Self-organization of Triblock Copolymer Melt Chains Physisorbed on Non-neutral Surfaces*

Polymer physisorption is an unavoidable event even when weakly attractive surfaces contact a polymer melt. We report the self-organization process of poly(styrene-b-ethylene/butadiene-b-styrene) (SEBS) triblock copolymer chains physically adsorbed on a non-neutral surface. The results revealed that the SEBS chains form the two different chain structures on the substrate simultaneously: (i) “flattened chains” with an average height of 2.5 nm, but without forming microdomain structures; (ii) “loosely adsorbed chains” with an average height of 11.0 nm forming perpendicular oriented cylindrical microdomains to the substrate surface. In addition, it was found that the lateral microdomain structures were distorted and the characteristic length of the microdomains varied from the bulk after reaching the quasi-equilibrium state. Furthermore, we highlight the role of the adsorbed chains in the self-assembling process of the entire SEBS thin film: A long-range perturbation propagates into the film interior, overwhelming the free surface effect associated with surface segregation of the lower surface tension of polystyrene blocks.