Preparation and characterization of looped polydimethylsiloxane brushes

We have synthesized and characterized a looped polymer that is covalently bonded to a surface at both chain termini. We used the 'grafting to' method to anchor polydimethylsiloxane (PDMS) onto a Si substrate by making use of triethoxysilyl terminal units. Atomic force microscopy revealed that a linear polymer brush provides a rough surface in water. As water is a poor solvent for PDMS, linear polymer brushes tend to be dewetted, forming aggregates. In contrast, a looped polymer brush surface is smooth in air and water. Aggregation was suppressed in the looped polymer brushes because both ends were tethered to the surface. As surface characteristics, the looped polymer brushes shows low water contact angle hysteresis and low sliding angle. Technologically useful surface properties are provided on the surface by the PDMS coatings.