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Hatsuo Ishida – 1st expert on this subject based on the ideXlab platform

  • Benzoxazine Chemistry in Solution and Melt
    Handbook of Benzoxazine Resins, 2020
    Co-Authors: Hatsuo Ishida


    Publisher Summary Benzoxazine synthesis and its chemical reactions with specific interest in polymerizing them are reviewed in this chapter. The very rich molecular design flexibility offers tremendous opportunity to design Benzoxazine resins that allows tailoring the polyBenzoxazine properties. The complex reaction occurring during the synthesis of the monomers and polymerization makes studies of Benzoxazine complex. Progress is made from a controlled, laboratory synthesis of Benzoxazines in homogeneous solutions at modest to low concentrations to more high solid and/or melt systems that are much more efficient for scale-up synthesis. It explains that difunctional Benzoxazines are also prepared from various combinations of difunctional primary amines and monofunctional phenols or difunctional phenols as well as polyhydric phenols with monofunctional primary amines. Recent reports for synthesizing linear polymers with Benzoxazine structure in the main chain offer new opportunities in property tailoring, it is nonetheless the variation of this small molecular weight chemistry that was extended to difunctional phenolic and amine compounds. This chapter illustrates that polymers containing fluorinated aromatic systems often exhibit exceptional thermal stability. Decreased friction coefficient, refractive index, and dielectric constant are some of the well-known benefits of the fluorine introduction. It is difficult to introduce more than two halogen atoms into each aromatic ring in phenolic materials due to the restriction imposed by the traditional phenolic chemistry.

  • Synthesis and ring-opening polymerization of 2-substituted 1,3-Benzoxazine: the first observation of the polymerization of oxazine ring-substituted Benzoxazines
    Polymer Chemistry, 2020
    Co-Authors: Seishi Ohashi, Francis Cassidy, Stephanie Huang, Kevin Chiou, Hatsuo Ishida


    2-Substituted 1,3-Benzoxazines (two Benzoxazine monomers used in this paper are abbreviated as PH-a-[2]ba and PH-pda-[2]ba) having a phenyl group as an oxazine ring substituent are synthesized with benzaldehyde through 2-hydroxy-N-phenylbenzylamine structures. The polymerization of these monomers is observed for the first time and confirmed using differential scanning calorimetry (DSC), thermogravimetric analysis (TGA), and Fourier transform infrared spectroscopy (FT-IR). The poly(PH-a-[2]ba) derived from 2-substituted 1,3-Benzoxazines exhibits good thermal properties based on TGA analysis, despite showing slight inferiority to poly(PH-a), an unsubstituted counterpart of PH-a-[2]ba. Additionally, benzylideneaniline is extracted during the polymerization, indicating that this compound is the byproduct of the polymerization mechanism. Structural verification is achieved by synthesizing benzylideneaniline and comparing its 1H-NMR spectrum with the reaction byproduct.

  • Poly(Benzoxazine-f-chitosan) films: The role of aldehyde neighboring groups on chemical interaction of Benzoxazine precursors with chitosan
    Carbohydrate Polymers, 2019
    Co-Authors: Almahdi A. Alhwaige, Hatsuo Ishida, Syed Qutubuddin


    Abstract This study reports the preparation and characterizations of chitosan-azomethine derivatives containing oxazine ring as new crosslinked polymers. The novel chitosan derivatives have been prepared by functionalization with reactive Benzoxazine precursors. Two types of aldehyde-terminated Benzoxazine precursors have been synthesized using two different polyetheramines (Jeffamines), 4-hydroxybenzaldehyde, and paraformaldehyde. The Benzoxazine precursors are covalently attached to chitosan via Schiff’s base formation. Benzoxazine structure is confirmed by proton nuclear magnetic resonance spectroscopy (1H-NMR) and Fourier transform infrared spectroscopy (FT-IR), whereas the imine-linkage formation is confirmed by FT-IR. The Benzoxazine-f-chitosan films are crosslinked by cationic ring-opening polymerization of Benzoxazine. Differential scanning calorimetry (DSC) and thermogravimetric analysis (TGA) are used to study the thermal behavior of the obtained films. Wettability behavior of the resulting films was studied by contact angle measurements and compared with wettability of the neat chitosan film.

