The role of interface on molecular mobility of glasses or ‘Can Cathedral Glasses Flow’

Abstract

Our investigation demonstrates the role of interfaces for molecular mobility of glasses. Usually, the role of the surface layer is neglected because it contains about 10 −8 of the number of molecules of the sample. However, the interface is important in several cases: For the thin films; for the processes taking part at the interface (e.g. surface crystallization) and in the cases when bulk molecules are practically immobile. We define a critical temperature T c, below which surface molecules have more important contribution then the bulk ones. As soon as this happens in the vicinity, or rather below, the glass transition temperature, the samples behave solid like. So, the contribution of the surface mobility is not sufficient to cause changes in human life period but it is large enough to permit tiny changes in historical periods. This could be an explanation why cathedral glasses are a couple of microns thicker at the bottom side.