Measurements of the physical properties of materials at interfaces are
very important in microelectronics packaging and interconnection, especially
as electronics devices decrease in size and interfaces become a larger proportion
of the device. In particular, polymers have recently been found to have
different thermal expansion and glass transition properties when in the
confined geometry of a thin film as opposed to the bulk state. These properties
are further perturbed from the bulk values when adhesive interactions are
present between the polymer film and the substrate. To deconvolute the effects
of wall adhesion and chain confinement on the thermal properties of polymeric
thin films, we have used neutron reflectometry to non-invasively probe the
thermal expansion of polymer thin films between two non-attractive polymer
confinement layers. The temperature dependence of the thickness of a deuterated
polystyrene (d-PS) layer, which is confined between two polycarbonate layers,
was measured to specifically examine the effect of confinement on the thermal
expansion and glass transition of the d-PS. The initial thickness of the
d-PS layer range from 30 nm - 900 nm. The results are compared to polystyrene
bulk behavior and previous thin film experiments which included free surfaces
as well as adhesive interactions between the layer of interest and substrate.