A Critical Examination of Transesterification‐Based Vitrimer With a Focus on Hygrothermal Aging Stability

ABSTRACT Vitrimers, leveraging dynamic covalent bonds for reprocessability, recyclability, and self‐healing, hold significant promise in applications such as composites, adhesives, and electronics; however, this dynamic nature acts as a double‐edged sword, potentially compromising long‐term stability under hygrothermal environments, where systematic investigations remain lacking. To fill this gap, this study investigates the performance evolution and deterioration mechanisms during hygrothermal aging of epoxy‐based vitrimers, prepared via an anhydride‐cured system featuring triazabicyclodecene (TBD) as the transesterification catalyst. After 504 h of 85°C/85% RH aging, the glass transition temperature declined from 135°C to 124°C, crosslink density reduced by 9.0%, and both mechanical and dielectric properties exhibited deterioration. Density functional theory calculations revealed a lower reaction barrier for the rate‐determining step in dynamic covalent bond hydrolysis (18.99 kcal/mol) compared to uncatalyzed ester hydrolysis (29.98 kcal/mol), indicating that TBD exacerbates ester bond hydrolysis, which disrupts the cross‐linked network and drives the observed deterioration. Additionally, water resistance assessments according to ISO 175 and TBD‐derived reinforcement strategies are explored. This work confirms that performance deterioration of vitrimers under hygrothermal aging stems from catalyst‐enhanced ester bond hydrolysis, underscores the need for a balance between the dynamic properties and hygrothermal aging resistance, providing new guidelines for next‐generation vitrimers.