next-generation smart wearables. To date, the creation of perceptual textiles capable of sensing potential dangers and accurately pinpointing finger touch remains elusive. In this study, we present the design and fabrication of intelligent perceptual textiles capable of electrically responding to external dangers and precisely detecting human touch, based on conductive silk fibroin-based ionic hydrogel (SIH) fibers. These fibers possess excellent fracture strength (55 MPa), extensibility (530%), stable and good conductivity (0.45 S·m-1) due to oriented structures and ionic incorporation. We fabricated SIH fiber-based protective textiles that can respond to fire, water, and sharp objects, protecting robots from potential injuries. Additionally, we designed perceptual textiles that can specifically pinpoint finger touch, serving as convenient human-machine interfaces. Our work sheds new light on the design of next-generation smart wearables and the reshaping of human-machine interfaces.

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.

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.

Development of an Atomic-Oxygen-Erosion-Resistant, Alumina-Fiber-Reinforced, Fluorinated Polybenzoxazine Composite for Low-Earth Orbital Applications

An atomic-oxygen-erosion-resistant fluorinated benzoxazine resin and composite were developed. The benzoxazine resin, abbreviated as “BAF-oda-fu,” consists of four benzoxazine rings, and was synthesized from bisphenol AF (BAF), 4,4′-oxydianiline (oda), furfurylamine (fu), and paraformaldehyde. The resin was characterized by infrared spectroscopy (FT-IR), proton nuclear magnetic resonance spectroscopy (1H NMR), differential scanning calorimetry (DSC), and thermogravimetric analysis (TGA). An analysis of the solvent-washed product showed a technical grade purity (>95%) and a yield of approximately 85%. Subsequent polymerization of the resin was successfully performed by heating step-wise and opening the benzoxazine rings to form a crosslinked network. Thermal analyses showed a melting temperature of 115 °C and polymerization temperature of 238 °C, both being characteristic values of benzoxazine monomers. The benzoxazine resin was also blended with polyoctahedral sisesquoxane (POSS) and reinforced with alumina fibers. The Tg of the resin, as determined by DMA of the composite, could reach as high as 308 °C when post-curing and the POSS additive were utilized. The low-Earth orbit atomic-oxygen erosion rate was simulated by an RF plasma asher/etcher. The atomic-oxygen resistance of poly(BAF-oda-fu) fell along an established trend line based on its fluorine content.

Tetrafluorophenylene-Containing Vinylbenzyl Ether-Terminated Oligo(2,6-dimethyl-1,4-phenylene ether) with Better Thermal, Dielectric, and Flame-Retardant Properties for Application in High-Frequency Communication

In an integrated circuit, signal propagation loss is proportional to the frequency, dissipation factor (D _f), and square root of dielectric constant (D _k). The loss becomes obvious as we move to high-frequency communication. Therefore, a polymer having low D _k and D _f is critical for copper-clad laminates at higher frequencies. For this purpose, a 4-vinylbenzyl ether phenoxy-2,3,5,6-tetrafluorophenylene-terminated OPE (VT-OPE) resin was synthesized and its properties were compared with the thermoset of commercial OPE-2St resin. The thermoset of VT-OPE shows a higher T _g (242 vs 229 °C), a relatively high cross-linking density (1.59 vs 1.41 mmole cm^-3), a lower coefficient of thermal expansion (55 vs 76 ppm/°C), better dielectric characteristic at 10 GHz (D _k values of 2.58 vs 2.75, D _f values of 0.005 vs 0.006), lower water absorption (0.135 vs 0.312 wt %), and better flame retardancy (UL-94 VTM-0 vs VTM-1 with dropping seriously) than the thermoset of OPE-2St. To verify the practicability of VT-OPE for copper-clad laminate, a laboratory process was also performed to prepare a copper-clad laminate, which shows a high peeling strength with copper foil (5.5 lb/in), high thermal reliability with a solder dipping test at 288 °C (>600 s), and the time for delamination of the laminate in thermal mechanical analysis (TMA) at 288 °C is over 60 min.

