Michael Erber

Glass Transition of Polymers with Different Architectures in the Confinement of Nanoscopic Films

The dynamic properties of nanoscopic polymeric films can significantly differ from the well-known bulk properties. In general, with decreasing film thickness the surface to volume ratio increases tremendously and interfacial interactions are expected to dominate the molecular dynamics of geometrically confined polymers. On the one hand, attractive interfacial interactions can inhibit cooperative dynamics and lead to a rise in \({T_g}\). On the other hand, repulsive interactions may depress \({T_g}\). However, the order of magnitude of the \({T_g}\) aberration in nanoscopic films is quite controversially discussed and some scientists even have doubt in the existence of confinement effects for films exceeding 10 nm in thickness. In the last few years, several factors were identified which may mimic confinement effects such as plasticizer effects due to solvent residues, degradation or oxidation processes and crosslinking. In this chapter we try to give a review about the determination and complexity of the glass transition of polymers in nanoscopic films and the unique role of temperature-dependent ellipsometry with its advantages but also methodical challenges therein.