Titanium Dioxide Nanoparticle-Decorated Polymer Microcapsules Enclosing Phase Change Material for Thermal Energy Storage and Photocatalysis

Titanium dioxide (TiO₂) nanoparticle decorated [poly­(4-methylstyrene-co-divinylbenzene)] microcapsules enclosing phase change material (PCM) were synthesized following a one-pot non-Pickering emulsion templated suspension polymerization. TiO₂ nanoparticles were hydrophobized using a trace amount of tertradecyltrimethylammonium bromide (TTAB, cationic stabilizer) through electrostatic interaction and employed as a particle stabilizer. The resulting microcapsules presented concurrent functionalities of thermal energy storage and photocatalytic activity. Scanning electron microscopy (SEM) identified that microencapsulated PCMs (microPCMs) exhibited a well-defined, core–shell structure with spherical morphology. The existence of TiO₂ over the polymeric shell was confirmed by energy-dispersive X-ray (EDX) and X-ray diffraction (XRD) analysis. Differential scanning calorimetry (DSC) analysis demonstrated that microPCM with 2.6 wt % TiO₂ achieved maximum phase change enthalpy of 174 J/g with an encapsulation efficiency of 76.6% and could maintain it even after 100 melting–freezing cycles. Thermogravimetric analysis (TGA) revealed that the addition of TiO₂ contributed in improving the thermal stability of microPCMs. Most of all, the produced microcapsules exhibited great photocatalytic activity through the synergistic photothermal effect. The bifunctional microcapsules reported in this work would stimulate wide applications in the biomedical field, residential buildings in polluted urban sites, and industrial establishments as thermal energy storage and depollution materials.