A Phosphorous-Containing Bio-Based Furfurylamine Type Benzoxazine and Its Application in Bisphenol-A Type Benzoxazine Resins: Preparation, Thermal Properties and Flammability

Polybenzoxazine (PBa) composites based on phosphorous-containing bio-based furfurylamine type benzoxazines (D-fu) and bisphenol-A type benzoxazines (Ba) were developed for flame retardation. The structure of D-fu was analyzed by Fourier transform infrared (FTIR) spectroscopy and ¹H-NMR spectroscopy. The curing temperature of Ba/D-fu mixtures was systematically studied by differential scanning calorimetry (DSC). Thermogravimetric analysis (TGA) demonstrated the excellent char formation ability of the PBa composites with the addition of phosphorous-containing D-fu. The flame retardancy of the PBa composite materials was tested by the limited oxygen index (LOI), vertical burning test (UL-94) and cone calorimeter (CONE). The LOI and UL-94 level of PBa/PD-fu-5% reached 34 and V0 rate, respectively. Notably, the incorporation of 5% D-fu into PBa led to a decrease of 21.9% at the peak of the heat-release rate and a mass-loss reduction of 8.0%. Moreover, the fire performance index increased, which demonstrated that the introduction of D-fu can diminish fire occurrence. The role of D-fu in the condensed and gas phases for the fire-resistant mechanism of the PBa matrix was supported by SEM-EDS and TGA/infrared spectrometry (TG-FTIR), respectively. Dynamic mechanical analysis (DMA) revealed that the Tg of PBa flame-retardant composites was around 230 °C. Therefore, PBa composites are promising fire-retardant polymers that can be applied as high-performance functional materials.

Synthesis of a triptycene-containing dioxazine benzoxazine monomer and a main-chain triptycene-polydimethysiloxane-benzoxazine copolymer with excellent comprehensive properties

A novel triptycene-containing dioxazine benzoxazine monomer and a main-chain benzoxazine copolymer have been synthesized and their corresponding thermosets exhibit excellent thermal stability, low flammability and low dielectric constants.

Recent Progress of High Performance Thermosets Based on Norbornene Functional Benzoxazine Resins

With the growing demand for high performance polymeric materials in industry, several types of thermosets such as bismaleimides, advanced epoxy resins, cyanate esters, and phenolic resins have been widely investigated to improve the performance of thermosetting products. Among them, benzoxazine resins have received wide attention due to their extraordinarily rich molecular design flexibility, which can customize our needs and adapt increasing requirements. To further improve the properties of polybenzoxiazines, researchers have found that the introduction of a norbornene functional group into the benzoxazine moiety can effectively improve the comprehensive performance of polybenzoxazine thermosets. This article focused on reviewing the recent development of high-performance thermosets based on norbornene functional benzoxazine thermosetting resins.

Propargylamine: an attractive amine source for designing high-performance benzoxazine resins with low polymerization temperatures

A series of benzoxazine resins using propargylamine as the amine source were synthesized to achieve highly thermally stable thermosets with low polymerization temperatures.

Elucidating the role of acetylene in ortho-phthalimide functional benzoxazines: design, synthesis, and structure–property investigations

Novel ortho-phthalimide-benzoxazines containing acetylene have been designed and their corresponding thermosets exhibit excellent thermal stability although the expected benzoxazole cyclization at a much higher temperature did not take place.

Design of High-Performance Polybenzoxazines with Tunable Extended Networks Based on Resveratrol and Allyl Functional Benzoxazine

A novel resveratrol-based bio-benzoxazine monomer (RES-al) containing an allyl group has been synthesized using resveratrol, allylamine, and paraformaldehyde via Mannich condensation reaction, and its chemical structures have been characterized by FT-IR spectroscopy and NMR techniques. The polymerization behavior of this benzoxazine resin has been investigated using in situ FT-IR and differential scanning calorimeter (DSC) measurements, and the thermal-mechanical properties of its corresponding polybenzoxazines are evaluated by DMA and TGA. We show that by controlling the curing process of the oxazine ring, the C=C bond in resveratrol, and the allyl group in RES-al, the cross-linking network of the polybenzoxazine can be manipulated, giving rise to tunable performance of thermosets. As all curable functionalities in RES-al are polymerized, the resulted polybenzoxazine exhibits a good thermal stability with a Tg temperature of 313 °C, a T_d5 value of 352 °C, and char yield of 53% at 800 °C under N₂.

