Microstructural Analysis of Benzoxazine Cationic Ring-Opening Polymerization Pathways.

Herein, an evaluation of the initial step of benzoxazine polymerization is presented by mass spectrometry, with a focus on differentiating the phenoxy and phenolic products formed by distinct pathways of the cationic ring opening polymerization (ROP) mechanism of polybenzoxazine formation. The use of infrared multiple photon dissociation (IRMPD) and ion mobility spectrometry (IMS) techniques allows for differentiation of the two pathways and provides valuable insights into the ROP mechanism. The results suggest that type I pathway is favored in the initial stages of the reaction yielding the phenoxy product, while type II product should be observed at later stages when the phenoxy product would interconvert to the most stable type II phenolic product. Overall, the findings presented here provide important information on the initial step of the benzoxazine polymerization, allowing the development of optimal polymerization conditions and represents a way to evaluate other multifunctional polymerization processes.

Design and Effects of the Cinnamic Acids Chemical Structures as Organocatalyst on the Polymerization of Benzoxazines.

This study focuses on the catalytic effect of the two geometric isomers of a cinnamic acid derivative, E and Z-forms of 3-methoxycinnamic acid (3OMeCA), analyzing the influence of their chemical structures. E and Z-3OMeCA isomers show very good catalytic effect in the polymerization of benzoxazines, decreasing by 40 and 55 °C, respectively, the polymerization temperatures, for catalyst contents of up to 10% w/w. Isothermal polymerizations show that polymerizations are easily realized and analyzed at temperatures as low as 130 °C and at much shorter times using Z-3OMeCA instead of E-3OMeCA. Thus, both cinnamic acids are good catalysts, with Z-3OMeCA being better. The molecular reasons for this difference and mechanistic implications in benzoxazine polymerizations are also presented.

Crystal structure of 2,2'-(ethane-1,2-di-yl)bis-(2,3-di-hydro-1H-naphtho-[1,2-e][1,3]oxazine): a prospective raw material for polybenzoxazines.

In the title compound, C26H24N2O2, the oxazine moiety is fused to a naphthalene ring system. The asymmetric unit consists of one half of the mol-ecule, which lies about an inversion centre. The C atoms of the ethyl-ene spacer group adopt an anti-periplanar arrangement. The oxazine ring adopts a half-chair conformation. In the crystal, supra-molecular chains running along the b axis are formed via short C-H⋯π contacts. The crystal studied was a non-merohedral twin with a fractional contribution of 0.168 (2) of the minor twin component.

C-I⋯N short contacts as tools for the construction of the crystal packing in the crystal structure of 3,3'-(ethane-1,2-di-yl)bis-(6-iodo-3,4-di-hydro-2H-1,3-benzoxazine).

The asymmetric unit of the title compound, C18H18I2N2O2, consists of one half-mol-ecule, completed by the application of inversion symmetry. The mol-ecule adopts the typical structure for this class of bis-benxozazines, characterized by an anti orientation of the two benzoxazine rings around the central C-C bond. The oxazinic ring adopts a half-chair conformation. In the crystal, mol-ecules are linked by C-I⋯N short contacts [I⋯N = 3.378 (2) Å], generating layers lying parallel to the bc plane.

Crystal structure of 1,2-bis-(6-bromo-3,4-dihydro-2H-benz[e][1,3]oxazin-3-yl)ethane: a bromine-containing bis-benzoxazine.

The title benzoxazine molecule, C18H18Br2N2O2, was prepared by a Mannich-type reaction of 4-bromo-phenol with ethane-1,2-di-amine and formaldehyde. The title compound crystallizes in the monoclinic space group C2/c with a centre of inversion located at the mid-point of the C-C bond of the central CH2CH2 spacer. The oxazinic ring adopts a half-chair conformation. The structure is compared to those of other functionalized benzoxazines synthesized in our laboratory. In the crystal, weak C-H⋯Br and C-H⋯O hydrogen bonds stack the mol-ecules along the b-axis direction.

Synthesis of Chiral 1,4,2-Oxazaphosphepines.

Synthesis and structural characterization of 1,4,2-oxazaphosphepines is described. The 1,4,2-oxazaphosphepines were obtained from reaction of chiral 1,3-benzoxazines with dichlorophenylphosphine or triethyl phosphite. The configuration of some of these compounds was stablished by X-ray analysis.