title: Competition between substrate-mediated π-π stacking and surface-mediated T(g) depression in ultrathin conjugated polymer films.
abstract: We report surface and interface effects in dynamics and chain conformation in the thin film of conjugated polymer PCDTBT. To probe dynamic anomalies, we measure the glass transition temperature (T(g)) of PCDTBT films as a function of thickness, and find that there is a significant depression in T(g) for films less than 100 nm thick; a result qualitatively similar to that observed in many other polymer film systems. However, for films less than 40 nm, the T(g) converges to a constant value of 20 K below its bulk value. Grazing incidence X-ray diffraction shows depth-dependent molecular organization that is associated with the unusual thickness-dependent dynamics.
authors.affiliation: Department of Physics and Astronomy, University of Sheffield, UK. t.wang@hotmail.com
authors.forename: Tao
authors.initials: T
authors.lastname: Wang
authors.forename: Andrew J
authors.initials: AJ
authors.lastname: Pearson
authors.forename: Alan D F
authors.initials: AD
authors.lastname: Dunbar
authors.forename: Paul A
authors.initials: PA
authors.lastname: Staniec
authors.forename: Darren C
authors.initials: DC
authors.lastname: Watters
authors.forename: David
authors.initials: D
authors.lastname: Coles
authors.forename: Hunan
authors.initials: H
authors.lastname: Yi
authors.forename: Ahmed
authors.initials: A
authors.lastname: Iraqi
authors.forename: David G
authors.initials: DG
authors.lastname: Lidzey
authors.forename: Richard A L
authors.initials: RA
authors.lastname: Jones