Morphology-driven anti-icing performance of fluorine-free alkylsilane coatings fabricated via candle soot templating

Ice accumulation on exposed surfaces remains a major challenge in transportation, energy, and outdoor infrastructures, motivating the development of environmentally friendly anti-icing coatings without fluorinated compounds. In this study, fluorine free hierarchical silica coatings were fabricated using a candle soot templating strategy followed by surface functionalization with methyl trichlorosilane (MTCS) and octadecyl trichlorosilane (OTCS). The influence of alkyl silane chain length on surface morphology, wettability, and anti-icing performance was systematically investigated. SEM and AFM analyses revealed that the MTCS modified surface developed a more pronounced micro/nano hierarchical structure with higher surface roughness compared to the OTCS modified counterpart. As a result, the MTCS coating exhibited superior superhydrophobicity with a water contact angle of 163.8°, whereas the OTCS coating showed lower hydrophobicity. Anti-icing tests demonstrated that the MTCS coated surface significantly delayed water freezing for up to ∼80 min at -20 °C and reduced ice adhesion strength to 24.2 ± 3.2 kPa. In addition, the coating maintained its superhydrophobic behavior after repeated freeze thaw cycles, abrasion, tape-peeling, thermal treatment, UV exposure, and chemical stability tests. The coating also exhibited efficient self-cleaning performance in both air and oil environments. The findings indicate that surface morphology makes a significant contribution to the observed water-repellency and anti-icing performance. However, it is believed that the observed performance results from the combined effects of alkyl chain length, the resulting silane network structure, and the reaction conditions applied. Furthermore, the developed coating system offers a promising approach for low-cost, PFAS-free, and multifunctional anti-icing coatings.