Synthesis and properties of microencapsulated n-octadecane with polyurea shells containing different soft segments for heat energy storage and thermal regulation

Microencapsulated n-octadecane with polyurea shells containing different soft segments were synthesized using 2,4-tolylene diisocyanate as an oil-soluble monomer and various amines as a water-soluble monomer through interfacial polycondensation. The Fourier transform infrared spectra and optical phase-contrast microscope confirmed that these polyurea shell materials were successfully fabricated onto the surface of n-octadecane. The morphological investigation suggested that the microcapsules synthesized using Jeffamine as the amine monomer had a smoother and more compact surface than those synthesized by ethylene diamine and diethylene triamine, and they possessed a larger particle size (about 16 μm) with a centralized size distribution as well. These microcapsules also exhibited much better phase change properties, higher encapsulation efficiency, and better anti-osmosis property than the other two. In addition, the microcapsules synthesized with a core/shell weight ratio of 70/30 are optimal when used as microencapsulated phase change materials.