Effect of the Preparation Methodology of Polydopamine-Containing Systems over Light-to-Thermal Energy Conversion Performance

Polydopamine (PDA) is an attractive material utilized for a wide range of scientific purposes, including light-to-thermal energy conversion, because of presenting plenty of advantages. The proper integration way of PDA into a system is critical to benefit from the PDA content in maximum. Here, the two main PDA-containing composite preparation methods were compared in terms of fundamental material properties and the light-to-thermal energy conversion ability of the final product. For this purpose, the classical emulsion polymerization method first synthesized an aqueous dispersion of polystyrene nanoparticles (PS). PDA was then integrated into the system via two different preparation methods: coating the surfaces of polystyrene nanoparticles with a PDA layer while PS is in a dispersion state (PS@PDA) and adding separately synthesized PDA nanoparticles into the PS dispersion medium (PS-PDA). Two prepared composite systems were fundamentally characterized by dynamic light scattering (DLS), ultraviolet-visible (UV-vis) spectroscopy, and scanning electron microscopy (SEM) while in their dispersion state, and by differential scanning calorimetry (DSC), thermogravimetric analysis (TGA), Fourier-transform infrared (FTIR) spectroscopy, and X-ray diffraction (XRD) while in their solid state, which was obtained after the water evaporated. As the targeted property, the solid forms of these were investigated in terms of light-to-thermal energy conversion performance with solar and laser light exposure under 1 SUN and at 808 nm, respectively. The results showed that the composite system prepared by coating surfaces of PS nanoparticles with the PDA layer had higher light-to-thermal energy conversion under both conditions than those prepared by separately added PDA nanoparticles into the dispersion system. To show one of the possible applications of the prepared composites, in addition to the main target, the solid form of the composite system, which was prepared by coating surfaces of PS nanoparticles with the PDA layer, was also evaluated in detail concerning the latent heat-storage ability with incorporation of PEG 4000 as a phase-change material (PCM) into the system. It was found that the prepared shape-stable phase-change composite with a ratio of 1:3 between PS@PDA and PEG 4000 resulted in a latent heat of 126.9 J/g.