Glass transition measurements of ultrathin polystyrene films
Authors: Buenviaje C., Dinelli F., Overney R.M.
Autors Affiliation: Department of Chemical Engineering, University of Washington, Seattle, WA 98195-1750, United States
Abstract: Data from various experiments suggest that the mechanical properties of thin polymer films depend, in a complex manner, on the film preparation process, in conjunction with interfacial interactions. In this paper, we discuss how and why interfacial interactions can affect the shear mechanical properties of spin-coated polymer films. For example, confinement effects due to the spin coating process have been observed to exceed the nearest neighbor interaction distances by one order of magnitude. We introduce shear modulation scanning probe microscopy (SPM) as a technique to measure local shear property changes in thin polymer films as a function of temperature. Comparisons with bulk and lateral force measurements demonstrate the reliability of the technique. Using the shear modulation SPM, we observe a molecular weight dependence on the bulk glass transition. Measurements taken on polystyrene surfaces of various film thickness provide insight into how the glass transition of films are affected by substrate confinement.
KeyWords: Glass transition; Polymer films; Scanning probe microscopy (SPM); Segmental dynamicsDOI: 10.1021/bk-2001-0781