Thermo-responsive hydrophilic amine microcapsules for an all-in-one epoxy system: effective adhesion, radiative cooling, and toughening via interpenetrating networks

Abstract

Despite significant advancements in functionalizing material systems today, most remain predominantly designed for two-part storage and a single function. Integrating disparate functionalities into a cohesive, unified material system remains a critical and urgent challenge. In this situation, microencapsulation techniques emerge as a reliable method for embedding reactive triggers within polymer matrices, creating cohesive all-in-one polymer systems. This study introduces a simplified, solvent-free liquid–liquid phase separation approach—melt-condensation—that utilizes perfluorotributylamine (PFTBA) as a cooling medium and polyethylene wax (PEW) mixtures as the shell for encapsulating tetraethylenepentamine (TEPA). By precisely controlling the interfacial tension between various phases, core–shell spherical microcapsules with ∼61.2 wt% core content were obtained. These microcapsules demonstrate robust sealing performance and possess temperature-triggered burst release capabilities (within 6 seconds at 105 °C). By introducing them into an epoxy matrix, an all-in-one system was successfully organized. This all-in-one system, as an adhesive, increased peel distance by 201% and demonstrated excellent bonding effects on aluminum and stainless-steel substrates; as a functional coating, it facilitated crack repair with a recovery rate of 86.7% and achieved passive cooling of nearly 7 °C during the daytime. Our research uniquely integrates distinct functions in a single system, establishing a new direction in novel material systems.