Patterning rigid microparticles on soft adhesives for control of interfacial properties

A method for controlling the adhesion of multilayer films is to pattern the interface with micro-asperities. An increase in adhesion is typically observed in the case of patterning a soft, polymer interface with rigid microparticles due to pinning or blunting of cracks. The enhancement in adhesion as a result of the patterning is dependent on a number of factors including strength of the particle-polymer interface as well as size, and distribution of the particles. However, few studies have investigated how processing of the material system affects adhesion. Here, we study the adhesive behavior for two different materials systems that have rigid microparticles deposited at the interface of a flexible film and a soft adhesive. The first is prepared by vacuum melt compression so that the adhesive fully wets the particle at the interface. The second is prepared by only applying force which results in the formation of annular cracks around the particles. Through 90⁰ peel experiments, we show the effects of near-perfect wetting versus the presence of a pre-crack at the particle interface on adhesion. We observed a transition from a continuous peel to a stick-slip type peel as rate increased in both material systems, despite the pre-crack of the second material system, signifying that there is some form of pinning and/or blunting of the crack as a result of the interfacial patterning. We also see that this effect is more pronounced in the vacuum melt compressed samples. We will discuss the underlying mechanism for this stick slip behavior. Understanding the fracture mechanism will help us determine the proper patterning features that are required to achieve a targeted adhesion strength.