Study of Supercooled Water Drop Impact on Icephobic Gradient Polymer Coatings

Supercooled liquid water drops, with temperatures below freezing point, are common in high-altitude clouds. These drops, despite being in a metastable state, can remain liquid for extended periods if temperatures are above the homogeneous nucleation point. Impact of such liquid drops with a cold solid surface is one of the reasons for ice accretion, which in many cases can represent a safety hazard. The study of supercooled drop impact dynamics is key to developing materials that provide resistance against the formation and accumulation of ice. In this work, the impact of supercooled water drops on dry icephobic coatings based on gradient polymers deposited via initiated chemical vapor deposition (iCVD) under several conditions is analyzed. Experimental results show that coated surfaces potentially decrease the freezing probability upon impact. The gradient polymer surfaces with higher roughness and lower wettability do not increase the freezing probability upon impact but result in rebound and eventual roll off the surface, indicating that surface hydrophobic properties prevailed over the impact. The findings demonstrate the remarkable efficacy of gradient polymer coatings in inhibiting drop freezing, even under high wind velocities, and provide insights for the design of durable and effective anti-icing coatings across diverse applications.