Ice Adhesion to Cationic, Anionic, Zwitterionic, and Nonionic Polymer Surfaces

Ionic polymer coatings have shown promising potential as passive anti-icing coatings due to reduced ice adhesion strength. Yet, a comprehensive understanding of the effects of polymer charge and coating cross-link density on the adhesion strength of ice to ionic polymer surfaces remains absent. To bridge this gap, we have developed a tailorable coating structure that provides thiol-ene curable coatings with cationic, anionic, zwitterionic, and nonionic functionalities, with additional tunability in the cross-link density. Shear ice adhesion on ionic polymer coatings exhibited a mechanism based on the physical state of hydration water, showing dependence on both the nature of the charge and the coating cross-link density. To affirm a phase transition, spectroscopic ellipsometry and differential scanning calorimetry were first used to investigate the swelling as a function of both polymer charge and cross-link density and polymer-induced freezing point depressions as a function of polymer concentration. Complementing these measurements, we were able to estimate the phase transition temperature of the hydration water inside the coatings, which strongly correlated with observed jumps in ice adhesion at specific temperatures. Additionally, low-temperature ice adhesion strength was also correlated to fractions of “non-freezable” water in the polymer coating, dependent solely on the nature of the charges present in the coating. These insights on the effects of charge and coating structure on ice adhesion strength reveal relationships that could be beneficial in the development of passive ionic anti-icing surfaces.