Dewetting photocontrol of poly(styrene) thin films by a photocrosslinkable monolayer in thermal nanoimprint lithography

In this article, we investigated dewetting behaviors of monodisperse-poly(styrene) thin films on a photocrosslinkable monolayer bearing a benzophenone moiety affected by ultraviolet light exposure dose, irradiation wavelength, and molecular weight. The thermally induced dewetting was suppressed by UV exposure at either 365-nm exposure dose of 200 J cm^-2 or 254-nm exposure dose of 1.0 J cm^-2. The dewetting behaviors were induced for low-molecular-weight poly(styrene) of the weight-average molecular weight (Mw) 2,200 g mol"1 and not observed for poly(styrene) of more than Mw = 10,800 g mol"1. The gel permeation chromatography analysis indicated that the thermally induced dewetting behaviors were not responsible for photochemistry of poly(styrene) such as depolyrnerization and disproportionation and responsible for monolayer photochemistry of the benzophenone moiety grafting poly(styrene) at the polymer/monolayer interface.