Tarek Agag – 2nd expert on this subject based on the ideXlab platform

  • polymerization behavior of methylol functional Benzoxazine monomer
    Reactive & Functional Polymers, 2013
    Co-Authors: Mohamed Baqar, Hatsuo Ishida, Tarek Agag, Syed Qutubuddin


    Abstract This study focuses on methylol functional Benzoxazines as precursors to build a network structure utilizing both Benzoxazine and resole chemistry. The first part is a review of systems that contain methylol groups which play a role on their crosslinking formation. The polymerization mechanism and properties of resoles will be highlighted as the most abundant polymers that are characterized by polymerization through condensation reaction of methylol group. In the second part, the effect of incorporating methylol group into Benzoxazine monomers is studied. Differential scanning calorimetry (DSC) is used to study the effect of methylol group on the rate of polymerization. Kissinger and Ozawa methods using non-isothermal DSC at different heating rates show that methylol monomer exhibits lower average activation energy compared to the un-functionalized monomer. The effect of adding catalysts into the monomers is also studied. p -Toluene sulfonic acid (PTSA) is found to be more efficient than 1-methyl-imidazole (IMD) and lithium iodide (LiI) in the case of methylol monomer due to its ability of accelerating both the methylol condensation and ring-opening polymerization. Additionally, thermal behavior of the monomers is studied using thermogravimetric analysis (TGA).

  • benzoxazole resin a novel class of thermoset polymer via smart Benzoxazine resin
    Macromolecules, 2012
    Co-Authors: Tarek Agag, Jia Liu, Robert Graf, Hans Wolfgang Spiess, Hatsuo Ishida


    Among the wide list of known high performance polymers, polybenzoxazoles (PBOs) have gained a prominent position as the most heat-resistant polyheterocyclic polymer. Nonetheless, PBOs have found applications in a rather restricted variety of technologies, mainly in the form of fibers. Herein, we report our pioneering work for producing cross-linked polybenzoxazole via a novel route using recently developed smart class of Benzoxazine resins as precursors. This class of Benzoxazines incorporates multiple smart features all in one molecule. The most attractive feature is its structural transformation into a more thermally stable cross-linked polybenzoxazole without the harmful consequences of traditional polybenzoxazole synthesis, such as the use of poly(phosphoric acid) as solvent. By this smart conversion, the flame-retardant oxazole moieties are successfully incorporated into the network structure. Further advantages of this new route for cross-linked polybenzoxazoles include outstanding flexibility in mo…

  • Mechanistic Pathways for the Polymerization of Methylol-Functional Benzoxazine Monomers
    Macromolecules, 2012
    Co-Authors: Mohamed Baqar, Tarek Agag, Syed Qutubuddin, Rongzhi Huang, Joao Maia, Hatsuo Ishida


    The polymerization mechanism of methylol-functional Benzoxazine monomers is reported using a series of monofunctional Benzoxazine monomers synthesized via a condensation reaction of ortho-, meta-, or para-methylol–phenol, aniline, and paraformaldehyde following the traditional route of Benzoxazine synthesis. A phenol/aniline-type monofunctional Benzoxazine monomer has been synthesized as a control. The structures of the synthesized monomers have been confirmed by 1H NMR and FT-IR. The polymerization behavior of methylol monomers is studied by DSC and shows an exothermic peak associated with condensation reaction of methylol groups and ring-opening polymerization of Benzoxazine at a lower temperature range than the control monomer. The presence of methylol group accelerates the ring-opening polymerization to give the ascending order of para-, meta-, and ortho-positions in comparison to the unfunctionalized monomer. Furthermore, rheological measurements show that the position of methylol group relative to b…

