Effect of B 2 O 3 Substitution for SiO 2 on the Network Structure and Degradation Behavior of Borosilicate Glasses

ABSTRACT The effects of B 2 O 3 substitution for SiO 2 on the network structure and in vitro degradation behavior of borosilicate glasses were investigated using a combined approach of molecular dynamics (MD) simulation and experimental methods. The results show that an increasing B 2 O 3 /SiO 2 molar ratio shifts the main network former from [SiO 4 ] to [BO 3 ] and [BO 4 ] units. Notably, [BO 3 ] units exhibit a tendency for spatial aggregation, which reduces network stability, whereas [SiO 4 ] tetrahedra increase their bridging oxygen connectivity to compensate and stabilize the network. These structural changes critically determine the degradation mechanism: For silicate‐rich glasses (e.g., 0B, 1B), a protective silica‐rich layer forms, leading to a fluctuating, layer‐by‐layer ion release of Ca, B, and Si. In contrast, for borate‐rich glasses (e.g., 2B, 3B), the network undergoes rapid, bulk disruption due to the vulnerability of clustered [BO 3 ] domains, resulting in the near‐synchronous and rapid release of B and Ca. Furthermore, the applicability of F n e t for predicting the ion release behaviors of borosilicate glasses is demonstrated. This study validates the integrated MD‐experimental approach for revealing the atomic‐scale origins of degradation behavior and demonstrates the potential of structural descriptors like F n e t for guiding the composition design of bioactive glasses with tailored ion release profiles.