Biobased Polymer Microcapsules with Controlled PCM Retention and Cu₂O Surface Functionalization for Thermal and...

Biobased polymer microcapsules combining thermal energy storage and surface reactivity are of interest for advanced coating applications. In this work, microcapsules encapsulating capric acid (CA) were prepared via suspension polymerization using cinnamyl methacrylate (CMA)-based copolymers. The effects of polymer composition on particle formation, morphology, and encapsulation behavior were examined. Formulations containing methyl methacrylate (MMA) or ethylene glycol dimethacrylate (EGDMA) produced spherical microcapsules with improved suspension stability, whereas CMA/MAA-rich systems led to particle coagulation. The CA-loaded microcapsules exhibited latent heat storage behavior, confirming effective encapsulation of the phase-change material (PCM). To introduce additional functionality, Cu₂O was deposited onto the microcapsule surface, yielding hybrid microcapsules with retained morphology and visible-light photocatalytic activity. Prior to Cu₂O deposition, thermogravimetric analysis indicated CA loadings of approximately 43-47 wt %. The retention of encapsulated CA during Cu₂O deposition strongly depended on the polymer network structure and deposition conditions. Under mild deposition conditions (∼30 °C), cross-linked P-(CMA-EGDMA-MAA)/CA microcapsules maintained relatively high PCM loading values, indicating improved structural stability and preservation of phase-change functionality after Cu₂O surface modification. The hybrid microcapsules achieved approximately 85% methylene blue removal within 300 min under visible-light irradiation. These results demonstrate that polymer composition influences encapsulation stability, while Cu₂O surface deposition imparts photocatalytic functionality. The developed biobased microcapsules show potential for thermal regulation and self-cleaning coating applications.