Synthesis and comprehensive spectroscopic-DFT investigation of an eco-friendly eugenol-derived benzoxazine for advanced polymer applications

Abstract

The growing demand for lightweight, sustainable gamma radiation shielding necessitates alternatives to traditional empirical design. This study employs a density functional theory (DFT)-guided strategy to develop a bio-based benzoxazine monomer synthesized from renewable eugenol and p-tert-butylaniline. DFT thermochemical calculations confirmed thermodynamic spontaneity (ΔG = −8.14 kcal/mol) and the exothermic nature (ΔH = −31.03 kcal/mol) of the monomer formation. Theoretical molecular geometries and predicted 1H NMR chemical shifts showed excellent agreement with experimental FT-IR and 1H NMR spectra, validating the predictive model. The monomer was thermally polymerized and reinforced with erbium oxide (Er 2 O 3 ) at various loadings (5–20 wt%). Gamma radiation shielding measurements revealed that attenuation properties improved progressively with filler content. At 20 wt% Er 2 O 3 loading, the composite achieved a superior mass attenuation coefficient of approximately 92.64 cm 2 /g, along with significantly enhanced linear attenuation and radiation protection efficiency compared to the neat polymer. These results demonstrate that combining DFT-assisted molecular design with high-Z rare-earth oxide reinforcement provides a highly effective route for engineering next-generation, sustainable radiation shielding materials.