title: Role of molecular architecture on the vitrification of polymer thin films.
abstract: We show that thin film star-shaped macromolecules exhibit significant differences in their average vitrification behavior, in both magnitude and thickness dependence, from their linear analogs. This behavior is dictated by a combination of their functionality and arm length. Additionally, the glass transition temperature at the free surface of a star-shaped molecule film may be higher than that of the interior, in contrast to their linear analogs where the opposite is true. These findings have implications for other properties, due largely to the origins, entropic, of this behavior.
authors.affiliation: Department of Materials Science and Engineering, University of Michigan, Ann Arbor, Michigan 48109, USA.
authors.forename: Emmanouil
authors.initials: E
authors.lastname: Glynos
authors.forename: Bradley
authors.initials: B
authors.lastname: Frieberg
authors.forename: Hyunjoon
authors.initials: H
authors.lastname: Oh
authors.forename: Ming
authors.initials: M
authors.lastname: Liu
authors.forename: David W
authors.initials: DW
authors.lastname: Gidley
authors.forename: Peter F
authors.initials: PF
authors.lastname: Green