Thermo-Responsive Hydrophilic Amine Microcapsules for All-in-one Epoxy System: Effective Adhesion, Radiative Cooling, and Toughening via Interpenetrating Networks

Abstract

Although there has been substantial progress in functionalizing material systems today, most are still mainly designed for two-part storage and a single function. Combining various functionalities into a cohesive, unified material system remains a critical and urgent challenge. In this context, microencapsulation techniques serve as a reliable and effective method for embedding reactive triggers within polymer matrices, creating cohesive multifunctional polymer systems. This study introduces a simplified, solvent-free liquid-liquid phase-separation approach, named melt-condensation, for encapsulating tetraethylenepentamine (TEPA) within a polyethylene wax (PEW) shell, using perfluorotributylamine (PFTBA) as a cooling medium. By precisely controlling the interfacial tension between different phases, core-shell spherical microcapsules with ~61.2 wt% core content can be obtained. These microcapsules demonstrate robust sealing performance and exhibit temperature-triggered burst release (within 6 seconds at 105°C). By introducing these thermo-responsive microcapsules into the epoxy matrix, a multifunctional resin system was successfully organized. This multifunctional system, as an adhesive, increased peel distance by 201% and demonstrated excellent adhesion to aluminum and stainless-steel substrates at typical room temperature; 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.