Starch-calcium inclusion complexes: Optimizing transparency, anti-fogging, and fluorescence in thermoplastic starch

With the increasing demand for anti-fogging transparent material and environmental concern, developing sustainable intrinsically hydrophilic and anti-fogging thermoplastic material is important. In this work, thermoplastic starch (TPS) films with good anti-fogging and optical properties were prepared via coordinative interactions with calcium chloride (CaCl₂), zinc chloride (ZnCl₂) and magnesium chloride (MgCl₂). Among them, TPS with the incorporation of CaCl₂ exhibited excellent anti-fogging and high optical transparency. Notably, the haze of TPS-0.2Ca just increased from 2.5 % to 3.8 %, with transparency remaining robust at 80 %. FTIR, XPS and 2D-WAXD results demonstrated the formation of inclusion complexes between Ca²⁺ and hydroxyl groups, which could modulate the hydrophobicity and hydrophilicity of TPS. Moreover, DMA, POM, and AFM results revealed that the formation of starch-calcium inclusion complex was crucial for achieving uniform intensity distribution, reduced crystalline areas, minimized light scattering, and decreased surface roughness, thereby contributing to the high transparency and low haze of TPS-Ca. Furthermore, TPS-Ca samples exhibited inherent fluorescent properties under UV light, showing the potential as disposable and eco-friendly fluorescence materials. This work provides new insights into design of sustainable TPS-based materials that combine robust antifogging performance with advanced optical property.