Thermoplastic elastomer monolayers grafted to a functionalized silicon surface

We fabricated a robust ultrathin film of a triblock copolymer, poly[styrene -b-(ethylene-co-butylene)-b-styrene] (SEBS), functionalized with 2% of male ic anhydride by melt/solution grafting to a chemically reactive silicon sur face. We used epoxy-terminated self-assembling monolayers to functionalize silicon surface. The thickness of grafted block polymer, t, was varied from 1.35 to 9.1 nm to test the limits of stability of microphase-separated str uctures of the triblock copolymer tethered under confined conditions. Accor dingly, the ratio tid was changed from 0.05 to 0.33, where d is the interdo main spacing. The contact angle measurements demonstrated that the surface of the complete block copolymer films was totally occupied by poly[ethylene -co-butene] (PEB) chains. When the SEES film thickness reached 8.4 nm, the film possessed the well-defined microphase structure of the typical thermop lastic elastomer material, where PS phase formed the microdomain network th at reinforced the elastomeric matrix. The microphase separation was complet ely suppressed only for ultrathin films with t/d < 0.08. We found that teth ered block copolymer monolayers were extremely stable and preserved their m icrodomain structure at elevated temperatures unlike physically adsorbed fi lms that dewetted under similar conditions.