Synthesis of ortho-methyltetrahydrophthalimide functional benzoxazine containing phthalonitrile group: Thermally activated polymerization behaviors and properties of its polymer

Two novel benzoxazine monomers, oHMTI-a and oHMTI-pn, have been obtained via the modified Mannich condensation from ortho-4-methyltetrahydrophalimide functional phenol, paraformaldehyde, and aniline/4-aminophthalonitrile, respectively. The chemical structures of both benzoxazine monomers have been studied by Fourier transform infrared (FT-IR) and 1H and 13C nuclear magnetic resonance (NMR) spectra. Their polymerization processes are investigated using in-situ FT-IR and different scanning calorimetry (DSC). Specifically, the phthalonitrile group in oHMTI-pn can react at a relatively lower temperature without adding any catalysts, which suggests the presence of the thermal synergistic polymerization effect in this benzoxazine monomer. In addition, the thermal and fire related properties of the resulting polybenzoxazines are evaluated by thermogravimetric analysis (TGA) and micro-scale combustion calorimetry (MCC). The polybenzoxazine derived from oHMTI-pn shows both high thermal stability and outstanding flame retardancy, with a T g of 350°C, a T d10 value of 417°C, a high char yield value of 65%, and a very low heat release capacity value of 35.2 J/(g·K).

A naringenin-based benzoxazine with an intramolecular hydrogen bond as both a thermal latent polymerization additive and property modifier for epoxy resins

Epoxy resins are constantly attracting attention from industrial applications due to their excellent comprehensive properties. However, the traditional curing agents for liquid epoxy resins react with epoxides even at room temperature, which causes difficulties in processing since such mixtures cannot be directly used as single-component materials. In order to improve the shelf life of the mixtures, we have designed an intramolecular hydrogen bond-containing benzoxazine monomer as a smart thermal latent polymerization agent for epoxy resins. The newly obtained benzoxazine, NAR-a, has been synthesized from the Mannich condensation of naringenin, aniline and paraformaldehyde. In addition to playing the role of a curing agent, NAR-a has also performed as an excellent property modifier for epoxy thermosetting systems. The resulting thermoset based on the NAR-a/epoxy thermosetting system exhibits high thermal stability and good intrinsic flame retardance, with a T _g temperature of 201 °C, a T _d5 temperature of 349 °C, a low CET value (32.4 ppm per °C) and low heat release capacity (HRC of 159.1 J g^-1 K^-1). The combined long-term storage stability and versatility of the intramolecular hydrogen bond-containing benzoxazine/epoxy system provide a new strategy for the development of one-component epoxy-related thermosetting resins for application in high-performance areas.

A high-performance functional phthalonitrile resin with a low melting point and a low dielectric constant

A monomer of fluorinated phthalonitrile, namely 4,4'-bis(p-perfluoro-phenol-(bis(p-phenol)propane-2,2-diyl)-p-oxy-diphthalonitrile) (PBDP), was synthesized by the nucleophilic substitution reaction of bisphenol A, decafluorobiphenyl and 4-nitrophthalonitrile. The structure of the monomer was characterized by nuclear magnetic resonance (NMR) spectroscopy and Fourier transform infrared (FTIR) spectroscopy. The results indicated that the PBDP monomer was synthesized successfully. The monomer was cured in the presence of 4-(aminophenoxy)phthalonitrile (APPH) and the curing behaviour was investigated by differential scanning calorimetry (DSC), suggesting a low melting point of 96 °C and an excellent processing window (96-262 °C). Thermogravimetric analysis (TGA) and dynamic mechanical analysis (DMA) showed that the fluorinated phthalonitrile resin possessed outstanding thermal and thermo-oxidative stabilities as well as good mechanical properties. The glass transition temperature was >400 °C and the 5% thermal degradation temperature was 501 °C. When the frequency was 50 MHz, the dielectric constant and dielectric loss of the polymer were 2.84 and 0.007, respectively. The PBDP resin has ultra-low water absorption of 0.77% and 1.4%, when exposed to an aqueous environment for 50 days at 24 °C and for 24 h at 100 °C, respectively. The prepared PBDP resin with outstanding thermal stability and low dielectric constant is an ideal candidate for aerospace industries, and microelectronic and other electronic packaging materials.

Easily Processable Thermosets with Outstanding Performance via Smart Twisted Small-Molecule Benzoxazines

High-performance aromatic polymers have excellent thermal, mechanical, and electrical properties and are lightweight, but it is highly challenging to deliver outstanding performances while still maintaining good processability of the precursors. Here, a new family of small-molecule benzoxazine resins with ortho-maleimide functionality is reported, which strikes an exceptional balance between the processability and performance. The excellent processability is attributed to the twisted molecular configurations of ortho-maleimide-substituted benzoxazines, which prevent intermolecular packing in the resin systems. The new benzoxazines can polymerize through multiple routes, which eliminate the twisted structures and create highly cross-linked polymer networks. The resulting new polymers are found to possess fascinating properties such as a high thermal stability (no T_g can be detected before 400 °C), excellent flame retardancy (a heat release capacity of 42.5 J g^-1 K^-1 ), and low dielectric constants (2.62-2.30 in the frequency range of 1 Hz to 10 MHz). The combined processability and versatility highlight the potential of smart benzoxazines in the preparation of high-performance thermosets, with important new applications that may span aerospace, transportation, and electronic packaging materials.

