title: A natural length scale for the glass transition of conjugated polymer film.
abstract: A study is reported of the anomalous glass transition temperature, Tg, in thin free-standing conjugated polymer films revealed by confocal Raman scattering. Full details of the dependence of Tgon film thicknesses d ranging from less than to greater than the polymer average end-to-end distance REEare presented. In contrast to ultrathin films (d<REE), which always exhibit a reduction of their Tgvalues due to the chain confinement effect, thick films within a certain range of thicknesses distinguish themselves by presenting anomalous enhancement of two Tgvalues; one is interpreted as at the interface, and the other in the core. This study is strongly suggestive of a new length scale L, which lies in the range of most polymer electronic devices studied over which the physical properties of the film are greatly perturbed by the presence of free surfaces.
authors.affiliation: Department of Industrial and Systems Engineering, Hong Kong Polytechnic University, Hung Hom, Kowloon, Hong Kong. Department of Materials Science and Engineering, University of California at Los Angeles, Los Angeles, CA 90095, USA.
authors.forename: H
authors.initials: H
authors.lastname: Liem