Vitrification of Thin Polymer Films: From Linear Chain to Soft Colloid-like Behavior

We show that the vitrification of star-shaped polystyrene (PS), of functionality f and molecular weight per arm Mwarm, thin films supported by silicon oxide, SiOx, is strongly dependent on Mwarm and f. When f is small, the vitrification behavior is similar to that of linear-chain PS where the average glass transition, Tg, decreases with decreasing film thickness (ΔTg 0. We show that the overall vitrification behavior of these thin film star-shaped polymers is due to compet...