1,720,991 research outputs found
Triggering effect caused by elemental sulfur as a mean to reduce the polymerization temperature of benzoxazine monomers
Full text linkMixtures of different benzoxazine resins and elemental sulfur (S8) are prepared and then reacted at 120 °C, below the temperature for radical formation of sulfur. The progress of the reaction and the chemical structures of the main products are monitored and characterized by proton nuclear magnetic resonance spectroscopy (1H NMR) and Fourier transform infrared spectroscopy (FT-IR). Thermal analysis of all reactive systems are also performed and studied by differential scanning calorimetry (DSC). The introduction of S8 into benzoxazines generates a new structure bearing a Schiff base and a phenolic -OH within the reactive system, which then triggers the reduction of the polymerization temperature in about 15% when as low as 5 mol% of S8 is added.Fil: Rodriguez Arza, Carlos. Case Western Reserve University; Estados UnidosFil: Froimowicz, Pablo. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Houssay. Instituto de Tecnología en Polímeros y Nanotecnología. Universidad de Buenos Aires. Facultad de Ingeniería. Instituto de Tecnología en Polímeros y Nanotecnología; Argentina. Case Western Reserve University; Estados UnidosFil: Ishida, Hatsuo. Case Western Reserve University; Estados Unido
Electronic effects of asymmetric and meta-alkoxy substituents on the polymerization behavior of bis-benzoxazines
Full text linkThree isomers of benzoxazine monomers based on m-alkoxyphenol and 4,4′-methylenedianiline were synthesized and successfully isolated by column chromatography. The molecular structures of benzoxazine monomers were confirmed by proton nuclear magnetic resonance (1H NMR) and Fourier-transform infrared (FT-IR) spectroscopy. The polymerization behavior evaluated by differential scanning calorimetry (DSC) shows that the asymmetric isomer, which has a methoxy group at the 5-position and 7-positions (5,7′MO-ddm), has only one exothermic peak between temperatures of the other two symmetric isomers. The 1H NMR spectrum of monomers shows that the type and position of alkoxy groups can exert different effects on the electron density of the oxazine ring, and may result in a sensitive trend of ring-opening. The difference in electron densities was verified by the Gaussian simulation calculation results of natural charges. In this work, we provide a fundamental molecular-level understanding of the polymerization mechanism of asymmetric bis-benzoxazines, which can provide possibilities for designing new benzoxazines in order to solve the potential disadvantages of benzoxazines/polybenzoxazines and/or enhance their advantages.Fil: Lyu, Ya. Case Western Reserve University; Estados UnidosFil: Rachita, Eric. Case Western Reserve University; Estados UnidosFil: Pogharian, Nicholas. Case Western Reserve University; Estados UnidosFil: Froimowicz, Pablo. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Houssay. Instituto de Tecnología en Polímeros y Nanotecnología. Universidad de Buenos Aires. Facultad de Ingeniería. Instituto de Tecnología en Polímeros y Nanotecnología; ArgentinaFil: Ishida, Hatsuo. Case Western Reserve University; Estados Unido
Tailor-made and chemically designed synthesis of coumarin-containing benzoxazines and their reactivity study toward their thermosets
Full text linkCoumarins are used as a natural renewable resource to synthesize coumarin-containing benzoxazine resins. The coumarin-containing benzoxazines are fully characterized in terms of their chemical structure by Fourier-transform infrared spectroscopy and proton nuclear magnetic resonance spectroscopy. The influence of electronic effects caused by the substituents on the polymerization temperature is also evaluated. Thermal properties of the resulting thermosets are characterized by differential scanning calorimetry and thermogravimetric analysis, showing good stability and char yields higher than 50%. The coumarin-containing polybenzoxazine thermosets show Tg values in the range between 160 and 190 °C. Thus, the herein presented coumarin-containing benzoxazine resins are proven to be competitive monomers when compared with other petroleum-based benzoxazine resins toward the generation of high-performance thermoset.Fil: Froimowicz, Pablo. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Houssay. Instituto de Tecnología En Polimeros y Nanotecnología. Universidad de Buenos Aires. Facultad de Ingeniería. Instituto de Tecnología En Polimeros y Nanotecnología; Argentina. Case Western Reserve University; Estados UnidosFil: Rodriguez Arza, Carlos. Case Western Reserve University; Estados Unidos. Consejo Nacional de Investigaciones Científicas y Técnicas; ArgentinaFil: Ohashi, Seishi. Case Western Reserve University; Estados UnidosFil: Ishida, Hatsuo. Case Western Reserve University; Estados Unido
