Tailoring Wetting Ridge Dynamics on Hybrid Acrylic Polymers: The Impact of Mechanical Properties on Continuous Wetting

This study examined the relationships among the wetting speed, the polymer mechanical properties, and the resulting deformation characteristics of various graft copolymers synthesized from acrylic monomers and acrylated l-lactide and ε-caprolactone macromonomers (MMs). The mechanical properties of the polymer films were manipulated with minimal impact on their static contact angles with water by varying their MM composition. The focus was on wetting speeds prior to the onset of stick-slip behavior, where ridges were smoothly pulled over the surfaces, thereby producing a transient deformation indicative of a wave pulse. The height of the propagated ridge structures quickly converged to a steady-state value, depending on the wetting speed and polymer properties, regardless of the initial size. The results show that the propagated ridge height correlates with the wetting speed, and the data are well fitted by the Kelvin-Voigt model, which yields two key parameters: the maximum ridge height at the limit of zero velocity and the characteristic wetting speed. Both parameters correlated linearly with the lactide content in the MMs, and the characteristic wetting speed correlated linearly with crossover frequencies from the rheological master curves of the polymers. Furthermore, the characteristic wetting speed was correlated with the peel force required to remove polymer films from the steel plates, establishing a connection between dynamic wetting and adhesive behavior. Our findings shed light on the interdependence between the material composition, mechanical properties, and wetting behavior. The insights presented offer significant potential for designing materials with controlled wetting properties, particularly for applications where capillary flow and surface interactions play critical roles.