How elastomers wet, swell and deform

Abstract

The work presented in this "sandwich'' thesis consists of three manuscripts detailing experimental projects which focus on the production and properties of thin elastomeric films. The first chapter introduces the fundamental physics explaining liquid properties, viscoelastic responses and measurement techniques. The next chapter covers the experimental details for the work contained in the remaining chapters. The first manuscript, in Chapter 3, focuses on preparation of thin elastomeric films. The preparation procedure ensures maximal removal of uncrosslinked chains and uses known chemical components. Our procedure produces ideal films to simplify the interpretation of experiments. The second manuscript, in Chapter 4, involves using ideal elastomeric films for liquid spreading experiments. Where Tanner's law characterizes the dynamics for a liquid droplet that completely wets a solid substrate, our experiments investigate the power law scaling for soft, permeable substrates. Varying the thickness of the elastomer films changes the mechanical response as well as the absorption potential of the films. We develop an empirically driven model which describes both the mechanical and absorption components. The final manuscript, contained in Chapter 5, examines the shape of capillary ridges in ideal elastomers. Capillary ridges form due to elastocapillary properties at the contact line between a liquid droplet atop a soft substrate. In Chapter 5 we probe the shape of these deformations with direct atomic force microscopy (AFM) measurements and characterize their size with varying elastomer thickness. This thesis provides the outline for creating ideal elastomeric substrates and describes their wettability and swelling behaviour as well as their elastocapillary deformations.