Photo-triggered surface relief formation of polystyrene films based on the Marangoni flow driven by a surface photoresponsive skin layer

Surface relief gratings (SRGs) are widely investigated in azobenzene-containing polymer films. We have recently demonstrated that a photoresponsive azobenzene layer existing only at the surface of a non-photoresponsive liquid crystalline polymer film can induce mass migration by patterned UV light irradiation, resulting in the SRG structure. This process is explained by the Marangoni flow triggered by the photoinduced surface tension change of the surface layer. In this work, we newly propose that the same strategy is applicable to an amorphous polymer material of polystyrene. The results obtained here indicate that photoinduced SRG formation is expanded for general amorphous polymers.