Simple and low energy consuming synthesis of cyanate ester functional naphthoxazines and their properties
Full text linkNaphthoxazines functionalized with a cyanate ester group are synthesized in high yield under moderate conditions, including room temperature synthesis, compared with general benzoxazine synthesis. Additionally, this synthesis can shorten reaction pathways for another cyanate ester functional benzoxazine whose polymer exhibits higher thermal properties than general polybenzoxazines. Catalytic polymerization evaluated by differential scanning calorimetry (DSC) indicates multiple exotherm maxima, seemingly including cyanate ester trimerization and polymerization of naphthoxazine. The nature of each exotherm is studied by Fourier transform infrared spectroscopy (FT-IR). Furthermore, their observed exothermic temperatures are lower than those of the reported normal benzoxazines, dicyanate ester blends and cyanate ester functional benzoxazines. Thermal properties determined by thermogravimetric analysis (TGA) and dynamic mechanical analysis (DMA), such as the char yield and glass transition temperature, are relatively high compared to those of ordinary polybenzoxazines, and polymerized blends of benzoxazines and dicyanate esters.Fil: Ohashi, Seishi. Case Western Reserve University; Estados UnidosFil: Pandey, Vivek. Case Western Reserve University; Estados UnidosFil: Rodriguez Arza, Carlos. Case Western Reserve University; Estados UnidosFil: Froimowicz, Pablo. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Houssay. Instituto de Tecnología en Polímeros y Nanotecnología. Universidad de Buenos Aires. Facultad de Ingeniería. Instituto de Tecnología en Polímeros y Nanotecnología; Argentina. Case Western Reserve University; Estados UnidosFil: Ishida, Hatsuo. Case Western Reserve University; Estados Unido
A Smart Latent Catalyst Containing o‑Trifluoroacetamide Functional Benzoxazine: Precursor for Low Temperature Formation of Very High Performance Polybenzoxazole with Low Dielectric Constant and High Thermal Stability
Full text linkA novel difunctional benzoxazine with o-trifluoroacetamide functionality has been synthesized via Mannich condensation. The chemical structure of synthesized monomer has also been confirmed by 1H, 13C, and 19F nuclear magnetic resonance (NMR) spectroscopy and Fourier transform infrared (FT-IR) spectroscopy. The ring-opening polymerization of the resin and the subsequent conversion of the freshly generated polybenzoxazine into polybenzoxazole are studied by FT-IR and differential scanning calorimetry (DSC). In addition to the advantage of low polymerization temperature as other reported o-amide benzoxazines, the o-trifluoroacetamide benzoxazine also exhibits an unexpected lower benzoxazole formation temperature. Furthermore, the resulting fluorinated polybenzoxazole derived from the benzoxazine monomer possesses the combined excellent properties of facile synthesis, easy processability, low dielectric constant, high thermal stability, and long shelf life, evidencing its potential applications in microelectronic industries, aerospace, and other high-performance areas.Fil: Zhang, Kan. Jiangsu University; ChinaFil: Han, Lu. Case Western Reserve University; Estados UnidosFil: Froimowicz, Pablo. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Houssay. Instituto de Tecnología en Polímeros y Nanotecnología. Universidad de Buenos Aires. Facultad de Ingeniería. Instituto de Tecnología en Polímeros y Nanotecnología; ArgentinaFil: Ishida, Hatsuo. Case Western Reserve University; Estados Unido
Quantitative studies on the: P -substituent effect of the phenolic component on the polymerization of benzoxazines
Full text linkThe pure monofunctional benzoxazines substituted by either electron donating or withdrawing groups are synthesized to verify the electronic effect on the polymerization behaviors without any complicated factors of the impurities. The analytical data of each compound are collected using 1H-NMR, 13C-NMR, and differential scanning calorimetry (DSC). In order to quantify the electronic effect on the polymerization behavior, the Hammett substituent constant is utilized and plotted against resonances of 1H-NMR, 13C-NMR spectra and DSC exotherm maximum temperature. The use of the Hammett substituent constant is reexamined by calculating the natural charge on the phenolic moiety via ab initio calculation using the Gaussian program and correlated with the polymerization exotherm temperature. The activation energies obtained using the Kissinger and Ozawa methods are related to the electronic effect of the substituents on the phenolic part.Fil: Ohashi, Seishi. Case Western Reserve University; Estados UnidosFil: Iguchi, Daniela. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Houssay. Instituto de Tecnología en Polímeros y Nanotecnología. Universidad de Buenos Aires. Facultad de Ingeniería. Instituto de Tecnología en Polímeros y Nanotecnología; Argentina. Case Western Reserve University; Estados UnidosFil: Heyl, Tyler R.. Case Western Reserve University; Estados UnidosFil: Froimowicz, Pablo. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Houssay. Instituto de Tecnología en Polímeros y Nanotecnología. Universidad de Buenos Aires. Facultad de Ingeniería. Instituto de Tecnología en Polímeros y Nanotecnología; Argentina. Case Western Reserve University; Estados UnidosFil: Ishida, Hatsuo. Case Western Reserve University; Estados Unido
