Designing TiO2-doped photothermal microcapsules via a novel green synthesis Pickering emulsion complex coacervation method and their application to cotton fabrics for thermal protective fabric

This paper presents the production of nano titanium dioxide (TiO₂)-doped n-tetradecanol/sodium alginate/chitosan microcapsules using a novel environmentally friendly method, capable of converting sunlight into thermal energy. It also explores the potential of these microcapsules to be used as a component in thermal protective fabrics for clothing. In the study, unlike the literature, microcapsule production was carried out by integrating eco-friendly Pickering emulsion with complex coacervation method, which has ecological properties. n-Tetradecanol containing sodium alginate/chitosan walled microcapsules were produced by Pickering emulsion complex coacervation method using TiO₂ Pickering stabilizer. Microcapsules were produced using three different concentrations of Pickering stabilizers (0.1–0.3–0.5 wt%); the highest heat storage capacity with 192.9 J/g was obtained at 0.1% wt. To impart photothermal properties to these microcapsules, TiO₂ was deposited on the surface of the microcapsules at three different ratios (3,4,5 wt%). Spherical microcapsules with good leak-proofing were found to store heat in the range of 104.6–165 J/g and exhibited good photothermal conversion performance with photothermal conversion efficiency ranging from 65.95 to 90.81%. Microcapsules doped with 5% TiO₂ were applied to cotton fabric at two different concentrations by pad-dry cure method. The fabric including microcapsules exhibited photothermal properties, reaching temperatures up to 6.6 °C higher than the untreated fabric within the same period. The addition of TiO₂-doped microcapsules to the fabric significantly increased its thermal conductivity. In contrast, microcapsule application had a significant effect on the air permeability, bending rigidity and warp tear strength of the fabric.