Glass and structural transitions measured at polymer surfaces on the nanoscale

This paper reviews our recent progress in determining the surface glass transition temperature, T-g, of free and substrate confined amorphous polymer films. We will introduce novel instrumental approaches and discuss surface and bulk concepts of T-g. The T-g of surfaces will be compared to the bulk, and we will discuss the effect of interfacial interactions (confinements), surface energy, disentanglement, adhesion forces, viscosity and structural changes on the glass transition. Measurements have been conducted with scanning force microscopy in two different shear modes: dynamic friction force mode and locally static shear modulation mode. The applicability of these two nano-contact modes to T-g will be discussed.