Study of the Effects of Intramolecular and Intermolecular Hydrogen-Bonding Systems on the Polymerization of Amide-Containing Benzoxazines
Full text linkPure para and ortho position amide benzoxazines, pHBA-a and oHBA-a, are synthesized. The hydrogen bonding interactions occurring in pHBA-a and oHBA-a are studied by Fourier transform infrared (FT-IR) spectroscopy and proton nuclear magnetic resonance (1H NMR) spectroscopy. FT-IR results show that, while pHBA-a presents intermolecular hydrogen bonding interactions, oHBA-a exhibits an intramolecular five-membered-ring hydrogenbonding system between the NH in the amide group and the oxygen in the oxazine ring. Differential scanning calorimetry (DSC) is used to study the thermal properties of the resins and their respective polymers. A deeper understanding of the hydrogen bond interactions in this family of resins is attempted to have better insights on how these systems influence the polymerization behavior not only with respect to the polymerization temperature but also with respect to the propagation step.Fil: Han, Lu. Case Western Reserve University; Estados UnidosFil: Zhang, Kan. Jiangsu University; ChinaFil: Ishida, Hatsuo. Case Western Reserve University; Estados UnidosFil: Froimowicz, Pablo. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Houssay. Instituto de Tecnología en Polímeros y Nanotecnología. Universidad de Buenos Aires. Facultad de Ingeniería. Instituto de Tecnología en Polímeros y Nanotecnología; Argentin
Using Molecular Simulation to Predict the Physical and Mechanical Properties of Polybenzoxazines
No full textThe aim of this chapter is to introduce the reader to the practical applications of modern molecular simulation techniques with literature examples drawn specifically from the field of polybenzoxazine research. The increases in computational power ensure that it is possible to apply molecular mechanics and molecular dynamics techniques to the visualization and simulation of comparatively large model structures comprising in some cases more than 6000 atoms (constructed from a repeat unit containing ca. 250 atoms). This, in turn, offers the potential to replicate a variety of physical and mechanical characteristics with a high degree of accuracy and precision. However, the apparent ease with which modeling may be carried out using modern software is beguiling; the need to validate simulations with real, empirical data is essential to ensure that the researcher obtains meaningful results
Developing Further Versatility in Benzoxazine Synthesis via Hydrolytic Ring-Opening
Full text linkIn 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.Fil: Cui, Shaoying. Sichuan University; ChinaFil: Arza, Carlos R.. Case Western Reserve University; Estados UnidosFil: Froimowicz, Pablo. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Houssay. Instituto de Tecnología en Polímeros y Nanotecnología. Universidad de Buenos Aires. Facultad de Ingeniería. Instituto de Tecnología en Polímeros y Nanotecnología; Argentina. Case Western Reserve University; Estados UnidosFil: Ishida, Hatsuo. Case Western Reserve University; Estados Unido
Smart, Sustainable, and Ecofriendly Chemical Design of Fully Bio-Based Thermally Stable Thermosets Based on Benzoxazine Chemistry
Full text linkA 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, 1H NMR spectroscopy and two-dimensional 1H–1H nuclear Overhauser effect spectroscopy (2D 1H–1H 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.Fil: Froimowicz, Pablo. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Houssay. Instituto de Tecnología en Polímeros y Nanotecnología. Universidad de Buenos Aires. Facultad de Ingeniería. Instituto de Tecnología en Polímeros y Nanotecnología; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Houssay. Instituto de Tecnología en Polímeros y Nanotecnología. Universidad de Buenos Aires. Facultad de Ingeniería. Instituto de Tecnología en Polímeros y Nanotecnología; ArgentinaFil: Arza, Carlos R.. Case Western Reserve University; Estados UnidosFil: Han, Lu. Case Western Reserve University; Estados UnidosFil: Ishida, Hatsuo. Case Western Reserve University; Estados Unido
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