Phase change n-Octadecane microencapsulated in titanium dioxide nanoparticle-doped polymer for photothermal conversion and photocatalysis

We microencapsulated the n-Octadecane (ODE) with titanium dioxide (TiO2) nanoparticle-doped styrene–divinylbenzene copolymer (SDB) via the suspension polymerization. The TiO2 was grafted with 3-Glycidoxypropyltrimethoxysilane (KH560) to obtain amphiphilic properties in order to enhance their anchoring capability at the oil-aqueous interface. Emphasis is placed on analyzing how the TiO2 nanoparticles affect the multiple functions of the prepared microcapsules for heat storage, photothermal conversion, and photodegradation. Under scanning electron microscope, the microcapsules show generally spherical shapes with rough surface and good dispersibility. The thermophysical property of the microcapsules was examined via the differential scanning calorimetry and thermogravimetric analyzer. The microcapsules prepared with 4.0 wt% TiO2 had the highest thermal storage capacity with molten and crystallized enthalpies of 105.3 ± 0.3 and 102.4 ± 0.7 J/g, respectively. The microcapsules with 4.0 wt% TiO2 achieved 48.0 ± 0.4% encapsulation. The doped-TiO2 nanoparticles improved the thermal stability of microcapsule samples. The initial decomposition temperature of the microcapsule sample with 4.0 wt% TiO2 is increased to 167.6 °C as compared to 115.1 °C for pure ODE. In the solar thermal conversion and photocatalytic tests, the microcapsule sample with 4.0 wt% TiO2 exhibited the best performance as well, with 42.80% photothermal conversion efficiency and 90.92% degradation rate. The multifunctional phase change microcapsules have broad application prospects as heat storage and depollution materials.