Synthesis and performance enhancement of novel polybenzoxazines with low surface free energy

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.

Integrating Benzoxazine-PDMS 3D Networks with Carbon Nanotubes for flexible Pressure Sensors

Shapeable and flexible pressure sensors with superior mechanical and electrical properties are of major interest as they can be employed in a wide range of applications. In this regard, elastomer-based composites incorporating carbon nanomaterials in the insulating matrix embody an appealing solution for designing flexible pressure sensors with specific properties. In this study, PDMS chains of different molecular weight were successfully functionalized with benzoxazine moieties in order to thermally cure them without adding a second component, nor a catalyst or an initiator. These precursors were then blended with 1 weight percent of multi-walled carbon nanotubes (CNTs) using an ultrasound probe, which induced a transition from a liquid-like to a gel-like behavior as CNTs generate an interconnected network within the matrix. After curing, the resulting nanocomposites exhibit mechanical and electrical properties making them highly promising materials for pressure-sensing applications.

Bio-based polybenzoxazines as an efficient coatings to protect mild steel surfaces from corrosion

New types of mono and bi-functional benzoxazine monomers were synthesized using cardanol (C) and 4-aminobenzonitrile (abn), p-phenylediamine ( ppda) along with paraformaldehyde. The synthesized benzoxazine monomers structure was elucidated by 1H, 13C-NMR and FTIR spectroscopic techniques. The polymerization temperature (Tp) of C-abn and C- ppda are noticed at 280oC and 237oC, respectively. It was also noticed that bi-functional benzoxazine (C- ppda) possesses lower curing temperature than mono-functional benzoxazine (C-abn). The ring opening polymerization of benzoxazine was confirmed by FTIR spectroscopy. Thermal analyses indicate that, benzoxazine [poly(C- ppda)] possesses higher thermal stability than poly(C-abn). The surface roughness of the benzoxazine coated MS specimen was analysed by atomic force microscope. The values of water contact angles obtained for poly(C-abn) and poly(C- ppda) are 145o and 148o, respectively. It was noticed that the mild steel specimen coated with bio-based benzoxazine C-abn exhibit excellent resistance to corrosion.

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.

Characteristics of Thermosetting Polymer Nanocomposites: Siloxane-Imide-Containing Benzoxazine with Silsesquioxane Epoxy Resins

A series of innovative thermosetting polymer nanocomposites comprising of polysiloxane-imide-containing benzoxazine (PSiBZ) as the matrix and double-decker silsesquioxane (DDSQ) epoxy or polyhedral oligomeric silsesquioxane (POSS) epoxy were prepared for improving thermosetting performance. Thermomechanical and dynamic mechanical characterizations indicated that both DDSQ and POSS could effectively lower the coefficient of thermal expansion by up to approximately 34% and considerably increase the storage modulus (up to 183%). Therefore, DDSQ and POSS are promising materials for low-stress encapsulation for electronic packaging applications.

Developing Further Versatility in Benzoxazine Synthesis via Hydrolytic Ring-Opening

In this study, 2-(aminomethyl)phenol and its derivatives, the reactants for 2-substituted 1,3-benzoxazines, are synthesized by HCl hydrolysis from the typical benzoxazines. The phenol/aniline-based mono-oxazine benzoxazine, PH-a, and the bisphenol A/aniline-based bis-oxazine benzoxazine, BA-a, are used as examples to demonstrate the feasibility of this new approach. Their chemical structures are characterized by nuclear magnetic resonance (NMR), Fourier transform infrared (FTIR) and Raman spectroscopies, and are further verified by elementary analysis. Their thermal properties are studied by differential scanning calorimetry (DSC). These two 2-(aminomethyl) phenolic derivatives are reacted with paraformaldehyde to close the oxazine rings. A benzoxazine with a phenyl substituent at the 2-position of the oxazine ring is obtained from the 2-((phenylamino)methyl)phenol (hPH-a) and benzaldehyde. All these results highlight the success of the HCl hydrolysis and the formation of stable intermediates, namely 2-(aminomethyl) phenolic derivatives, from readily available benzoxazine monomers. This further demonstrates the feasibility of using these intermediates as reactants for a novel benzoxazine synthesis.

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).

Outstanding dielectric and thermal properties of main chain-type poly(benzoxazine-co-imide-co-siloxane)-based cross-linked networks

A high performance cross-linked polymer with a very low dielectric constant was achieved via a newly designed main-chain type poly(benzoxazine-co-imide-co-siloxane).

Modification of benzoxazine with aryl-ether-ether-ketone diphenol: preparation and characterization

A modified benzoxazine resin system with “high strength, high modulus and high toughness” was prepared by introducing an efficient modifier (m-DHPBP) with high catalytic activity and an aryl-ether-ether-ketone (PEEK) structure.

Effect of hydrogen bonds on the polymerization of benzoxazines: influence and control

Type I –OH⋯N hydrogen bonds blocked high-degree polymerization of benzoxazines and controlling them by introducing additional hydrogen-bonds acceptors can afford high-degree polymerization.

Studies on synthesis and characterization of multi-walled carbon nanotube-reinforced polyimide nanocomposites based on a siloxane-modified anhydride

A novel series of multi-walled carbon nanotube (MWCNT) reinforced siloxane dianhydride based polyimide (PI) nanocomposites were designed and developed using in situ polymerization approach via thermal imidization. The polyamic acid obtained from the reaction of siloxane dianhydride and pyridine diamine/ p-phenylenediamine was then incorporated with varying percentages of MWCNTs, which then undergoes thermal imidization to form MWCNT-PI nanocomposites. The synthesized PIs were then characterized using analytical methods. From thermal analysis, it can be seen that the glass transition temperature increased significantly by incorporating acid functionalized MWCNTs into the PI matrix than that of neat PI. This is due to the constraint effect of MWCNTs as well as the reduction in the movement of polymer chains. It exhibits an increased dielectric constant with the increase in weight percentage of MWCNTs to PI matrix. No aggregation and homogeneous dispersion of MWCNTs throughout the PI matrix have been achieved as evidenced by scanning electron microscopy and transmission electron microscopy. The newly designed PI system is responsible for the significant improvement of dispersion, thus enhancing attractive flame retardancy and dielectric properties.