Dynamic Synergy of Photocatalysis and Hydrophobicity in PDMS-Grafted TiO2 Coatings for Long-Lasting Self-Cleaning

A fundamental conflict in self-cleaning coatings lies in the trade-off between photocatalytic activity (requiring hydrophilic TiO2) and hydrophobic repellency (requiring low-surface-energy polymers). Here, this bottleneck is broken through an in-situ grafting strategy that anchors polydimethylsiloxane (PDMS) chains onto TiO2 surfaces via robust Si-O-Ti covalent bonds. By controlling the loading amount of TiO2 in the sol, it enables the adjustment of the water contact angle, light transmittance, as well as self-cleaning performance of the coating. The resultant M-TiO2 nanocatalyst exhibits excellent dispersion in hydrophobic media and imparts the composite coating with a water contact angle up to 163°. The dynamic photocatalytic process, decomposing organic stains while maintaining surface non-wettability, is systematically elucidated. Remarkably, the optimal coating (0.75 wt.% M-TiO2) sustains a steady-state degradation rate of rhodamine B under UV light, achieving >90% conversion within 85 h, without compromising its water-repellent function. The covalent interface acts as a bridge between the organic components and the inorganic catalyst, significantly improving the dispersion uniformity and stability of TiO2 nanoparticles in PDMS, thus endowing the resulting coating with good light transmittance in visible region, excellent self-cleaning performance and satisfied service durability. This work demonstrates that rational interface engineering can transform the inherent photocatalysis vs. hydrophobicity antagonism into a durable, dynamic synergy, providing a versatile platform for next-generation photocatalytic self-cleaning materials.