Ph.D. student, Case Western Reserve University
A phenol/aniline type monofunctional benzoxazine monomer, PH-a, is synthesized and highly purified into single crystals to study the intrinsic thermal ring-opening polymerization of benzoxazines without the influence of any impurity. The successful synthesis of the monomer and its corresponding chemical structure are confirmed by Fourier transform infrared spectroscopy (FT-IR) and 1H nuclear magnetic resonance (1H NMR) spectroscopy. Purity of the compound is evaluated through differential scanning calorimetry (DSC) as well as elemental analysis (EA). Moreover, the thermal behavior of benzoxazine monomer toward polymerization is also studied by DSC, indicating that the highly purified benzoxazine monomer actually polymerize upon heating. The results present evidence of an intrinsic tendency for 1,3-benzoxazines to undergo thermally induced ring-opening polymerization upon heating only without any impurity participating during the reaction. This reveals that polybenzoxazines can be obtained by both the traditional thermally accelerated (or activated) polymerization, where impurities or purposefully added initiators are involved in the reaction; or, by the classic thermal polymerization, where only heat is enough to initiate the reaction.
Abstract: Self-reinforcement gel-like halloysite nanotube (g-HNT) hybrids with various viscoelastic behaviors were fabricated by firstly treating with various concentrations of sodium hydroxide (NaOH) solution and then grafting tertiary amine and ion-exchange reacting with sulfonate anions. The morphology, composition, thermal stability and rheological behavior of the g-HNT hybrids were systematically characterized and analyzed using various methods. It is found that the viscoelasticity of g-HNT hybrids can be easily regulated by using different NaOH solution-treated HNTs as inorganic core and temperatures. In addition, the g-HNT hybrids treated with medium concentration of NaOH (0.06 mol L−1) have the lowest viscosity and highest level of dispersion compared with those treated with other concentrations of NaOH solution. Due to the amphiphilic nature of g-HNT hybrids and their lower viscosity than HNT powder, as novel hybrid fillers, they were utilized to prepare polystyrene composites by direct melt blending for achieving simultaneous reinforcement and plasticization effects. Besides the above mentioned advantages, the thermal conductivity of polystyrene composites is also surprisingly improved by reducing the interfacial mismatch between the filler and polymer matrix. The solvent-free and self-reinforcement hybrids provide a convenient and green path for fabricating high-performance polymer composites. © 2017 Society of Chemical Industry
Pub.: 12 May '17, Pinned: 27 Jun '17
Abstract: A 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.
Pub.: 01 Jul '16, Pinned: 27 Jun '17
Abstract: Monofunctional benzoxazine with ortho-methylol functionality has been synthesized and highly purified. The chemical structure of the synthesized monomer has been confirmed by 1H and 13C nuclear magnetic resonance spectroscopy (NMR), Fourier transform infrared spectroscopy (FT-IR) and elemental analysis. One-dimensional (1D) 1H NMR is used with respect to varied concentration of benzoxazines to study the specific nature of hydrogen bonding in both ortho-methylol functional benzoxazine and its para counterpart. The polymerization behavior of benzoxazine monomer has been also studied by in situ FT-IR and differential scanning calorimetry, experimentally supporting the polymerization mechanism of ortho-methylol functional benzoxazine we proposed before. © 2016 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2016
Pub.: 12 Aug '16, Pinned: 27 Jun '17