Syntheses of Atypically Fluorinated Peptidyl Macrocycles through Sequential Vinylic Substitutions

Small peptides containing combinations of cysteine, tyrosine, histidine, and serine residues react with octafluorocyclopentene (OFCP) to afford atypically structured macrocycles through successive vinylic substitutions. The reactions proceed rapidly in air at 0 °C and are tolerant of spectating tryptophan, asparagine, glutamine, and threonine residues. Hexapeptides of consensus sequence YXCXXC displace four fluorine atoms from OFCP to generate fluorinated macrobicyclic compounds that display dual-turn surfaces. The method provides facile access to a wide range of previously unknown heterocyclic structures.

Biomass materials derived from anethole: conversion and application

Renewable biomass has attracted much attention because of its advantages over fossil fuels. Of these biomasses, anethole has been developed as a reliable monomer or precursor for diverse materials with potential applications.

An apigenin-based bio-benzoxazine with three polymerizable functionalities: sustainable synthesis, thermal latent polymerization, and excellent thermal properties of its thermosets

An apigenin-based benzoxazine exhibiting a thermal latent polymerization behavior, high thermal stability and low flammability has been synthesized from sustainable resources.

Perfluorocyclohexenyl (PFCH) aromatic ether polymers from perfluorocyclohexene and polycyclic aromatic bisphenols

Semi-fluorinated Perfluorocycloalkenyl (PFCA) aromatic polymers prepared from polycyclic aromatic hydrocarbon (PAH) bisphenols and contain reactive fluoroalkene linkages.

Synthesis of Highly Thermally Stable Daidzein-Based Main-Chain-Type Benzoxazine Resins

In recent years, main-chain-type benzoxazine resins have been extensively investigated due to their excellent comprehensive properties for many potential applications. In this work, two new types of main-chain benzoxazine polymers were synthesized from daidzein, aromatic/aliphatic diamine, and paraformaldehyde. Unlike the approaches used synthesizing traditional main-chain-type benzoxazine polymers, the precursors derived from daidzein can undergo a further cross-linking polymerization in addition to the ring-opening polymerization of the oxazine ring. The structures of the new polymers were then studied by ¹H nuclear magnetic resonance spectroscopy (NMR) and Fourier-transform infrared spectroscopy (FT-IR), and the molecular weights were determined by using gel permeation chromatography (GPC). We also monitored the polymerization process by differential scanning calorimetry (DSC) and in situ FT-IR. In addition, the thermal stability and flame-retardant properties of the resulting polybenzoxazines were investigated using TGA and microscale combustion calorimeter (MCC). The polybenzoxazines obtained in this study exhibited a very high thermal stability and low flammability, with a T_g value greater than 400 °C, and a heat release capacity (HRC) value lower than 30 J/(g K).

Effects of End-Caps on the Atropisomerization, Polymerization, and the Thermal Properties of ortho-Imide Functional Benzoxazines

A new type of atropisomerism has recently been discovered in 1,3-benzoxazines, where the intramolecular repulsion between negatively charged oxygen atoms on the imide and the oxazine ring hinders the rotation about the C⁻N bond. The imide group offers a high degree of flexibility for functionalization, allowing a variety of functional groups to be attached, and producing different types of end-caps. In this work, the effects of end-caps on the atropisomerism, thermally activated polymerization of ortho-imide functional benzoxazines, and the associated properties of polybenzoxazines have been systematically investigated. Several end-caps, with different electronic characteristics and rigidities, were designed. ¹H and 13C nuclear magnetic resonance (NMR) spectroscopy and density functional theory (DFT) calculations were employed to obtain structural information, and differential scanning calorimetry (DSC) and in situ Fourier transform infrared (FT-IR) spectroscopy were also performed to study the thermally activated polymerization process of benzoxazine monomers. We demonstrated that the atropisomerization can be switched on/off by the manipulation of the steric structure of the end-caps, and polymerization behaviors can be well-controlled by the electronic properties of the end-caps. Moreover, a trade-off effect were found between the thermal properties and the rigidity of the end-caps in polybenzoxazines.