Surface-Segregation-Induced Nanopapillae on FDTS-Blended PDMS Film and Implications in Wettability, Adhesion, and Friction Behaviors.

Polymer composites have been extensively used to tune the surface property (e.g., wettability, friction, and adhesion) for its advantages of cost-effectiveness, high efficiency, and ease of fabrication. In this work, different amount of trichloro(1H,1H,2H,2H-perfluorooctyl)silane (FDTS) was added into poly(dimethylsiloxane) elastomer to prepare polymer composite films and were selected as a model to illustrate the effects of surface segregation on surface topology, wettability, friction, and adhesion. The results show that the added FDTS forms aggregations and increasing the content of FDTS leads to the difficulty of air bubble elimination, increase in viscosity, and drop in transparency. Driven by the differences of chemical potential, FDTS aggregations migrate to the air-polymer interface, resulting in surface enrichment and formation of nanopapillae (1-200 nm). This phenomenon becomes more significant with the increment in FDTS. The change in surface composition and structure generates profound effects on wettability, friction, and adhesion. The addition of FDTS makes the surface relatively oleophobic and further increasing the content of FDTS does not helpful in improving the oleophobicity due to the notable aggregation. Friction forces first grow with the increasing content of FDTS and then decline after the maximum point at 1.0 wt % of FDTS, which is attributed to the generated regular larger nanopappillae at high concentration. However, these larger nanopapillae lead to the increase in adhesion because more interactions are formed. The findings demonstrate the behaviors of FDTS in polymer composites and provide important guidance for controlling the formation of nanostructures via aggregation and phase segregation and exploring their implications on surface properties.