Polymerization of benzoxazine resins is indicated by the disappearance of a 960-900 cm band in infrared spectroscopy (IR). Historically, this band was assigned to the C-H out-of-plane bending of the benzene to which the oxazine ring is attached. This study shows that this band is a mixture of the O-C stretching of the oxazine ring and the phenolic ring vibrational modes. Vibrational frequencies of 3-phenyl-3,4-dihydro-2H-benzo[e][1,3]oxazine (PH-a) and 3-(tert-butyl)-3,4-dihydro-2H-benzo[e][1,3]oxazine (PH-t) are compared with isotope-exchanged and all-substituted compounds. Deuterated benzoxazine monomers, N-isotope exchanged benzoxazine monomers, and all-substituted benzoxazine monomers without aromatic C-H groups are synthesized and studied meticulously. The various isotopic-exchanges involved deuteration around the benzene ring of phenol, selective deuteration of each CH in the O-CH-N (2) and N-CH-Ar (4) positions on the oxazine ring, or simultaneous deuteration of both positions. The chemical structures were confirmed by H nuclear magnetic resonance spectroscopy (H NMR). The IR and Raman spectra of each compound are compared. Further analysis of N isotope-exchanged PH-a indicates the influence of the nitrogen isotope on the band position, both experimentally and theoretically. This finding is important for polymerization studies of benzoxazines that utilize vibrational spectroscopy.

What inspired you for the cover image? Perhapst he analogy with as pace travel across the universe where no matter the direction there are always new amazing 'things' to be discovered, letting us know and appreciate deeper what we have in hand. Af ew years ago, only very few examples of naturally based benzoxazines were known.T hat was the early stages of aj our-ney that today may be seen as the development of an ovel full topic, biomass-based benzoxazinesa nd polybenzoxazines. Nowadays, new materials based on natural renewable raw materials are investigated, studied, formulated, and applied. Those early 'launches' helpedt o'launch' this novel yet established field within the benzoxazines'a rena, represented in the cover as the 'Green Galaxyo fBenzoxazines'. What is in your opinion an upcoming research theme likely to becomeo ne of the 'hot topics' in the near future? It is hard to make futurology in this sense because there are so many different and equally relevant fields, each of them with their respective subdisciplines. Nevertheless, what we can envisage is that regardless what the upcomingh ot topic or topics might be, they will certainly have to involve the right tools to efficientlyd esign and develop novel materials exploiting good chemistry based on renewable natural resources and sustainability.T his last concept applies not only to the materials themselves but also to their raw materials and methodolo-gies used. Invited for this month'sc over are the groups at the

Amino-functional benzoxazine monomers have been successfully prepared. Several routes have been applied to incorporate amino group into benzoxazine structure. These approaches include reduction of the corresponding nitro-functional benzoxazines and deprotection of protected aminofunctional benzoxazine monomers. Various approaches that allow primary amine groups to be prepared without damaging the existing benzoxazine groups have been evaluated. Tetrachlorophthalimide and trifluoroacetyl are found to be suitable protecting groups. In addition, a model compound of amidefunctional benzoxazines is prepared from primary amine-functional benzoxazine. Fourier transform infrared spectroscopy (FTIR) and 1 H and 13 C nuclear magnetic resonance spectroscopy (NMR) are used to characterize the structure of the monomers. The polymerization behavior of amino-functional monomers and model compound are studied by differential scanning calorimetry (DSC).

Sesamol and furfurylamine are used to synthesize a novel benzoxazine monomer as part of the quest to develop greener benzoxazine monomers simultaneously fulfilling two Principles of Green Chemistry, the use of renewable feedstocks and safer solvents and auxiliaries. Respecting principle 5, the so-called preferred solvents (ethanol and ethyl acetate) are used in both the syntheses and purification processes. The chemical structure of the synthesized monomer is verified by proton and carbon nuclear magnetic resonance spectroscopy (1H and 13C NMR), 2D 1H–13C heteronuclear single quantum correlation (HSQC) spectroscopy, and Fourier transform infrared spectroscopy (FT-IR). The polymerization behavior of the monomer and the thermal stability of fully polymerized polybenzoxazine are studied by differential scanning calorimetry (DSC) and thermogravimetric analysis (TGA). A thermally stable polymer has been obtained as shown by the 5% and 10% weight reduction temperature (T d5 and T d10) values of 374 and 419 °C, respectively, and a char yield of 64%, making this thermoset a promising candidate for fire-resistant applications.

A naphthoxazine containing a latent catalyst based on −OH as part of its monomer structure has been synthesized through a simple one-pot reaction at room temperature. The chemical structure of this naphthoxazine monomer has been confirmed by 1H NMR, 13C NMR, and FT-IR and its purity by elemental analysis. Differential scanning calorimetry (DSC) and in situ FT-IR have been used to investigate the active and inactive conditions for the latent catalysis. DSC and thermogravimetric analysis (TGA) studies indicate that this naphthoxazine polymerizes quickly before the monomer evaporation, as is often the case for conventional naphthoxazines, minimizing the monomer loss during polymerization. The intramolecular interactions between the −OH group and oxazine ring and pyrrolidine ring of the monomer have been investigated in detail by using the homonuclear two-dimensional (2D) NMR technique 1H–1H nuclear Overhauser effect spectroscopy (NOESY). The −OH interacts with the N in the pyrrolidine ring and oxazine ring through stable intramolecular hydrogen bonds instead of presenting free −OH at room temperature, leading to the enhanced shelf life of the monomer. The free phenolic −OH initiates and catalyzes the polymerization once the hydrogen-bonded interactions are weakened or disrupted upon increasing temperature, showing a latent catalytic effect.

A systematic study has been carried out to develop a material with significant protection properties from galactic cosmic radiation and solar energetic particles. The research focused on the development of hydrogen-rich benzoxazines, which are particularly effective for shielding against such radiation. Newly developed benzoxazine resin can be polymerized at 120 °C, which meets the low-temperature processing requirements for use with ultrahigh molecular weight polyethylene (UHMWPE) fiber, a hydrogen-rich composite reinforcement. This highly reactive benzoxazine resin also exhibits low viscosity and good shelf-life. The structure of the benzoxazine monomer is confirmed by proton nuclear magnetic resonance and Fourier transform infrared spectroscopy. Polymerization behavior and thermal properties are evaluated by differential scanning calorimetry and thermogravimetric analysis. Dynamic mechanical analysis is used to study chemorheological properties of the benzoxazine monomer, rheological properties of the cross-linked polybenzoxazine, and rheological properties of UHMWPE-reinforced polybenzoxazine composites. The theoretical radiation shielding capability of the composite is also evaluated using computer-based simulations.

Bio-based non-ionic hyperbranched polymers were synthesized as non-leachable antibacterial additives for other biopolymers.

A smart synthetic chemical design incorporating a natural renewable resource, umbelliferone, is presented to synthesize thermoset materials with good thermal properties.