An explanation of how nanoconfinement affects the control of local dynamic relaxation*

The dynamics of local segmental relaxation in glass forming systems is linked to fundamental material properties and control variables that reflect the influence of thermodynamics on the relaxation time, tau. In the Cooperative Free Volume (CFV) model the key variables are temperature (T) and free volume (Vfree), which is related to density. The general CFV result is that log tau ~ (1/Vfree)x f(T). We find that our result for f(T) works equally well for the bulk under highly varying pressure conditions, and for all types of confinement. The presence of Vfree in the CFV expression for log tau results in a sensitivity to density changes that becomes strong at low T, and also reflective of the presence of interfaces, whether in film or nanocomposite. In this talk these CFV features will be illustrated through extensive connection with experimental data on a variety of systems.