The majority of the published bio-based benzoxazine research has focused almost exclusively on different phenolic and amine compounds, while the aldehyde portion of the oxazine ring remains the same.

Three isomers of benzoxazine monomers based on m-alkoxyphenol and 4,4′-methylenedianiline were synthesized and successfully isolated by column chromatography.

Main chain-type elastomeric polybenzoxazines (abbreviated as CA-pdms-fu) with very high char yield have been developed. Seven compositions of elastomeric benzoxazine adhesives are synthesized to find the optimum structure by changing the chain length of the siloxane component. The successful synthesis of CApdms-fu derived from catechol is confirmed with 1 H NMR and FT-IR spectroscopy. Polymerization characteristics, including polymerization temperature, enthalpy of polymerization, and extent of polymerization for all seven compounds, are analyzed from FT-IR and DSC data. The TGA results indicate remarkable superiority of CA-pdms-fu over traditional epoxy and polyurethane adhesives, with 93% higher char yield than polyurethane elastomer. The flammability of the elastomeric polymer was quantified by heat release capacity using microscale combustion calorimetry (MCC). The seven compositions of elastomeric polybenzoxazines exhibit heat release capacities between 48 and 63 J/g•K, which are within the noncombustible material range, without added flame retardants. Adhesive failure strengths are determined by lap shear strength, making a single lap shear joint on aluminum and copper rectangular bars. The lap shear strength for cross-linked poly(CA-pdms(2)-fu) is comparable to polyurethane adhesives, and the low flammability and very high char yield make this polymer suitable for developing fire-resistant elastomeric materials.

Mono and difunctional 1,3-benzothiazines (PH-a-BZT, PH-ddm-BZT) have been synthesized by a method different from the one reported in the literature.

Correction for ‘A truly bio-based benzoxazine derived from three natural reactants obtained under environmentally friendly conditions and its polymer properties’ by Irlaine Machado et al., Green Chem., 2021, 23, 4051–4064, DOI: 10.1039/D1GC00951F.