Exploring boratrane's potential to enhance the thermal stability of phenol-formaldehyde resins by borate bridge as a crosslinker and the mechanistic formation of boron species in carbonaceous materials: A comprehensive study

In advanced material science, we explore the potential of boratrane, a promising agent for enhancing thermal stability. By combining rigorous Density Functional Theory (DFT) calculations with groundbreaking experimental analyses, we reveal the intricate interplay of radical intermediates and mechanisms underlying the thermal evolution of boratrane-infused materials. Our innovative approach illuminates dynamic structural transformations and elucidates boratrane's pivotal role in fortifying thermal resilience. The DFT calculations identify radical intermediates and mechanisms of thermal degradation, highlighting the role of borate bridges in delocalizing π-electrons in aromatic rings through Gibbs free energy (∆G_RXN), Highest Occupied Molecular Orbital (HOMO), Lowest Unoccupied Molecular Orbital (LUMO), and electrostatic potential (ESP) analyses. Fukui function analysis provides insights into the reactivity of these structures towards free radical attacks. Our findings demonstrate that boratrane-modified resins exhibit a stable BO₄^- structure, which prevents self-condensation of boratrane to B₂O₃ and enhances the thermal stability of oxygenated resins. This improvement is due to the formation of intramolecular hydrogen bonds, contributing to helix-like structures that strengthen the resin. The mechanism by which the BO₄^- structure terminates radical agents and transforms into carbonaceous material is elucidated through thermodynamic values, revealing the plausible reactions and chemical structure of boron in the resulting material.