Role of Free Polymer Chains in the Adhesion of Polydimethylsiloxane Elastomers to Solids

Foulants like barnacles and ice cause many problems for infrastructure due to their strong adhesion to unprotected surfaces. One of the most common types of mitigation used to reduce foulant adhesion is simply coating a surface with a relatively soft elastomer. Further reductions in adhesion are often gained by the inclusion of “oils” or uncross-linked chains in the elastomer; however, the physics behind these reductions is not clear. Here, we show that adhesion reductions can occur without a fluid layer forming on the elastomer surface. Specifically, we use the Johnson–Kendall–Roberts (JKR) method to measure adhesion in polydimethylsiloxane elastomers infused with four different polymer chains (polydimethylsiloxane, phenylmethylsiloxane, random diphenylsiloxane-dimethylsiloxane, or random phenylmethylsiloxane-dimethylsiloxane copolymer). Adhesion is shown to correlate with elastomer modulus, which itself is influenced by the inclusion of free chain diluents during cross-linking. Accounting for the modulus dependence, we show that phenyl-containing oils lead to the greatest reduction in adhesion.