Dependence of Surface Free Energy of Polystyrene Thin Films on Temperature for Grafting Treatment

Abstract

End-grafted polymer monolayers play an important role in colloidal stabilization, adhesion, and biocompatibility of artificial organs in medicine. There are two main methods to form end-grafting polymer layer:grafting-to and grafting-from methods. Grafting-to method has merit that is easy to conduct and easy to set a homogeneous degree of polymerization. We formed end-grafted polystyrene monolayers by a grafting-to method;a vinyl terminated polystyrene reacted with a H-terminated Si wafer and the polystyrene grafted to it. To clarify surface properties of the grafted polystyrene layer on the grafting density, we controlled it by a reaction temperature;The density could be controlled from 0.09 to 0.20 chains/nm2. At a lower grafting density region, the layer has high surface energy, high layer density, thin thickness, and smooth surface morphology. While at a higher grafting density region, the layer has low surface energy, low layer density, thick thickness, and smooth surface morphology.