Ultrathin Polymer Films: Interfacial and Annealing Dependence of Confinement Effects

摘要

Ultrathin film of poly (vinyl acetate) supported on different metallic substrates have been investigated to study confinement effects on relaxation dynamics. The characteristic frequency of structural relaxation increases on decreasing thickness when the interfacial energy is less than roughly 3 mJ/m~2, whereas it is thickness independent at about 3.5 mJ/m~2. The growth of an interfacial polymer layer, insoluble in the commonly used solvent, has been found to grow during annealing for several days at a temperature much above the glass transition. The presence of such layer reduces the average confinement effect on the film. Such finding seems to reconcile several contradicting results previously reported.