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.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

Electronic effects of asymmetric and meta-alkoxy substituents on the polymerization behavior of bis-benzoxazines

Three 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

Examining the Influence of Bisphenol A on the Polymerisation and Network Properties of An Aromatic Benzoxazine

A series of reactive blends, comprising a commercial benzoxazine monomer, 2,2-bis(3,4-dihydro-3-phenyl-2H-1,3-benzoxazine)propane, and bisphenol A is prepared and characterized. Thermal analysis and dynamic rheology reveal how the introduction of up to 15 wt % bisphenol A lead to a significant increase in reactivity (the exothermic peak maximum of thermal polymerization is reduced from 245 °C to 215 °C), with a small penalty in glass transition temperature (reduction of 15 K), but similar thermal stability (onset of degradation = 283 °C, char yield = 26%). With higher concentrations of bisphenol A (e.g. 25 wt %), a significantly more reactive blend is produced (exothermic peak maximum = 192 °C), but with a significantly lower thermal stability (onset of degradation = 265 °C, char yield = 22%) and glass transition temperature (128 °C). Attempts to produce a cured plaque containing 35 wt % bisphenol A were unsuccessful, due to brittleness. Molecular modelling is used to replicate successfully the glass transition temperatures (measured using thermal analysis) of a range of copolymers