Yusuf Yagci – 3rd expert on this subject based on the ideXlab platform

  • Benzoxazine resins as smart materials and future perspectives
    Thermosets, 2020
    Co-Authors: Baris Kiskan, Yusuf Yagci


    Abstract PolyBenzoxazines are high-performance thermosets having a range of properties and capability to overcome drawbacks of traditional resole- and novolac-type phenolics. They exhibit low water absorption, high T g , high char yield, flame resistance, low shrinkage, and also limited or no release of by-products during curing, and they have comparable mechanical performance with bismaleimide resins. In this chapter, we provide an overview of polyBenzoxazines highlighting in the progress in the synthesis of both Benzoxazine monomers and polyBenzoxazine prepolymers, their resulting materials, and their composites. Moreover, industrially important Benzoxazines and current advances of Benzoxazine applications as smart materials ranging from self-healing materials to electroactive coatings were reviewed.

  • Side- and End-Chain Benzoxazine Functional Polymers
    Handbook of Benzoxazine Resins, 2020
    Co-Authors: Baris Kiskan, Yusuf Yagci


    Publisher Summary This chapter describes synthetic pathways for the synthesis of side- and end-chain Benzoxazine functional polymers by using controlled and conventional polymerization methods involving free radical and rhodium catalysts. It presents numerous synthetic methods to combine Benzoxazines with polymers and contribute to increase the performance and property characteristics of these resins. These approaches may serve a valuable guideline for preparing polyBenzoxazines with desired properties to fulfill industrial demands. The synthesis of the polyBenzoxazine by cross-linking bifunctional Benzoxazine monomer through a ring-opening reaction is reported and the benefits of this family of compounds are identified. PolyBenzoxazines can offer various superior properties compared to the conventional novolac or resole or epoxy type resins. Though Benzoxazine based materials possess several advantages, they are not very attractive to the chemical industry because of problems of processability, brittleness, and high curing temperatures. Recently a new type of addition-cure phenolic system, polyBenzoxazine is developed. These materials offer low water absorption, high char yield, resistance against flame, high modulus, high strength, high glass transition temperatures, chemical resistance, and long shelf life; they have very limited volumetric change upon curing; and strong acid catalysts are not required for curing. Though polyBenzoxazines have such superior properties, pure Benzoxazine based thermosettings suffer from high curing temperatures (200 °C or higher), difficulty in processing, and brittleness. Another encouraging approach is the synthesis of novel polymeric Benzoxazine precursors, designed to impart flexibility and processability. Incorporation of Benzoxazine groups into a polymer backbone as a side chain is an important way to obtain a dense network. Various synthetic methods can be used to obtain such kinds of precursors.

  • Chapter 13 – Thiol-Benzoxazine Chemistry for Macromolecular Modifications
    Advanced and Emerging Polybenzoxazine Science and Technology, 2020
    Co-Authors: Baris Kiskan, A. Musa, E. Semerci, Yusuf Yagci


    This chapter deals with the synthetic pathways of obtaining materials with thermally curable Benzoxazine moieties by using the catalytic opening of the lateral Benzoxazine rings by thiols (COLBERT), or in other words the thiol-Benzoxazine reaction to further improve special properties, particularly processibility and toughness or for designing new materials. The combination of COLBERT with photolytic thiol-ene, postpolymer modifications of main chain polyBenzoxazines, synthesis of linear, block copolymers, and hybrid networks are presented. The advantages of the thiol-Benzoxazine approach can be listed as fast and easy reaction conditions at ambient temperature or even below, 100% atom economy, and the availability of wide range of thiol compounds. Apart from these, the conventional benefits of Benzoxazine chemistry, like the ease of Benzoxazine synthesis and its design flexibility, can be considered additional virtues of thiol-Benzoxazine chemistry.